text: /* lpf.c
  
     Linux packet filter code, contributed by Brian Murrel at Interlinx
     Support Services in Vancouver, B.C. */
  
  /*
   * Copyright (c) 2009,2012 by Internet Systems Consortium, Inc. ("ISC")
   * Copyright (c) 2004,2007 by Internet Systems Consortium, Inc. ("ISC")
   * Copyright (c) 1996-2003 by Internet Software Consortium
   *
   * Permission to use, copy, modify, and distribute this software for any
   * purpose with or without fee is hereby granted, provided that the above
   * copyright notice and this permission notice appear in all copies.
   *
   * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
   * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
   * MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR
   * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
   * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
   * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
   * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
   *
   *   Internet Systems Consortium, Inc.
   *   950 Charter Street
   *   Redwood City, CA 94063
   *   <info@isc.org>
   *   https://www.isc.org/
   */
  
  #include "dhcpd.h"
  #if defined (USE_LPF_SEND) || defined (USE_LPF_RECEIVE)
  #include <sys/ioctl.h>
  #include <sys/uio.h>
  #include <errno.h>
  
  #include <asm/types.h>
  #include <linux/filter.h>
  #include <linux/if_ether.h>
  #include <netinet/in_systm.h>
  #include <net/if_packet.h>
  #include "includes/netinet/ip.h"
  #include "includes/netinet/udp.h"
  #include "includes/netinet/if_ether.h"
  #include <net/if.h>
  
  /* Reinitializes the specified interface after an address change.   This
     is not required for packet-filter APIs. */
  
  #ifdef USE_LPF_SEND
  void if_reinitialize_send (info)
  	struct interface_info *info;
  {
  }
  #endif
  
  #ifdef USE_LPF_RECEIVE
  void if_reinitialize_receive (info)
  	struct interface_info *info;
  {
  }
  #endif
  
  /* Called by get_interface_list for each interface that's discovered.
     Opens a packet filter for each interface and adds it to the select
     mask. */
  
  int if_register_lpf (info)
  	struct interface_info *info;
  {
  	int sock;
  	struct sockaddr sa;
  
  	/* Make an LPF socket. */
  	if ((sock = socket(PF_PACKET, SOCK_PACKET,
  			   htons((short)ETH_P_ALL))) < 0) {
  		if (errno == ENOPROTOOPT || errno == EPROTONOSUPPORT ||
  		    errno == ESOCKTNOSUPPORT || errno == EPFNOSUPPORT ||
  		    errno == EAFNOSUPPORT || errno == EINVAL) {
  			log_error ("socket: %m - make sure");
  			log_error ("CONFIG_PACKET (Packet socket) %s",
  				   "and CONFIG_FILTER");
  			log_error ("(Socket Filtering) are enabