text: /*
   *  pcap-linux.c: Packet capture interface to the Linux kernel
   *
   *  Copyright (c) 2000 Torsten Landschoff <torsten@debian.org>
   *  		       Sebastian Krahmer  <krahmer@cs.uni-potsdam.de>
   *
   *  License: BSD
   *
   *  Redistribution and use in source and binary forms, with or without
   *  modification, are permitted provided that the following conditions
   *  are met:
   *
   *  1. Redistributions of source code must retain the above copyright
   *     notice, this list of conditions and the following disclaimer.
   *  2. Redistributions in binary form must reproduce the above copyright
   *     notice, this list of conditions and the following disclaimer in
   *     the documentation and/or other materials provided with the
   *     distribution.
   *  3. The names of the authors may not be used to endorse or promote
   *     products derived from this software without specific prior
   *     written permission.
   *
   *  THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
   *  IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
   *  WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
   *
   *  Modifications:     Added PACKET_MMAP support
   *                     Paolo Abeni <paolo.abeni@email.it>
   *                     Added TPACKET_V3 support
   *                     Gabor Tatarka <gabor.tatarka@ericsson.com>
   *
   *                     based on previous works of:
   *                     Simon Patarin <patarin@cs.unibo.it>
   *                     Phil Wood <cpw@lanl.gov>
   *
   * Monitor-mode support for mac80211 includes code taken from the iw
   * command; the copyright notice for that code is
   *
   * Copyright (c) 2007, 2008	Johannes Berg
   * Copyright (c) 2007		Andy Lutomirski
   * Copyright (c) 2007		Mike Kershaw
   * Copyright (c) 2008		Gábor Stefanik
   *
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   * 3. The name of the author may not be used to endorse or promote products
   *    derived from this software without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
   * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
   * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
   * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
   * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
   * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE.
   */
  
  /*
   * Known problems with 2.0[.x] kernels:
   *
   *   - The loopback device gives every packet twice; on 2.2[.x] kernels,
   *     if we use PF_PACKET, we can filter out the transmitted version
   *     of the packet by using data in the "sockaddr_ll" returned by
   *     "recvfrom()", but, on 2.0[.x] kernels, we have to use
   *     PF_INET/SOCK_PACKET, which means "recvfrom()" supplies a
   *     "sockaddr_pkt" which doesn't give us enough information to let
   *     us do that.
   *
   *   - We have to set the interface's IFF_PROMISC flag ourselves, if
   *     we're to run in promiscuous mode, which means we have to turn
   *     it off ourselves when we're done; the kernel doesn't keep track
   *     of how many sockets are listening promiscuously, which means
   *     it won't get turned off automatically when no sockets are
   *     listening promiscuously.  We catch "pcap_close()" and, for
   *     interfaces we put into promiscuous mode, take them out of
   *     promiscuous mode - which isn't necessarily the right thing to
   *     do, if another socket also requested promiscuous mode between
   *     the time when we opened the socket and the time when we close
   *     the socket.
   *
   *   - MSG_TRUNC isn't supported, so you can't specify that "recvfrom()"
   *     return the amount of data that you could have read, rather than
   *     the amount that was returned, so we can't just allocate a buffer
   *     whose size is the snapshot length and pass the snapshot length
   *     as the byte count, and also pass MSG_TRUNC, so that the return
   *     value tells us how long the packet was on the wire.
   *
   *     This means that, if we want to get the actual size of the packet,
   *     so we can return it in the "len" field of the packet header,
   *     we have to read the entire packet, not just the part that fits
   *     within the snapshot length, and thus waste CPU time copying data
   *     from the kernel that our caller won't see.
   *
   *     We have to get the actual size, and supply it in "len", because
   *     otherwise, the IP dissector in tcpdump, for example, will complain
   *     about "truncated-ip", as the packet will appear to have been
   *     shorter, on the wire, than the IP header said it should have been.
   */
  
  
  #define _GNU_SOURCE
  
  #ifdef HAVE_CONFIG_H
  #include "config.h"
  #endif
  
  #include <errno.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <ctype.h>
  #include <unistd.h>
  #include <fcntl.h>
  #include <string.h>
  #include <limits.h>
  #include <sys/stat.h>
  #include <sys/socket.h>
  #include <sys/ioctl.h>
  #include <sys/utsname.h>
  #include <sys/mman.h>
  #include <linux/if.h>
  #include <linux/if_packet.h>
  #include <linux/sockios.h>
  #include <netinet/in.h>
  #include <linux/if_ether.h>
  #include <net/if_arp.h>
  #include <poll.h>
  #include <dirent.h>
  
  #include "pcap-int.h"
  #include "pcap/sll.h"
  #include "pcap/vlan.h"
  
  /*
   * If PF_PACKET is defined, we can use {SOCK_RAW,SOCK_DGRAM}/PF_PACKET
   * sockets rather than SOCK_PACKET sockets.
   *
   * To use them, we include <linux/if_packet.h> rather than
   * <netpacket/packet.h>; we do so because
   *
   *	some Linux distributions (e.g., Slackware 4.0) have 2.2 or
   *	later kernels and libc5, and don't provide a <netpacket/packet.h>
   *	file;
   *
   *	not all versions of glibc2 have a <netpacket/packet.h> file
   *	that defines stuff needed for some of the 2.4-or-later-kernel
   *	features, so if the system has a 2.4 or later kernel, we
   *	still can't use those features.
   *
   * We're already including a number of other <linux/XXX.h> headers, and
   * this code is Linux-specific (no other OS has PF_PACKET sockets as
   * a raw packet capture mechanism), so it's not as if you gain any
   * useful portability by using <netpacket/packet.h>
   *
   * XXX - should we just include <linux/if_packet.h> even if PF_PACKET
   * isn't defined?  It only defines one data structure in 2.0.x, so
   * it shouldn't cause any problems.
   */
  #ifdef PF_PACKET
  # include <linux/if_packet.h>
  
   /*
    * On at least some Linux distributions (for example, Red Hat 5.2),
    * there's no <netpacket/packet.h> file, but PF_PACKET is defined if
    * you include <sys/socket.h>, but <linux/if_packet.h> doesn't define
    * any of the PF_PACKET stuff such as "struct sockaddr_ll" or any of
    * the PACKET_xxx stuff.
    *
    * So we check whether PACKET_HOST is defined, and assume that we have
    * PF_PACKET sockets only if it is defined.
    */
  # ifdef PACKET_HOST
  #  define HAVE_PF_PACKET_SOCKETS
  #  ifdef PACKET_AUXDATA
  #   define HAVE_PACKET_AUXDATA
  #  endif /* PACKET_AUXDATA */
  # endif /* PACKET_HOST */
  
  
   /* check for memory mapped access avaibility. We assume every needed
    * struct is defined if the macro TPACKET_HDRLEN is defined, because it
    * uses many ring related structs and macros */
  # ifdef PCAP_SUPPORT_PACKET_RING
  # ifdef TPACKET_HDRLEN
  #  define HAVE_PACKET_RING
  #  ifdef TPACKET3_HDRLEN
  #   define HAVE_TPACKET3
  #  endif /* TPACKET3_HDRLEN */
  #  ifdef TPACKET2_HDRLEN
  #   define HAVE_TPACKET2
  #  else  /* TPACKET2_HDRLEN */
  #   define TPACKET_V1	0    /* Old kernel with only V1, so no TPACKET_Vn defined */
  #  endif /* TPACKET2_HDRLEN */
  # endif /* TPACKET_HDRLEN */
  # endif /* PCAP_SUPPORT_PACKET_RING */
  #endif /* PF_PACKET */
  
  #ifdef SO_ATTACH_FILTER
  #include <linux/types.h>
  #include <linux/filter.h>
  #endif
  
  #ifdef HAVE_LINUX_NET_TSTAMP_H
  #include <linux/net_tstamp.h>
  #endif
  
  #ifdef HAVE_LINUX_SOCKIOS_H
  #include <linux/sockios.h>
  #endif
  
  #ifdef HAVE_LINUX_IF_BONDING_H
  #include <linux/if_bonding.h>
  #endif
  
  /*
   * Got Wireless Extensions?
   */
  #ifdef HAVE_LINUX_WIRELESS_H
  #include <linux/wireless.h>
  #endif /* HAVE_LINUX_WIRELESS_H */
  
  /*
   * Got libnl?
   */
  #ifdef HAVE_LIBNL
  #include <linux/nl80211.h>
  
  #include <netlink/genl/genl.h>
  #include <netlink/genl/family.h>
  #include <netlink/genl/ctrl.h>
  #include <netlink/msg.h>
  #include <netlink/attr.h>
  #endif /* HAVE_LIBNL */
  
  /*
   * Got ethtool support?
   */
  #ifdef HAVE_LINUX_ETHTOOL_H
  #include <linux/ethtool.h>
  #endif
  
  #ifndef HAVE_SOCKLEN_T
  typedef int		socklen_t;
  #endif
  
  #ifndef MSG_TRUNC
  /*
   * This is being compiled on a system that lacks MSG_TRUNC; define it
   * with the value it has in the 2.2 and later kernels, so that, on
   * those kernels, when we pass it in the flags argument to "recvfrom()"
   * we're passing the right value and thus get the MSG_TRUNC behavior
   * we want.  (We don't get that behavior on 2.0[.x] kernels, because
   * they didn't support MSG_TRUNC.)
   */
  #define MSG_TRUNC	0x20
  #endif
  
  #ifndef SOL_PACKET
  /*
   * This is being compiled on a system that lacks SOL_PACKET; define it
   * with the value it has in the 2.2 and later kernels, so that we can
   * set promiscuous mode in the good modern way rather than the old
   * 2.0-kernel crappy way.
   */
  #define SOL_PACKET	263
  #endif
  
  #define MAX_LINKHEADER_SIZE	256
  
  /*
   * When capturing on all interfaces we use this as the buffer size.
   * Should be bigger then all MTUs that occur in real life.
   * 64kB should be enough for now.
   */
  #define BIGGER_THAN_ALL_MTUS	(64*1024)
  
  /*
   * Private data for capturing on Linux SOCK_PACKET or PF_PACKET sockets.
   */
  struct pcap_linux {
  	u_int	packets_read;	/* count of packets read with recvfrom() */
  	long	proc_dropped;	/* packets reported dropped by /proc/net/dev */
  	struct pcap_stat stat;
  
  	char	*device;	/* device name */
  	int	filter_in_userland; /* must filter in userland */
  	int	blocks_to_filter_in_userland;
  	int	must_do_on_close; /* stuff we must do when we close */
  	int	timeout;	/* timeout for buffering */
  	int	sock_packet;	/* using Linux 2.0 compatible interface */
  	int	cooked;		/* using SOCK_DGRAM rather than SOCK_RAW */
  	int	ifindex;	/* interface index of device we're bound to */
  	int	lo_ifindex;	/* interface index of the loopback device */
  	bpf_u_int32 oldmode;	/* mode to restore when turning monitor mode off */
  	char	*mondevice;	/* mac80211 monitor device we created */
  	u_char	*mmapbuf;	/* memory-mapped region pointer */
  	size_t	mmapbuflen;	/* size of region */
  	int	vlan_offset;	/* offset at which to insert vlan tags; if -1, don't insert */
  	u_int	tp_version;	/* version of tpacket_hdr for mmaped ring */
  	u_int	tp_hdrlen;	/* hdrlen of tpacket_hdr for mmaped ring */
  	u_char	*oneshot_buffer; /* buffer for copy of packet */
  #ifdef HAVE_TPACKET3
  	unsigned char *current_packet; /* Current packet within the TPACKET_V3 block. Move to next block if NULL. */
  	int packets_left; /* Unhandled packets left within the block from previous call to pcap_read_linux_mmap_v3 in case of TPACKET_V3. */
  #endif
  };
  
  /*
   * Stuff to do when we close.
   */
  #define MUST_CLEAR_PROMISC	0x00000001	/* clear promiscuous mode */
  #define MUST_CLEAR_RFMON	0x00000002	/* clear rfmon (monitor) mode */
  #define MUST_DELETE_MONIF	0x00000004	/* delete monitor-mode interface */
  
  /*
   * Prototypes for internal functions and methods.
   */
  static void map_arphrd_to_dlt(pcap_t *, int, int, const char *, int);
  #ifdef HAVE_PF_PACKET_SOCKETS
  static short int map_packet_type_to_sll_type(short int);
  #endif
  static int pcap_activate_linux(pcap_t *);
  static int activate_old(pcap_t *);
  static int activate_new(pcap_t *);
  static int activate_mmap(pcap_t *, int *);
  static int pcap_can_set_rfmon_linux(pcap_t *);
  static int pcap_read_linux(pcap_t *, int, pcap_handler, u_char *);
  static int pcap_read_packet(pcap_t *, pcap_handler, u_char *);
  static int pcap_inject_linux(pcap_t *, const void *, size_t);
  static int pcap_stats_linux(pcap_t *, struct pcap_stat *);
  static int pcap_setfilter_linux(pcap_t *, struct bpf_program *);
  static int pcap_setdirection_linux(pcap_t *, pcap_direction_t);
  static int pcap_set_datalink_linux(pcap_t *, int);
  static void pcap_cleanup_linux(pcap_t *);
  
  /*
   * This is what the header structure looks like in a 64-bit kernel;
   * we use this, rather than struct tpacket_hdr, if we're using
   * TPACKET_V1 in 32-bit code running on a 64-bit kernel.
   */
  struct tpacket_hdr_64 {
  	uint64_t	tp_status;
  	unsigned int	tp_len;
  	unsigned int	tp_snaplen;
  	unsigned short	tp_mac;
  	unsigned short	tp_net;
  	unsigned int	tp_sec;
  	unsigned int	tp_usec;
  };
  
  /*
   * We use this internally as the tpacket version for TPACKET_V1 in
   * 32-bit code on a 64-bit kernel.
   */
  #define TPACKET_V1_64 99
  
  union thdr {
  	struct tpacket_hdr		*h1;
  	struct tpacket_hdr_64		*h1_64;
  #ifdef HAVE_TPACKET2
  	struct tpacket2_hdr		*h2;
  #endif
  #ifdef HAVE_TPACKET3
  	struct tpacket_block_desc	*h3;
  #endif
  	void				*raw;
  };
  
  #ifdef HAVE_PACKET_RING
  #define RING_GET_FRAME(h) (((union thdr **)h->buffer)[h->offset])
  
  static void destroy_ring(pcap_t *handle);
  static int create_ring(pcap_t *handle, int *status);
  static int prepare_tpacket_socket(pcap_t *handle);
  static void pcap_cleanup_linux_mmap(pcap_t *);
  static int pcap_read_linux_mmap_v1(pcap_t *, int, pcap_handler , u_char *);
  static int pcap_read_linux_mmap_v1_64(pcap_t *, int, pcap_handler , u_char *);
  #ifdef HAVE_TPACKET2
  static int pcap_read_linux_mmap_v2(pcap_t *, int, pcap_handler , u_char *);
  #endif
  #ifdef HAVE_TPACKET3
  static int pcap_read_linux_mmap_v3(pcap_t *, int, pcap_handler , u_char *);
  #endif
  static int pcap_setfilter_linux_mmap(pcap_t *, struct bpf_program *);
  static int pcap_setnonblock_mmap(pcap_t *p, int nonblock, char *errbuf);
  static int pcap_getnonblock_mmap(pcap_t *p, char *errbuf);
  static void pcap_oneshot_mmap(u_char *user, const struct pcap_pkthdr *h,
      const u_char *bytes);
  #endif
  
  #ifdef TP_STATUS_VLAN_TPID_VALID
  # define VLAN_TPID(hdr, hv)	(((hv)->tp_vlan_tpid || ((hdr)->tp_status & TP_STATUS_VLAN_TPID_VALID)) ? (hv)->tp_vlan_tpid : ETH_P_8021Q)
  #else
  # define VLAN_TPID(hdr, hv)	ETH_P_8021Q
  #endif
  
  /*
   * Wrap some ioctl calls
   */
  #ifdef HAVE_PF_PACKET_SOCKETS
  static int	iface_get_id(int fd, const char *device, char *ebuf);
  #endif /* HAVE_PF_PACKET_SOCKETS */
  static int	iface_get_mtu(int fd, const char *device, char *ebuf);
  static int 	iface_get_arptype(int fd, const char *device, char *ebuf);
  #ifdef HAVE_PF_PACKET_SOCKETS
  static int 	iface_bind(int fd, int ifindex, char *ebuf);
  #ifdef IW_MODE_MONITOR
  static int	has_wext(int sock_fd, const char *device, char *ebuf);
  #endif /* IW_MODE_MONITOR */
  static int	enter_rfmon_mode(pcap_t *handle, int sock_fd,
      const char *device);
  #endif /* HAVE_PF_PACKET_SOCKETS */
  #if defined(HAVE_LINUX_NET_TSTAMP_H) && defined(PACKET_TIMESTAMP)
  static int	iface_ethtool_get_ts_info(pcap_t *handle, char *ebuf);
  #endif
  #ifdef HAVE_PACKET_RING
  static int	iface_get_offload(pcap_t *handle);
  #endif
  static int 	iface_bind_old(int fd, const char *device, char *ebuf);
  
  #ifdef SO_ATTACH_FILTER
  static int	fix_program(pcap_t *handle, struct sock_fprog *fcode,
      int is_mapped);
  static int	fix_offset(struct bpf_insn *p);
  static int	set_kernel_filter(pcap_t *handle, struct sock_fprog *fcode);
  static int	reset_kernel_filter(pcap_t *handle);
  
  static struct sock_filter	total_insn
  	= BPF_STMT(BPF_RET | BPF_K, 0);
  static struct sock_fprog	total_fcode
  	= { 1, &total_insn };
  #endif /* SO_ATTACH_FILTER */
  
  #ifdef HAVE_PF_RING
  static u_int8_t pf_ring_active_poll = 0;
  #endif
  
  pcap_t *
  pcap_create_interface(const char *device, char *ebuf)
  {
  	pcap_t *handle;
  
  	handle = pcap_create_common(device, ebuf, sizeof (struct pcap_linux));
  	if (handle == NULL)
  		return NULL;
  
  	handle->activate_op = pcap_activate_linux;
  	handle->can_set_rfmon_op = pcap_can_set_rfmon_linux;
  
  #if defined(HAVE_LINUX_NET_TSTAMP_H) && defined(PACKET_TIMESTAMP)
  	/*
  	 * See what time stamp types we support.
  	 */
  	if (iface_ethtool_get_ts_info(handle, ebuf) == -1) {
  		free(handle);
  		return NULL;
  	}
  #endif
  
  #if defined(SIOCGSTAMPNS) && defined(SO_TIMESTAMPNS)
  	/*
  	 * We claim that we support microsecond and nanosecond time
  	 * stamps.
  	 *
  	 * XXX - with adapter-supplied time stamps, can we choose
  	 * microsecond or nanosecond time stamps on arbitrary
  	 * adapters?
  	 */
  	handle->tstamp_precision_count = 2;
  	handle->tstamp_precision_list = malloc(2 * sizeof(u_int));
  	if (handle->tstamp_precision_list == NULL) {
  		snprintf(ebuf, PCAP_ERRBUF_SIZE, "malloc: %s",
  		    pcap_strerror(errno));
  		if (handle->tstamp_type_list != NULL)
  			free(handle->tstamp_type_list);
  		free(handle);
  		return NULL;
  	}
  	handle->tstamp_precision_list[0] = PCAP_TSTAMP_PRECISION_MICRO;
  	handle->tstamp_precision_list[1] = PCAP_TSTAMP_PRECISION_NANO;
  #endif /* defined(SIOCGSTAMPNS) && defined(SO_TIMESTAMPNS) */
  
  	return handle;
  }
  
  #ifdef HAVE_LIBNL
  /*
   * If interface {if} is a mac80211 driver, the file
   * /sys/class/net/{if}/phy80211 is a symlink to
   * /sys/class/ieee80211/{phydev}, for some {phydev}.
   *
   * On Fedora 9, with a 2.6.26.3-29 kernel, my Zydas stick, at
   * least, has a "wmaster0" device and a "wlan0" device; the
   * latter is the one with the IP address.  Both show up in
   * "tcpdump -D" output.  Capturing on the wmaster0 device
   * captures with 802.11 headers.
   *
   * airmon-ng searches through /sys/class/net for devices named
   * monN, starting with mon0; as soon as one *doesn't* exist,
   * it chooses that as the monitor device name.  If the "iw"
   * command exists, it does "iw dev {if} interface add {monif}
   * type monitor", where {monif} is the monitor device.  It
   * then (sigh) sleeps .1 second, and then configures the
   * device up.  Otherwise, if /sys/class/ieee80211/{phydev}/add_iface
   * is a file, it writes {mondev}, without a newline, to that file,
   * and again (sigh) sleeps .1 second, and then iwconfig's that
   * device into monitor mode and configures it up.  Otherwise,
   * you can't do monitor mode.
   *
   * All these devices are "glued" together by having the
   * /sys/class/net/{device}/phy80211 links pointing to the same
   * place, so, given a wmaster, wlan, or mon device, you can
   * find the other devices by looking for devices with
   * the same phy80211 link.
   *
   * To turn monitor mode off, delete the monitor interface,
   * either with "iw dev {monif} interface del" or by sending
   * {monif}, with no NL, down /sys/class/ieee80211/{phydev}/remove_iface
   *
   * Note: if you try to create a monitor device named "monN", and
   * there's already a "monN" device, it fails, as least with
   * the netlink interface (which is what iw uses), with a return
   * value of -ENFILE.  (Return values are negative errnos.)  We
   * could probably use that to find an unused device.
   *
   * Yes, you can have multiple monitor devices for a given
   * physical device.
  */
  
  /*
   * Is this a mac80211 device?  If so, fill in the physical device path and
   * return 1; if not, return 0.  On an error, fill in handle->errbuf and
   * return PCAP_ERROR.
   */
  static int
  get_mac80211_phydev(pcap_t *handle, const char *device, char *phydev_path,
      size_t phydev_max_pathlen)
  {
  	char *pathstr;
  	ssize_t bytes_read;
  
  	/*
  	 * Generate the path string for the symlink to the physical device.
  	 */
  	if (asprintf(&pathstr, "/sys/class/net/%s/phy80211", device) == -1) {
  		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  		    "%s: Can't generate path name string for /sys/class/net device",
  		    device);
  		return PCAP_ERROR;
  	}
  	bytes_read = readlink(pathstr, phydev_path, phydev_max_pathlen);
  	if (bytes_read == -1) {
  		if (errno == ENOENT || errno == EINVAL) {
  			/*
  			 * Doesn't exist, or not a symlink; assume that
  			 * means it's not a mac80211 device.
  			 */
  			free(pathstr);
  			return 0;
  		}
  		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  		    "%s: Can't readlink %s: %s", device, pathstr,
  		    strerror(errno));
  		free(pathstr);
  		return PCAP_ERROR;
  	}
  	free(pathstr);
  	phydev_path[bytes_read] = '\0';
  	return 1;
  }
  
  #ifdef HAVE_LIBNL_SOCKETS
  #define get_nl_errmsg	nl_geterror
  #else
  /* libnl 2.x compatibility code */
  
  #define nl_sock nl_handle
  
  static inline struct nl_handle *
  nl_socket_alloc(void)
  {
  	return nl_handle_alloc();
  }
  
  static inline void
  nl_socket_free(struct nl_handle *h)
  {
  	nl_handle_destroy(h);
  }
  
  #define get_nl_errmsg	strerror
  
  static inline int
  __genl_ctrl_alloc_cache(struct nl_handle *h, struct nl_cache **cache)
  {
  	struct nl_cache *tmp = genl_ctrl_alloc_cache(h);
  	if (!tmp)
  		return -ENOMEM;
  	*cache = tmp;
  	return 0;
  }
  #define genl_ctrl_alloc_cache __genl_ctrl_alloc_cache
  #endif /* !HAVE_LIBNL_SOCKETS */
  
  struct nl80211_state {
  	struct nl_sock *nl_sock;
  	struct nl_cache *nl_cache;
  	struct genl_family *nl80211;
  };
  
  static int
  nl80211_init(pcap_t *handle, struct nl80211_state *state, const char *device)
  {
  	int err;
  
  	state->nl_sock = nl_socket_alloc();
  	if (!state->nl_sock) {
  		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  		    "%s: failed to allocate netlink handle", device);
  		return PCAP_ERROR;
  	}
  
  	if (genl_connect(state->nl_sock)) {
  		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  		    "%s: failed to connect to generic netlink", device);
  		goto out_handle_destroy;
  	}
  
  	err = genl_ctrl_alloc_cache(state->nl_sock, &state->nl_cache);
  	if (err < 0) {
  		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  		    "%s: failed to allocate generic netlink cache: %s",
  		    device, get_nl_errmsg(-err));
  		goto out_handle_destroy;
  	}
  
  	state->nl80211 = genl_ctrl_search_by_name(state->nl_cache, "nl80211");
  	if (!state->nl80211) {
  		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  		    "%s: nl80211 not found", device);
  		goto out_cache_free;
  	}
  
  	return 0;
  
  out_cache_free:
  	nl_cache_free(state->nl_cache);
  out_handle_destroy:
  	nl_socket_free(state->nl_sock);
  	return PCAP_ERROR;
  }
  
  static void
  nl80211_cleanup(struct nl80211_state *state)
  {
  	genl_family_put(state->nl80211);
  	nl_cache_free(state->nl_cache);
  	nl_socket_free(state->nl_sock);
  }
  
  static int
  add_mon_if(pcap_t *handle, int sock_fd, struct nl80211_state *state,
      const char *device, const char *mondevice)
  {
  	int ifindex;
  	struct nl_msg *msg;
  	int err;
  
  	ifindex = iface_get_id(sock_fd, device, handle->errbuf);
  	if (ifindex == -1)
  		return PCAP_ERROR;
  
  	msg = nlmsg_alloc();
  	if (!msg) {
  		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  		    "%s: failed to allocate netlink msg", device);
  		return PCAP_ERROR;
  	}
  
  	genlmsg_put(msg, 0, 0, genl_family_get_id(state->nl80211), 0,
  		    0, NL80211_CMD_NEW_INTERFACE, 0);
  	NLA_PUT_U32(msg, NL80211_ATTR_IFINDEX, ifindex);
  	NLA_PUT_STRING(msg, NL80211_ATTR_IFNAME, mondevice);
  	NLA_PUT_U32(msg, NL80211_ATTR_IFTYPE, NL80211_IFTYPE_MONITOR);
  
  	err = nl_send_auto_complete(state->nl_sock, msg);
  	if (err < 0) {
  #if defined HAVE_LIBNL_NLE
  		if (err == -NLE_FAILURE) {
  #else
  		if (err == -ENFILE) {
  #endif
  			/*
  			 * Device not available; our caller should just
  			 * keep trying.  (libnl 2.x maps ENFILE to
  			 * NLE_FAILURE; it can also map other errors
  			 * to that, but there's not much we can do
  			 * about that.)
  			 */
  			nlmsg_free(msg);
  			return 0;
  		} else {
  			/*
  			 * Real failure, not just "that device is not
  			 * available.
  			 */
  			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  			    "%s: nl_send_auto_complete failed adding %s interface: %s",
  			    device, mondevice, get_nl_errmsg(-err));
  			nlmsg_free(msg);
  			return PCAP_ERROR;
  		}
  	}
  	err = nl_wait_for_ack(state->nl_sock);
  	if (err < 0) {
  #if defined HAVE_LIBNL_NLE
  		if (err == -NLE_FAILURE) {
  #else
  		if (err == -ENFILE) {
  #endif
  			/*
  			 * Device not available; our caller should just
  			 * keep trying.  (libnl 2.x maps ENFILE to
  			 * NLE_FAILURE; it can also map other errors
  			 * to that, but there's not much we can do
  			 * about that.)
  			 */
  			nlmsg_free(msg);
  			return 0;
  		} else {
  			/*
  			 * Real failure, not just "that device is not
  			 * available.
  			 */
  			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  			    "%s: nl_wait_for_ack failed adding %s interface: %s",
  			    device, mondevice, get_nl_errmsg(-err));
  			nlmsg_free(msg);
  			return PCAP_ERROR;
  		}
  	}
  
  	/*
  	 * Success.
  	 */
  	nlmsg_free(msg);
  	return 1;
  
  nla_put_failure:
  	snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  	    "%s: nl_put failed adding %s interface",
  	    device, mondevice);
  	nlmsg_free(msg);
  	return PCAP_ERROR;
  }
  
  static int
  del_mon_if(pcap_t *handle, int sock_fd, struct nl80211_state *state,
      const char *device, const char *mondevice)
  {
  	int ifindex;
  	struct nl_msg *msg;
  	int err;
  
  	ifindex = iface_get_id(sock_fd, mondevice, handle->errbuf);
  	if (ifindex == -1)
  		return PCAP_ERROR;
  
  	msg = nlmsg_alloc();
  	if (!msg) {
  		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  		    "%s: failed to allocate netlink msg", device);
  		return PCAP_ERROR;
  	}
  
  	genlmsg_put(msg, 0, 0, genl_family_get_id(state->nl80211), 0,
  		    0, NL80211_CMD_DEL_INTERFACE, 0);
  	NLA_PUT_U32(msg, NL80211_ATTR_IFINDEX, ifindex);
  
  	err = nl_send_auto_complete(state->nl_sock, msg);
  	if (err < 0) {
  		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  		    "%s: nl_send_auto_complete failed deleting %s interface: %s",
  		    device, mondevice, get_nl_errmsg(-err));
  		nlmsg_free(msg);
  		return PCAP_ERROR;
  	}
  	err = nl_wait_for_ack(state->nl_sock);
  	if (err < 0) {
  		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  		    "%s: nl_wait_for_ack failed adding %s interface: %s",
  		    device, mondevice, get_nl_errmsg(-err));
  		nlmsg_free(msg);
  		return PCAP_ERROR;
  	}
  
  	/*
  	 * Success.
  	 */
  	nlmsg_free(msg);
  	return 1;
  
  nla_put_failure:
  	snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  	    "%s: nl_put failed deleting %s interface",
  	    device, mondevice);
  	nlmsg_free(msg);
  	return PCAP_ERROR;
  }
  
  static int
  enter_rfmon_mode_mac80211(pcap_t *handle, int sock_fd, const char *device)
  {
  	struct pcap_linux *handlep = handle->priv;
  	int ret;
  	char phydev_path[PATH_MAX+1];
  	struct nl80211_state nlstate;
  	struct ifreq ifr;
  	u_int n;
  
  	/*
  	 * Is this a mac80211 device?
  	 */
  	ret = get_mac80211_phydev(handle, device, phydev_path, PATH_MAX);
  	if (ret < 0)
  		return ret;	/* error */
  	if (ret == 0)
  		return 0;	/* no error, but not mac80211 device */
  
  	/*
  	 * XXX - is this already a monN device?
  	 * If so, we're done.
  	 * Is that determined by old Wireless Extensions ioctls?
  	 */
  
  	/*
  	 * OK, it's apparently a mac80211 device.
  	 * Try to find an unused monN device for it.
  	 */
  	ret = nl80211_init(handle, &nlstate, device);
  	if (ret != 0)
  		return ret;
  	for (n = 0; n < UINT_MAX; n++) {
  		/*
  		 * Try mon{n}.
  		 */
  		char mondevice[3+10+1];	/* mon{UINT_MAX}\0 */
  
  		snprintf(mondevice, sizeof mondevice, "mon%u", n);
  		ret = add_mon_if(handle, sock_fd, &nlstate, device, mondevice);
  		if (ret == 1) {
  			handlep->mondevice = strdup(mondevice);
  			goto added;
  		}
  		if (ret < 0) {
  			/*
  			 * Hard failure.  Just return ret; handle->errbuf
  			 * has already been set.
  			 */
  			nl80211_cleanup(&nlstate);
  			return ret;
  		}
  	}
  
  	snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  	    "%s: No free monN interfaces", device);
  	nl80211_cleanup(&nlstate);
  	return PCAP_ERROR;
  
  added:
  
  #if 0
  	/*
  	 * Sleep for .1 seconds.
  	 */
  	delay.tv_sec = 0;
  	delay.tv_nsec = 500000000;
  	nanosleep(&delay, NULL);
  #endif
  
  	/*
  	 * If we haven't already done so, arrange to have
  	 * "pcap_close_all()" called when we exit.
  	 */
  	if (!pcap_do_addexit(handle)) {
  		/*
  		 * "atexit()" failed; don't put the interface
  		 * in rfmon mode, just give up.
  		 */
  		return PCAP_ERROR_RFMON_NOTSUP;
  	}
  
  	/*
  	 * Now configure the monitor interface up.
  	 */
  	memset(&ifr, 0, sizeof(ifr));
  	strlcpy(ifr.ifr_name, handlep->mondevice, sizeof(ifr.ifr_name));
  	if (ioctl(sock_fd, SIOCGIFFLAGS, &ifr) == -1) {
  		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  		    "%s: Can't get flags for %s: %s", device,
  		    handlep->mondevice, strerror(errno));
  		del_mon_if(handle, sock_fd, &nlstate, device,
  		    handlep->mondevice);
  		nl80211_cleanup(&nlstate);
  		return PCAP_ERROR;
  	}
  	ifr.ifr_flags |= IFF_UP|IFF_RUNNING;
  	if (ioctl(sock_fd, SIOCSIFFLAGS, &ifr) == -1) {
  		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  		    "%s: Can't set flags for %s: %s", device,
  		    handlep->mondevice, strerror(errno));
  		del_mon_if(handle, sock_fd, &nlstate, device,
  		    handlep->mondevice);
  		nl80211_cleanup(&nlstate);
  		return PCAP_ERROR;
  	}
  
  	/*
  	 * Success.  Clean up the libnl state.
  	 */
  	nl80211_cleanup(&nlstate);
  
  	/*
  	 * Note that we have to delete the monitor device when we close
  	 * the handle.
  	 */
  	handlep->must_do_on_close |= MUST_DELETE_MONIF;
  
  	/*
  	 * Add this to the list of pcaps to close when we exit.
  	 */
  	pcap_add_to_pcaps_to_close(handle);
  
  	return 1;
  }
  #endif /* HAVE_LIBNL */
  
  #ifdef IW_MODE_MONITOR
  /*
   * Bonding devices mishandle unknown ioctls; they fail with ENODEV
   * rather than ENOTSUP, EOPNOTSUPP, or ENOTTY, so Wireless Extensions
   * will fail with ENODEV if we try to do them on a bonding device,
   * making us return a "no such device" indication rather than just
   * saying "no Wireless Extensions".
   *
   * So we check for bonding devices, if we can, before trying those
   * ioctls, by trying a bonding device information query ioctl to see
   * whether it succeeds.
   */
  static int
  is_bonding_device(int fd, const char *device)
  {
  #if defined(BOND_INFO_QUERY_OLD) || defined(SIOCBONDINFOQUERY)
  	struct ifreq ifr;
  	ifbond ifb;
  
  	memset(&ifr, 0, sizeof ifr);
  	strlcpy(ifr.ifr_name, device, sizeof ifr.ifr_name);
  	memset(&ifb, 0, sizeof ifb);
  	ifr.ifr_data = (caddr_t)&ifb;
  #ifdef SIOCBONDINFOQUERY
  	if (ioctl(fd, SIOCBONDINFOQUERY, &ifr) == 0)
  #else /* SIOCBONDINFOQUERY */
  	if (ioctl(fd, BOND_INFO_QUERY_OLD, &ifr) == 0)
  #endif /* SIOCBONDINFOQUERY */
  		return 1;	/* success, so it's a bonding device */
  #endif /* defined(BOND_INFO_QUERY_OLD) || defined(SIOCBONDINFOQUERY) */
  
  	return 0;	/* no, it's not a bonding device */
  }
  #endif /* IW_MODE_MONITOR */
  
  static int
  pcap_can_set_rfmon_linux(pcap_t *handle)
  {
  #ifdef HAVE_LIBNL
  	char phydev_path[PATH_MAX+1];
  	int ret;
  #endif
  #ifdef IW_MODE_MONITOR
  	int sock_fd;
  	struct iwreq ireq;
  #endif
  
  	if (strcmp(handle->opt.source, "any") == 0) {
  		/*
  		 * Monitor mode makes no sense on the "any" device.
  		 */
  		return 0;
  	}
  
  #ifdef HAVE_LIBNL
  	/*
  	 * Bleah.  There doesn't seem to be a way to ask a mac80211
  	 * device, through libnl, whether it supports monitor mode;
  	 * we'll just check whether the device appears to be a
  	 * mac80211 device and, if so, assume the device supports
  	 * monitor mode.
  	 *
  	 * wmaster devices don't appear to support the Wireless
  	 * Extensions, but we can create a mon device for a
  	 * wmaster device, so we don't bother checking whether
  	 * a mac80211 device supports the Wireless Extensions.
  	 */
  	ret = get_mac80211_phydev(handle, handle->opt.source, phydev_path,
  	    PATH_MAX);
  	if (ret < 0)
  		return ret;	/* error */
  	if (ret == 1)
  		return 1;	/* mac80211 device */
  #endif
  
  #ifdef IW_MODE_MONITOR
  	/*
  	 * Bleah.  There doesn't appear to be an ioctl to use to ask
  	 * whether a device supports monitor mode; we'll just do
  	 * SIOCGIWMODE and, if it succeeds, assume the device supports
  	 * monitor mode.
  	 *
  	 * Open a socket on which to attempt to get the mode.
  	 * (We assume that if we have Wireless Extensions support
  	 * we also have PF_PACKET support.)
  	 */
  	sock_fd = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL));
  	if (sock_fd == -1) {
  		(void)snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  		    "socket: %s", pcap_strerror(errno));
  		return PCAP_ERROR;
  	}
  
  	if (is_bonding_device(sock_fd, handle->opt.source)) {
  		/* It's a bonding device, so don't even try. */
  		close(sock_fd);
  		return 0;
  	}
  
  	/*
  	 * Attempt to get the current mode.
  	 */
  	strlcpy(ireq.ifr_ifrn.ifrn_name, handle->opt.source,
  	    sizeof ireq.ifr_ifrn.ifrn_name);
  	if (ioctl(sock_fd, SIOCGIWMODE, &ireq) != -1) {
  		/*
  		 * Well, we got the mode; assume we can set it.
  		 */
  		close(sock_fd);
  		return 1;
  	}
  	if (errno == ENODEV) {
  		/* The device doesn't even exist. */
  		(void)snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  		    "SIOCGIWMODE failed: %s", pcap_strerror(errno));
  		close(sock_fd);
  		return PCAP_ERROR_NO_SUCH_DEVICE;
  	}
  	close(sock_fd);
  #endif
  	return 0;
  }
  
  /*
   * Grabs the number of dropped packets by the interface from /proc/net/dev.
   *
   * XXX - what about /sys/class/net/{interface name}/rx_*?  There are
   * individual devices giving, in ASCII, various rx_ and tx_ statistics.
   *
   * Or can we get them in binary form from netlink?
   */
  static long int
  linux_if_drops(const char * if_name)
  {
  	char buffer[512];
  	char * bufptr;
  	FILE * file;
  	int field_to_convert = 3, if_name_sz = strlen(if_name);
  	long int dropped_pkts = 0;
  
  	file = fopen("/proc/net/dev", "r");
  	if (!file)
  		return 0;
  
  	while (!dropped_pkts && fgets( buffer, sizeof(buffer), file ))
  	{
  		/* 	search for 'bytes' -- if its in there, then
  			that means we need to grab the fourth field. otherwise
  			grab the third field. */
  		if (field_to_convert != 4 && strstr(buffer, "bytes"))
  		{
  			field_to_convert = 4;
  			continue;
  		}
  
  		/* find iface and make sure it actually matches -- space before the name and : after it */
  		if ((bufptr = strstr(buffer, if_name)) &&
  			(bufptr == buffer || *(bufptr-1) == ' ') &&
  			*(bufptr + if_name_sz) == ':')
  		{
  			bufptr = bufptr + if_name_sz + 1;
  
  			/* grab the nth field from it */
  			while( --field_to_convert && *bufptr != '\0')
  			{
  				while (*bufptr != '\0' && *(bufptr++) == ' ');
  				while (*bufptr != '\0' && *(bufptr++) != ' ');
  			}
  
  			/* get rid of any final spaces */
  			while (*bufptr != '\0' && *bufptr == ' ') bufptr++;
  
  			if (*bufptr != '\0')
  				dropped_pkts = strtol(bufptr, NULL, 10);
  
  			break;
  		}
  	}
  
  	fclose(file);
  	return dropped_pkts;
  }
  
  
  /*
   * With older kernels promiscuous mode is kind of interesting because we
   * have to reset the interface before exiting. The problem can't really
   * be solved without some daemon taking care of managing usage counts.
   * If we put the interface into promiscuous mode, we set a flag indicating
   * that we must take it out of that mode when the interface is closed,
   * and, when closing the interface, if that flag is set we take it out
   * of promiscuous mode.
   *
   * Even with newer kernels, we have the same issue with rfmon mode.
   */
  
  static void	pcap_cleanup_linux( pcap_t *handle )
  {
  	struct pcap_linux *handlep = handle->priv;
  	struct ifreq	ifr;
  #ifdef HAVE_LIBNL
  	struct nl80211_state nlstate;
  	int ret;
  #endif /* HAVE_LIBNL */
  #ifdef IW_MODE_MONITOR
  	int oldflags;
  	struct iwreq ireq;
  #endif /* IW_MODE_MONITOR */
  
  #ifdef HAVE_PF_RING
  	if(handle->ring != NULL) {
  		pfring_close(handle->ring);
  		handle->ring = NULL;
  		return;
  	}
  #endif
  
  	if (handlep->must_do_on_close != 0) {
  		/*
  		 * There's something we have to do when closing this
  		 * pcap_t.
  		 */
  		if (handlep->must_do_on_close & MUST_CLEAR_PROMISC) {
  			/*
  			 * We put the interface into promiscuous mode;
  			 * take it out of promiscuous mode.
  			 *
  			 * XXX - if somebody else wants it in promiscuous
  			 * mode, this code cannot know that, so it'll take
  			 * it out of promiscuous mode.  That's not fixable
  			 * in 2.0[.x] kernels.
  			 */
  			memset(&ifr, 0, sizeof(ifr));
  			strlcpy(ifr.ifr_name, handlep->device,
  			    sizeof(ifr.ifr_name));
  			if (ioctl(handle->fd, SIOCGIFFLAGS, &ifr) == -1) {
  				fprintf(stderr,
  				    "Can't restore interface %s flags (SIOCGIFFLAGS failed: %s).\n"
  				    "Please adjust manually.\n"
  				    "Hint: This can't happen with Linux >= 2.2.0.\n",
  				    handlep->device, strerror(errno));
  			} else {
  				if (ifr.ifr_flags & IFF_PROMISC) {
  					/*
  					 * Promiscuous mode is currently on;
  					 * turn it off.
  					 */
  					ifr.ifr_flags &= ~IFF_PROMISC;
  					if (ioctl(handle->fd, SIOCSIFFLAGS,
  					    &ifr) == -1) {
  						fprintf(stderr,
  						    "Can't restore interface %s flags (SIOCSIFFLAGS failed: %s).\n"
  						    "Please adjust manually.\n"
  						    "Hint: This can't happen with Linux >= 2.2.0.\n",
  						    handlep->device,
  						    strerror(errno));
  					}
  				}
  			}
  		}
  
  #ifdef HAVE_LIBNL
  		if (handlep->must_do_on_close & MUST_DELETE_MONIF) {
  			ret = nl80211_init(handle, &nlstate, handlep->device);
  			if (ret >= 0) {
  				ret = del_mon_if(handle, handle->fd, &nlstate,
  				    handlep->device, handlep->mondevice);
  				nl80211_cleanup(&nlstate);
  			}
  			if (ret < 0) {
  				fprintf(stderr,
  				    "Can't delete monitor interface %s (%s).\n"
  				    "Please delete manually.\n",
  				    handlep->mondevice, handle->errbuf);
  			}
  		}
  #endif /* HAVE_LIBNL */
  
  #ifdef IW_MODE_MONITOR
  		if (handlep->must_do_on_close & MUST_CLEAR_RFMON) {
  			/*
  			 * We put the interface into rfmon mode;
  			 * take it out of rfmon mode.
  			 *
  			 * XXX - if somebody else wants it in rfmon
  			 * mode, this code cannot know that, so it'll take
  			 * it out of rfmon mode.
  			 */
  
  			/*
  			 * First, take the interface down if it's up;
  			 * otherwise, we might get EBUSY.
  			 * If we get errors, just drive on and print
  			 * a warning if we can't restore the mode.
  			 */
  			oldflags = 0;
  			memset(&ifr, 0, sizeof(ifr));
  			strlcpy(ifr.ifr_name, handlep->device,
  			    sizeof(ifr.ifr_name));
  			if (ioctl(handle->fd, SIOCGIFFLAGS, &ifr) != -1) {
  				if (ifr.ifr_flags & IFF_UP) {
  					oldflags = ifr.ifr_flags;
  					ifr.ifr_flags &= ~IFF_UP;
  					if (ioctl(handle->fd, SIOCSIFFLAGS, &ifr) == -1)
  						oldflags = 0;	/* didn't set, don't restore */
  				}
  			}
  
  			/*
  			 * Now restore the mode.
  			 */
  			strlcpy(ireq.ifr_ifrn.ifrn_name, handlep->device,
  			    sizeof ireq.ifr_ifrn.ifrn_name);
  			ireq.u.mode = handlep->oldmode;
  			if (ioctl(handle->fd, SIOCSIWMODE, &ireq) == -1) {
  				/*
  				 * Scientist, you've failed.
  				 */
  				fprintf(stderr,
  				    "Can't restore interface %s wireless mode (SIOCSIWMODE failed: %s).\n"
  				    "Please adjust manually.\n",
  				    handlep->device, strerror(errno));
  			}
  
  			/*
  			 * Now bring the interface back up if we brought
  			 * it down.
  			 */
  			if (oldflags != 0) {
  				ifr.ifr_flags = oldflags;
  				if (ioctl(handle->fd, SIOCSIFFLAGS, &ifr) == -1) {
  					fprintf(stderr,
  					    "Can't bring interface %s back up (SIOCSIFFLAGS failed: %s).\n"
  					    "Please adjust manually.\n",
  					    handlep->device, strerror(errno));
  				}
  			}
  		}
  #endif /* IW_MODE_MONITOR */
  
  		/*
  		 * Take this pcap out of the list of pcaps for which we
  		 * have to take the interface out of some mode.
  		 */
  		pcap_remove_from_pcaps_to_close(handle);
  	}
  
  	if (handlep->mondevice != NULL) {
  		free(handlep->mondevice);
  		handlep->mondevice = NULL;
  	}
  	if (handlep->device != NULL) {
  		free(handlep->device);
  		handlep->device = NULL;
  	}
  	pcap_cleanup_live_common(handle);
  }
  
  /*
   *  Get a handle for a live capture from the given device. You can
   *  pass NULL as device to get all packages (without link level
   *  information of course). If you pass 1 as promisc the interface
   *  will be set to promiscous mode (XXX: I think this usage should
   *  be deprecated and functions be added to select that later allow
   *  modification of that values -- Torsten).
   */
  static int
  pcap_activate_linux(pcap_t *handle)
  {
  	struct pcap_linux *handlep = handle->priv;
  	const char	*device;
  	struct ifreq	ifr;
  	int		status = 0;
  	int		ret;
  
  	device = handle->opt.source;
  
  	/*
  	 * Make sure the name we were handed will fit into the ioctls we
  	 * might perform on the device; if not, return a "No such device"
  	 * indication, as the Linux kernel shouldn't support creating
  	 * a device whose name won't fit into those ioctls.
  	 *
  	 * "Will fit" means "will fit, complete with a null terminator",
  	 * so if the length, which does *not* include the null terminator,
  	 * is greater than *or equal to* the size of the field into which
  	 * we'll be copying it, that won't fit.
  	 */
  	if (strlen(device) >= sizeof(ifr.ifr_name)) {
  		status = PCAP_ERROR_NO_SUCH_DEVICE;
  		goto fail;
  	}
  
  	handle->inject_op = pcap_inject_linux;
  	handle->setfilter_op = pcap_setfilter_linux;
  	handle->setdirection_op = pcap_setdirection_linux;
  	handle->set_datalink_op = pcap_set_datalink_linux;
  	handle->getnonblock_op = pcap_getnonblock_fd;
  	handle->setnonblock_op = pcap_setnonblock_fd;
  	handle->cleanup_op = pcap_cleanup_linux;
  	handle->read_op = pcap_read_linux;
  	handle->stats_op = pcap_stats_linux;
  
  	/*
  	 * The "any" device is a special device which causes us not
  	 * to bind to a particular device and thus to look at all
  	 * devices.
  	 */
  	if (strcmp(device, "any") == 0) {
  		if (handle->opt.promisc) {
  			handle->opt.promisc = 0;
  #ifndef HAVE_PF_RING
  			/* Just a warning. */
  			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  			    "Promiscuous mode not supported on the \"any\" device");
  			status = PCAP_WARNING_PROMISC_NOTSUP;
  #endif
  		}
  	}
  
  	handlep->device	= strdup(device);
  	if (handlep->device == NULL) {
  		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "strdup: %s",
  			 pcap_strerror(errno) );
  		return PCAP_ERROR;
  	}
  
  #ifdef HAVE_PF_RING
  	if (!getenv("PCAP_NO_PF_RING")) {
  		/* Code courtesy of Chris Wakelin <c.d.wakelin@reading.ac.uk> */
  		char *clusterId;
  		int flags = PF_RING_TIMESTAMP;
  		char *appname, *active = getenv("PCAP_PF_RING_ACTIVE_POLL"), *rss_rehash;
  
  		if (handle->opt.promisc) flags |= PF_RING_PROMISC;
  		if (getenv("PCAP_PF_RING_DNA_RSS" /* deprecated (backward compatibility) */ )) flags |= PF_RING_ZC_SYMMETRIC_RSS;
  		if (getenv("PCAP_PF_RING_ZC_RSS"))  flags |= PF_RING_ZC_SYMMETRIC_RSS;
  		if (getenv("PCAP_PF_RING_STRIP_HW_TIMESTAMP")) flags |= PF_RING_STRIP_HW_TIMESTAMP;
  		if (getenv("PCAP_PF_RING_HW_TIMESTAMP") || handle->opt.tstamp_precision == PCAP_TSTAMP_PRECISION_NANO) flags |= PF_RING_HW_TIMESTAMP;
  
  		if (active) pf_ring_active_poll = atoi(active);
  		handle->ring = pfring_open((char*)device, handle->snapshot, flags);
  
  		if (handle->ring != NULL) {
  
  			if (getenv("PCAP_PF_RING_RECV_ONLY")) pfring_set_socket_mode(handle->ring, recv_only_mode);
  
  			if (clusterId = getenv("PCAP_PF_RING_CLUSTER_ID")) {
  				if (atoi(clusterId) > 0 && atoi(clusterId) < 255) {
  					if (getenv("PCAP_PF_RING_USE_CLUSTER_PER_FLOW"))
  						pfring_set_cluster(handle->ring, atoi(clusterId), cluster_per_flow);
                  			else if (getenv("PCAP_PF_RING_USE_CLUSTER_PER_FLOW_2_TUPLE"))
                  				pfring_set_cluster(handle->ring, atoi(clusterId), cluster_per_flow_2_tuple);
                  			else if (getenv("PCAP_PF_RING_USE_CLUSTER_PER_FLOW_4_TUPLE"))
                  				pfring_set_cluster(handle->ring, atoi(clusterId), cluster_per_flow_4_tuple);
                  			else if (getenv("PCAP_PF_RING_USE_CLUSTER_PER_FLOW_TCP_5_TUPLE"))
                  				pfring_set_cluster(handle->ring, atoi(clusterId), cluster_per_flow_tcp_5_tuple);
                  			else if (getenv("PCAP_PF_RING_USE_CLUSTER_PER_FLOW_5_TUPLE"))
                  				pfring_set_cluster(handle->ring, atoi(clusterId), cluster_per_flow_5_tuple);
  					else
  						pfring_set_cluster(handle->ring, atoi(clusterId), cluster_round_robin);
                			}
  	    		}
  
  			if (appname = getenv("PCAP_PF_RING_APPNAME"))
  			if (strlen(appname) > 0 && strlen(appname) <= 32)
  				pfring_set_application_name(handle->ring, appname);
              
  			if (rss_rehash = getenv("PCAP_PF_RING_RSS_REHASH")) {
  				if (atoi(rss_rehash))
  					pfring_enable_rss_rehash(handle->ring);
  			}
  			pfring_set_poll_watermark(handle->ring, 1 /* watermark */);
  		}
  	} else
          	handle->ring = NULL;
  
  	if (handle->ring != NULL) {
  		handle->fd = handle->ring->fd;
  		handle->bufsize = handle->snapshot;
  		handle->linktype = DLT_EN10MB;
  		handle->offset = 2;
  		handle->setnonblock_op = pcap_setnonblock_mmap;
  		handle->getnonblock_op = pcap_getnonblock_mmap;
  
  		handlep->vlan_offset = -1; /* unknown */
  		handlep->timeout = handle->opt.timeout; /* copy timeout value */
  
  		/* printf("Open HAVE_PF_RING(%s)\n", device); */
  	} else {
  		/* printf("Open HAVE_PF_RING(%s) failed. Fallback to pcap\n", device); */
  #endif
  
  	/* copy timeout value */
  	handlep->timeout = handle->opt.timeout;
  
  	/*
  	 * If we're in promiscuous mode, then we probably want
  	 * to see when the interface drops packets too, so get an
  	 * initial count from /proc/net/dev
  	 */
  	if (handle->opt.promisc)
  		handlep->proc_dropped = linux_if_drops(handlep->device);
  
  	/*
  	 * Current Linux kernels use the protocol family PF_PACKET to
  	 * allow direct access to all packets on the network while
  	 * older kernels had a special socket type SOCK_PACKET to
  	 * implement this feature.
  	 * While this old implementation is kind of obsolete we need
  	 * to be compatible with older kernels for a while so we are
  	 * trying both methods with the newer method preferred.
  	 */
  	ret = activate_new(handle);
  	if (ret < 0) {
  		/*
  		 * Fatal error with the new way; just fail.
  		 * ret has the error return; if it's PCAP_ERROR,
  		 * handle->errbuf has been set appropriately.
  		 */
  		status = ret;
  		goto fail;
  	}
  	if (ret == 1) {
  		/*
  		 * Success.
  		 * Try to use memory-mapped access.
  		 */
  		switch (activate_mmap(handle, &status)) {
  
  		case 1:
  			/*
  			 * We succeeded.  status has been
  			 * set to the status to return,
  			 * which might be 0, or might be
  			 * a PCAP_WARNING_ value.
  			 */
  			return status;
  
  		case 0:
  			/*
  			 * Kernel doesn't support it - just continue
  			 * with non-memory-mapped access.
  			 */
  			break;
  
  		case -1:
  			/*
  			 * We failed to set up to use it, or the kernel
  			 * supports it, but we failed to enable it.
  			 * ret has been set to the error status to
  			 * return and, if it's PCAP_ERROR, handle->errbuf
  			 * contains the error message.
  			 */
  			status = ret;
  			goto fail;
  		}
  	}
  	else if (ret == 0) {
  		/* Non-fatal error; try old way */
  		if ((ret = activate_old(handle)) != 1) {
  			/*
  			 * Both methods to open the packet socket failed.
  			 * Tidy up and report our failure (handle->errbuf
  			 * is expected to be set by the functions above).
  			 */
  			status = ret;
  			goto fail;
  		}
  	}
  
  	/*
  	 * We set up the socket, but not with memory-mapped access.
  	 */
  	if (handle->opt.buffer_size != 0) {
  		/*
  		 * Set the socket buffer size to the specified value.
  		 */
  		if (setsockopt(handle->fd, SOL_SOCKET, SO_RCVBUF,
  		    &handle->opt.buffer_size,
  		    sizeof(handle->opt.buffer_size)) == -1) {
  			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  				 "SO_RCVBUF: %s", pcap_strerror(errno));
  			status = PCAP_ERROR;
  			goto fail;
  		}
  	}
  
  #ifdef HAVE_PF_RING
          }
  #endif
  	/* Allocate the buffer */
  
  	handle->buffer	 = malloc(handle->bufsize + handle->offset);
  	if (!handle->buffer) {
  		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  			 "malloc: %s", pcap_strerror(errno));
  		status = PCAP_ERROR;
  		goto fail;
  	}
  
  	/*
  	 * "handle->fd" is a socket, so "select()" and "poll()"
  	 * should work on it.
  	 */
  #ifdef HAVE_PF_RING
  	if (handle->ring != NULL) {
          	pfring_enable_ring(handle->ring);
  		handle->selectable_fd = pfring_get_selectable_fd(handle->ring);
  	} else
  #endif
  	handle->selectable_fd = handle->fd;
  
  	return status;
  
  fail:
  	pcap_cleanup_linux(handle);
  	return status;
  }
  
  #ifdef HAVE_PF_RING
  void pcap_set_appl_name_linux(pcap_t *handle, char *appl_name)
  {
  	if (handle->ring)
  		pfring_set_application_name(handle->ring, appl_name);
  }
  
  void pcap_set_cluster(pcap_t *handle, u_int cluster_id)
  {
  	if (handle->ring)
  		pfring_set_cluster(handle->ring, cluster_id, cluster_per_flow);
  }
  #endif
  
  /*
   *  Read at most max_packets from the capture stream and call the callback
   *  for each of them. Returns the number of packets handled or -1 if an
   *  error occured.
   */
  static int
  pcap_read_linux(pcap_t *handle, int max_packets, pcap_handler callback, u_char *user)
  {
  	/*
  	 * Currently, on Linux only one packet is delivered per read,
  	 * so we don't loop.
  	 */
  	return pcap_read_packet(handle, callback, user);
  }
  
  static int
  pcap_set_datalink_linux(pcap_t *handle, int dlt)
  {
  	handle->linktype = dlt;
  	return 0;
  }
  
  /*
   * linux_check_direction()
   *
   * Do checks based on packet direction.
   */
  static inline int
  linux_check_direction(const pcap_t *handle, const struct sockaddr_ll *sll)
  {
  	struct pcap_linux	*handlep = handle->priv;
  
  	if (sll->sll_pkttype == PACKET_OUTGOING) {
  		/*
  		 * Outgoing packet.
  		 * If this is from the loopback device, reject it;
  		 * we'll see the packet as an incoming packet as well,
  		 * and we don't want to see it twice.
  		 */
  		if (sll->sll_ifindex == handlep->lo_ifindex)
  			return 0;
  
  		/*
  		 * If the user only wants incoming packets, reject it.
  		 */
  		if (handle->direction == PCAP_D_IN)
  			return 0;
  	} else {
  		/*
  		 * Incoming packet.
  		 * If the user only wants outgoing packets, reject it.
  		 */
  		if (handle->direction == PCAP_D_OUT)
  			return 0;
  	}
  	return 1;
  }
  
  /*
   *  Read a packet from the socket calling the handler provided by
   *  the user. Returns the number of packets received or -1 if an
   *  error occured.
   */
  static int
  pcap_read_packet(pcap_t *handle, pcap_handler callback, u_char *userdata)
  {
  	struct pcap_linux	*handlep = handle->priv;
  	u_char			*bp;
  	int			offset;
  #ifdef HAVE_PF_PACKET_SOCKETS
  	struct sockaddr_ll	from;
  	struct sll_header	*hdrp;
  #else
  	struct sockaddr		from;
  #endif
  #if defined(HAVE_PACKET_AUXDATA) && defined(HAVE_LINUX_TPACKET_AUXDATA_TP_VLAN_TCI)
  	struct iovec		iov;
  	struct msghdr		msg;
  	struct cmsghdr		*cmsg;
  	union {
  		struct cmsghdr	cmsg;
  		char		buf[CMSG_SPACE(sizeof(struct tpacket_auxdata))];
  	} cmsg_buf;
  #else /* defined(HAVE_PACKET_AUXDATA) && defined(HAVE_LINUX_TPACKET_AUXDATA_TP_VLAN_TCI) */
  	socklen_t		fromlen;
  #endif /* defined(HAVE_PACKET_AUXDATA) && defined(HAVE_LINUX_TPACKET_AUXDATA_TP_VLAN_TCI) */
  	int			packet_len, caplen;
  #ifdef HAVE_PF_RING
          struct pfring_pkthdr    pcap_header;
  #else
  	struct pcap_pkthdr	pcap_header;
  #endif
          struct bpf_aux_data     aux_data;
  
  #ifdef HAVE_PF_RING
  	if (handle->ring) {
  		char *packet;
  		int wait_for_incoming_packet = (pf_ring_active_poll || (handlep->timeout < 0)) ? 0 : 1;
  		int ret = 0;
  
  		do {
  			if (handle->break_loop) {
  				/*
  				 * Yes - clear the flag that indicates that it
  				 * has, and return -2 as an indication that we
  				 * were told to break out of the loop.
  				 *
  				 * Patch courtesy of Michael Stiller <ms@2scale.net>
  				 */
  				handle->break_loop = 0;
  				return -2;
  			}
  
  			pcap_header.ts.tv_sec = 0;
  			errno = 0;
  
  			ret = pfring_recv(handle->ring, (u_char**)&packet, 0, &pcap_header, wait_for_incoming_packet);
  
  			if (ret == 0) {
  				if (wait_for_incoming_packet) 
  					continue;
  				return 0; /* non-blocking */
  			} else if (ret > 0) {
  				bp = packet;
  				pcap_header.caplen = min(pcap_header.caplen, handle->bufsize);
  				caplen = pcap_header.caplen, packet_len = pcap_header.len;
  				if (handle->opt.tstamp_precision == PCAP_TSTAMP_PRECISION_NANO) {
  					if (pcap_header.extended_hdr.timestamp_ns) {
  						pcap_header.ts.tv_sec  = pcap_header.extended_hdr.timestamp_ns / 1000000000;
  						pcap_header.ts.tv_usec = pcap_header.extended_hdr.timestamp_ns % 1000000000;
  					} else if (pcap_header.ts.tv_sec == 0)
  						clock_gettime(CLOCK_REALTIME, (struct timespec *) &pcap_header.ts);
  					else
  						pcap_header.ts.tv_usec = pcap_header.ts.tv_usec * 1000;
  				} else if (pcap_header.ts.tv_sec == 0)
  						gettimeofday((struct timeval *) &pcap_header.ts, NULL);
  
  				break;
  			} else {
  				if (wait_for_incoming_packet && (errno == EINTR || errno == ENETDOWN))
  					continue;
  				return -1;
  			}
  		} while (1);
  
  		goto pfring_pcap_read_packet;
  	}
  #endif
  
  #ifdef HAVE_PF_PACKET_SOCKETS
  	/*
  	 * If this is a cooked device, leave extra room for a
  	 * fake packet header.
  	 */
  	if (handlep->cooked)
  		offset = SLL_HDR_LEN;
  	else
  		offset = 0;
  #else
  	/*
  	 * This system doesn't have PF_PACKET sockets, so it doesn't
  	 * support cooked devices.
  	 */
  	offset = 0;
  #endif
  
  	/*
  	 * Receive a single packet from the kernel.
  	 * We ignore EINTR, as that might just be due to a signal
  	 * being delivered - if the signal should interrupt the
  	 * loop, the signal handler should call pcap_breakloop()
  	 * to set handle->break_loop (we ignore it on other
  	 * platforms as well).
  	 * We also ignore ENETDOWN, so that we can continue to
  	 * capture traffic if the interface goes down and comes
  	 * back up again; comments in the kernel indicate that
  	 * we'll just block waiting for packets if we try to
  	 * receive from a socket that delivered ENETDOWN, and,
  	 * if we're using a memory-mapped buffer, we won't even
  	 * get notified of "network down" events.
  	 */
  	bp = handle->buffer + handle->offset;
  
  #if defined(HAVE_PACKET_AUXDATA) && defined(HAVE_LINUX_TPACKET_AUXDATA_TP_VLAN_TCI)
  	msg.msg_name		= &from;
  	msg.msg_namelen		= sizeof(from);
  	msg.msg_iov		= &iov;
  	msg.msg_iovlen		= 1;
  	msg.msg_control		= &cmsg_buf;
  	msg.msg_controllen	= sizeof(cmsg_buf);
  	msg.msg_flags		= 0;
  
  	iov.iov_len		= handle->bufsize - offset;
  	iov.iov_base		= bp + offset;
  #endif /* defined(HAVE_PACKET_AUXDATA) && defined(HAVE_LINUX_TPACKET_AUXDATA_TP_VLAN_TCI) */
  
  	do {
  		/*
  		 * Has "pcap_breakloop()" been called?
  		 */
  		if (handle->break_loop) {
  			/*
  			 * Yes - clear the flag that indicates that it has,
  			 * and return PCAP_ERROR_BREAK as an indication that
  			 * we were told to break out of the loop.
  			 */
  			handle->break_loop = 0;
  			return PCAP_ERROR_BREAK;
  		}
  
  #if defined(HAVE_PACKET_AUXDATA) && defined(HAVE_LINUX_TPACKET_AUXDATA_TP_VLAN_TCI)
  		packet_len = recvmsg(handle->fd, &msg, MSG_TRUNC);
  #else /* defined(HAVE_PACKET_AUXDATA) && defined(HAVE_LINUX_TPACKET_AUXDATA_TP_VLAN_TCI) */
  		fromlen = sizeof(from);
  		packet_len = recvfrom(
  			handle->fd, bp + offset,
  			handle->bufsize - offset, MSG_TRUNC,
  			(struct sockaddr *) &from, &fromlen);
  #endif /* defined(HAVE_PACKET_AUXDATA) && defined(HAVE_LINUX_TPACKET_AUXDATA_TP_VLAN_TCI) */
  	} while (packet_len == -1 && errno == EINTR);
  
  	/* Check if an error occured */
  
  	if (packet_len == -1) {
  		switch (errno) {
  
  		case EAGAIN:
  			return 0;	/* no packet there */
  
  		case ENETDOWN:
  			/*
  			 * The device on which we're capturing went away.
  			 *
  			 * XXX - we should really return
  			 * PCAP_ERROR_IFACE_NOT_UP, but pcap_dispatch()
  			 * etc. aren't defined to return that.
  			 */
  			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  				"The interface went down");
  			return PCAP_ERROR;
  
  		default:
  			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  				 "recvfrom: %s", pcap_strerror(errno));
  			return PCAP_ERROR;
  		}
  	}
  
  #ifdef HAVE_PF_PACKET_SOCKETS
  	if (!handlep->sock_packet) {
  		/*
  		 * Unfortunately, there is a window between socket() and
  		 * bind() where the kernel may queue packets from any
  		 * interface.  If we're bound to a particular interface,
  		 * discard packets not from that interface.
  		 *
  		 * (If socket filters are supported, we could do the
  		 * same thing we do when changing the filter; however,
  		 * that won't handle packet sockets without socket
  		 * filter support, and it's a bit more complicated.
  		 * It would save some instructions per packet, however.)
  		 */
  		if (handlep->ifindex != -1 &&
  		    from.sll_ifindex != handlep->ifindex)
  			return 0;
  
  		/*
  		 * Do checks based on packet direction.
  		 * We can only do this if we're using PF_PACKET; the
  		 * address returned for SOCK_PACKET is a "sockaddr_pkt"
  		 * which lacks the relevant packet type information.
  		 */
  		if (!linux_check_direction(handle, &from))
  			return 0;
  	}
  #endif
  
  #ifdef HAVE_PF_PACKET_SOCKETS
  	/*
  	 * If this is a cooked device, fill in the fake packet header.
  	 */
  	if (handlep->cooked) {
  		/*
  		 * Add the length of the fake header to the length
  		 * of packet data we read.
  		 */
  		packet_len += SLL_HDR_LEN;
  
  		hdrp = (struct sll_header *)bp;
  		hdrp->sll_pkttype = map_packet_type_to_sll_type(from.sll_pkttype);
  		hdrp->sll_hatype = htons(from.sll_hatype);
  		hdrp->sll_halen = htons(from.sll_halen);
  		memcpy(hdrp->sll_addr, from.sll_addr,
  		    (from.sll_halen > SLL_ADDRLEN) ?
  		      SLL_ADDRLEN :
  		      from.sll_halen);
  		hdrp->sll_protocol = from.sll_protocol;
  	}
  
  #ifdef HAVE_PF_RING
  pfring_pcap_read_packet:
  #endif
  
  #if defined(HAVE_PACKET_AUXDATA) && defined(HAVE_LINUX_TPACKET_AUXDATA_TP_VLAN_TCI)
  	if (handlep->vlan_offset != -1) {
  		for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
  			struct tpacket_auxdata *aux;
  			unsigned int len;
  			struct vlan_tag *tag;
  
  			if (cmsg->cmsg_len < CMSG_LEN(sizeof(struct tpacket_auxdata)) ||
  			    cmsg->cmsg_level != SOL_PACKET ||
  			    cmsg->cmsg_type != PACKET_AUXDATA)
  				continue;
  
  			aux = (struct tpacket_auxdata *)CMSG_DATA(cmsg);
  #if defined(TP_STATUS_VLAN_VALID)
  			if ((aux->tp_vlan_tci == 0) && !(aux->tp_status & TP_STATUS_VLAN_VALID))
  #else
  			if (aux->tp_vlan_tci == 0) /* this is ambigious but without the
  						TP_STATUS_VLAN_VALID flag, there is
  						nothing that we can do */
  #endif
  				continue;
  
  			len = packet_len > iov.iov_len ? iov.iov_len : packet_len;
  			if (len < (unsigned int) handlep->vlan_offset)
  				break;
  
  			bp -= VLAN_TAG_LEN;
  			memmove(bp, bp + VLAN_TAG_LEN, handlep->vlan_offset);
  
  			tag = (struct vlan_tag *)(bp + handlep->vlan_offset);
  			tag->vlan_tpid = htons(VLAN_TPID(aux, aux));
  			tag->vlan_tci = htons(aux->tp_vlan_tci);
  
                          /* store vlan tci to bpf_aux_data struct for userland bpf filter */
  #if defined(TP_STATUS_VLAN_VALID)
                          aux_data.vlan_tag = htons(aux->tp_vlan_tci) & 0x0fff;
                          aux_data.vlan_tag_present = (aux->tp_status & TP_STATUS_VLAN_VALID);
  #endif
  			packet_len += VLAN_TAG_LEN;
  		}
  	}
  #endif /* defined(HAVE_PACKET_AUXDATA) && defined(HAVE_LINUX_TPACKET_AUXDATA_TP_VLAN_TCI) */
  #endif /* HAVE_PF_PACKET_SOCKETS */
  
  	/*
  	 * XXX: According to the kernel source we should get the real
  	 * packet len if calling recvfrom with MSG_TRUNC set. It does
  	 * not seem to work here :(, but it is supported by this code
  	 * anyway.
  	 * To be honest the code RELIES on that feature so this is really
  	 * broken with 2.2.x kernels.
  	 * I spend a day to figure out what's going on and I found out
  	 * that the following is happening:
  	 *
  	 * The packet comes from a random interface and the packet_rcv
  	 * hook is called with a clone of the packet. That code inserts
  	 * the packet into the receive queue of the packet socket.
  	 * If a filter is attached to that socket that filter is run
  	 * first - and there lies the problem. The default filter always
  	 * cuts the packet at the snaplen:
  	 *
  	 * # tcpdump -d
  	 * (000) ret      #68
  	 *
  	 * So the packet filter cuts down the packet. The recvfrom call
  	 * says "hey, it's only 68 bytes, it fits into the buffer" with
  	 * the result that we don't get the real packet length. This
  	 * is valid at least until kernel 2.2.17pre6.
  	 *
  	 * We currently handle this by making a copy of the filter
  	 * program, fixing all "ret" instructions with non-zero
  	 * operands to have an operand of MAXIMUM_SNAPLEN so that the
  	 * filter doesn't truncate the packet, and supplying that modified
  	 * filter to the kernel.
  	 */
  
  	caplen = packet_len;
  	if (caplen > handle->snapshot)
  		caplen = handle->snapshot;
  
  	/* Run the packet filter if not using kernel filter */
  	if (handlep->filter_in_userland && handle->fcode.bf_insns) {
  		if (bpf_filter_with_aux_data(handle->fcode.bf_insns, bp,
  		    packet_len, caplen, &aux_data) == 0) {
  			/* rejected by filter */
  			return 0;
  		}
  	}
  
  	/* Fill in our own header data */
  
  #ifdef HAVE_PF_RING
          if (!handle->ring) {
  #endif
  
  	/* get timestamp for this packet */
  #if defined(SIOCGSTAMPNS) && defined(SO_TIMESTAMPNS)
  	if (handle->opt.tstamp_precision == PCAP_TSTAMP_PRECISION_NANO) {
  		if (ioctl(handle->fd, SIOCGSTAMPNS, &pcap_header.ts) == -1) {
  			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  					"SIOCGSTAMPNS: %s", pcap_strerror(errno));
  			return PCAP_ERROR;
  		}
          } else
  #endif
  	{
  		if (ioctl(handle->fd, SIOCGSTAMP, &pcap_header.ts) == -1) {
  			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  					"SIOCGSTAMP: %s", pcap_strerror(errno));
  			return PCAP_ERROR;
  		}
          }
  
  	pcap_header.caplen	= caplen;
  	pcap_header.len		= packet_len;
  
  #ifdef HAVE_PF_RING
          }
  #endif
  
  	/*
  	 * Count the packet.
  	 *
  	 * Arguably, we should count them before we check the filter,
  	 * as on many other platforms "ps_recv" counts packets
  	 * handed to the filter rather than packets that passed
  	 * the filter, but if filtering is done in the kernel, we
  	 * can't get a count of packets that passed the filter,
  	 * and that would mean the meaning of "ps_recv" wouldn't
  	 * be the same on all Linux systems.
  	 *
  	 * XXX - it's not the same on all systems in any case;
  	 * ideally, we should have a "get the statistics" call
  	 * that supplies more counts and indicates which of them
  	 * it supplies, so that we supply a count of packets
  	 * handed to the filter only on platforms where that
  	 * information is available.
  	 *
  	 * We count them here even if we can get the packet count
  	 * from the kernel, as we can only determine at run time
  	 * whether we'll be able to get it from the kernel (if
  	 * HAVE_TPACKET_STATS isn't defined, we can't get it from
  	 * the kernel, but if it is defined, the library might
  	 * have been built with a 2.4 or later kernel, but we
  	 * might be running on a 2.2[.x] kernel without Alexey
  	 * Kuznetzov's turbopacket patches, and thus the kernel
  	 * might not be able to supply those statistics).  We
  	 * could, I guess, try, when opening the socket, to get
  	 * the statistics, and if we can not increment the count
  	 * here, but it's not clear that always incrementing
  	 * the count is more expensive than always testing a flag
  	 * in memory.
  	 *
  	 * We keep the count in "handlep->packets_read", and use that
  	 * for "ps_recv" if we can't get the statistics from the kernel.
  	 * We do that because, if we *can* get the statistics from
  	 * the kernel, we use "handlep->stat.ps_recv" and
  	 * "handlep->stat.ps_drop" as running counts, as reading the
  	 * statistics from the kernel resets the kernel statistics,
  	 * and if we directly increment "handlep->stat.ps_recv" here,
  	 * that means it will count packets *twice* on systems where
  	 * we can get kernel statistics - once here, and once in
  	 * pcap_stats_linux().
  	 */
  	handlep->packets_read++;
  
  	/* Call the user supplied callback function */
  #ifdef HAVE_PF_RING
  	callback(userdata, (struct pcap_pkthdr*) &pcap_header, bp);
  #else
  	callback(userdata, &pcap_header, bp);
  #endif
  
  	return 1;
  }
  
  static int
  pcap_inject_linux(pcap_t *handle, const void *buf, size_t size)
  {
  	struct pcap_linux *handlep = handle->priv;
  	int ret;
  
  #ifdef HAVE_PF_PACKET_SOCKETS
  	if (!handlep->sock_packet) {
  		/* PF_PACKET socket */
  		if (handlep->ifindex == -1) {
  			/*
  			 * We don't support sending on the "any" device.
  			 */
  			strlcpy(handle->errbuf,
  			    "Sending packets isn't supported on the \"any\" device",
  			    PCAP_ERRBUF_SIZE);
  			return (-1);
  		}
  
  		if (handlep->cooked) {
  			/*
  			 * We don't support sending on the "any" device.
  			 *
  			 * XXX - how do you send on a bound cooked-mode
  			 * socket?
  			 * Is a "sendto()" required there?
  			 */
  			strlcpy(handle->errbuf,
  			    "Sending packets isn't supported in cooked mode",
  			    PCAP_ERRBUF_SIZE);
  			return (-1);
  		}
  	}
  #endif
  
  #ifdef HAVE_PF_RING
  	if (handle->ring != NULL)
  		return pfring_send(handle->ring, (char*)buf, size, 1 /* FIX: set it to 1 */);
  #endif
  
  	ret = send(handle->fd, buf, size, 0);
  	if (ret == -1) {
  		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "send: %s",
  		    pcap_strerror(errno));
  		return (-1);
  	}
  	return (ret);
  }
  
  /*
   *  Get the statistics for the given packet capture handle.
   *  Reports the number of dropped packets iff the kernel supports
   *  the PACKET_STATISTICS "getsockopt()" argument (2.4 and later
   *  kernels, and 2.2[.x] kernels with Alexey Kuznetzov's turbopacket
   *  patches); otherwise, that information isn't available, and we lie
   *  and report 0 as the count of dropped packets.
   */
  static int
  pcap_stats_linux(pcap_t *handle, struct pcap_stat *stats)
  {
  	struct pcap_linux *handlep = handle->priv;
  #ifdef HAVE_TPACKET_STATS
  #ifdef HAVE_TPACKET3
  	/*
  	 * For sockets using TPACKET_V1 or TPACKET_V2, the extra
  	 * stuff at the end of a struct tpacket_stats_v3 will not
  	 * be filled in, and we don't look at it so this is OK even
  	 * for those sockets.  In addition, the PF_PACKET socket
  	 * code in the kernel only uses the length parameter to
  	 * compute how much data to copy out and to indicate how
  	 * much data was copied out, so it's OK to base it on the
  	 * size of a struct tpacket_stats.
  	 *
  	 * XXX - it's probably OK, in fact, to just use a
  	 * struct tpacket_stats for V3 sockets, as we don't
  	 * care about the tp_freeze_q_cnt stat.
  	 */
  	struct tpacket_stats_v3 kstats;
  #else /* HAVE_TPACKET3 */
  	struct tpacket_stats kstats;
  #endif /* HAVE_TPACKET3 */
  	socklen_t len = sizeof (struct tpacket_stats);
  #endif /* HAVE_TPACKET_STATS */
  
  	long if_dropped = 0;
  
  #ifdef HAVE_PF_RING
  	if (handle->ring != NULL) {
  		pfring_stat ring_stats;
  
  		if (pfring_stats(handle->ring, &ring_stats) == 0) {
  			handlep->stat.ps_recv = ring_stats.recv;
  #if 0
  			/* tcpdump reports ps_drop as "packets dropped by kernel",
  			 * that is wrong with ZC, so we should set ps_ifdrop. 
  			 * But snort ignores ps_ifdrop, so it is best to set ps_drop in any case. */
  			if (handle->ring->zc_device)
  				handlep->stat.ps_ifdrop = ring_stats.drop;
  			else
  #else
  				handlep->stat.ps_drop = ring_stats.drop;
  #endif
  			*stats = handlep->stat;
  			return 0;
  		}
  	}
  #endif
  
  	/*
  	 *	To fill in ps_ifdrop, we parse /proc/net/dev for the number
  	 */
  	if (handle->opt.promisc)
  	{
  		if_dropped = handlep->proc_dropped;
  		handlep->proc_dropped = linux_if_drops(handlep->device);
  		handlep->stat.ps_ifdrop += (handlep->proc_dropped - if_dropped);
  	}
  
  #ifdef HAVE_TPACKET_STATS
  	/*
  	 * Try to get the packet counts from the kernel.
  	 */
  	if (getsockopt(handle->fd, SOL_PACKET, PACKET_STATISTICS,
  			&kstats, &len) > -1) {
  		/*
  		 * On systems where the PACKET_STATISTICS "getsockopt()"
  		 * argument is supported on PF_PACKET sockets:
  		 *
  		 *	"ps_recv" counts only packets that *passed* the
  		 *	filter, not packets that didn't pass the filter.
  		 *	This includes packets later dropped because we
  		 *	ran out of buffer space.
  		 *
  		 *	"ps_drop" counts packets dropped because we ran
  		 *	out of buffer space.  It doesn't count packets
  		 *	dropped by the interface driver.  It counts only
  		 *	packets that passed the filter.
  		 *
  		 *	See above for ps_ifdrop.
  		 *
  		 *	Both statistics include packets not yet read from
  		 *	the kernel by libpcap, and thus not yet seen by
  		 *	the application.
  		 *
  		 * In "linux/net/packet/af_packet.c", at least in the
  		 * 2.4.9 kernel, "tp_packets" is incremented for every
  		 * packet that passes the packet filter *and* is
  		 * successfully queued on the socket; "tp_drops" is
  		 * incremented for every packet dropped because there's
  		 * not enough free space in the socket buffer.
  		 *
  		 * When the statistics are returned for a PACKET_STATISTICS
  		 * "getsockopt()" call, "tp_drops" is added to "tp_packets",
  		 * so that "tp_packets" counts all packets handed to
  		 * the PF_PACKET socket, including packets dropped because
  		 * there wasn't room on the socket buffer - but not
  		 * including packets that didn't pass the filter.
  		 *
  		 * In the BSD BPF, the count of received packets is
  		 * incremented for every packet handed to BPF, regardless
  		 * of whether it passed the filter.
  		 *
  		 * We can't make "pcap_stats()" work the same on both
  		 * platforms, but the best approximation is to return
  		 * "tp_packets" as the count of packets and "tp_drops"
  		 * as the count of drops.
  		 *
  		 * Keep a running total because each call to
  		 *    getsockopt(handle->fd, SOL_PACKET, PACKET_STATISTICS, ....
  		 * resets the counters to zero.
  		 */
  		handlep->stat.ps_recv += kstats.tp_packets;
  		handlep->stat.ps_drop += kstats.tp_drops;
  		*stats = handlep->stat;
  		return 0;
  	}
  	else
  	{
  		/*
  		 * If the error was EOPNOTSUPP, fall through, so that
  		 * if you build the library on a system with
  		 * "struct tpacket_stats" and run it on a system
  		 * that doesn't, it works as it does if the library
  		 * is built on a system without "struct tpacket_stats".
  		 */
  		if (errno != EOPNOTSUPP) {
  			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  			    "pcap_stats: %s", pcap_strerror(errno));
  			return -1;
  		}
  	}
  #endif
  	/*
  	 * On systems where the PACKET_STATISTICS "getsockopt()" argument
  	 * is not supported on PF_PACKET sockets:
  	 *
  	 *	"ps_recv" counts only packets that *passed* the filter,
  	 *	not packets that didn't pass the filter.  It does not
  	 *	count packets dropped because we ran out of buffer
  	 *	space.
  	 *
  	 *	"ps_drop" is not supported.
  	 *
  	 *	"ps_ifdrop" is supported. It will return the number
  	 *	of drops the interface reports in /proc/net/dev,
  	 *	if that is available.
  	 *
  	 *	"ps_recv" doesn't include packets not yet read from
  	 *	the kernel by libpcap.
  	 *
  	 * We maintain the count of packets processed by libpcap in
  	 * "handlep->packets_read", for reasons described in the comment
  	 * at the end of pcap_read_packet().  We have no idea how many
  	 * packets were dropped by the kernel buffers -- but we know
  	 * how many the interface dropped, so we can return that.
  	 */
  
  	stats->ps_recv = handlep->packets_read;
  	stats->ps_drop = 0;
  	stats->ps_ifdrop = handlep->stat.ps_ifdrop;
  	return 0;
  }
  
  static int
  add_linux_if(pcap_if_t **devlistp, const char *ifname, int fd, char *errbuf)
  {
  	const char *p;
  	char name[512];	/* XXX - pick a size */
  	char *q, *saveq;
  	struct ifreq ifrflags;
  
  	/*
  	 * Get the interface name.
  	 */
  	p = ifname;
  	q = &name[0];
  	while (*p != '\0' && isascii(*p) && !isspace(*p)) {
  		if (*p == ':') {
  			/*
  			 * This could be the separator between a
  			 * name and an alias number, or it could be
  			 * the separator between a name with no
  			 * alias number and the next field.
  			 *
  			 * If there's a colon after digits, it
  			 * separates the name and the alias number,
  			 * otherwise it separates the name and the
  			 * next field.
  			 */
  			saveq = q;
  			while (isascii(*p) && isdigit(*p))
  				*q++ = *p++;
  			if (*p != ':') {
  				/*
  				 * That was the next field,
  				 * not the alias number.
  				 */
  				q = saveq;
  			}
  			break;
  		} else
  			*q++ = *p++;
  	}
  	*q = '\0';
  
  	/*
  	 * Get the flags for this interface.
  	 */
  	strlcpy(ifrflags.ifr_name, name, sizeof(ifrflags.ifr_name));
  	if (ioctl(fd, SIOCGIFFLAGS, (char *)&ifrflags) < 0) {
  		if (errno == ENXIO || errno == ENODEV)
  			return (0);	/* device doesn't actually exist - ignore it */
  		(void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
  		    "SIOCGIFFLAGS: %.*s: %s",
  		    (int)sizeof(ifrflags.ifr_name),
  		    ifrflags.ifr_name,
  		    pcap_strerror(errno));
  		return (-1);
  	}
  
  	/*
  	 * Add an entry for this interface, with no addresses.
  	 */
  	if (pcap_add_if(devlistp, name, ifrflags.ifr_flags, NULL,
  	    errbuf) == -1) {
  		/*
  		 * Failure.
  		 */
  		return (-1);
  	}
  
  	return (0);
  }
  
  /*
   * Get from "/sys/class/net" all interfaces listed there; if they're
   * already in the list of interfaces we have, that won't add another
   * instance, but if they're not, that'll add them.
   *
   * We don't bother getting any addresses for them; it appears you can't
   * use SIOCGIFADDR on Linux to get IPv6 addresses for interfaces, and,
   * although some other types of addresses can be fetched with SIOCGIFADDR,
   * we don't bother with them for now.
   *
   * We also don't fail if we couldn't open "/sys/class/net"; we just leave
   * the list of interfaces as is, and return 0, so that we can try
   * scanning /proc/net/dev.
   *
   * Otherwise, we return 1 if we don't get an error and -1 if we do.
   */
  static int
  scan_sys_class_net(pcap_if_t **devlistp, char *errbuf)
  {
  	DIR *sys_class_net_d;
  	int fd;
  	struct dirent *ent;
  	char subsystem_path[PATH_MAX+1];
  	struct stat statb;
  	int ret = 1;
  
  	sys_class_net_d = opendir("/sys/class/net");
  	if (sys_class_net_d == NULL) {
  		/*
  		 * Don't fail if it doesn't exist at all.
  		 */
  		if (errno == ENOENT)
  			return (0);
  
  		/*
  		 * Fail if we got some other error.
  		 */
  		(void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
  		    "Can't open /sys/class/net: %s", pcap_strerror(errno));
  		return (-1);
  	}
  
  	/*
  	 * Create a socket from which to fetch interface information.
  	 */
  	fd = socket(AF_INET, SOCK_DGRAM, 0);
  	if (fd < 0) {
  		(void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
  		    "socket: %s", pcap_strerror(errno));
  		(void)closedir(sys_class_net_d);
  		return (-1);
  	}
  
  	for (;;) {
  		errno = 0;
  		ent = readdir(sys_class_net_d);
  		if (ent == NULL) {
  			/*
  			 * Error or EOF; if errno != 0, it's an error.
  			 */
  			break;
  		}
  
  		/*
  		 * Ignore "." and "..".
  		 */
  		if (strcmp(ent->d_name, ".") == 0 ||
  		    strcmp(ent->d_name, "..") == 0)
  			continue;
  
  		/*
  		 * Ignore plain files; they do not have subdirectories
  		 * and thus have no attributes.
  		 */
  		if (ent->d_type == DT_REG)
  			continue;
  
  		/*
  		 * Is there an "ifindex" file under that name?
  		 * (We don't care whether it's a directory or
  		 * a symlink; older kernels have directories
  		 * for devices, newer kernels have symlinks to
  		 * directories.)
  		 */
  		snprintf(subsystem_path, sizeof subsystem_path,
  		    "/sys/class/net/%s/ifindex", ent->d_name);
  		if (lstat(subsystem_path, &statb) != 0) {
  			/*
  			 * Stat failed.  Either there was an error
  			 * other than ENOENT, and we don't know if
  			 * this is an interface, or it's ENOENT,
  			 * and either some part of "/sys/class/net/{if}"
  			 * disappeared, in which case it probably means
  			 * the interface disappeared, or there's no
  			 * "ifindex" file, which means it's not a
  			 * network interface.
  			 */
  			continue;
  		}
  
  		/*
  		 * Attempt to add the interface.
  		 */
  		if (add_linux_if(devlistp, &ent->d_name[0], fd, errbuf) == -1) {
  			/* Fail. */
  			ret = -1;
  			break;
  		}
  	}
  	if (ret != -1) {
  		/*
  		 * Well, we didn't fail for any other reason; did we
  		 * fail due to an error reading the directory?
  		 */
  		if (errno != 0) {
  			(void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
  			    "Error reading /sys/class/net: %s",
  			    pcap_strerror(errno));
  			ret = -1;
  		}
  	}
  
  	(void)close(fd);
  	(void)closedir(sys_class_net_d);
  	return (ret);
  }
  
  /*
   * Get from "/proc/net/dev" all interfaces listed there; if they're
   * already in the list of interfaces we have, that won't add another
   * instance, but if they're not, that'll add them.
   *
   * See comments from scan_sys_class_net().
   */
  static int
  scan_proc_net_dev(pcap_if_t **devlistp, char *errbuf)
  {
  	FILE *proc_net_f;
  	int fd;
  	char linebuf[512];
  	int linenum;
  	char *p;
  	int ret = 0;
  
  	proc_net_f = fopen("/proc/net/dev", "r");
  	if (proc_net_f == NULL) {
  		/*
  		 * Don't fail if it doesn't exist at all.
  		 */
  		if (errno == ENOENT)
  			return (0);
  
  		/*
  		 * Fail if we got some other error.
  		 */
  		(void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
  		    "Can't open /proc/net/dev: %s", pcap_strerror(errno));
  		return (-1);
  	}
  
  	/*
  	 * Create a socket from which to fetch interface information.
  	 */
  	fd = socket(AF_INET, SOCK_DGRAM, 0);
  	if (fd < 0) {
  		(void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
  		    "socket: %s", pcap_strerror(errno));
  		(void)fclose(proc_net_f);
  		return (-1);
  	}
  
  	for (linenum = 1;
  	    fgets(linebuf, sizeof linebuf, proc_net_f) != NULL; linenum++) {
  		/*
  		 * Skip the first two lines - they're headers.
  		 */
  		if (linenum <= 2)
  			continue;
  
  		p = &linebuf[0];
  
  		/*
  		 * Skip leading white space.
  		 */
  		while (*p != '\0' && isascii(*p) && isspace(*p))
  			p++;
  		if (*p == '\0' || *p == '\n')
  			continue;	/* blank line */
  
  		/*
  		 * Attempt to add the interface.
  		 */
  		if (add_linux_if(devlistp, p, fd, errbuf) == -1) {
  			/* Fail. */
  			ret = -1;
  			break;
  		}
  	}
  	if (ret != -1) {
  		/*
  		 * Well, we didn't fail for any other reason; did we
  		 * fail due to an error reading the file?
  		 */
  		if (ferror(proc_net_f)) {
  			(void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
  			    "Error reading /proc/net/dev: %s",
  			    pcap_strerror(errno));
  			ret = -1;
  		}
  	}
  
  	(void)close(fd);
  	(void)fclose(proc_net_f);
  	return (ret);
  }
  
  /*
   * Description string for the "any" device.
   */
  static const char any_descr[] = "Pseudo-device that captures on all interfaces";
  
  int
  pcap_platform_finddevs(pcap_if_t **alldevsp, char *errbuf)
  {
  	int ret;
  
  	/*
  	 * Read "/sys/class/net", and add to the list of interfaces all
  	 * interfaces listed there that we don't already have, because,
  	 * on Linux, SIOCGIFCONF reports only interfaces with IPv4 addresses,
  	 * and even getifaddrs() won't return information about
  	 * interfaces with no addresses, so you need to read "/sys/class/net"
  	 * to get the names of the rest of the interfaces.
  	 */
  	ret = scan_sys_class_net(alldevsp, errbuf);
  	if (ret == -1)
  		return (-1);	/* failed */
  	if (ret == 0) {
  		/*
  		 * No /sys/class/net; try reading /proc/net/dev instead.
  		 */
  		if (scan_proc_net_dev(alldevsp, errbuf) == -1)
  			return (-1);
  	}
  
  	/*
  	 * Add the "any" device.
  	 */
  	if (pcap_add_if(alldevsp, "any", IFF_UP|IFF_RUNNING,
  	    any_descr, errbuf) < 0)
  		return (-1);
  
  	return (0);
  }
  
  /*
   *  Attach the given BPF code to the packet capture device.
   */
  static int
  pcap_setfilter_linux_common(pcap_t *handle, struct bpf_program *filter,
      int is_mmapped)
  {
  	struct pcap_linux *handlep;
  #ifdef SO_ATTACH_FILTER
  	struct sock_fprog	fcode;
  	int			can_filter_in_kernel;
  	int			err = 0;
  #endif
  
  	if (!handle)
  		return -1;
  	if (!filter) {
  	        strlcpy(handle->errbuf, "setfilter: No filter specified",
  			PCAP_ERRBUF_SIZE);
  		return -1;
  	}
  
  	handlep = handle->priv;
  
  	/* Make our private copy of the filter */
  
  	if (install_bpf_program(handle, filter) < 0)
  		/* install_bpf_program() filled in errbuf */
  		return -1;
  
  	/*
  	 * Run user level packet filter by default. Will be overriden if
  	 * installing a kernel filter succeeds.
  	 */
  	handlep->filter_in_userland = 1;
  
  	/* Install kernel level filter if possible */
  
  #ifdef SO_ATTACH_FILTER
  #ifdef USHRT_MAX
  	if (handle->fcode.bf_len > USHRT_MAX) {
  		/*
  		 * fcode.len is an unsigned short for current kernel.
  		 * I have yet to see BPF-Code with that much
  		 * instructions but still it is possible. So for the
  		 * sake of correctness I added this check.
  		 */
  		fprintf(stderr, "Warning: Filter too complex for kernel\n");
  		fcode.len = 0;
  		fcode.filter = NULL;
  		can_filter_in_kernel = 0;
  	} else
  #endif /* USHRT_MAX */
  	{
  		/*
  		 * Oh joy, the Linux kernel uses struct sock_fprog instead
  		 * of struct bpf_program and of course the length field is
  		 * of different size. Pointed out by Sebastian
  		 *
  		 * Oh, and we also need to fix it up so that all "ret"
  		 * instructions with non-zero operands have MAXIMUM_SNAPLEN
  		 * as the operand if we're not capturing in memory-mapped
  		 * mode, and so that, if we're in cooked mode, all memory-
  		 * reference instructions use special magic offsets in
  		 * references to the link-layer header and assume that the
  		 * link-layer payload begins at 0; "fix_program()" will do
  		 * that.
  		 */
  		switch (fix_program(handle, &fcode, is_mmapped)) {
  
  		case -1:
  		default:
  			/*
  			 * Fatal error; just quit.
  			 * (The "default" case shouldn't happen; we
  			 * return -1 for that reason.)
  			 */
  			return -1;
  
  		case 0:
  			/*
  			 * The program performed checks that we can't make
  			 * work in the kernel.
  			 */
  			can_filter_in_kernel = 0;
  			break;
  
  		case 1:
  			/*
  			 * We have a filter that'll work in the kernel.
  			 */
  			can_filter_in_kernel = 1;
  			break;
  		}
  	}
  
  #ifdef HAVE_PF_RING
  	if (can_filter_in_kernel && handle->ring != NULL) {
  		int if_index;
  		if (handle->ring->zc_device /* ZC: we need to filter in userland as kernel is bypassed */
  		    || pfring_get_bound_device_ifindex(handle->ring, &if_index) != 0 /* not a physical device */)
  			can_filter_in_kernel = 0;
  	}
  #endif
  
  	/*
  	 * NOTE: at this point, we've set both the "len" and "filter"
  	 * fields of "fcode".  As of the 2.6.32.4 kernel, at least,
  	 * those are the only members of the "sock_fprog" structure,
  	 * so we initialize every member of that structure.
  	 *
  	 * If there is anything in "fcode" that is not initialized,
  	 * it is either a field added in a later kernel, or it's
  	 * padding.
  	 *
  	 * If a new field is added, this code needs to be updated
  	 * to set it correctly.
  	 *
  	 * If there are no other fields, then:
  	 *
  	 *	if the Linux kernel looks at the padding, it's
  	 *	buggy;
  	 *
  	 *	if the Linux kernel doesn't look at the padding,
  	 *	then if some tool complains that we're passing
  	 *	uninitialized data to the kernel, then the tool
  	 *	is buggy and needs to understand that it's just
  	 *	padding.
  	 */
  	if (can_filter_in_kernel) {
  		if ((err = set_kernel_filter(handle, &fcode)) == 0)
  		{
  			/*
  			 * Installation succeded - using kernel filter,
  			 * so userland filtering not needed.
  			 */
  			handlep->filter_in_userland = 0;
  		}
  		else if (err == -1)	/* Non-fatal error */
  		{
  			/*
  			 * Print a warning if we weren't able to install
  			 * the filter for a reason other than "this kernel
  			 * isn't configured to support socket filters.
  			 */
  			if (errno != ENOPROTOOPT && errno != EOPNOTSUPP) {
  				fprintf(stderr,
  				    "Warning: Kernel filter failed: %s\n",
  					pcap_strerror(errno));
  			}
  		}
  	}
  
  	/*
  	 * If we're not using the kernel filter, get rid of any kernel
  	 * filter that might've been there before, e.g. because the
  	 * previous filter could work in the kernel, or because some other
  	 * code attached a filter to the socket by some means other than
  	 * calling "pcap_setfilter()".  Otherwise, the kernel filter may
  	 * filter out packets that would pass the new userland filter.
  	 */
  	if (handlep->filter_in_userland) {
  		if (reset_kernel_filter(handle) == -1) {
  			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  			    "can't remove kernel filter: %s",
  			    pcap_strerror(errno));
  			err = -2;	/* fatal error */
  		}
  	}
  
  	/*
  	 * Free up the copy of the filter that was made by "fix_program()".
  	 */
  	if (fcode.filter != NULL)
  		free(fcode.filter);
  
  	if (err == -2)
  		/* Fatal error */
  		return -1;
  #endif /* SO_ATTACH_FILTER */
  
  	return 0;
  }
  
  static int
  pcap_setfilter_linux(pcap_t *handle, struct bpf_program *filter)
  {
  	return pcap_setfilter_linux_common(handle, filter, 0);
  }
  
  
  /*
   * Set direction flag: Which packets do we accept on a forwarding
   * single device? IN, OUT or both?
   */
  static int
  pcap_setdirection_linux(pcap_t *handle, pcap_direction_t d)
  {
  #ifdef HAVE_PF_RING
  	if (handle->ring != NULL) {
  		packet_direction direction;
  
  		switch (d) {
  			case PCAP_D_INOUT: direction = rx_and_tx_direction; break;
  			case PCAP_D_IN:    direction = rx_only_direction; break;
  			case PCAP_D_OUT:   direction = tx_only_direction; break;
  		}
  
  		return(pfring_set_direction(handle->ring, direction));
  	}
  #endif
  
  #ifdef HAVE_PF_PACKET_SOCKETS
  	struct pcap_linux *handlep = handle->priv;
  
  	if (!handlep->sock_packet) {
  		handle->direction = d;
  		return 0;
  	}
  #endif
  	/*
  	 * We're not using PF_PACKET sockets, so we can't determine
  	 * the direction of the packet.
  	 */
  	snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  	    "Setting direction is not supported on SOCK_PACKET sockets");
  	return -1;
  }
  
  #ifdef HAVE_PF_PACKET_SOCKETS
  /*
   * Map the PACKET_ value to a LINUX_SLL_ value; we
   * want the same numerical value to be used in
   * the link-layer header even if the numerical values
   * for the PACKET_ #defines change, so that programs
   * that look at the packet type field will always be
   * able to handle DLT_LINUX_SLL captures.
   */
  static short int
  map_packet_type_to_sll_type(short int sll_pkttype)
  {
  	switch (sll_pkttype) {
  
  	case PACKET_HOST:
  		return htons(LINUX_SLL_HOST);
  
  	case PACKET_BROADCAST:
  		return htons(LINUX_SLL_BROADCAST);
  
  	case PACKET_MULTICAST:
  		return  htons(LINUX_SLL_MULTICAST);
  
  	case PACKET_OTHERHOST:
  		return htons(LINUX_SLL_OTHERHOST);
  
  	case PACKET_OUTGOING:
  		return htons(LINUX_SLL_OUTGOING);
  
  	default:
  		return -1;
  	}
  }
  #endif
  
  static int
  is_wifi(int sock_fd
  #ifndef IW_MODE_MONITOR
  _U_
  #endif
  , const char *device)
  {
  	char *pathstr;
  	struct stat statb;
  #ifdef IW_MODE_MONITOR
  	char errbuf[PCAP_ERRBUF_SIZE];
  #endif
  
  	/*
  	 * See if there's a sysfs wireless directory for it.
  	 * If so, it's a wireless interface.
  	 */
  	if (asprintf(&pathstr, "/sys/class/net/%s/wireless", device) == -1) {
  		/*
  		 * Just give up here.
  		 */
  		return 0;
  	}
  	if (stat(pathstr, &statb) == 0) {
  		free(pathstr);
  		return 1;
  	}
  	free(pathstr);
  
  #ifdef IW_MODE_MONITOR
  	/*
  	 * OK, maybe it's not wireless, or maybe this kernel doesn't
  	 * support sysfs.  Try the wireless extensions.
  	 */
  	if (has_wext(sock_fd, device, errbuf) == 1) {
  		/*
  		 * It supports the wireless extensions, so it's a Wi-Fi
  		 * device.
  		 */
  		return 1;
  	}
  #endif
  	return 0;
  }
  
  /*
   *  Linux uses the ARP hardware type to identify the type of an
   *  interface. pcap uses the DLT_xxx constants for this. This
   *  function takes a pointer to a "pcap_t", and an ARPHRD_xxx
   *  constant, as arguments, and sets "handle->linktype" to the
   *  appropriate DLT_XXX constant and sets "handle->offset" to
   *  the appropriate value (to make "handle->offset" plus link-layer
   *  header length be a multiple of 4, so that the link-layer payload
   *  will be aligned on a 4-byte boundary when capturing packets).
   *  (If the offset isn't set here, it'll be 0; add code as appropriate
   *  for cases where it shouldn't be 0.)
   *
   *  If "cooked_ok" is non-zero, we can use DLT_LINUX_SLL and capture
   *  in cooked mode; otherwise, we can't use cooked mode, so we have
   *  to pick some type that works in raw mode, or fail.
   *
   *  Sets the link type to -1 if unable to map the type.
   */
  static void map_arphrd_to_dlt(pcap_t *handle, int sock_fd, int arptype,
  			      const char *device, int cooked_ok)
  {
  	static const char cdma_rmnet[] = "cdma_rmnet";
  
  	switch (arptype) {
  
  	case ARPHRD_ETHER:
  		/*
  		 * For various annoying reasons having to do with DHCP
  		 * software, some versions of Android give the mobile-
  		 * phone-network interface an ARPHRD_ value of
  		 * ARPHRD_ETHER, even though the packets supplied by
  		 * that interface have no link-layer header, and begin
  		 * with an IP header, so that the ARPHRD_ value should
  		 * be ARPHRD_NONE.
  		 *
  		 * Detect those devices by checking the device name, and
  		 * use DLT_RAW for them.
  		 */
  		if (strncmp(device, cdma_rmnet, sizeof cdma_rmnet - 1) == 0) {
  			handle->linktype = DLT_RAW;
  			return;
  		}
  
  		/*
  		 * Is this a real Ethernet device?  If so, give it a
  		 * link-layer-type list with DLT_EN10MB and DLT_DOCSIS, so
  		 * that an application can let you choose it, in case you're
  		 * capturing DOCSIS traffic that a Cisco Cable Modem
  		 * Termination System is putting out onto an Ethernet (it
  		 * doesn't put an Ethernet header onto the wire, it puts raw
  		 * DOCSIS frames out on the wire inside the low-level
  		 * Ethernet framing).
  		 *
  		 * XXX - are there any other sorts of "fake Ethernet" that
  		 * have ARPHRD_ETHER but that shouldn't offer DLT_DOCSIS as
  		 * a Cisco CMTS won't put traffic onto it or get traffic
  		 * bridged onto it?  ISDN is handled in "activate_new()",
  		 * as we fall back on cooked mode there, and we use
  		 * is_wifi() to check for 802.11 devices; are there any
  		 * others?
  		 */
  		if (!is_wifi(sock_fd, device)) {
  			/*
  			 * It's not a Wi-Fi device; offer DOCSIS.
  			 */
  			handle->dlt_list = (u_int *) malloc(sizeof(u_int) * 2);
  			/*
  			 * If that fails, just leave the list empty.
  			 */
  			if (handle->dlt_list != NULL) {
  				handle->dlt_list[0] = DLT_EN10MB;
  				handle->dlt_list[1] = DLT_DOCSIS;
  				handle->dlt_count = 2;
  			}
  		}
  		/* FALLTHROUGH */
  
  	case ARPHRD_METRICOM:
  	case ARPHRD_LOOPBACK:
  		handle->linktype = DLT_EN10MB;
  		handle->offset = 2;
  		break;
  
  	case ARPHRD_EETHER:
  		handle->linktype = DLT_EN3MB;
  		break;
  
  	case ARPHRD_AX25:
  		handle->linktype = DLT_AX25_KISS;
  		break;
  
  	case ARPHRD_PRONET:
  		handle->linktype = DLT_PRONET;
  		break;
  
  	case ARPHRD_CHAOS:
  		handle->linktype = DLT_CHAOS;
  		break;
  #ifndef ARPHRD_CAN
  #define ARPHRD_CAN 280
  #endif
  	case ARPHRD_CAN:
  		handle->linktype = DLT_CAN_SOCKETCAN;
  		break;
  
  #ifndef ARPHRD_IEEE802_TR
  #define ARPHRD_IEEE802_TR 800	/* From Linux 2.4 */
  #endif
  	case ARPHRD_IEEE802_TR:
  	case ARPHRD_IEEE802:
  		handle->linktype = DLT_IEEE802;
  		handle->offset = 2;
  		break;
  
  	case ARPHRD_ARCNET:
  		handle->linktype = DLT_ARCNET_LINUX;
  		break;
  
  #ifndef ARPHRD_FDDI	/* From Linux 2.2.13 */
  #define ARPHRD_FDDI	774
  #endif
  	case ARPHRD_FDDI:
  		handle->linktype = DLT_FDDI;
  		handle->offset = 3;
  		break;
  
  #ifndef ARPHRD_ATM  /* FIXME: How to #include this? */
  #define ARPHRD_ATM 19
  #endif
  	case ARPHRD_ATM:
  		/*
  		 * The Classical IP implementation in ATM for Linux
  		 * supports both what RFC 1483 calls "LLC Encapsulation",
  		 * in which each packet has an LLC header, possibly
  		 * with a SNAP header as well, prepended to it, and
  		 * what RFC 1483 calls "VC Based Multiplexing", in which
  		 * different virtual circuits carry different network
  		 * layer protocols, and no header is prepended to packets.
  		 *
  		 * They both have an ARPHRD_ type of ARPHRD_ATM, so
  		 * you can't use the ARPHRD_ type to find out whether
  		 * captured packets will have an LLC header, and,
  		 * while there's a socket ioctl to *set* the encapsulation
  		 * type, there's no ioctl to *get* the encapsulation type.
  		 *
  		 * This means that
  		 *
  		 *	programs that dissect Linux Classical IP frames
  		 *	would have to check for an LLC header and,
  		 *	depending on whether they see one or not, dissect
  		 *	the frame as LLC-encapsulated or as raw IP (I
  		 *	don't know whether there's any traffic other than
  		 *	IP that would show up on the socket, or whether
  		 *	there's any support for IPv6 in the Linux
  		 *	Classical IP code);
  		 *
  		 *	filter expressions would have to compile into
  		 *	code that checks for an LLC header and does
  		 *	the right thing.
  		 *
  		 * Both of those are a nuisance - and, at least on systems
  		 * that support PF_PACKET sockets, we don't have to put
  		 * up with those nuisances; instead, we can just capture
  		 * in cooked mode.  That's what we'll do, if we can.
  		 * Otherwise, we'll just fail.
  		 */
  		if (cooked_ok)
  			handle->linktype = DLT_LINUX_SLL;
  		else
  			handle->linktype = -1;
  		break;
  
  #ifndef ARPHRD_IEEE80211  /* From Linux 2.4.6 */
  #define ARPHRD_IEEE80211 801
  #endif
  	case ARPHRD_IEEE80211:
  		handle->linktype = DLT_IEEE802_11;
  		break;
  
  #ifndef ARPHRD_IEEE80211_PRISM  /* From Linux 2.4.18 */
  #define ARPHRD_IEEE80211_PRISM 802
  #endif
  	case ARPHRD_IEEE80211_PRISM:
  		handle->linktype = DLT_PRISM_HEADER;
  		break;
  
  #ifndef ARPHRD_IEEE80211_RADIOTAP /* new */
  #define ARPHRD_IEEE80211_RADIOTAP 803
  #endif
  	case ARPHRD_IEEE80211_RADIOTAP:
  		handle->linktype = DLT_IEEE802_11_RADIO;
  		break;
  
  	case ARPHRD_PPP:
  		/*
  		 * Some PPP code in the kernel supplies no link-layer
  		 * header whatsoever to PF_PACKET sockets; other PPP
  		 * code supplies PPP link-layer headers ("syncppp.c");
  		 * some PPP code might supply random link-layer
  		 * headers (PPP over ISDN - there's code in Ethereal,
  		 * for example, to cope with PPP-over-ISDN captures
  		 * with which the Ethereal developers have had to cope,
  		 * heuristically trying to determine which of the
  		 * oddball link-layer headers particular packets have).
  		 *
  		 * As such, we just punt, and run all PPP interfaces
  		 * in cooked mode, if we can; otherwise, we just treat
  		 * it as DLT_RAW, for now - if somebody needs to capture,
  		 * on a 2.0[.x] kernel, on PPP devices that supply a
  		 * link-layer header, they'll have to add code here to
  		 * map to the appropriate DLT_ type (possibly adding a
  		 * new DLT_ type, if necessary).
  		 */
  		if (cooked_ok)
  			handle->linktype = DLT_LINUX_SLL;
  		else {
  			/*
  			 * XXX - handle ISDN types here?  We can't fall
  			 * back on cooked sockets, so we'd have to
  			 * figure out from the device name what type of
  			 * link-layer encapsulation it's using, and map
  			 * that to an appropriate DLT_ value, meaning
  			 * we'd map "isdnN" devices to DLT_RAW (they
  			 * supply raw IP packets with no link-layer
  			 * header) and "isdY" devices to a new DLT_I4L_IP
  			 * type that has only an Ethernet packet type as
  			 * a link-layer header.
  			 *
  			 * But sometimes we seem to get random crap
  			 * in the link-layer header when capturing on
  			 * ISDN devices....
  			 */
  			handle->linktype = DLT_RAW;
  		}
  		break;
  
  #ifndef ARPHRD_CISCO
  #define ARPHRD_CISCO 513 /* previously ARPHRD_HDLC */
  #endif
  	case ARPHRD_CISCO:
  		handle->linktype = DLT_C_HDLC;
  		break;
  
  	/* Not sure if this is correct for all tunnels, but it
  	 * works for CIPE */
  	case ARPHRD_TUNNEL:
  #ifndef ARPHRD_SIT
  #define ARPHRD_SIT 776	/* From Linux 2.2.13 */
  #endif
  	case ARPHRD_SIT:
  	case ARPHRD_CSLIP:
  	case ARPHRD_SLIP6:
  	case ARPHRD_CSLIP6:
  	case ARPHRD_ADAPT:
  	case ARPHRD_SLIP:
  #ifndef ARPHRD_RAWHDLC
  #define ARPHRD_RAWHDLC 518
  #endif
  	case ARPHRD_RAWHDLC:
  #ifndef ARPHRD_DLCI
  #define ARPHRD_DLCI 15
  #endif
  	case ARPHRD_DLCI:
  		/*
  		 * XXX - should some of those be mapped to DLT_LINUX_SLL
  		 * instead?  Should we just map all of them to DLT_LINUX_SLL?
  		 */
  		handle->linktype = DLT_RAW;
  		break;
  
  #ifndef ARPHRD_FRAD
  #define ARPHRD_FRAD 770
  #endif
  	case ARPHRD_FRAD:
  		handle->linktype = DLT_FRELAY;
  		break;
  
  	case ARPHRD_LOCALTLK:
  		handle->linktype = DLT_LTALK;
  		break;
  
  	case 18:
  		/*
  		 * RFC 4338 defines an encapsulation for IP and ARP
  		 * packets that's compatible with the RFC 2625
  		 * encapsulation, but that uses a different ARP
  		 * hardware type and hardware addresses.  That
  		 * ARP hardware type is 18; Linux doesn't define
  		 * any ARPHRD_ value as 18, but if it ever officially
  		 * supports RFC 4338-style IP-over-FC, it should define
  		 * one.
  		 *
  		 * For now, we map it to DLT_IP_OVER_FC, in the hopes
  		 * that this will encourage its use in the future,
  		 * should Linux ever officially support RFC 4338-style
  		 * IP-over-FC.
  		 */
  		handle->linktype = DLT_IP_OVER_FC;
  		break;
  
  #ifndef ARPHRD_FCPP
  #define ARPHRD_FCPP	784
  #endif
  	case ARPHRD_FCPP:
  #ifndef ARPHRD_FCAL
  #define ARPHRD_FCAL	785
  #endif
  	case ARPHRD_FCAL:
  #ifndef ARPHRD_FCPL
  #define ARPHRD_FCPL	786
  #endif
  	case ARPHRD_FCPL:
  #ifndef ARPHRD_FCFABRIC
  #define ARPHRD_FCFABRIC	787
  #endif
  	case ARPHRD_FCFABRIC:
  		/*
  		 * Back in 2002, Donald Lee at Cray wanted a DLT_ for
  		 * IP-over-FC:
  		 *
  		 *	http://www.mail-archive.com/tcpdump-workers@sandelman.ottawa.on.ca/msg01043.html
  		 *
  		 * and one was assigned.
  		 *
  		 * In a later private discussion (spun off from a message
  		 * on the ethereal-users list) on how to get that DLT_
  		 * value in libpcap on Linux, I ended up deciding that
  		 * the best thing to do would be to have him tweak the
  		 * driver to set the ARPHRD_ value to some ARPHRD_FCxx
  		 * type, and map all those types to DLT_IP_OVER_FC:
  		 *
  		 *	I've checked into the libpcap and tcpdump CVS tree
  		 *	support for DLT_IP_OVER_FC.  In order to use that,
  		 *	you'd have to modify your modified driver to return
  		 *	one of the ARPHRD_FCxxx types, in "fcLINUXfcp.c" -
  		 *	change it to set "dev->type" to ARPHRD_FCFABRIC, for
  		 *	example (the exact value doesn't matter, it can be
  		 *	any of ARPHRD_FCPP, ARPHRD_FCAL, ARPHRD_FCPL, or
  		 *	ARPHRD_FCFABRIC).
  		 *
  		 * 11 years later, Christian Svensson wanted to map
  		 * various ARPHRD_ values to DLT_FC_2 and
  		 * DLT_FC_2_WITH_FRAME_DELIMS for raw Fibre Channel
  		 * frames:
  		 *
  		 *	https://github.com/mcr/libpcap/pull/29
  		 *
  		 * There doesn't seem to be any network drivers that uses
  		 * any of the ARPHRD_FC* values for IP-over-FC, and
  		 * it's not exactly clear what the "Dummy types for non
  		 * ARP hardware" are supposed to mean (link-layer
  		 * header type?  Physical network type?), so it's
  		 * not exactly clear why the ARPHRD_FC* types exist
  		 * in the first place.
  		 *
  		 * For now, we map them to DLT_FC_2, and provide an
  		 * option of DLT_FC_2_WITH_FRAME_DELIMS, as well as
  		 * DLT_IP_OVER_FC just in case there's some old
  		 * driver out there that uses one of those types for
  		 * IP-over-FC on which somebody wants to capture
  		 * packets.
  		 */
  		handle->dlt_list = (u_int *) malloc(sizeof(u_int) * 2);
  		/*
  		 * If that fails, just leave the list empty.
  		 */
  		if (handle->dlt_list != NULL) {
  			handle->dlt_list[0] = DLT_FC_2;
  			handle->dlt_list[1] = DLT_FC_2_WITH_FRAME_DELIMS;
  			handle->dlt_list[2] = DLT_IP_OVER_FC;
  			handle->dlt_count = 3;
  		}
  		handle->linktype = DLT_FC_2;
  		break;
  
  #ifndef ARPHRD_IRDA
  #define ARPHRD_IRDA	783
  #endif
  	case ARPHRD_IRDA:
  		/* Don't expect IP packet out of this interfaces... */
  		handle->linktype = DLT_LINUX_IRDA;
  		/* We need to save packet direction for IrDA decoding,
  		 * so let's use "Linux-cooked" mode. Jean II
  		 *
  		 * XXX - this is handled in activate_new(). */
  		//handlep->cooked = 1;
  		break;
  
  	/* ARPHRD_LAPD is unofficial and randomly allocated, if reallocation
  	 * is needed, please report it to <daniele@orlandi.com> */
  #ifndef ARPHRD_LAPD
  #define ARPHRD_LAPD	8445
  #endif
  	case ARPHRD_LAPD:
  		/* Don't expect IP packet out of this interfaces... */
  		handle->linktype = DLT_LINUX_LAPD;
  		break;
  
  #ifndef ARPHRD_NONE
  #define ARPHRD_NONE	0xFFFE
  #endif
  	case ARPHRD_NONE:
  		/*
  		 * No link-layer header; packets are just IP
  		 * packets, so use DLT_RAW.
  		 */
  		handle->linktype = DLT_RAW;
  		break;
  
  #ifndef ARPHRD_IEEE802154
  #define ARPHRD_IEEE802154      804
  #endif
         case ARPHRD_IEEE802154:
                 handle->linktype =  DLT_IEEE802_15_4_NOFCS;
                 break;
  
  #ifndef ARPHRD_NETLINK
  #define ARPHRD_NETLINK	824
  #endif
  	case ARPHRD_NETLINK:
  		handle->linktype = DLT_NETLINK;
  		/*
  		 * We need to use cooked mode, so that in sll_protocol we
  		 * pick up the netlink protocol type such as NETLINK_ROUTE,
  		 * NETLINK_GENERIC, NETLINK_FIB_LOOKUP, etc.
  		 *
  		 * XXX - this is handled in activate_new().
  		 */
  		//handlep->cooked = 1;
  		break;
  
  	default:
  		handle->linktype = -1;
  		break;
  	}
  }
  
  /* ===== Functions to interface to the newer kernels ================== */
  
  /*
   * Try to open a packet socket using the new kernel PF_PACKET interface.
   * Returns 1 on success, 0 on an error that means the new interface isn't
   * present (so the old SOCK_PACKET interface should be tried), and a
   * PCAP_ERROR_ value on an error that means that the old mechanism won't
   * work either (so it shouldn't be tried).
   */
  static int
  activate_new(pcap_t *handle)
  {
  #ifdef HAVE_PF_PACKET_SOCKETS
  	struct pcap_linux *handlep = handle->priv;
  	const char		*device = handle->opt.source;
  	int			is_any_device = (strcmp(device, "any") == 0);
  	int			sock_fd = -1, arptype;
  #ifdef HAVE_PACKET_AUXDATA
  	int			val;
  #endif
  	int			err = 0;
  	struct packet_mreq	mr;
  #ifdef SO_BPF_EXTENSIONS
  	int			bpf_extensions;
  	socklen_t		len = sizeof(bpf_extensions);
  #endif
  
  	/*
  	 * Open a socket with protocol family packet. If the
  	 * "any" device was specified, we open a SOCK_DGRAM
  	 * socket for the cooked interface, otherwise we first
  	 * try a SOCK_RAW socket for the raw interface.
  	 */
  	sock_fd = is_any_device ?
  		socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_ALL)) :
  		socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL));
  
  	if (sock_fd == -1) {
  		if (errno == EINVAL || errno == EAFNOSUPPORT) {
  			/*
  			 * We don't support PF_PACKET/SOCK_whatever
  			 * sockets; try the old mechanism.
  			 */
  			return 0;
  		}
  
  		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "socket: %s",
  			 pcap_strerror(errno) );
  		if (errno == EPERM || errno == EACCES) {
  			/*
  			 * You don't have permission to open the
  			 * socket.
  			 */
  			return PCAP_ERROR_PERM_DENIED;
  		} else {
  			/*
  			 * Other error.
  			 */
  			return PCAP_ERROR;
  		}
  	}
  
  	/* It seems the kernel supports the new interface. */
  	handlep->sock_packet = 0;
  
  	/*
  	 * Get the interface index of the loopback device.
  	 * If the attempt fails, don't fail, just set the
  	 * "handlep->lo_ifindex" to -1.
  	 *
  	 * XXX - can there be more than one device that loops
  	 * packets back, i.e. devices other than "lo"?  If so,
  	 * we'd need to find them all, and have an array of
  	 * indices for them, and check all of them in
  	 * "pcap_read_packet()".
  	 */
  	handlep->lo_ifindex = iface_get_id(sock_fd, "lo", handle->errbuf);
  
  	/*
  	 * Default value for offset to align link-layer payload
  	 * on a 4-byte boundary.
  	 */
  	handle->offset	 = 0;
  
  	/*
  	 * What kind of frames do we have to deal with? Fall back
  	 * to cooked mode if we have an unknown interface type
  	 * or a type we know doesn't work well in raw mode.
  	 */
  	if (!is_any_device) {
  		/* Assume for now we don't need cooked mode. */
  		handlep->cooked = 0;
  
  		if (handle->opt.rfmon) {
  			/*
  			 * We were asked to turn on monitor mode.
  			 * Do so before we get the link-layer type,
  			 * because entering monitor mode could change
  			 * the link-layer type.
  			 */
  			err = enter_rfmon_mode(handle, sock_fd, device);
  			if (err < 0) {
  				/* Hard failure */
  				close(sock_fd);
  				return err;
  			}
  			if (err == 0) {
  				/*
  				 * Nothing worked for turning monitor mode
  				 * on.
  				 */
  				close(sock_fd);
  				return PCAP_ERROR_RFMON_NOTSUP;
  			}
  
  			/*
  			 * Either monitor mode has been turned on for
  			 * the device, or we've been given a different
  			 * device to open for monitor mode.  If we've
  			 * been given a different device, use it.
  			 */
  			if (handlep->mondevice != NULL)
  				device = handlep->mondevice;
  		}
  		arptype	= iface_get_arptype(sock_fd, device, handle->errbuf);
  		if (arptype < 0) {
  			close(sock_fd);
  			return arptype;
  		}
  		map_arphrd_to_dlt(handle, sock_fd, arptype, device, 1);
  		if (handle->linktype == -1 ||
  		    handle->linktype == DLT_LINUX_SLL ||
  		    handle->linktype == DLT_LINUX_IRDA ||
  		    handle->linktype == DLT_LINUX_LAPD ||
  		    handle->linktype == DLT_NETLINK ||
  		    (handle->linktype == DLT_EN10MB &&
  		     (strncmp("isdn", device, 4) == 0 ||
  		      strncmp("isdY", device, 4) == 0))) {
  			/*
  			 * Unknown interface type (-1), or a
  			 * device we explicitly chose to run
  			 * in cooked mode (e.g., PPP devices),
  			 * or an ISDN device (whose link-layer
  			 * type we can only determine by using
  			 * APIs that may be different on different
  			 * kernels) - reopen in cooked mode.
  			 */
  			if (close(sock_fd) == -1) {
  				snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  					 "close: %s", pcap_strerror(errno));
  				return PCAP_ERROR;
  			}
  			sock_fd = socket(PF_PACKET, SOCK_DGRAM,
  			    htons(ETH_P_ALL));
  			if (sock_fd == -1) {
  				snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  				    "socket: %s", pcap_strerror(errno));
  				if (errno == EPERM || errno == EACCES) {
  					/*
  					 * You don't have permission to
  					 * open the socket.
  					 */
  					return PCAP_ERROR_PERM_DENIED;
  				} else {
  					/*
  					 * Other error.
  					 */
  					return PCAP_ERROR;
  				}
  			}
  			handlep->cooked = 1;
  
  			/*
  			 * Get rid of any link-layer type list
  			 * we allocated - this only supports cooked
  			 * capture.
  			 */
  			if (handle->dlt_list != NULL) {
  				free(handle->dlt_list);
  				handle->dlt_list = NULL;
  				handle->dlt_count = 0;
  			}
  
  			if (handle->linktype == -1) {
  				/*
  				 * Warn that we're falling back on
  				 * cooked mode; we may want to
  				 * update "map_arphrd_to_dlt()"
  				 * to handle the new type.
  				 */
  				snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  					"arptype %d not "
  					"supported by libpcap - "
  					"falling back to cooked "
  					"socket",
  					arptype);
  			}
  
  			/*
  			 * IrDA capture is not a real "cooked" capture,
  			 * it's IrLAP frames, not IP packets.  The
  			 * same applies to LAPD capture.
  			 */
  			if (handle->linktype != DLT_LINUX_IRDA &&
  			    handle->linktype != DLT_LINUX_LAPD &&
  			    handle->linktype != DLT_NETLINK)
  				handle->linktype = DLT_LINUX_SLL;
  		}
  
  		handlep->ifindex = iface_get_id(sock_fd, device,
  		    handle->errbuf);
  		if (handlep->ifindex == -1) {
  			close(sock_fd);
  			return PCAP_ERROR;
  		}
  
  		if ((err = iface_bind(sock_fd, handlep->ifindex,
  		    handle->errbuf)) != 1) {
  		    	close(sock_fd);
  			if (err < 0)
  				return err;
  			else
  				return 0;	/* try old mechanism */
  		}
  	} else {
  		/*
  		 * The "any" device.
  		 */
  		if (handle->opt.rfmon) {
  			/*
  			 * It doesn't support monitor mode.
  			 */
  			close(sock_fd);
  			return PCAP_ERROR_RFMON_NOTSUP;
  		}
  
  		/*
  		 * It uses cooked mode.
  		 */
  		handlep->cooked = 1;
  		handle->linktype = DLT_LINUX_SLL;
  
  		/*
  		 * We're not bound to a device.
  		 * For now, we're using this as an indication
  		 * that we can't transmit; stop doing that only
  		 * if we figure out how to transmit in cooked
  		 * mode.
  		 */
  		handlep->ifindex = -1;
  	}
  
  	/*
  	 * Select promiscuous mode on if "promisc" is set.
  	 *
  	 * Do not turn allmulti mode on if we don't select
  	 * promiscuous mode - on some devices (e.g., Orinoco
  	 * wireless interfaces), allmulti mode isn't supported
  	 * and the driver implements it by turning promiscuous
  	 * mode on, and that screws up the operation of the
  	 * card as a normal networking interface, and on no
  	 * other platform I know of does starting a non-
  	 * promiscuous capture affect which multicast packets
  	 * are received by the interface.
  	 */
  
  	/*
  	 * Hmm, how can we set promiscuous mode on all interfaces?
  	 * I am not sure if that is possible at all.  For now, we
  	 * silently ignore attempts to turn promiscuous mode on
  	 * for the "any" device (so you don't have to explicitly
  	 * disable it in programs such as tcpdump).
  	 */
  
  	if (!is_any_device && handle->opt.promisc) {
  		memset(&mr, 0, sizeof(mr));
  		mr.mr_ifindex = handlep->ifindex;
  		mr.mr_type    = PACKET_MR_PROMISC;
  		if (setsockopt(sock_fd, SOL_PACKET, PACKET_ADD_MEMBERSHIP,
  		    &mr, sizeof(mr)) == -1) {
  			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  				"setsockopt: %s", pcap_strerror(errno));
  			close(sock_fd);
  			return PCAP_ERROR;
  		}
  	}
  
  	/* Enable auxillary data if supported and reserve room for
  	 * reconstructing VLAN headers. */
  #ifdef HAVE_PACKET_AUXDATA
  	val = 1;
  	if (setsockopt(sock_fd, SOL_PACKET, PACKET_AUXDATA, &val,
  		       sizeof(val)) == -1 && errno != ENOPROTOOPT) {
  		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  			 "setsockopt: %s", pcap_strerror(errno));
  		close(sock_fd);
  		return PCAP_ERROR;
  	}
  	handle->offset += VLAN_TAG_LEN;
  #endif /* HAVE_PACKET_AUXDATA */
  
  	/*
  	 * This is a 2.2[.x] or later kernel (we know that
  	 * because we're not using a SOCK_PACKET socket -
  	 * PF_PACKET is supported only in 2.2 and later
  	 * kernels).
  	 *
  	 * We can safely pass "recvfrom()" a byte count
  	 * based on the snapshot length.
  	 *
  	 * If we're in cooked mode, make the snapshot length
  	 * large enough to hold a "cooked mode" header plus
  	 * 1 byte of packet data (so we don't pass a byte
  	 * count of 0 to "recvfrom()").
  	 */
  	if (handlep->cooked) {
  		if (handle->snapshot < SLL_HDR_LEN + 1)
  			handle->snapshot = SLL_HDR_LEN + 1;
  	}
  	handle->bufsize = handle->snapshot;
  
  	/*
  	 * Set the offset at which to insert VLAN tags.
  	 */
  	switch (handle->linktype) {
  
  	case DLT_EN10MB:
  		handlep->vlan_offset = 2 * ETH_ALEN;
  		break;
  
  	case DLT_LINUX_SLL:
  		handlep->vlan_offset = 14;
  		break;
  
  	default:
  		handlep->vlan_offset = -1; /* unknown */
  		break;
  	}
  
  #if defined(SIOCGSTAMPNS) && defined(SO_TIMESTAMPNS)
  	if (handle->opt.tstamp_precision == PCAP_TSTAMP_PRECISION_NANO) {
  		int nsec_tstamps = 1;
  
  		if (setsockopt(sock_fd, SOL_SOCKET, SO_TIMESTAMPNS, &nsec_tstamps, sizeof(nsec_tstamps)) < 0) {
  			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "setsockopt: unable to set SO_TIMESTAMPNS");
  			close(sock_fd);
  			return PCAP_ERROR;
  		}
  	}
  #endif /* defined(SIOCGSTAMPNS) && defined(SO_TIMESTAMPNS) */
  
  	/*
  	 * We've succeeded. Save the socket FD in the pcap structure.
  	 */
  	handle->fd = sock_fd;
  
  #ifdef SO_BPF_EXTENSIONS
  	/*
  	 * Can we generate special code for VLAN checks?
  	 * (XXX - what if we need the special code but it's not supported
  	 * by the OS?  Is that possible?)
  	 */
  	if (getsockopt(sock_fd, SOL_SOCKET, SO_BPF_EXTENSIONS,
  	    &bpf_extensions, &len) == 0) {
  		if (bpf_extensions >= SKF_AD_VLAN_TAG_PRESENT) {
  			/*
  			 * Yes, we can.  Request that we do so.
  			 */
  			handle->bpf_codegen_flags |= BPF_SPECIAL_VLAN_HANDLING;
  		}
  	}
  #endif /* SO_BPF_EXTENSIONS */
  
  	return 1;
  #else /* HAVE_PF_PACKET_SOCKETS */
  	strlcpy(ebuf,
  		"New packet capturing interface not supported by build "
  		"environment", PCAP_ERRBUF_SIZE);
  	return 0;
  #endif /* HAVE_PF_PACKET_SOCKETS */
  }
  
  #ifdef HAVE_PACKET_RING
  /*
   * Attempt to activate with memory-mapped access.
   *
   * On success, returns 1, and sets *status to 0 if there are no warnings
   * or to a PCAP_WARNING_ code if there is a warning.
   *
   * On failure due to lack of support for memory-mapped capture, returns
   * 0.
   *
   * On error, returns -1, and sets *status to the appropriate error code;
   * if that is PCAP_ERROR, sets handle->errbuf to the appropriate message.
   */
  static int
  activate_mmap(pcap_t *handle, int *status)
  {
  	struct pcap_linux *handlep = handle->priv;
  	int ret;
  
  	/*
  	 * Attempt to allocate a buffer to hold the contents of one
  	 * packet, for use by the oneshot callback.
  	 */
  	handlep->oneshot_buffer = malloc(handle->snapshot);
  	if (handlep->oneshot_buffer == NULL) {
  		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  			 "can't allocate oneshot buffer: %s",
  			 pcap_strerror(errno));
  		*status = PCAP_ERROR;
  		return -1;
  	}
  
  	if (handle->opt.buffer_size == 0) {
  		/* by default request 2M for the ring buffer */
  		handle->opt.buffer_size = 2*1024*1024;
  	}
  	ret = prepare_tpacket_socket(handle);
  	if (ret == -1) {
  		free(handlep->oneshot_buffer);
  		*status = PCAP_ERROR;
  		return ret;
  	}
  	ret = create_ring(handle, status);
  	if (ret == 0) {
  		/*
  		 * We don't support memory-mapped capture; our caller
  		 * will fall back on reading from the socket.
  		 */
  		free(handlep->oneshot_buffer);
  		return 0;
  	}
  	if (ret == -1) {
  		/*
  		 * Error attempting to enable memory-mapped capture;
  		 * fail.  create_ring() has set *status.
  		 */
  		free(handlep->oneshot_buffer);
  		return -1;
  	}
  
  	/*
  	 * Success.  *status has been set either to 0 if there are no
  	 * warnings or to a PCAP_WARNING_ value if there is a warning.
  	 *
  	 * Override some defaults and inherit the other fields from
  	 * activate_new.
  	 * handle->offset is used to get the current position into the rx ring.
  	 * handle->cc is used to store the ring size.
  	 */
  
  	switch (handlep->tp_version) {
  	case TPACKET_V1:
  		handle->read_op = pcap_read_linux_mmap_v1;
  		break;
  	case TPACKET_V1_64:
  		handle->read_op = pcap_read_linux_mmap_v1_64;
  		break;
  #ifdef HAVE_TPACKET2
  	case TPACKET_V2:
  		handle->read_op = pcap_read_linux_mmap_v2;
  		break;
  #endif
  #ifdef HAVE_TPACKET3
  	case TPACKET_V3:
  		handle->read_op = pcap_read_linux_mmap_v3;
  		break;
  #endif
  	}
  	handle->cleanup_op = pcap_cleanup_linux_mmap;
  	handle->setfilter_op = pcap_setfilter_linux_mmap;
  	handle->setnonblock_op = pcap_setnonblock_mmap;
  	handle->getnonblock_op = pcap_getnonblock_mmap;
  	handle->oneshot_callback = pcap_oneshot_mmap;
  	handle->selectable_fd = handle->fd;
  	return 1;
  }
  #else /* HAVE_PACKET_RING */
  static int
  activate_mmap(pcap_t *handle _U_, int *status _U_)
  {
  	return 0;
  }
  #endif /* HAVE_PACKET_RING */
  
  #ifdef HAVE_PACKET_RING
  
  #if defined(HAVE_TPACKET2) || defined(HAVE_TPACKET3)
  /*
   * Attempt to set the socket to the specified version of the memory-mapped
   * header.
   *
   * Return 0 if we succeed; return 1 if we fail because that version isn't
   * supported; return -1 on any other error, and set handle->errbuf.
   */
  static int
  init_tpacket(pcap_t *handle, int version, const char *version_str)
  {
  	struct pcap_linux *handlep = handle->priv;
  	int val = version;
  	socklen_t len = sizeof(val);
  
  	/*
  	 * Probe whether kernel supports the specified TPACKET version;
  	 * this also gets the length of the header for that version.
  	 */
  	if (getsockopt(handle->fd, SOL_PACKET, PACKET_HDRLEN, &val, &len) < 0) {
  		if (errno == ENOPROTOOPT || errno == EINVAL)
  			return 1;	/* no */
  
  		/* Failed to even find out; this is a fatal error. */
  		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  			"can't get %s header len on packet socket: %s",
  			version_str,
  			pcap_strerror(errno));
  		return -1;
  	}
  	handlep->tp_hdrlen = val;
  
  	val = version;
  	if (setsockopt(handle->fd, SOL_PACKET, PACKET_VERSION, &val,
  			   sizeof(val)) < 0) {
  		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  			"can't activate %s on packet socket: %s",
  			version_str,
  			pcap_strerror(errno));
  		return -1;
  	}
  	handlep->tp_version = version;
  
  	/* Reserve space for VLAN tag reconstruction */
  	val = VLAN_TAG_LEN;
  	if (setsockopt(handle->fd, SOL_PACKET, PACKET_RESERVE, &val,
  			   sizeof(val)) < 0) {
  		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  			"can't set up reserve on packet socket: %s",
  			pcap_strerror(errno));
  		return -1;
  	}
  
  	return 0;
  }
  #endif /* defined HAVE_TPACKET2 || defined HAVE_TPACKET3 */
  
  /*
   * If the instruction set for which we're compiling has both 32-bit
   * and 64-bit versions, and Linux support for the 64-bit version
   * predates TPACKET_V2, define ISA_64_BIT as the .machine value
   * you get from uname() for the 64-bit version.  Otherwise, leave
   * it undefined.  (This includes ARM, which has a 64-bit version,
   * but Linux support for it appeared well after TPACKET_V2 support
   * did, so there should never be a case where 32-bit ARM code is
   * running o a 64-bit kernel that only supports TPACKET_V1.)
   *
   * If we've omitted your favorite such architecture, please contribute
   * a patch.  (No patch is needed for architectures that are 32-bit-only
   * or for which Linux has no support for 32-bit userland - or for which,
   * as noted, 64-bit support appeared in Linux after TPACKET_V2 support
   * did.)
   */
  #if defined(__i386__)
  #define ISA_64_BIT	"x86_64"
  #elif defined(__ppc__)
  #define ISA_64_BIT	"ppc64"
  #elif defined(__sparc__)
  #define ISA_64_BIT	"sparc64"
  #elif defined(__s390__)
  #define ISA_64_BIT	"s390x"
  #elif defined(__mips__)
  #define ISA_64_BIT	"mips64"
  #elif defined(__hppa__)
  #define ISA_64_BIT	"parisc64"
  #endif
  
  /*
   * Attempt to set the socket to version 3 of the memory-mapped header and,
   * if that fails because version 3 isn't supported, attempt to fall
   * back to version 2.  If version 2 isn't supported, just leave it at
   * version 1.
   *
   * Return 1 if we succeed or if we fail because neither version 2 nor 3 is
   * supported; return -1 on any other error, and set handle->errbuf.
   */
  static int
  prepare_tpacket_socket(pcap_t *handle)
  {
  	struct pcap_linux *handlep = handle->priv;
  #if defined(HAVE_TPACKET2) || defined(HAVE_TPACKET3)
  	int ret;
  #endif
  
  #ifdef HAVE_TPACKET3
  	/*
  	 * Try setting the version to TPACKET_V3.
  	 *
  	 * The only mode in which buffering is done on PF_PACKET
  	 * sockets, so that packets might not be delivered
  	 * immediately, is TPACKET_V3 mode.
  	 *
  	 * The buffering cannot be disabled in that mode, so
  	 * if the user has requested immediate mode, we don't
  	 * use TPACKET_V3.
  	 */
  	if (!handle->opt.immediate) {
  		ret = init_tpacket(handle, TPACKET_V3, "TPACKET_V3");
  		if (ret == 0) {
  			/*
  			 * Success.
  			 */
  			return 1;
  		}
  		if (ret == -1) {
  			/*
  			 * We failed for some reason other than "the
  			 * kernel doesn't support TPACKET_V3".
  			 */
  			return -1;
  		}
  	}
  #endif /* HAVE_TPACKET3 */
  
  #ifdef HAVE_TPACKET2
  	/*
  	 * Try setting the version to TPACKET_V2.
  	 */
  	ret = init_tpacket(handle, TPACKET_V2, "TPACKET_V2");
  	if (ret == 0) {
  		/*
  		 * Success.
  		 */
  		return 1;
  	}
  	if (ret == -1) {
  		/*
  		 * We failed for some reason other than "the
  		 * kernel doesn't support TPACKET_V2".
  		 */
  		return -1;
  	}
  #endif /* HAVE_TPACKET2 */
  
  	/*
  	 * OK, we're using TPACKET_V1, as that's all the kernel supports.
  	 */
  	handlep->tp_version = TPACKET_V1;
  	handlep->tp_hdrlen = sizeof(struct tpacket_hdr);
  
  #ifdef ISA_64_BIT
  	/*
  	 * 32-bit userspace + 64-bit kernel + TPACKET_V1 are not compatible with
  	 * each other due to platform-dependent data type size differences.
  	 *
  	 * If we have a 32-bit userland and a 64-bit kernel, use an
  	 * internally-defined TPACKET_V1_64, with which we use a 64-bit
  	 * version of the data structures.
  	 */
  	if (sizeof(long) == 4) {
  		/*
  		 * This is 32-bit code.
  		 */
  		struct utsname utsname;
  
  		if (uname(&utsname) == -1) {
  			/*
  			 * Failed.
  			 */
  			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  			    "uname failed: %s", pcap_strerror(errno));
  			return -1;
  		}
  		if (strcmp(utsname.machine, ISA_64_BIT) == 0) {
  			/*
  			 * uname() tells us the machine is 64-bit,
  			 * so we presumably have a 64-bit kernel.
  			 *
  			 * XXX - this presumes that uname() won't lie
  			 * in 32-bit code and claim that the machine
  			 * has the 32-bit version of the ISA.
  			 */
  			handlep->tp_version = TPACKET_V1_64;
  			handlep->tp_hdrlen = sizeof(struct tpacket_hdr_64);
  		}
  	}
  #endif
  
  	return 1;
  }
  
  /*
   * Attempt to set up memory-mapped access.
   *
   * On success, returns 1, and sets *status to 0 if there are no warnings
   * or to a PCAP_WARNING_ code if there is a warning.
   *
   * On failure due to lack of support for memory-mapped capture, returns
   * 0.
   *
   * On error, returns -1, and sets *status to the appropriate error code;
   * if that is PCAP_ERROR, sets handle->errbuf to the appropriate message.
   */
  static int
  create_ring(pcap_t *handle, int *status)
  {
  	struct pcap_linux *handlep = handle->priv;
  	unsigned i, j, frames_per_block;
  #ifdef HAVE_TPACKET3
  	/*
  	 * For sockets using TPACKET_V1 or TPACKET_V2, the extra
  	 * stuff at the end of a struct tpacket_req3 will be
  	 * ignored, so this is OK even for those sockets.
  	 */
  	struct tpacket_req3 req;
  #else
  	struct tpacket_req req;
  #endif
  	socklen_t len;
  	unsigned int sk_type, tp_reserve, maclen, tp_hdrlen, netoff, macoff;
  	unsigned int frame_size;
  
  	/*
  	 * Start out assuming no warnings or errors.
  	 */
  	*status = 0;
  
  	switch (handlep->tp_version) {
  
  	case TPACKET_V1:
  	case TPACKET_V1_64:
  #ifdef HAVE_TPACKET2
  	case TPACKET_V2:
  #endif
  		/* Note that with large snapshot length (say 64K, which is
  		 * the default for recent versions of tcpdump, the value that
  		 * "-s 0" has given for a long time with tcpdump, and the
  		 * default in Wireshark/TShark/dumpcap), if we use the snapshot
  		 * length to calculate the frame length, only a few frames
  		 * will be available in the ring even with pretty
  		 * large ring size (and a lot of memory will be unused).
  		 *
  		 * Ideally, we should choose a frame length based on the
  		 * minimum of the specified snapshot length and the maximum
  		 * packet size.  That's not as easy as it sounds; consider,
  		 * for example, an 802.11 interface in monitor mode, where
  		 * the frame would include a radiotap header, where the
  		 * maximum radiotap header length is device-dependent.
  		 *
  		 * So, for now, we just do this for Ethernet devices, where
  		 * there's no metadata header, and the link-layer header is
  		 * fixed length.  We can get the maximum packet size by
  		 * adding 18, the Ethernet header length plus the CRC length
  		 * (just in case we happen to get the CRC in the packet), to
  		 * the MTU of the interface; we fetch the MTU in the hopes
  		 * that it reflects support for jumbo frames.  (Even if the
  		 * interface is just being used for passive snooping, the
  		 * driver might set the size of buffers in the receive ring
  		 * based on the MTU, so that the MTU limits the maximum size
  		 * of packets that we can receive.)
  		 *
  		 * We don't do that if segmentation/fragmentation or receive
  		 * offload are enabled, so we don't get rudely surprised by
  		 * "packets" bigger than the MTU. */
  		frame_size = handle->snapshot;
  		if (handle->linktype == DLT_EN10MB) {
  			int mtu;
  			int offload;
  
  			offload = iface_get_offload(handle);
  			if (offload == -1) {
  				*status = PCAP_ERROR;
  				return -1;
  			}
  			if (!offload) {
  				mtu = iface_get_mtu(handle->fd, handle->opt.source,
  				    handle->errbuf);
  				if (mtu == -1) {
  					*status = PCAP_ERROR;
  					return -1;
  				}
  				if (frame_size > mtu + 18)
  					frame_size = mtu + 18;
  			}
  		}
  
  		/* NOTE: calculus matching those in tpacket_rcv()
  		 * in linux-2.6/net/packet/af_packet.c
  		 */
  		len = sizeof(sk_type);
  		if (getsockopt(handle->fd, SOL_SOCKET, SO_TYPE, &sk_type,
  		    &len) < 0) {
  			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  			    "getsockopt: %s", pcap_strerror(errno));
  			*status = PCAP_ERROR;
  			return -1;
  		}
  #ifdef PACKET_RESERVE
  		len = sizeof(tp_reserve);
  		if (getsockopt(handle->fd, SOL_PACKET, PACKET_RESERVE,
  		    &tp_reserve, &len) < 0) {
  			if (errno != ENOPROTOOPT) {
  				/*
  				 * ENOPROTOOPT means "kernel doesn't support
  				 * PACKET_RESERVE", in which case we fall back
  				 * as best we can.
  				 */
  				snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  				    "getsockopt: %s", pcap_strerror(errno));
  				*status = PCAP_ERROR;
  				return -1;
  			}
  			tp_reserve = 0;	/* older kernel, reserve not supported */
  		}
  #else
  		tp_reserve = 0;	/* older kernel, reserve not supported */
  #endif
  		maclen = (sk_type == SOCK_DGRAM) ? 0 : MAX_LINKHEADER_SIZE;
  			/* XXX: in the kernel maclen is calculated from
  			 * LL_ALLOCATED_SPACE(dev) and vnet_hdr.hdr_len
  			 * in:  packet_snd()           in linux-2.6/net/packet/af_packet.c
  			 * then packet_alloc_skb()     in linux-2.6/net/packet/af_packet.c
  			 * then sock_alloc_send_pskb() in linux-2.6/net/core/sock.c
  			 * but I see no way to get those sizes in userspace,
  			 * like for instance with an ifreq ioctl();
  			 * the best thing I've found so far is MAX_HEADER in
  			 * the kernel part of linux-2.6/include/linux/netdevice.h
  			 * which goes up to 128+48=176; since pcap-linux.c
  			 * defines a MAX_LINKHEADER_SIZE of 256 which is
  			 * greater than that, let's use it.. maybe is it even
  			 * large enough to directly replace macoff..
  			 */
  		tp_hdrlen = TPACKET_ALIGN(handlep->tp_hdrlen) + sizeof(struct sockaddr_ll) ;
  		netoff = TPACKET_ALIGN(tp_hdrlen + (maclen < 16 ? 16 : maclen)) + tp_reserve;
  			/* NOTE: AFAICS tp_reserve may break the TPACKET_ALIGN
  			 * of netoff, which contradicts
  			 * linux-2.6/Documentation/networking/packet_mmap.txt
  			 * documenting that:
  			 * "- Gap, chosen so that packet data (Start+tp_net)
  			 * aligns to TPACKET_ALIGNMENT=16"
  			 */
  			/* NOTE: in linux-2.6/include/linux/skbuff.h:
  			 * "CPUs often take a performance hit
  			 *  when accessing unaligned memory locations"
  			 */
  		macoff = netoff - maclen;
  		req.tp_frame_size = TPACKET_ALIGN(macoff + frame_size);
  		req.tp_frame_nr = handle->opt.buffer_size/req.tp_frame_size;
  		break;
  
  #ifdef HAVE_TPACKET3
  	case TPACKET_V3:
  		/* The "frames" for this are actually buffers that
  		 * contain multiple variable-sized frames.
  		 *
  		 * We pick a "frame" size of 128K to leave enough
  		 * room for at least one reasonably-sized packet
  		 * in the "frame". */
  		req.tp_frame_size = MAXIMUM_SNAPLEN;
  		req.tp_frame_nr = handle->opt.buffer_size/req.tp_frame_size;
  		break;
  #endif
  	default:
  		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  		    "Internal error: unknown TPACKET_ value %u",
  		    handlep->tp_version);
  		*status = PCAP_ERROR;
  		return -1;
  	}
  
  	/* compute the minumum block size that will handle this frame.
  	 * The block has to be page size aligned.
  	 * The max block size allowed by the kernel is arch-dependent and
  	 * it's not explicitly checked here. */
  	req.tp_block_size = getpagesize();
  	while (req.tp_block_size < req.tp_frame_size)
  		req.tp_block_size <<= 1;
  
  	frames_per_block = req.tp_block_size/req.tp_frame_size;
  
  	/*
  	 * PACKET_TIMESTAMP was added after linux/net_tstamp.h was,
  	 * so we check for PACKET_TIMESTAMP.  We check for
  	 * linux/net_tstamp.h just in case a system somehow has
  	 * PACKET_TIMESTAMP but not linux/net_tstamp.h; that might
  	 * be unnecessary.
  	 *
  	 * SIOCSHWTSTAMP was introduced in the patch that introduced
  	 * linux/net_tstamp.h, so we don't bother checking whether
  	 * SIOCSHWTSTAMP is defined (if your Linux system has
  	 * linux/net_tstamp.h but doesn't define SIOCSHWTSTAMP, your
  	 * Linux system is badly broken).
  	 */
  #if defined(HAVE_LINUX_NET_TSTAMP_H) && defined(PACKET_TIMESTAMP)
  	/*
  	 * If we were told to do so, ask the kernel and the driver
  	 * to use hardware timestamps.
  	 *
  	 * Hardware timestamps are only supported with mmapped
  	 * captures.
  	 */
  	if (handle->opt.tstamp_type == PCAP_TSTAMP_ADAPTER ||
  	    handle->opt.tstamp_type == PCAP_TSTAMP_ADAPTER_UNSYNCED) {
  		struct hwtstamp_config hwconfig;
  		struct ifreq ifr;
  		int timesource;
  
  		/*
  		 * Ask for hardware time stamps on all packets,
  		 * including transmitted packets.
  		 */
  		memset(&hwconfig, 0, sizeof(hwconfig));
  		hwconfig.tx_type = HWTSTAMP_TX_ON;
  		hwconfig.rx_filter = HWTSTAMP_FILTER_ALL;
  
  		memset(&ifr, 0, sizeof(ifr));
  		strlcpy(ifr.ifr_name, handle->opt.source, sizeof(ifr.ifr_name));
  		ifr.ifr_data = (void *)&hwconfig;
  
  		if (ioctl(handle->fd, SIOCSHWTSTAMP, &ifr) < 0) {
  			switch (errno) {
  
  			case EPERM:
  				/*
  				 * Treat this as an error, as the
  				 * user should try to run this
  				 * with the appropriate privileges -
  				 * and, if they can't, shouldn't
  				 * try requesting hardware time stamps.
  				 */
  				*status = PCAP_ERROR_PERM_DENIED;
  				return -1;
  
  			case EOPNOTSUPP:
  				/*
  				 * Treat this as a warning, as the
  				 * only way to fix the warning is to
  				 * get an adapter that supports hardware
  				 * time stamps.  We'll just fall back
  				 * on the standard host time stamps.
  				 */
  				*status = PCAP_WARNING_TSTAMP_TYPE_NOTSUP;
  				break;
  
  			default:
  				snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  					"SIOCSHWTSTAMP failed: %s",
  					pcap_strerror(errno));
  				*status = PCAP_ERROR;
  				return -1;
  			}
  		} else {
  			/*
  			 * Well, that worked.  Now specify the type of
  			 * hardware time stamp we want for this
  			 * socket.
  			 */
  			if (handle->opt.tstamp_type == PCAP_TSTAMP_ADAPTER) {
  				/*
  				 * Hardware timestamp, synchronized
  				 * with the system clock.
  				 */
  				timesource = SOF_TIMESTAMPING_SYS_HARDWARE;
  			} else {
  				/*
  				 * PCAP_TSTAMP_ADAPTER_UNSYNCED - hardware
  				 * timestamp, not synchronized with the
  				 * system clock.
  				 */
  				timesource = SOF_TIMESTAMPING_RAW_HARDWARE;
  			}
  			if (setsockopt(handle->fd, SOL_PACKET, PACKET_TIMESTAMP,
  				(void *)&timesource, sizeof(timesource))) {
  				snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  					"can't set PACKET_TIMESTAMP: %s",
  					pcap_strerror(errno));
  				*status = PCAP_ERROR;
  				return -1;
  			}
  		}
  	}
  #endif /* HAVE_LINUX_NET_TSTAMP_H && PACKET_TIMESTAMP */
  
  	/* ask the kernel to create the ring */
  retry:
  	req.tp_block_nr = req.tp_frame_nr / frames_per_block;
  
  	/* req.tp_frame_nr is requested to match frames_per_block*req.tp_block_nr */
  	req.tp_frame_nr = req.tp_block_nr * frames_per_block;
  
  #ifdef HAVE_TPACKET3
  	/* timeout value to retire block - use the configured buffering timeout, or default if <0. */
  	req.tp_retire_blk_tov = (handlep->timeout>=0)?handlep->timeout:0;
  	/* private data not used */
  	req.tp_sizeof_priv = 0;
  	/* Rx ring - feature request bits - none (rxhash will not be filled) */
  	req.tp_feature_req_word = 0;
  #endif
  
  	if (setsockopt(handle->fd, SOL_PACKET, PACKET_RX_RING,
  					(void *) &req, sizeof(req))) {
  		if ((errno == ENOMEM) && (req.tp_block_nr > 1)) {
  			/*
  			 * Memory failure; try to reduce the requested ring
  			 * size.
  			 *
  			 * We used to reduce this by half -- do 5% instead.
  			 * That may result in more iterations and a longer
  			 * startup, but the user will be much happier with
  			 * the resulting buffer size.
  			 */
  			if (req.tp_frame_nr < 20)
  				req.tp_frame_nr -= 1;
  			else
  				req.tp_frame_nr -= req.tp_frame_nr/20;
  			goto retry;
  		}
  		if (errno == ENOPROTOOPT) {
  			/*
  			 * We don't have ring buffer support in this kernel.
  			 */
  			return 0;
  		}
  		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  		    "can't create rx ring on packet socket: %s",
  		    pcap_strerror(errno));
  		*status = PCAP_ERROR;
  		return -1;
  	}
  
  	/* memory map the rx ring */
  	handlep->mmapbuflen = req.tp_block_nr * req.tp_block_size;
  	handlep->mmapbuf = mmap(0, handlep->mmapbuflen,
  	    PROT_READ|PROT_WRITE, MAP_SHARED, handle->fd, 0);
  	if (handlep->mmapbuf == MAP_FAILED) {
  		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  		    "can't mmap rx ring: %s", pcap_strerror(errno));
  
  		/* clear the allocated ring on error*/
  		destroy_ring(handle);
  		*status = PCAP_ERROR;
  		return -1;
  	}
  
  	/* allocate a ring for each frame header pointer*/
  	handle->cc = req.tp_frame_nr;
  	handle->buffer = malloc(handle->cc * sizeof(union thdr *));
  	if (!handle->buffer) {
  		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  		    "can't allocate ring of frame headers: %s",
  		    pcap_strerror(errno));
  
  		destroy_ring(handle);
  		*status = PCAP_ERROR;
  		return -1;
  	}
  
  	/* fill the header ring with proper frame ptr*/
  	handle->offset = 0;
  	for (i=0; i<req.tp_block_nr; ++i) {
  		void *base = &handlep->mmapbuf[i*req.tp_block_size];
  		for (j=0; j<frames_per_block; ++j, ++handle->offset) {
  			RING_GET_FRAME(handle) = base;
  			base += req.tp_frame_size;
  		}
  	}
  
  	handle->bufsize = req.tp_frame_size;
  	handle->offset = 0;
  	return 1;
  }
  
  /* free all ring related resources*/
  static void
  destroy_ring(pcap_t *handle)
  {
  	struct pcap_linux *handlep = handle->priv;
  
  	/* tell the kernel to destroy the ring*/
  	struct tpacket_req req;
  	memset(&req, 0, sizeof(req));
  	/* do not test for setsockopt failure, as we can't recover from any error */
  	(void)setsockopt(handle->fd, SOL_PACKET, PACKET_RX_RING,
  				(void *) &req, sizeof(req));
  
  	/* if ring is mapped, unmap it*/
  	if (handlep->mmapbuf) {
  		/* do not test for mmap failure, as we can't recover from any error */
  		(void)munmap(handlep->mmapbuf, handlep->mmapbuflen);
  		handlep->mmapbuf = NULL;
  	}
  }
  
  /*
   * Special one-shot callback, used for pcap_next() and pcap_next_ex(),
   * for Linux mmapped capture.
   *
   * The problem is that pcap_next() and pcap_next_ex() expect the packet
   * data handed to the callback to be valid after the callback returns,
   * but pcap_read_linux_mmap() has to release that packet as soon as
   * the callback returns (otherwise, the kernel thinks there's still
   * at least one unprocessed packet available in the ring, so a select()
   * will immediately return indicating that there's data to process), so,
   * in the callback, we have to make a copy of the packet.
   *
   * Yes, this means that, if the capture is using the ring buffer, using
   * pcap_next() or pcap_next_ex() requires more copies than using
   * pcap_loop() or pcap_dispatch().  If that bothers you, don't use
   * pcap_next() or pcap_next_ex().
   */
  static void
  pcap_oneshot_mmap(u_char *user, const struct pcap_pkthdr *h,
      const u_char *bytes)
  {
  	struct oneshot_userdata *sp = (struct oneshot_userdata *)user;
  	pcap_t *handle = sp->pd;
  	struct pcap_linux *handlep = handle->priv;
  
  	*sp->hdr = *h;
  	memcpy(handlep->oneshot_buffer, bytes, h->caplen);
  	*sp->pkt = handlep->oneshot_buffer;
  }
  
  static void
  pcap_cleanup_linux_mmap( pcap_t *handle )
  {
  	struct pcap_linux *handlep = handle->priv;
  
  	destroy_ring(handle);
  	if (handlep->oneshot_buffer != NULL) {
  		free(handlep->oneshot_buffer);
  		handlep->oneshot_buffer = NULL;
  	}
  	pcap_cleanup_linux(handle);
  }
  
  
  static int
  pcap_getnonblock_mmap(pcap_t *p, char *errbuf)
  {
  	struct pcap_linux *handlep = p->priv;
  
  	/* use negative value of timeout to indicate non blocking ops */
  	return (handlep->timeout<0);
  }
  
  static int
  pcap_setnonblock_mmap(pcap_t *p, int nonblock, char *errbuf)
  {
  	struct pcap_linux *handlep = p->priv;
  
  	/*
  	 * Set the file descriptor to non-blocking mode, as we use
  	 * it for sending packets.
  	 */
  	if (pcap_setnonblock_fd(p, nonblock, errbuf) == -1)
  		return -1;
  
  	/*
  	 * Map each value to their corresponding negation to
  	 * preserve the timeout value provided with pcap_set_timeout.
  	 */
  	if (nonblock) {
  		if (handlep->timeout >= 0) {
  			/*
  			 * Indicate that we're switching to
  			 * non-blocking mode.
  			 */
  			handlep->timeout = ~handlep->timeout;
  		}
  	} else {
  		if (handlep->timeout < 0) {
  			handlep->timeout = ~handlep->timeout;
  		}
  	}
  	return 0;
  }
  
  static inline union thdr *
  pcap_get_ring_frame(pcap_t *handle, int status)
  {
  	struct pcap_linux *handlep = handle->priv;
  	union thdr h;
  
  	h.raw = RING_GET_FRAME(handle);
  	switch (handlep->tp_version) {
  	case TPACKET_V1:
  		if (status != (h.h1->tp_status ? TP_STATUS_USER :
  						TP_STATUS_KERNEL))
  			return NULL;
  		break;
  	case TPACKET_V1_64:
  		if (status != (h.h1_64->tp_status ? TP_STATUS_USER :
  						TP_STATUS_KERNEL))
  			return NULL;
  		break;
  #ifdef HAVE_TPACKET2
  	case TPACKET_V2:
  		if (status != (h.h2->tp_status ? TP_STATUS_USER :
  						TP_STATUS_KERNEL))
  			return NULL;
  		break;
  #endif
  #ifdef HAVE_TPACKET3
  	case TPACKET_V3:
  		if (status != (h.h3->hdr.bh1.block_status ? TP_STATUS_USER :
  						TP_STATUS_KERNEL))
  			return NULL;
  		break;
  #endif
  	}
  	return h.raw;
  }
  
  #ifndef POLLRDHUP
  #define POLLRDHUP 0
  #endif
  
  /* wait for frames availability.*/
  static int pcap_wait_for_frames_mmap(pcap_t *handle)
  {
  	if (!pcap_get_ring_frame(handle, TP_STATUS_USER)) {
  		struct pcap_linux *handlep = handle->priv;
  		int timeout;
  		char c;
  		struct pollfd pollinfo;
  		int ret;
  
  		pollinfo.fd = handle->fd;
  		pollinfo.events = POLLIN;
  
  		if (handlep->timeout == 0) {
  #ifdef HAVE_TPACKET3
  			/*
  			 * XXX - due to a set of (mis)features in the
  			 * TPACKET_V3 kernel code, blocking forever with
  			 * a TPACKET_V3 socket can, if few packets
  			 * are arriving and passing the socket filter,
  			 * cause most packets to be dropped.  See
  			 * libpcap issue #335 for the full painful
  			 * story.  The workaround is to have poll()
  			 * time out very quickly, so we grab the
  			 * frames handed to us, and return them to
  			 * the kernel, ASAP.
  			 *
  			 * If those issues are ever fixed, we might
  			 * want to check the kernel version and block
  			 * forever with TPACKET_V3 if we're running
  			 * with a kernel that has the fix.
  			 */
  			if (handlep->tp_version == TPACKET_V3)
  				timeout = 1;	/* don't block for very long */
  			else
  #endif
  				timeout = -1;	/* block forever */
  		} else if (handlep->timeout > 0)
  			timeout = handlep->timeout;	/* block for that amount of time */
  		else
  			timeout = 0;	/* non-blocking mode - poll to pick up errors */
  		do {
  			ret = poll(&pollinfo, 1, timeout);
  			if (ret < 0 && errno != EINTR) {
  				snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  					"can't poll on packet socket: %s",
  					pcap_strerror(errno));
  				return PCAP_ERROR;
  			} else if (ret > 0 &&
  				(pollinfo.revents & (POLLHUP|POLLRDHUP|POLLERR|POLLNVAL))) {
  				/*
  				 * There's some indication other than
  				 * "you can read on this descriptor" on
  				 * the descriptor.
  				 */
  				if (pollinfo.revents & (POLLHUP | POLLRDHUP)) {
  					snprintf(handle->errbuf,
  						PCAP_ERRBUF_SIZE,
  						"Hangup on packet socket");
  					return PCAP_ERROR;
  				}
  				if (pollinfo.revents & POLLERR) {
  					/*
  					 * A recv() will give us the
  					 * actual error code.
  					 *
  					 * XXX - make the socket non-blocking?
  					 */
  					if (recv(handle->fd, &c, sizeof c,
  						MSG_PEEK) != -1)
  						continue;	/* what, no error? */
  					if (errno == ENETDOWN) {
  						/*
  						 * The device on which we're
  						 * capturing went away.
  						 *
  						 * XXX - we should really return
  						 * PCAP_ERROR_IFACE_NOT_UP,
  						 * but pcap_dispatch() etc.
  						 * aren't defined to return
  						 * that.
  						 */
  						snprintf(handle->errbuf,
  							PCAP_ERRBUF_SIZE,
  							"The interface went down");
  					} else {
  						snprintf(handle->errbuf,
  							PCAP_ERRBUF_SIZE,
  							"Error condition on packet socket: %s",
  							strerror(errno));
  					}
  					return PCAP_ERROR;
  				}
  				if (pollinfo.revents & POLLNVAL) {
  					snprintf(handle->errbuf,
  						PCAP_ERRBUF_SIZE,
  						"Invalid polling request on packet socket");
  					return PCAP_ERROR;
  				}
  			}
  			/* check for break loop condition on interrupted syscall*/
  			if (handle->break_loop) {
  				handle->break_loop = 0;
  				return PCAP_ERROR_BREAK;
  			}
  		} while (ret < 0);
  	}
  	return 0;
  }
  
  /* handle a single memory mapped packet */
  static int pcap_handle_packet_mmap(
  		pcap_t *handle,
  		pcap_handler callback,
  		u_char *user,
  		unsigned char *frame,
  		unsigned int tp_len,
  		unsigned int tp_mac,
  		unsigned int tp_snaplen,
  		unsigned int tp_sec,
  		unsigned int tp_usec,
  		int tp_vlan_tci_valid,
  		__u16 tp_vlan_tci,
  		__u16 tp_vlan_tpid)
  {
  	struct pcap_linux *handlep = handle->priv;
  	unsigned char *bp;
  	struct sockaddr_ll *sll;
  	struct pcap_pkthdr pcaphdr;
  
  	/* perform sanity check on internal offset. */
  	if (tp_mac + tp_snaplen > handle->bufsize) {
  		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  			"corrupted frame on kernel ring mac "
  			"offset %u + caplen %u > frame len %d",
  			tp_mac, tp_snaplen, handle->bufsize);
  		return -1;
  	}
  
  	/* run filter on received packet
  	 * If the kernel filtering is enabled we need to run the
  	 * filter until all the frames present into the ring
  	 * at filter creation time are processed.
  	 * In this case, blocks_to_filter_in_userland is used
  	 * as a counter for the packet we need to filter.
  	 * Note: alternatively it could be possible to stop applying
  	 * the filter when the ring became empty, but it can possibly
  	 * happen a lot later... */
  	bp = frame + tp_mac;
  
  	/* if required build in place the sll header*/
  	sll = (void *)frame + TPACKET_ALIGN(handlep->tp_hdrlen);
  	if (handlep->cooked) {
  		struct sll_header *hdrp;
  
  		/*
  		 * The kernel should have left us with enough
  		 * space for an sll header; back up the packet
  		 * data pointer into that space, as that'll be
  		 * the beginning of the packet we pass to the
  		 * callback.
  		 */
  		bp -= SLL_HDR_LEN;
  
  		/*
  		 * Let's make sure that's past the end of
  		 * the tpacket header, i.e. >=
  		 * ((u_char *)thdr + TPACKET_HDRLEN), so we
  		 * don't step on the header when we construct
  		 * the sll header.
  		 */
  		if (bp < (u_char *)frame +
  				   TPACKET_ALIGN(handlep->tp_hdrlen) +
  				   sizeof(struct sockaddr_ll)) {
  			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  				"cooked-mode frame doesn't have room for sll header");
  			return -1;
  		}
  
  		/*
  		 * OK, that worked; construct the sll header.
  		 */
  		hdrp = (struct sll_header *)bp;
  		hdrp->sll_pkttype = map_packet_type_to_sll_type(
  						sll->sll_pkttype);
  		hdrp->sll_hatype = htons(sll->sll_hatype);
  		hdrp->sll_halen = htons(sll->sll_halen);
  		memcpy(hdrp->sll_addr, sll->sll_addr, SLL_ADDRLEN);
  		hdrp->sll_protocol = sll->sll_protocol;
  	}
  
  	if (handlep->filter_in_userland && handle->fcode.bf_insns) {
  		struct bpf_aux_data aux_data;
  
  		aux_data.vlan_tag = tp_vlan_tci & 0x0fff;
  		aux_data.vlan_tag_present = tp_vlan_tci_valid;
  
  		if (bpf_filter_with_aux_data(handle->fcode.bf_insns, bp,
  		    tp_len, tp_snaplen, &aux_data) == 0)
  			return 0;
  	}
  
  	if (!linux_check_direction(handle, sll))
  		return 0;
  
  	/* get required packet info from ring header */
  	pcaphdr.ts.tv_sec = tp_sec;
  	pcaphdr.ts.tv_usec = tp_usec;
  	pcaphdr.caplen = tp_snaplen;
  	pcaphdr.len = tp_len;
  
  	/* if required build in place the sll header*/
  	if (handlep->cooked) {
  		/* update packet len */
  		pcaphdr.caplen += SLL_HDR_LEN;
  		pcaphdr.len += SLL_HDR_LEN;
  	}
  
  #if defined(HAVE_TPACKET2) || defined(HAVE_TPACKET3)
  	if (tp_vlan_tci_valid &&
  		handlep->vlan_offset != -1 &&
  		tp_snaplen >= (unsigned int) handlep->vlan_offset)
  	{
  		struct vlan_tag *tag;
  
  		bp -= VLAN_TAG_LEN;
  		memmove(bp, bp + VLAN_TAG_LEN, handlep->vlan_offset);
  
  		tag = (struct vlan_tag *)(bp + handlep->vlan_offset);
  		tag->vlan_tpid = htons(tp_vlan_tpid);
  		tag->vlan_tci = htons(tp_vlan_tci);
  
  		pcaphdr.caplen += VLAN_TAG_LEN;
  		pcaphdr.len += VLAN_TAG_LEN;
  	}
  #endif
  
  	/*
  	 * The only way to tell the kernel to cut off the
  	 * packet at a snapshot length is with a filter program;
  	 * if there's no filter program, the kernel won't cut
  	 * the packet off.
  	 *
  	 * Trim the snapshot length to be no longer than the
  	 * specified snapshot length.
  	 */
  	if (pcaphdr.caplen > handle->snapshot)
  		pcaphdr.caplen = handle->snapshot;
  
  	/* pass the packet to the user */
  	callback(user, &pcaphdr, bp);
  
  	return 1;
  }
  
  static int
  pcap_read_linux_mmap_v1(pcap_t *handle, int max_packets, pcap_handler callback,
  		u_char *user)
  {
  	struct pcap_linux *handlep = handle->priv;
  	int pkts = 0;
  	int ret;
  
  	/* wait for frames availability.*/
  	ret = pcap_wait_for_frames_mmap(handle);
  	if (ret) {
  		return ret;
  	}
  
  	/* non-positive values of max_packets are used to require all
  	 * packets currently available in the ring */
  	while ((pkts < max_packets) || PACKET_COUNT_IS_UNLIMITED(max_packets)) {
  		union thdr h;
  
  		h.raw = pcap_get_ring_frame(handle, TP_STATUS_USER);
  		if (!h.raw)
  			break;
  
  		ret = pcap_handle_packet_mmap(
  				handle,
  				callback,
  				user,
  				h.raw,
  				h.h1->tp_len,
  				h.h1->tp_mac,
  				h.h1->tp_snaplen,
  				h.h1->tp_sec,
  				h.h1->tp_usec,
  				0,
  				0,
  				0);
  		if (ret == 1) {
  			pkts++;
  			handlep->packets_read++;
  		} else if (ret < 0) {
  			return ret;
  		}
  
  		/*
  		 * Hand this block back to the kernel, and, if we're
  		 * counting blocks that need to be filtered in userland
  		 * after having been filtered by the kernel, count
  		 * the one we've just processed.
  		 */
  		h.h1->tp_status = TP_STATUS_KERNEL;
  		if (handlep->blocks_to_filter_in_userland > 0) {
  			handlep->blocks_to_filter_in_userland--;
  			if (handlep->blocks_to_filter_in_userland == 0) {
  				/*
  				 * No more blocks need to be filtered
  				 * in userland.
  				 */
  				handlep->filter_in_userland = 0;
  			}
  		}
  
  		/* next block */
  		if (++handle->offset >= handle->cc)
  			handle->offset = 0;
  
  		/* check for break loop condition*/
  		if (handle->break_loop) {
  			handle->break_loop = 0;
  			return PCAP_ERROR_BREAK;
  		}
  	}
  	return pkts;
  }
  
  static int
  pcap_read_linux_mmap_v1_64(pcap_t *handle, int max_packets, pcap_handler callback,
  		u_char *user)
  {
  	struct pcap_linux *handlep = handle->priv;
  	int pkts = 0;
  	int ret;
  
  	/* wait for frames availability.*/
  	ret = pcap_wait_for_frames_mmap(handle);
  	if (ret) {
  		return ret;
  	}
  
  	/* non-positive values of max_packets are used to require all
  	 * packets currently available in the ring */
  	while ((pkts < max_packets) || PACKET_COUNT_IS_UNLIMITED(max_packets)) {
  		union thdr h;
  
  		h.raw = pcap_get_ring_frame(handle, TP_STATUS_USER);
  		if (!h.raw)
  			break;
  
  		ret = pcap_handle_packet_mmap(
  				handle,
  				callback,
  				user,
  				h.raw,
  				h.h1_64->tp_len,
  				h.h1_64->tp_mac,
  				h.h1_64->tp_snaplen,
  				h.h1_64->tp_sec,
  				h.h1_64->tp_usec,
  				0,
  				0,
  				0);
  		if (ret == 1) {
  			pkts++;
  			handlep->packets_read++;
  		} else if (ret < 0) {
  			return ret;
  		}
  
  		/*
  		 * Hand this block back to the kernel, and, if we're
  		 * counting blocks that need to be filtered in userland
  		 * after having been filtered by the kernel, count
  		 * the one we've just processed.
  		 */
  		h.h1_64->tp_status = TP_STATUS_KERNEL;
  		if (handlep->blocks_to_filter_in_userland > 0) {
  			handlep->blocks_to_filter_in_userland--;
  			if (handlep->blocks_to_filter_in_userland == 0) {
  				/*
  				 * No more blocks need to be filtered
  				 * in userland.
  				 */
  				handlep->filter_in_userland = 0;
  			}
  		}
  
  		/* next block */
  		if (++handle->offset >= handle->cc)
  			handle->offset = 0;
  
  		/* check for break loop condition*/
  		if (handle->break_loop) {
  			handle->break_loop = 0;
  			return PCAP_ERROR_BREAK;
  		}
  	}
  	return pkts;
  }
  
  #ifdef HAVE_TPACKET2
  static int
  pcap_read_linux_mmap_v2(pcap_t *handle, int max_packets, pcap_handler callback,
  		u_char *user)
  {
  	struct pcap_linux *handlep = handle->priv;
  	int pkts = 0;
  	int ret;
  
  	/* wait for frames availability.*/
  	ret = pcap_wait_for_frames_mmap(handle);
  	if (ret) {
  		return ret;
  	}
  
  	/* non-positive values of max_packets are used to require all
  	 * packets currently available in the ring */
  	while ((pkts < max_packets) || PACKET_COUNT_IS_UNLIMITED(max_packets)) {
  		union thdr h;
  
  		h.raw = pcap_get_ring_frame(handle, TP_STATUS_USER);
  		if (!h.raw)
  			break;
  
  		ret = pcap_handle_packet_mmap(
  				handle,
  				callback,
  				user,
  				h.raw,
  				h.h2->tp_len,
  				h.h2->tp_mac,
  				h.h2->tp_snaplen,
  				h.h2->tp_sec,
  				handle->opt.tstamp_precision == PCAP_TSTAMP_PRECISION_NANO ? h.h2->tp_nsec : h.h2->tp_nsec / 1000,
  #if defined(TP_STATUS_VLAN_VALID)
  				(h.h2->tp_vlan_tci || (h.h2->tp_status & TP_STATUS_VLAN_VALID)),
  #else
  				h.h2->tp_vlan_tci != 0,
  #endif
  				h.h2->tp_vlan_tci,
  				VLAN_TPID(h.h2, h.h2));
  		if (ret == 1) {
  			pkts++;
  			handlep->packets_read++;
  		} else if (ret < 0) {
  			return ret;
  		}
  
  		/*
  		 * Hand this block back to the kernel, and, if we're
  		 * counting blocks that need to be filtered in userland
  		 * after having been filtered by the kernel, count
  		 * the one we've just processed.
  		 */
  		h.h2->tp_status = TP_STATUS_KERNEL;
  		if (handlep->blocks_to_filter_in_userland > 0) {
  			handlep->blocks_to_filter_in_userland--;
  			if (handlep->blocks_to_filter_in_userland == 0) {
  				/*
  				 * No more blocks need to be filtered
  				 * in userland.
  				 */
  				handlep->filter_in_userland = 0;
  			}
  		}
  
  		/* next block */
  		if (++handle->offset >= handle->cc)
  			handle->offset = 0;
  
  		/* check for break loop condition*/
  		if (handle->break_loop) {
  			handle->break_loop = 0;
  			return PCAP_ERROR_BREAK;
  		}
  	}
  	return pkts;
  }
  #endif /* HAVE_TPACKET2 */
  
  #ifdef HAVE_TPACKET3
  static int
  pcap_read_linux_mmap_v3(pcap_t *handle, int max_packets, pcap_handler callback,
  		u_char *user)
  {
  	struct pcap_linux *handlep = handle->priv;
  	union thdr h;
  	int pkts = 0;
  	int ret;
  
  again:
  	if (handlep->current_packet == NULL) {
  		/* wait for frames availability.*/
  		ret = pcap_wait_for_frames_mmap(handle);
  		if (ret) {
  			return ret;
  		}
  	}
  	h.raw = pcap_get_ring_frame(handle, TP_STATUS_USER);
  	if (!h.raw) {
  		if (pkts == 0 && handlep->timeout == 0) {
  			/* Block until we see a packet. */
  			goto again;
  		}
  		return pkts;
  	}
  
  	/* non-positive values of max_packets are used to require all
  	 * packets currently available in the ring */
  	while ((pkts < max_packets) || PACKET_COUNT_IS_UNLIMITED(max_packets)) {
  		if (handlep->current_packet == NULL) {
  			h.raw = pcap_get_ring_frame(handle, TP_STATUS_USER);
  			if (!h.raw)
  				break;
  
  			handlep->current_packet = h.raw + h.h3->hdr.bh1.offset_to_first_pkt;
  			handlep->packets_left = h.h3->hdr.bh1.num_pkts;
  		}
  		int packets_to_read = handlep->packets_left;
  
  		if (!PACKET_COUNT_IS_UNLIMITED(max_packets) && packets_to_read > max_packets) {
  			packets_to_read = max_packets;
  		}
  
  		while(packets_to_read--) {
  			struct tpacket3_hdr* tp3_hdr = (struct tpacket3_hdr*) handlep->current_packet;
  			ret = pcap_handle_packet_mmap(
  					handle,
  					callback,
  					user,
  					handlep->current_packet,
  					tp3_hdr->tp_len,
  					tp3_hdr->tp_mac,
  					tp3_hdr->tp_snaplen,
  					tp3_hdr->tp_sec,
  					handle->opt.tstamp_precision == PCAP_TSTAMP_PRECISION_NANO ? tp3_hdr->tp_nsec : tp3_hdr->tp_nsec / 1000,
  #if defined(TP_STATUS_VLAN_VALID)
  					(tp3_hdr->hv1.tp_vlan_tci || (tp3_hdr->tp_status & TP_STATUS_VLAN_VALID)),
  #else
  					tp3_hdr->hv1.tp_vlan_tci != 0,
  #endif
  					tp3_hdr->hv1.tp_vlan_tci,
  					VLAN_TPID(tp3_hdr, &tp3_hdr->hv1));
  			if (ret == 1) {
  				pkts++;
  				handlep->packets_read++;
  			} else if (ret < 0) {
  				handlep->current_packet = NULL;
  				return ret;
  			}
  			handlep->current_packet += tp3_hdr->tp_next_offset;
  			handlep->packets_left--;
  		}
  
  		if (handlep->packets_left <= 0) {
  			/*
  			 * Hand this block back to the kernel, and, if
  			 * we're counting blocks that need to be
  			 * filtered in userland after having been
  			 * filtered by the kernel, count the one we've
  			 * just processed.
  			 */
  			h.h3->hdr.bh1.block_status = TP_STATUS_KERNEL;
  			if (handlep->blocks_to_filter_in_userland > 0) {
  				handlep->blocks_to_filter_in_userland--;
  				if (handlep->blocks_to_filter_in_userland == 0) {
  					/*
  					 * No more blocks need to be filtered
  					 * in userland.
  					 */
  					handlep->filter_in_userland = 0;
  				}
  			}
  
  			/* next block */
  			if (++handle->offset >= handle->cc)
  				handle->offset = 0;
  
  			handlep->current_packet = NULL;
  		}
  
  		/* check for break loop condition*/
  		if (handle->break_loop) {
  			handle->break_loop = 0;
  			return PCAP_ERROR_BREAK;
  		}
  	}
  	if (pkts == 0 && handlep->timeout == 0) {
  		/* Block until we see a packet. */
  		goto again;
  	}
  	return pkts;
  }
  #endif /* HAVE_TPACKET3 */
  
  static int
  pcap_setfilter_linux_mmap(pcap_t *handle, struct bpf_program *filter)
  {
  	struct pcap_linux *handlep = handle->priv;
  	int n, offset;
  	int ret;
  
  	/*
  	 * Don't rewrite "ret" instructions; we don't need to, as
  	 * we're not reading packets with recvmsg(), and we don't
  	 * want to, as, by not rewriting them, the kernel can avoid
  	 * copying extra data.
  	 */
  	ret = pcap_setfilter_linux_common(handle, filter, 1);
  	if (ret < 0)
  		return ret;
  
  	/*
  	 * If we're filtering in userland, there's nothing to do;
  	 * the new filter will be used for the next packet.
  	 */
  	if (handlep->filter_in_userland)
  		return ret;
  
  	/*
  	 * We're filtering in the kernel; the packets present in
  	 * all blocks currently in the ring were already filtered
  	 * by the old filter, and so will need to be filtered in
  	 * userland by the new filter.
  	 *
  	 * Get an upper bound for the number of such blocks; first,
  	 * walk the ring backward and count the free blocks.
  	 */
  	offset = handle->offset;
  	if (--handle->offset < 0)
  		handle->offset = handle->cc - 1;
  	for (n=0; n < handle->cc; ++n) {
  		if (--handle->offset < 0)
  			handle->offset = handle->cc - 1;
  		if (!pcap_get_ring_frame(handle, TP_STATUS_KERNEL))
  			break;
  	}
  
  	/*
  	 * If we found free blocks, decrement the count of free
  	 * blocks by 1, just in case we lost a race with another
  	 * thread of control that was adding a packet while
  	 * we were counting and that had run the filter before
  	 * we changed it.
  	 *
  	 * XXX - could there be more than one block added in
  	 * this fashion?
  	 *
  	 * XXX - is there a way to avoid that race, e.g. somehow
  	 * wait for all packets that passed the old filter to
  	 * be added to the ring?
  	 */
  	if (n != 0)
  		n--;
  
  	/* be careful to not change current ring position */
  	handle->offset = offset;
  
  	/*
  	 * Set the count of blocks worth of packets to filter
  	 * in userland to the total number of blocks in the
  	 * ring minus the number of free blocks we found, and
  	 * turn on userland filtering.  (The count of blocks
  	 * worth of packets to filter in userland is guaranteed
  	 * not to be zero - n, above, couldn't be set to a
  	 * value > handle->cc, and if it were equal to
  	 * handle->cc, it wouldn't be zero, and thus would
  	 * be decremented to handle->cc - 1.)
  	 */
  	handlep->blocks_to_filter_in_userland = handle->cc - n;
  	handlep->filter_in_userland = 1;
  	return ret;
  }
  
  #endif /* HAVE_PACKET_RING */
  
  
  #ifdef HAVE_PF_PACKET_SOCKETS
  /*
   *  Return the index of the given device name. Fill ebuf and return
   *  -1 on failure.
   */
  static int
  iface_get_id(int fd, const char *device, char *ebuf)
  {
  	struct ifreq	ifr;
  
  	memset(&ifr, 0, sizeof(ifr));
  	strlcpy(ifr.ifr_name, device, sizeof(ifr.ifr_name));
  
  	if (ioctl(fd, SIOCGIFINDEX, &ifr) == -1) {
  		snprintf(ebuf, PCAP_ERRBUF_SIZE,
  			 "SIOCGIFINDEX: %s", pcap_strerror(errno));
  		return -1;
  	}
  
  	return ifr.ifr_ifindex;
  }
  
  /*
   *  Bind the socket associated with FD to the given device.
   *  Return 1 on success, 0 if we should try a SOCK_PACKET socket,
   *  or a PCAP_ERROR_ value on a hard error.
   */
  static int
  iface_bind(int fd, int ifindex, char *ebuf)
  {
  	struct sockaddr_ll	sll;
  	int			err;
  	socklen_t		errlen = sizeof(err);
  
  	memset(&sll, 0, sizeof(sll));
  	sll.sll_family		= AF_PACKET;
  	sll.sll_ifindex		= ifindex;
  	sll.sll_protocol	= htons(ETH_P_ALL);
  
  	if (bind(fd, (struct sockaddr *) &sll, sizeof(sll)) == -1) {
  		if (errno == ENETDOWN) {
  			/*
  			 * Return a "network down" indication, so that
  			 * the application can report that rather than
  			 * saying we had a mysterious failure and
  			 * suggest that they report a problem to the
  			 * libpcap developers.
  			 */
  			return PCAP_ERROR_IFACE_NOT_UP;
  		} else {
  			snprintf(ebuf, PCAP_ERRBUF_SIZE,
  				 "bind: %s", pcap_strerror(errno));
  			return PCAP_ERROR;
  		}
  	}
  
  	/* Any pending errors, e.g., network is down? */
  
  	if (getsockopt(fd, SOL_SOCKET, SO_ERROR, &err, &errlen) == -1) {
  		snprintf(ebuf, PCAP_ERRBUF_SIZE,
  			"getsockopt: %s", pcap_strerror(errno));
  		return 0;
  	}
  
  	if (err == ENETDOWN) {
  		/*
  		 * Return a "network down" indication, so that
  		 * the application can report that rather than
  		 * saying we had a mysterious failure and
  		 * suggest that they report a problem to the
  		 * libpcap developers.
  		 */
  		return PCAP_ERROR_IFACE_NOT_UP;
  	} else if (err > 0) {
  		snprintf(ebuf, PCAP_ERRBUF_SIZE,
  			"bind: %s", pcap_strerror(err));
  		return 0;
  	}
  
  	return 1;
  }
  
  #ifdef IW_MODE_MONITOR
  /*
   * Check whether the device supports the Wireless Extensions.
   * Returns 1 if it does, 0 if it doesn't, PCAP_ERROR_NO_SUCH_DEVICE
   * if the device doesn't even exist.
   */
  static int
  has_wext(int sock_fd, const char *device, char *ebuf)
  {
  	struct iwreq ireq;
  
  	if (is_bonding_device(sock_fd, device))
  		return 0;	/* bonding device, so don't even try */
  
  	strlcpy(ireq.ifr_ifrn.ifrn_name, device,
  	    sizeof ireq.ifr_ifrn.ifrn_name);
  	if (ioctl(sock_fd, SIOCGIWNAME, &ireq) >= 0)
  		return 1;	/* yes */
  	snprintf(ebuf, PCAP_ERRBUF_SIZE,
  	    "%s: SIOCGIWNAME: %s", device, pcap_strerror(errno));
  	if (errno == ENODEV)
  		return PCAP_ERROR_NO_SUCH_DEVICE;
  	return 0;
  }
  
  /*
   * Per me si va ne la citta dolente,
   * Per me si va ne l'etterno dolore,
   *	...
   * Lasciate ogne speranza, voi ch'intrate.
   *
   * XXX - airmon-ng does special stuff with the Orinoco driver and the
   * wlan-ng driver.
   */
  typedef enum {
  	MONITOR_WEXT,
  	MONITOR_HOSTAP,
  	MONITOR_PRISM,
  	MONITOR_PRISM54,
  	MONITOR_ACX100,
  	MONITOR_RT2500,
  	MONITOR_RT2570,
  	MONITOR_RT73,
  	MONITOR_RTL8XXX
  } monitor_type;
  
  /*
   * Use the Wireless Extensions, if we have them, to try to turn monitor mode
   * on if it's not already on.
   *
   * Returns 1 on success, 0 if we don't support the Wireless Extensions
   * on this device, or a PCAP_ERROR_ value if we do support them but
   * we weren't able to turn monitor mode on.
   */
  static int
  enter_rfmon_mode_wext(pcap_t *handle, int sock_fd, const char *device)
  {
  	/*
  	 * XXX - at least some adapters require non-Wireless Extensions
  	 * mechanisms to turn monitor mode on.
  	 *
  	 * Atheros cards might require that a separate "monitor virtual access
  	 * point" be created, with later versions of the madwifi driver.
  	 * airmon-ng does "wlanconfig ath create wlandev {if} wlanmode
  	 * monitor -bssid", which apparently spits out a line "athN"
  	 * where "athN" is the monitor mode device.  To leave monitor
  	 * mode, it destroys the monitor mode device.
  	 *
  	 * Some Intel Centrino adapters might require private ioctls to get
  	 * radio headers; the ipw2200 and ipw3945 drivers allow you to
  	 * configure a separate "rtapN" interface to capture in monitor
  	 * mode without preventing the adapter from operating normally.
  	 * (airmon-ng doesn't appear to use that, though.)
  	 *
  	 * It would be Truly Wonderful if mac80211 and nl80211 cleaned this
  	 * up, and if all drivers were converted to mac80211 drivers.
  	 *
  	 * If interface {if} is a mac80211 driver, the file
  	 * /sys/class/net/{if}/phy80211 is a symlink to
  	 * /sys/class/ieee80211/{phydev}, for some {phydev}.
  	 *
  	 * On Fedora 9, with a 2.6.26.3-29 kernel, my Zydas stick, at
  	 * least, has a "wmaster0" device and a "wlan0" device; the
  	 * latter is the one with the IP address.  Both show up in
  	 * "tcpdump -D" output.  Capturing on the wmaster0 device
  	 * captures with 802.11 headers.
  	 *
  	 * airmon-ng searches through /sys/class/net for devices named
  	 * monN, starting with mon0; as soon as one *doesn't* exist,
  	 * it chooses that as the monitor device name.  If the "iw"
  	 * command exists, it does "iw dev {if} interface add {monif}
  	 * type monitor", where {monif} is the monitor device.  It
  	 * then (sigh) sleeps .1 second, and then configures the
  	 * device up.  Otherwise, if /sys/class/ieee80211/{phydev}/add_iface
  	 * is a file, it writes {mondev}, without a newline, to that file,
  	 * and again (sigh) sleeps .1 second, and then iwconfig's that
  	 * device into monitor mode and configures it up.  Otherwise,
  	 * you can't do monitor mode.
  	 *
  	 * All these devices are "glued" together by having the
  	 * /sys/class/net/{device}/phy80211 links pointing to the same
  	 * place, so, given a wmaster, wlan, or mon device, you can
  	 * find the other devices by looking for devices with
  	 * the same phy80211 link.
  	 *
  	 * To turn monitor mode off, delete the monitor interface,
  	 * either with "iw dev {monif} interface del" or by sending
  	 * {monif}, with no NL, down /sys/class/ieee80211/{phydev}/remove_iface
  	 *
  	 * Note: if you try to create a monitor device named "monN", and
  	 * there's already a "monN" device, it fails, as least with
  	 * the netlink interface (which is what iw uses), with a return
  	 * value of -ENFILE.  (Return values are negative errnos.)  We
  	 * could probably use that to find an unused device.
  	 */
  	struct pcap_linux *handlep = handle->priv;
  	int err;
  	struct iwreq ireq;
  	struct iw_priv_args *priv;
  	monitor_type montype;
  	int i;
  	__u32 cmd;
  	struct ifreq ifr;
  	int oldflags;
  	int args[2];
  	int channel;
  
  	/*
  	 * Does this device *support* the Wireless Extensions?
  	 */
  	err = has_wext(sock_fd, device, handle->errbuf);
  	if (err <= 0)
  		return err;	/* either it doesn't or the device doesn't even exist */
  	/*
  	 * Start out assuming we have no private extensions to control
  	 * radio metadata.
  	 */
  	montype = MONITOR_WEXT;
  	cmd = 0;
  
  	/*
  	 * Try to get all the Wireless Extensions private ioctls
  	 * supported by this device.
  	 *
  	 * First, get the size of the buffer we need, by supplying no
  	 * buffer and a length of 0.  If the device supports private
  	 * ioctls, it should return E2BIG, with ireq.u.data.length set
  	 * to the length we need.  If it doesn't support them, it should
  	 * return EOPNOTSUPP.
  	 */
  	memset(&ireq, 0, sizeof ireq);
  	strlcpy(ireq.ifr_ifrn.ifrn_name, device,
  	    sizeof ireq.ifr_ifrn.ifrn_name);
  	ireq.u.data.pointer = (void *)args;
  	ireq.u.data.length = 0;
  	ireq.u.data.flags = 0;
  	if (ioctl(sock_fd, SIOCGIWPRIV, &ireq) != -1) {
  		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  		    "%s: SIOCGIWPRIV with a zero-length buffer didn't fail!",
  		    device);
  		return PCAP_ERROR;
  	}
  	if (errno != EOPNOTSUPP) {
  		/*
  		 * OK, it's not as if there are no private ioctls.
  		 */
  		if (errno != E2BIG) {
  			/*
  			 * Failed.
  			 */
  			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  			    "%s: SIOCGIWPRIV: %s", device,
  			    pcap_strerror(errno));
  			return PCAP_ERROR;
  		}
  
  		/*
  		 * OK, try to get the list of private ioctls.
  		 */
  		priv = malloc(ireq.u.data.length * sizeof (struct iw_priv_args));
  		if (priv == NULL) {
  			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  			    "malloc: %s", pcap_strerror(errno));
  			return PCAP_ERROR;
  		}
  		ireq.u.data.pointer = (void *)priv;
  		if (ioctl(sock_fd, SIOCGIWPRIV, &ireq) == -1) {
  			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  			    "%s: SIOCGIWPRIV: %s", device,
  			    pcap_strerror(errno));
  			free(priv);
  			return PCAP_ERROR;
  		}
  
  		/*
  		 * Look for private ioctls to turn monitor mode on or, if
  		 * monitor mode is on, to set the header type.
  		 */
  		for (i = 0; i < ireq.u.data.length; i++) {
  			if (strcmp(priv[i].name, "monitor_type") == 0) {
  				/*
  				 * Hostap driver, use this one.
  				 * Set monitor mode first.
  				 * You can set it to 0 to get DLT_IEEE80211,
  				 * 1 to get DLT_PRISM, 2 to get
  				 * DLT_IEEE80211_RADIO_AVS, and, with more
  				 * recent versions of the driver, 3 to get
  				 * DLT_IEEE80211_RADIO.
  				 */
  				if ((priv[i].set_args & IW_PRIV_TYPE_MASK) != IW_PRIV_TYPE_INT)
  					break;
  				if (!(priv[i].set_args & IW_PRIV_SIZE_FIXED))
  					break;
  				if ((priv[i].set_args & IW_PRIV_SIZE_MASK) != 1)
  					break;
  				montype = MONITOR_HOSTAP;
  				cmd = priv[i].cmd;
  				break;
  			}
  			if (strcmp(priv[i].name, "set_prismhdr") == 0) {
  				/*
  				 * Prism54 driver, use this one.
  				 * Set monitor mode first.
  				 * You can set it to 2 to get DLT_IEEE80211
  				 * or 3 or get DLT_PRISM.
  				 */
  				if ((priv[i].set_args & IW_PRIV_TYPE_MASK) != IW_PRIV_TYPE_INT)
  					break;
  				if (!(priv[i].set_args & IW_PRIV_SIZE_FIXED))
  					break;
  				if ((priv[i].set_args & IW_PRIV_SIZE_MASK) != 1)
  					break;
  				montype = MONITOR_PRISM54;
  				cmd = priv[i].cmd;
  				break;
  			}
  			if (strcmp(priv[i].name, "forceprismheader") == 0) {
  				/*
  				 * RT2570 driver, use this one.
  				 * Do this after turning monitor mode on.
  				 * You can set it to 1 to get DLT_PRISM or 2
  				 * to get DLT_IEEE80211.
  				 */
  				if ((priv[i].set_args & IW_PRIV_TYPE_MASK) != IW_PRIV_TYPE_INT)
  					break;
  				if (!(priv[i].set_args & IW_PRIV_SIZE_FIXED))
  					break;
  				if ((priv[i].set_args & IW_PRIV_SIZE_MASK) != 1)
  					break;
  				montype = MONITOR_RT2570;
  				cmd = priv[i].cmd;
  				break;
  			}
  			if (strcmp(priv[i].name, "forceprism") == 0) {
  				/*
  				 * RT73 driver, use this one.
  				 * Do this after turning monitor mode on.
  				 * Its argument is a *string*; you can
  				 * set it to "1" to get DLT_PRISM or "2"
  				 * to get DLT_IEEE80211.
  				 */
  				if ((priv[i].set_args & IW_PRIV_TYPE_MASK) != IW_PRIV_TYPE_CHAR)
  					break;
  				if (priv[i].set_args & IW_PRIV_SIZE_FIXED)
  					break;
  				montype = MONITOR_RT73;
  				cmd = priv[i].cmd;
  				break;
  			}
  			if (strcmp(priv[i].name, "prismhdr") == 0) {
  				/*
  				 * One of the RTL8xxx drivers, use this one.
  				 * It can only be done after monitor mode
  				 * has been turned on.  You can set it to 1
  				 * to get DLT_PRISM or 0 to get DLT_IEEE80211.
  				 */
  				if ((priv[i].set_args & IW_PRIV_TYPE_MASK) != IW_PRIV_TYPE_INT)
  					break;
  				if (!(priv[i].set_args & IW_PRIV_SIZE_FIXED))
  					break;
  				if ((priv[i].set_args & IW_PRIV_SIZE_MASK) != 1)
  					break;
  				montype = MONITOR_RTL8XXX;
  				cmd = priv[i].cmd;
  				break;
  			}
  			if (strcmp(priv[i].name, "rfmontx") == 0) {
  				/*
  				 * RT2500 or RT61 driver, use this one.
  				 * It has one one-byte parameter; set
  				 * u.data.length to 1 and u.data.pointer to
  				 * point to the parameter.
  				 * It doesn't itself turn monitor mode on.
  				 * You can set it to 1 to allow transmitting
  				 * in monitor mode(?) and get DLT_IEEE80211,
  				 * or set it to 0 to disallow transmitting in
  				 * monitor mode(?) and get DLT_PRISM.
  				 */
  				if ((priv[i].set_args & IW_PRIV_TYPE_MASK) != IW_PRIV_TYPE_INT)
  					break;
  				if ((priv[i].set_args & IW_PRIV_SIZE_MASK) != 2)
  					break;
  				montype = MONITOR_RT2500;
  				cmd = priv[i].cmd;
  				break;
  			}
  			if (strcmp(priv[i].name, "monitor") == 0) {
  				/*
  				 * Either ACX100 or hostap, use this one.
  				 * It turns monitor mode on.
  				 * If it takes two arguments, it's ACX100;
  				 * the first argument is 1 for DLT_PRISM
  				 * or 2 for DLT_IEEE80211, and the second
  				 * argument is the channel on which to
  				 * run.  If it takes one argument, it's
  				 * HostAP, and the argument is 2 for
  				 * DLT_IEEE80211 and 3 for DLT_PRISM.
  				 *
  				 * If we see this, we don't quit, as this
  				 * might be a version of the hostap driver
  				 * that also supports "monitor_type".
  				 */
  				if ((priv[i].set_args & IW_PRIV_TYPE_MASK) != IW_PRIV_TYPE_INT)
  					break;
  				if (!(priv[i].set_args & IW_PRIV_SIZE_FIXED))
  					break;
  				switch (priv[i].set_args & IW_PRIV_SIZE_MASK) {
  
  				case 1:
  					montype = MONITOR_PRISM;
  					cmd = priv[i].cmd;
  					break;
  
  				case 2:
  					montype = MONITOR_ACX100;
  					cmd = priv[i].cmd;
  					break;
  
  				default:
  					break;
  				}
  			}
  		}
  		free(priv);
  	}
  
  	/*
  	 * XXX - ipw3945?  islism?
  	 */
  
  	/*
  	 * Get the old mode.
  	 */
  	strlcpy(ireq.ifr_ifrn.ifrn_name, device,
  	    sizeof ireq.ifr_ifrn.ifrn_name);
  	if (ioctl(sock_fd, SIOCGIWMODE, &ireq) == -1) {
  		/*
  		 * We probably won't be able to set the mode, either.
  		 */
  		return PCAP_ERROR_RFMON_NOTSUP;
  	}
  
  	/*
  	 * Is it currently in monitor mode?
  	 */
  	if (ireq.u.mode == IW_MODE_MONITOR) {
  		/*
  		 * Yes.  Just leave things as they are.
  		 * We don't offer multiple link-layer types, as
  		 * changing the link-layer type out from under
  		 * somebody else capturing in monitor mode would
  		 * be considered rude.
  		 */
  		return 1;
  	}
  	/*
  	 * No.  We have to put the adapter into rfmon mode.
  	 */
  
  	/*
  	 * If we haven't already done so, arrange to have
  	 * "pcap_close_all()" called when we exit.
  	 */
  	if (!pcap_do_addexit(handle)) {
  		/*
  		 * "atexit()" failed; don't put the interface
  		 * in rfmon mode, just give up.
  		 */
  		return PCAP_ERROR_RFMON_NOTSUP;
  	}
  
  	/*
  	 * Save the old mode.
  	 */
  	handlep->oldmode = ireq.u.mode;
  
  	/*
  	 * Put the adapter in rfmon mode.  How we do this depends
  	 * on whether we have a special private ioctl or not.
  	 */
  	if (montype == MONITOR_PRISM) {
  		/*
  		 * We have the "monitor" private ioctl, but none of
  		 * the other private ioctls.  Use this, and select
  		 * the Prism header.
  		 *
  		 * If it fails, just fall back on SIOCSIWMODE.
  		 */
  		memset(&ireq, 0, sizeof ireq);
  		strlcpy(ireq.ifr_ifrn.ifrn_name, device,
  		    sizeof ireq.ifr_ifrn.ifrn_name);
  		ireq.u.data.length = 1;	/* 1 argument */
  		args[0] = 3;	/* request Prism header */
  		memcpy(ireq.u.name, args, sizeof (int));
  		if (ioctl(sock_fd, cmd, &ireq) != -1) {
  			/*
  			 * Success.
  			 * Note that we have to put the old mode back
  			 * when we close the device.
  			 */
  			handlep->must_do_on_close |= MUST_CLEAR_RFMON;
  
  			/*
  			 * Add this to the list of pcaps to close
  			 * when we exit.
  			 */
  			pcap_add_to_pcaps_to_close(handle);
  
  			return 1;
  		}
  
  		/*
  		 * Failure.  Fall back on SIOCSIWMODE.
  		 */
  	}
  
  	/*
  	 * First, take the interface down if it's up; otherwise, we
  	 * might get EBUSY.
  	 */
  	memset(&ifr, 0, sizeof(ifr));
  	strlcpy(ifr.ifr_name, device, sizeof(ifr.ifr_name));
  	if (ioctl(sock_fd, SIOCGIFFLAGS, &ifr) == -1) {
  		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  		    "%s: Can't get flags: %s", device, strerror(errno));
  		return PCAP_ERROR;
  	}
  	oldflags = 0;
  	if (ifr.ifr_flags & IFF_UP) {
  		oldflags = ifr.ifr_flags;
  		ifr.ifr_flags &= ~IFF_UP;
  		if (ioctl(sock_fd, SIOCSIFFLAGS, &ifr) == -1) {
  			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  			    "%s: Can't set flags: %s", device, strerror(errno));
  			return PCAP_ERROR;
  		}
  	}
  
  	/*
  	 * Then turn monitor mode on.
  	 */
  	strlcpy(ireq.ifr_ifrn.ifrn_name, device,
  	    sizeof ireq.ifr_ifrn.ifrn_name);
  	ireq.u.mode = IW_MODE_MONITOR;
  	if (ioctl(sock_fd, SIOCSIWMODE, &ireq) == -1) {
  		/*
  		 * Scientist, you've failed.
  		 * Bring the interface back up if we shut it down.
  		 */
  		ifr.ifr_flags = oldflags;
  		if (ioctl(sock_fd, SIOCSIFFLAGS, &ifr) == -1) {
  			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  			    "%s: Can't set flags: %s", device, strerror(errno));
  			return PCAP_ERROR;
  		}
  		return PCAP_ERROR_RFMON_NOTSUP;
  	}
  
  	/*
  	 * XXX - airmon-ng does "iwconfig {if} key off" after setting
  	 * monitor mode and setting the channel, and then does
  	 * "iwconfig up".
  	 */
  
  	/*
  	 * Now select the appropriate radio header.
  	 */
  	switch (montype) {
  
  	case MONITOR_WEXT:
  		/*
  		 * We don't have any private ioctl to set the header.
  		 */
  		break;
  
  	case MONITOR_HOSTAP:
  		/*
  		 * Try to select the radiotap header.
  		 */
  		memset(&ireq, 0, sizeof ireq);
  		strlcpy(ireq.ifr_ifrn.ifrn_name, device,
  		    sizeof ireq.ifr_ifrn.ifrn_name);
  		args[0] = 3;	/* request radiotap header */
  		memcpy(ireq.u.name, args, sizeof (int));
  		if (ioctl(sock_fd, cmd, &ireq) != -1)
  			break;	/* success */
  
  		/*
  		 * That failed.  Try to select the AVS header.
  		 */
  		memset(&ireq, 0, sizeof ireq);
  		strlcpy(ireq.ifr_ifrn.ifrn_name, device,
  		    sizeof ireq.ifr_ifrn.ifrn_name);
  		args[0] = 2;	/* request AVS header */
  		memcpy(ireq.u.name, args, sizeof (int));
  		if (ioctl(sock_fd, cmd, &ireq) != -1)
  			break;	/* success */
  
  		/*
  		 * That failed.  Try to select the Prism header.
  		 */
  		memset(&ireq, 0, sizeof ireq);
  		strlcpy(ireq.ifr_ifrn.ifrn_name, device,
  		    sizeof ireq.ifr_ifrn.ifrn_name);
  		args[0] = 1;	/* request Prism header */
  		memcpy(ireq.u.name, args, sizeof (int));
  		ioctl(sock_fd, cmd, &ireq);
  		break;
  
  	case MONITOR_PRISM:
  		/*
  		 * The private ioctl failed.
  		 */
  		break;
  
  	case MONITOR_PRISM54:
  		/*
  		 * Select the Prism header.
  		 */
  		memset(&ireq, 0, sizeof ireq);
  		strlcpy(ireq.ifr_ifrn.ifrn_name, device,
  		    sizeof ireq.ifr_ifrn.ifrn_name);
  		args[0] = 3;	/* request Prism header */
  		memcpy(ireq.u.name, args, sizeof (int));
  		ioctl(sock_fd, cmd, &ireq);
  		break;
  
  	case MONITOR_ACX100:
  		/*
  		 * Get the current channel.
  		 */
  		memset(&ireq, 0, sizeof ireq);
  		strlcpy(ireq.ifr_ifrn.ifrn_name, device,
  		    sizeof ireq.ifr_ifrn.ifrn_name);
  		if (ioctl(sock_fd, SIOCGIWFREQ, &ireq) == -1) {
  			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  			    "%s: SIOCGIWFREQ: %s", device,
  			    pcap_strerror(errno));
  			return PCAP_ERROR;
  		}
  		channel = ireq.u.freq.m;
  
  		/*
  		 * Select the Prism header, and set the channel to the
  		 * current value.
  		 */
  		memset(&ireq, 0, sizeof ireq);
  		strlcpy(ireq.ifr_ifrn.ifrn_name, device,
  		    sizeof ireq.ifr_ifrn.ifrn_name);
  		args[0] = 1;		/* request Prism header */
  		args[1] = channel;	/* set channel */
  		memcpy(ireq.u.name, args, 2*sizeof (int));
  		ioctl(sock_fd, cmd, &ireq);
  		break;
  
  	case MONITOR_RT2500:
  		/*
  		 * Disallow transmission - that turns on the
  		 * Prism header.
  		 */
  		memset(&ireq, 0, sizeof ireq);
  		strlcpy(ireq.ifr_ifrn.ifrn_name, device,
  		    sizeof ireq.ifr_ifrn.ifrn_name);
  		args[0] = 0;	/* disallow transmitting */
  		memcpy(ireq.u.name, args, sizeof (int));
  		ioctl(sock_fd, cmd, &ireq);
  		break;
  
  	case MONITOR_RT2570:
  		/*
  		 * Force the Prism header.
  		 */
  		memset(&ireq, 0, sizeof ireq);
  		strlcpy(ireq.ifr_ifrn.ifrn_name, device,
  		    sizeof ireq.ifr_ifrn.ifrn_name);
  		args[0] = 1;	/* request Prism header */
  		memcpy(ireq.u.name, args, sizeof (int));
  		ioctl(sock_fd, cmd, &ireq);
  		break;
  
  	case MONITOR_RT73:
  		/*
  		 * Force the Prism header.
  		 */
  		memset(&ireq, 0, sizeof ireq);
  		strlcpy(ireq.ifr_ifrn.ifrn_name, device,
  		    sizeof ireq.ifr_ifrn.ifrn_name);
  		ireq.u.data.length = 1;	/* 1 argument */
  		ireq.u.data.pointer = "1";
  		ireq.u.data.flags = 0;
  		ioctl(sock_fd, cmd, &ireq);
  		break;
  
  	case MONITOR_RTL8XXX:
  		/*
  		 * Force the Prism header.
  		 */
  		memset(&ireq, 0, sizeof ireq);
  		strlcpy(ireq.ifr_ifrn.ifrn_name, device,
  		    sizeof ireq.ifr_ifrn.ifrn_name);
  		args[0] = 1;	/* request Prism header */
  		memcpy(ireq.u.name, args, sizeof (int));
  		ioctl(sock_fd, cmd, &ireq);
  		break;
  	}
  
  	/*
  	 * Now bring the interface back up if we brought it down.
  	 */
  	if (oldflags != 0) {
  		ifr.ifr_flags = oldflags;
  		if (ioctl(sock_fd, SIOCSIFFLAGS, &ifr) == -1) {
  			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  			    "%s: Can't set flags: %s", device, strerror(errno));
  
  			/*
  			 * At least try to restore the old mode on the
  			 * interface.
  			 */
  			if (ioctl(handle->fd, SIOCSIWMODE, &ireq) == -1) {
  				/*
  				 * Scientist, you've failed.
  				 */
  				fprintf(stderr,
  				    "Can't restore interface wireless mode (SIOCSIWMODE failed: %s).\n"
  				    "Please adjust manually.\n",
  				    strerror(errno));
  			}
  			return PCAP_ERROR;
  		}
  	}
  
  	/*
  	 * Note that we have to put the old mode back when we
  	 * close the device.
  	 */
  	handlep->must_do_on_close |= MUST_CLEAR_RFMON;
  
  	/*
  	 * Add this to the list of pcaps to close when we exit.
  	 */
  	pcap_add_to_pcaps_to_close(handle);
  
  	return 1;
  }
  #endif /* IW_MODE_MONITOR */
  
  /*
   * Try various mechanisms to enter monitor mode.
   */
  static int
  enter_rfmon_mode(pcap_t *handle, int sock_fd, const char *device)
  {
  #if defined(HAVE_LIBNL) || defined(IW_MODE_MONITOR)
  	int ret;
  #endif
  
  #ifdef HAVE_LIBNL
  	ret = enter_rfmon_mode_mac80211(handle, sock_fd, device);
  	if (ret < 0)
  		return ret;	/* error attempting to do so */
  	if (ret == 1)
  		return 1;	/* success */
  #endif /* HAVE_LIBNL */
  
  #ifdef IW_MODE_MONITOR
  	ret = enter_rfmon_mode_wext(handle, sock_fd, device);
  	if (ret < 0)
  		return ret;	/* error attempting to do so */
  	if (ret == 1)
  		return 1;	/* success */
  #endif /* IW_MODE_MONITOR */
  
  	/*
  	 * Either none of the mechanisms we know about work or none
  	 * of those mechanisms are available, so we can't do monitor
  	 * mode.
  	 */
  	return 0;
  }
  
  #if defined(HAVE_LINUX_NET_TSTAMP_H) && defined(PACKET_TIMESTAMP)
  /*
   * Map SOF_TIMESTAMPING_ values to PCAP_TSTAMP_ values.
   */
  static const struct {
  	int soft_timestamping_val;
  	int pcap_tstamp_val;
  } sof_ts_type_map[3] = {
  	{ SOF_TIMESTAMPING_SOFTWARE, PCAP_TSTAMP_HOST },
  	{ SOF_TIMESTAMPING_SYS_HARDWARE, PCAP_TSTAMP_ADAPTER },
  	{ SOF_TIMESTAMPING_RAW_HARDWARE, PCAP_TSTAMP_ADAPTER_UNSYNCED }
  };
  #define NUM_SOF_TIMESTAMPING_TYPES	(sizeof sof_ts_type_map / sizeof sof_ts_type_map[0])
  
  static void
  iface_set_default_ts_types(pcap_t *handle)
  {
  	int i;
  
  	handle->tstamp_type_count = NUM_SOF_TIMESTAMPING_TYPES;
  	handle->tstamp_type_list = malloc(NUM_SOF_TIMESTAMPING_TYPES * sizeof(u_int));
  	for (i = 0; i < NUM_SOF_TIMESTAMPING_TYPES; i++)
  		handle->tstamp_type_list[i] = sof_ts_type_map[i].pcap_tstamp_val;
  }
  
  #ifdef ETHTOOL_GET_TS_INFO
  /*
   * Get a list of time stamping capabilities.
   */
  static int
  iface_ethtool_get_ts_info(pcap_t *handle, char *ebuf)
  {
  	int fd;
  	struct ifreq ifr;
  	struct ethtool_ts_info info;
  	int num_ts_types;
  	int i, j;
  
  	/*
  	 * This doesn't apply to the "any" device; you have to ask
  	 * specific devices for their capabilities, so just default
  	 * to saying we support all of them.
  	 */
  	if (strcmp(handle->opt.source, "any") == 0) {
  		iface_set_default_ts_types(handle);
  		return 0;
  	}
  
  	/*
  	 * Create a socket from which to fetch time stamping capabilities.
  	 */
  	fd = socket(AF_INET, SOCK_DGRAM, 0);
  	if (fd < 0) {
  		(void)snprintf(ebuf, PCAP_ERRBUF_SIZE,
  		    "socket for SIOCETHTOOL(ETHTOOL_GET_TS_INFO): %s", pcap_strerror(errno));
  		return -1;
  	}
  
  	memset(&ifr, 0, sizeof(ifr));
  	strlcpy(ifr.ifr_name, handle->opt.source, sizeof(ifr.ifr_name));
  	memset(&info, 0, sizeof(info));
  	info.cmd = ETHTOOL_GET_TS_INFO;
  	ifr.ifr_data = (caddr_t)&info;
  	if (ioctl(fd, SIOCETHTOOL, &ifr) == -1) {
  		close(fd);
  #ifndef HAVE_PF_RING
  		if (errno == EOPNOTSUPP || errno == EINVAL) {
  #endif
  			/*
  			 * OK, let's just return all the possible time
  			 * stamping types.
  			 */
  			iface_set_default_ts_types(handle);
  			return 0;
  #ifndef HAVE_PF_RING
  		}
  		snprintf(ebuf, PCAP_ERRBUF_SIZE,
  		    "%s: SIOCETHTOOL(ETHTOOL_GET_TS_INFO) ioctl failed: %s", handle->opt.source,
  		    strerror(errno));
  		return -1;
  #endif
  	}
  	close(fd);
  
  	num_ts_types = 0;
  	for (i = 0; i < NUM_SOF_TIMESTAMPING_TYPES; i++) {
  		if (info.so_timestamping & sof_ts_type_map[i].soft_timestamping_val)
  			num_ts_types++;
  	}
  	handle->tstamp_type_count = num_ts_types;
  	if (num_ts_types != 0) {
  		handle->tstamp_type_list = malloc(num_ts_types * sizeof(u_int));
  		for (i = 0, j = 0; i < NUM_SOF_TIMESTAMPING_TYPES; i++) {
  			if (info.so_timestamping & sof_ts_type_map[i].soft_timestamping_val) {
  				handle->tstamp_type_list[j] = sof_ts_type_map[i].pcap_tstamp_val;
  				j++;
  			}
  		}
  	} else
  		handle->tstamp_type_list = NULL;
  
  	return 0;
  }
  #else /* ETHTOOL_GET_TS_INFO */
  static int
  iface_ethtool_get_ts_info(pcap_t *handle, char *ebuf _U_)
  {
  	/*
  	 * We don't have an ioctl to use to ask what's supported,
  	 * so say we support everything.
  	 */
  	iface_set_default_ts_types(handle);
  	return 0;
  }
  #endif /* ETHTOOL_GET_TS_INFO */
  
  #endif /* defined(HAVE_LINUX_NET_TSTAMP_H) && defined(PACKET_TIMESTAMP) */
  
  #ifdef HAVE_PACKET_RING
  /*
   * Find out if we have any form of fragmentation/reassembly offloading.
   *
   * We do so using SIOCETHTOOL checking for various types of offloading;
   * if SIOCETHTOOL isn't defined, or we don't have any #defines for any
   * of the types of offloading, there's nothing we can do to check, so
   * we just say "no, we don't".
   */
  #if defined(SIOCETHTOOL) && (defined(ETHTOOL_GTSO) || defined(ETHTOOL_GUFO) || defined(ETHTOOL_GGSO) || defined(ETHTOOL_GFLAGS) || defined(ETHTOOL_GGRO))
  static int
  iface_ethtool_flag_ioctl(pcap_t *handle, int cmd, const char *cmdname)
  {
  	struct ifreq	ifr;
  	struct ethtool_value eval;
  
  	memset(&ifr, 0, sizeof(ifr));
  	strlcpy(ifr.ifr_name, handle->opt.source, sizeof(ifr.ifr_name));
  	eval.cmd = cmd;
  	eval.data = 0;
  	ifr.ifr_data = (caddr_t)&eval;
  	if (ioctl(handle->fd, SIOCETHTOOL, &ifr) == -1) {
  		if (errno == EOPNOTSUPP || errno == EINVAL) {
  			/*
  			 * OK, let's just return 0, which, in our
  			 * case, either means "no, what we're asking
  			 * about is not enabled" or "all the flags
  			 * are clear (i.e., nothing is enabled)".
  			 */
  			return 0;
  		}
  		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  		    "%s: SIOCETHTOOL(%s) ioctl failed: %s", handle->opt.source,
  		    cmdname, strerror(errno));
  		return -1;
  	}
  	return eval.data;
  }
  
  static int
  iface_get_offload(pcap_t *handle)
  {
  	int ret;
  
  #ifdef ETHTOOL_GTSO
  	ret = iface_ethtool_flag_ioctl(handle, ETHTOOL_GTSO, "ETHTOOL_GTSO");
  	if (ret == -1)
  		return -1;
  	if (ret)
  		return 1;	/* TCP segmentation offloading on */
  #endif
  
  #ifdef ETHTOOL_GUFO
  	ret = iface_ethtool_flag_ioctl(handle, ETHTOOL_GUFO, "ETHTOOL_GUFO");
  	if (ret == -1)
  		return -1;
  	if (ret)
  		return 1;	/* UDP fragmentation offloading on */
  #endif
  
  #ifdef ETHTOOL_GGSO
  	/*
  	 * XXX - will this cause large unsegmented packets to be
  	 * handed to PF_PACKET sockets on transmission?  If not,
  	 * this need not be checked.
  	 */
  	ret = iface_ethtool_flag_ioctl(handle, ETHTOOL_GGSO, "ETHTOOL_GGSO");
  	if (ret == -1)
  		return -1;
  	if (ret)
  		return 1;	/* generic segmentation offloading on */
  #endif
  
  #ifdef ETHTOOL_GFLAGS
  	ret = iface_ethtool_flag_ioctl(handle, ETHTOOL_GFLAGS, "ETHTOOL_GFLAGS");
  	if (ret == -1)
  		return -1;
  	if (ret & ETH_FLAG_LRO)
  		return 1;	/* large receive offloading on */
  #endif
  
  #ifdef ETHTOOL_GGRO
  	/*
  	 * XXX - will this cause large reassembled packets to be
  	 * handed to PF_PACKET sockets on receipt?  If not,
  	 * this need not be checked.
  	 */
  	ret = iface_ethtool_flag_ioctl(handle, ETHTOOL_GGRO, "ETHTOOL_GGRO");
  	if (ret == -1)
  		return -1;
  	if (ret)
  		return 1;	/* generic (large) receive offloading on */
  #endif
  
  	return 0;
  }
  #else /* SIOCETHTOOL */
  static int
  iface_get_offload(pcap_t *handle _U_)
  {
  	/*
  	 * XXX - do we need to get this information if we don't
  	 * have the ethtool ioctls?  If so, how do we do that?
  	 */
  	return 0;
  }
  #endif /* SIOCETHTOOL */
  
  #endif /* HAVE_PACKET_RING */
  
  #endif /* HAVE_PF_PACKET_SOCKETS */
  
  /* ===== Functions to interface to the older kernels ================== */
  
  /*
   * Try to open a packet socket using the old kernel interface.
   * Returns 1 on success and a PCAP_ERROR_ value on an error.
   */
  static int
  activate_old(pcap_t *handle)
  {
  	struct pcap_linux *handlep = handle->priv;
  	int		arptype;
  	struct ifreq	ifr;
  	const char	*device = handle->opt.source;
  	struct utsname	utsname;
  	int		mtu;
  
  	/* Open the socket */
  
  	handle->fd = socket(PF_INET, SOCK_PACKET, htons(ETH_P_ALL));
  	if (handle->fd == -1) {
  		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  			 "socket: %s", pcap_strerror(errno));
  		if (errno == EPERM || errno == EACCES) {
  			/*
  			 * You don't have permission to open the
  			 * socket.
  			 */
  			return PCAP_ERROR_PERM_DENIED;
  		} else {
  			/*
  			 * Other error.
  			 */
  			return PCAP_ERROR;
  		}
  	}
  
  	/* It worked - we are using the old interface */
  	handlep->sock_packet = 1;
  
  	/* ...which means we get the link-layer header. */
  	handlep->cooked = 0;
  
  	/* Bind to the given device */
  
  	if (strcmp(device, "any") == 0) {
  		strlcpy(handle->errbuf, "pcap_activate: The \"any\" device isn't supported on 2.0[.x]-kernel systems",
  			PCAP_ERRBUF_SIZE);
  		return PCAP_ERROR;
  	}
  	if (iface_bind_old(handle->fd, device, handle->errbuf) == -1)
  		return PCAP_ERROR;
  
  	/*
  	 * Try to get the link-layer type.
  	 */
  	arptype = iface_get_arptype(handle->fd, device, handle->errbuf);
  	if (arptype < 0)
  		return PCAP_ERROR;
  
  	/*
  	 * Try to find the DLT_ type corresponding to that
  	 * link-layer type.
  	 */
  	map_arphrd_to_dlt(handle, handle->fd, arptype, device, 0);
  	if (handle->linktype == -1) {
  		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  			 "unknown arptype %d", arptype);
  		return PCAP_ERROR;
  	}
  
  	/* Go to promisc mode if requested */
  
  	if (handle->opt.promisc) {
  		memset(&ifr, 0, sizeof(ifr));
  		strlcpy(ifr.ifr_name, device, sizeof(ifr.ifr_name));
  		if (ioctl(handle->fd, SIOCGIFFLAGS, &ifr) == -1) {
  			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  				 "SIOCGIFFLAGS: %s", pcap_strerror(errno));
  			return PCAP_ERROR;
  		}
  		if ((ifr.ifr_flags & IFF_PROMISC) == 0) {
  			/*
  			 * Promiscuous mode isn't currently on,
  			 * so turn it on, and remember that
  			 * we should turn it off when the
  			 * pcap_t is closed.
  			 */
  
  			/*
  			 * If we haven't already done so, arrange
  			 * to have "pcap_close_all()" called when
  			 * we exit.
  			 */
  			if (!pcap_do_addexit(handle)) {
  				/*
  				 * "atexit()" failed; don't put
  				 * the interface in promiscuous
  				 * mode, just give up.
  				 */
  				return PCAP_ERROR;
  			}
  
  			ifr.ifr_flags |= IFF_PROMISC;
  			if (ioctl(handle->fd, SIOCSIFFLAGS, &ifr) == -1) {
  			        snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  					 "SIOCSIFFLAGS: %s",
  					 pcap_strerror(errno));
  				return PCAP_ERROR;
  			}
  			handlep->must_do_on_close |= MUST_CLEAR_PROMISC;
  
  			/*
  			 * Add this to the list of pcaps
  			 * to close when we exit.
  			 */
  			pcap_add_to_pcaps_to_close(handle);
  		}
  	}
  
  	/*
  	 * Compute the buffer size.
  	 *
  	 * We're using SOCK_PACKET, so this might be a 2.0[.x]
  	 * kernel, and might require special handling - check.
  	 */
  	if (uname(&utsname) < 0 ||
  	    strncmp(utsname.release, "2.0", 3) == 0) {
  		/*
  		 * Either we couldn't find out what kernel release
  		 * this is, or it's a 2.0[.x] kernel.
  		 *
  		 * In the 2.0[.x] kernel, a "recvfrom()" on
  		 * a SOCK_PACKET socket, with MSG_TRUNC set, will
  		 * return the number of bytes read, so if we pass
  		 * a length based on the snapshot length, it'll
  		 * return the number of bytes from the packet
  		 * copied to userland, not the actual length
  		 * of the packet.
  		 *
  		 * This means that, for example, the IP dissector
  		 * in tcpdump will get handed a packet length less
  		 * than the length in the IP header, and will
  		 * complain about "truncated-ip".
  		 *
  		 * So we don't bother trying to copy from the
  		 * kernel only the bytes in which we're interested,
  		 * but instead copy them all, just as the older
  		 * versions of libpcap for Linux did.
  		 *
  		 * The buffer therefore needs to be big enough to
  		 * hold the largest packet we can get from this
  		 * device.  Unfortunately, we can't get the MRU
  		 * of the network; we can only get the MTU.  The
  		 * MTU may be too small, in which case a packet larger
  		 * than the buffer size will be truncated *and* we
  		 * won't get the actual packet size.
  		 *
  		 * However, if the snapshot length is larger than
  		 * the buffer size based on the MTU, we use the
  		 * snapshot length as the buffer size, instead;
  		 * this means that with a sufficiently large snapshot
  		 * length we won't artificially truncate packets
  		 * to the MTU-based size.
  		 *
  		 * This mess just one of many problems with packet
  		 * capture on 2.0[.x] kernels; you really want a
  		 * 2.2[.x] or later kernel if you want packet capture
  		 * to work well.
  		 */
  		mtu = iface_get_mtu(handle->fd, device, handle->errbuf);
  		if (mtu == -1)
  			return PCAP_ERROR;
  		handle->bufsize = MAX_LINKHEADER_SIZE + mtu;
  		if (handle->bufsize < handle->snapshot)
  			handle->bufsize = handle->snapshot;
  	} else {
  		/*
  		 * This is a 2.2[.x] or later kernel.
  		 *
  		 * We can safely pass "recvfrom()" a byte count
  		 * based on the snapshot length.
  		 */
  		handle->bufsize = handle->snapshot;
  	}
  
  	/*
  	 * Default value for offset to align link-layer payload
  	 * on a 4-byte boundary.
  	 */
  	handle->offset	 = 0;
  
  	/*
  	 * SOCK_PACKET sockets don't supply information from
  	 * stripped VLAN tags.
  	 */
  	handlep->vlan_offset = -1; /* unknown */
  
  	return 1;
  }
  
  /*
   *  Bind the socket associated with FD to the given device using the
   *  interface of the old kernels.
   */
  static int
  iface_bind_old(int fd, const char *device, char *ebuf)
  {
  	struct sockaddr	saddr;
  	int		err;
  	socklen_t	errlen = sizeof(err);
  
  	memset(&saddr, 0, sizeof(saddr));
  	strlcpy(saddr.sa_data, device, sizeof(saddr.sa_data));
  	if (bind(fd, &saddr, sizeof(saddr)) == -1) {
  		snprintf(ebuf, PCAP_ERRBUF_SIZE,
  			 "bind: %s", pcap_strerror(errno));
  		return -1;
  	}
  
  	/* Any pending errors, e.g., network is down? */
  
  	if (getsockopt(fd, SOL_SOCKET, SO_ERROR, &err, &errlen) == -1) {
  		snprintf(ebuf, PCAP_ERRBUF_SIZE,
  			"getsockopt: %s", pcap_strerror(errno));
  		return -1;
  	}
  
  	if (err > 0) {
  		snprintf(ebuf, PCAP_ERRBUF_SIZE,
  			"bind: %s", pcap_strerror(err));
  		return -1;
  	}
  
  	return 0;
  }
  
  
  /* ===== System calls available on all supported kernels ============== */
  
  /*
   *  Query the kernel for the MTU of the given interface.
   */
  static int
  iface_get_mtu(int fd, const char *device, char *ebuf)
  {
  	struct ifreq	ifr;
  
  	if (!device)
  		return BIGGER_THAN_ALL_MTUS;
  
  	memset(&ifr, 0, sizeof(ifr));
  	strlcpy(ifr.ifr_name, device, sizeof(ifr.ifr_name));
  
  	if (ioctl(fd, SIOCGIFMTU, &ifr) == -1) {
  		snprintf(ebuf, PCAP_ERRBUF_SIZE,
  			 "SIOCGIFMTU: %s", pcap_strerror(errno));
  		return -1;
  	}
  
  	return ifr.ifr_mtu;
  }
  
  /*
   *  Get the hardware type of the given interface as ARPHRD_xxx constant.
   */
  static int
  iface_get_arptype(int fd, const char *device, char *ebuf)
  {
  	struct ifreq	ifr;
  
  	memset(&ifr, 0, sizeof(ifr));
  	strlcpy(ifr.ifr_name, device, sizeof(ifr.ifr_name));
  
  	if (ioctl(fd, SIOCGIFHWADDR, &ifr) == -1) {
  		snprintf(ebuf, PCAP_ERRBUF_SIZE,
  			 "SIOCGIFHWADDR: %s", pcap_strerror(errno));
  		if (errno == ENODEV) {
  			/*
  			 * No such device.
  			 */
  			return PCAP_ERROR_NO_SUCH_DEVICE;
  		}
  		return PCAP_ERROR;
  	}
  
  	return ifr.ifr_hwaddr.sa_family;
  }
  
  #ifdef HAVE_PF_RING
  /*
   * Don't use the pcap buffer but instead use the one passed by the user.
   * This solution allows multiple threads to read from the same pcap
   * without having to be serialized through a mutex/semaphore.
   */
  const u_char *
  pcap_next_pkt(pcap_t *p, struct pcap_pkthdr *h, u_char *buf, u_short bufsize, int *rc)
  {
  	const u_char *_buf = pcap_next(p, h);
  	if (_buf) *rc = 1; else *rc = 0;
  	return _buf;
  }
  #endif
  
  #ifdef SO_ATTACH_FILTER
  static int
  fix_program(pcap_t *handle, struct sock_fprog *fcode, int is_mmapped)
  {
  	struct pcap_linux *handlep = handle->priv;
  	size_t prog_size;
  	register int i;
  	register struct bpf_insn *p;
  	struct bpf_insn *f;
  	int len;
  
  	/*
  	 * Make a copy of the filter, and modify that copy if
  	 * necessary.
  	 */
  	prog_size = sizeof(*handle->fcode.bf_insns) * handle->fcode.bf_len;
  	len = handle->fcode.bf_len;
  	f = (struct bpf_insn *)malloc(prog_size);
  	if (f == NULL) {
  		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  			 "malloc: %s", pcap_strerror(errno));
  		return -1;
  	}
  	memcpy(f, handle->fcode.bf_insns, prog_size);
  	fcode->len = len;
  	fcode->filter = (struct sock_filter *) f;
  
  	for (i = 0; i < len; ++i) {
  		p = &f[i];
  		/*
  		 * What type of instruction is this?
  		 */
  		switch (BPF_CLASS(p->code)) {
  
  		case BPF_RET:
  			/*
  			 * It's a return instruction; are we capturing
  			 * in memory-mapped mode?
  			 */
  			if (!is_mmapped) {
  				/*
  				 * No; is the snapshot length a constant,
  				 * rather than the contents of the
  				 * accumulator?
  				 */
  				if (BPF_MODE(p->code) == BPF_K) {
  					/*
  					 * Yes - if the value to be returned,
  					 * i.e. the snapshot length, is
  					 * anything other than 0, make it
  					 * MAXIMUM_SNAPLEN, so that the packet
  					 * is truncated by "recvfrom()",
  					 * not by the filter.
  					 *
  					 * XXX - there's nothing we can
  					 * easily do if it's getting the
  					 * value from the accumulator; we'd
  					 * have to insert code to force
  					 * non-zero values to be
  					 * MAXIMUM_SNAPLEN.
  					 */
  					if (p->k != 0)
  						p->k = MAXIMUM_SNAPLEN;
  				}
  			}
  			break;
  
  		case BPF_LD:
  		case BPF_LDX:
  			/*
  			 * It's a load instruction; is it loading
  			 * from the packet?
  			 */
  			switch (BPF_MODE(p->code)) {
  
  			case BPF_ABS:
  			case BPF_IND:
  			case BPF_MSH:
  				/*
  				 * Yes; are we in cooked mode?
  				 */
  				if (handlep->cooked) {
  					/*
  					 * Yes, so we need to fix this
  					 * instruction.
  					 */
  					if (fix_offset(p) < 0) {
  						/*
  						 * We failed to do so.
  						 * Return 0, so our caller
  						 * knows to punt to userland.
  						 */
  						return 0;
  					}
  				}
  				break;
  			}
  			break;
  		}
  	}
  	return 1;	/* we succeeded */
  }
  
  static int
  fix_offset(struct bpf_insn *p)
  {
  	/*
  	 * What's the offset?
  	 */
  	if (p->k >= SLL_HDR_LEN) {
  		/*
  		 * It's within the link-layer payload; that starts at an
  		 * offset of 0, as far as the kernel packet filter is
  		 * concerned, so subtract the length of the link-layer
  		 * header.
  		 */
  		p->k -= SLL_HDR_LEN;
  	} else if (p->k == 0) {
  		/*
  		 * It's the packet type field; map it to the special magic
  		 * kernel offset for that field.
  		 */
  		p->k = SKF_AD_OFF + SKF_AD_PKTTYPE;
  	} else if (p->k == 14) {
  		/*
  		 * It's the protocol field; map it to the special magic
  		 * kernel offset for that field.
  		 */
  		p->k = SKF_AD_OFF + SKF_AD_PROTOCOL;
  	} else if ((bpf_int32)(p->k) > 0) {
  		/*
  		 * It's within the header, but it's not one of those
  		 * fields; we can't do that in the kernel, so punt
  		 * to userland.
  		 */
  		return -1;
  	}
  	return 0;
  }
  
  static int
  set_kernel_filter(pcap_t *handle, struct sock_fprog *fcode)
  {
  	int total_filter_on = 0;
  	int save_mode;
  	int ret;
  	int save_errno;
  
  	/*
  	 * The socket filter code doesn't discard all packets queued
  	 * up on the socket when the filter is changed; this means
  	 * that packets that don't match the new filter may show up
  	 * after the new filter is put onto the socket, if those
  	 * packets haven't yet been read.
  	 *
  	 * This means, for example, that if you do a tcpdump capture
  	 * with a filter, the first few packets in the capture might
  	 * be packets that wouldn't have passed the filter.
  	 *
  	 * We therefore discard all packets queued up on the socket
  	 * when setting a kernel filter.  (This isn't an issue for
  	 * userland filters, as the userland filtering is done after
  	 * packets are queued up.)
  	 *
  	 * To flush those packets, we put the socket in read-only mode,
  	 * and read packets from the socket until there are no more to
  	 * read.
  	 *
  	 * In order to keep that from being an infinite loop - i.e.,
  	 * to keep more packets from arriving while we're draining
  	 * the queue - we put the "total filter", which is a filter
  	 * that rejects all packets, onto the socket before draining
  	 * the queue.
  	 *
  	 * This code deliberately ignores any errors, so that you may
  	 * get bogus packets if an error occurs, rather than having
  	 * the filtering done in userland even if it could have been
  	 * done in the kernel.
  	 */
  	if (setsockopt(handle->fd, 
  #ifdef HAVE_PF_RING
  		       (handle->ring != NULL) ? 0 :
  #endif
  		       SOL_SOCKET, 
  		       SO_ATTACH_FILTER,
  		       &total_fcode, sizeof(total_fcode)) == 0) {
  		char drain[1];
  
  		/*
  		 * Note that we've put the total filter onto the socket.
  		 */
  		total_filter_on = 1;
  
  #ifndef HAVE_PF_RING
  		/*
  		 * Save the socket's current mode, and put it in
  		 * non-blocking mode; we drain it by reading packets
  		 * until we get an error (which is normally a
  		 * "nothing more to be read" error).
  		 */
  		save_mode = fcntl(handle->fd, F_GETFL, 0);
  		if (save_mode == -1) {
  			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  			    "can't get FD flags when changing filter: %s",
  			    pcap_strerror(errno));
  			return -2;
  		}
  		if (fcntl(handle->fd, F_SETFL, save_mode | O_NONBLOCK) < 0) {
  			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  			    "can't set nonblocking mode when changing filter: %s",
  			    pcap_strerror(errno));
  			return -2;
  		}
  		while (recv(handle->fd, &drain, sizeof drain, MSG_TRUNC) >= 0)
  			;
  		save_errno = errno;
  		if (save_errno != EAGAIN) {
  			/*
  			 * Fatal error.
  			 *
  			 * If we can't restore the mode or reset the
  			 * kernel filter, there's nothing we can do.
  			 */
  			(void)fcntl(handle->fd, F_SETFL, save_mode);
  			(void)reset_kernel_filter(handle);
  			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  			    "recv failed when changing filter: %s",
  			    pcap_strerror(save_errno));
  			return -2;
  		}
  		if (fcntl(handle->fd, F_SETFL, save_mode) == -1) {
  			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  			    "can't restore FD flags when changing filter: %s",
  			    pcap_strerror(save_errno));
  			return -2;
  		}
  #endif
  	}
  
  	/*
  	 * Now attach the new filter.
  	 */
  	ret = setsockopt(handle->fd,
  #ifdef HAVE_PF_RING
  		       (handle->ring != NULL) ? 0 :
  #endif
  			 SOL_SOCKET,
  			 SO_ATTACH_FILTER,
  			 fcode, sizeof(*fcode));
  	if (ret == -1 && total_filter_on) {
  		/*
  		 * Well, we couldn't set that filter on the socket,
  		 * but we could set the total filter on the socket.
  		 *
  		 * This could, for example, mean that the filter was
  		 * too big to put into the kernel, so we'll have to
  		 * filter in userland; in any case, we'll be doing
  		 * filtering in userland, so we need to remove the
  		 * total filter so we see packets.
  		 */
  		save_errno = errno;
  
  		/*
  		 * If this fails, we're really screwed; we have the
  		 * total filter on the socket, and it won't come off.
  		 * Report it as a fatal error.
  		 */
  		if (reset_kernel_filter(handle) == -1) {
  			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
  			    "can't remove kernel total filter: %s",
  			    pcap_strerror(errno));
  			return -2;	/* fatal error */
  		}
  
  		errno = save_errno;
  	}
  	return ret;
  }
  
  static int
  reset_kernel_filter(pcap_t *handle)
  {
  	/*
  	 * setsockopt() barfs unless it get a dummy parameter.
  	 * valgrind whines unless the value is initialized,
  	 * as it has no idea that setsockopt() ignores its
  	 * parameter.
  	 */
  	int dummy = 0;
  
  #ifdef HAVE_PF_RING
  	if (handle->ring != NULL)
  		return 0;
  #endif
  
  	return setsockopt(handle->fd, 
  			  SOL_SOCKET,
  			  SO_DETACH_FILTER,
  			  &dummy, sizeof(dummy));
  }
  #endif
  
  #ifdef HAVE_PF_RING
  u_int32_t
  pcap_get_pfring_id(pcap_t *handle) 
  {
  	if (handle->ring == NULL)
  		return(0);
  
  	return pfring_get_ring_id(handle->ring);
  }
  
  int
  pcap_set_master_id(pcap_t *handle, u_int32_t master_id) 
  {
  	return pfring_set_master_id(handle->ring, master_id);
  }
  
  int
  pcap_set_master(pcap_t *handle, pcap_t *master) 
  {
  	return pfring_set_master(handle->ring, master->ring);
  }
  
  int
  pcap_set_application_name(pcap_t *handle, char *name) 
  {
  	return pfring_set_application_name(handle->ring, name);
  }
  
  int
  pcap_set_watermark(pcap_t *handle, u_int watermark) 
  {
  	int ret = -1;
  
  	if (handle->ring) {
  		ret = pfring_set_poll_watermark(handle->ring, watermark);
  	}
  
  	return ret;
  }
  #endif
  
  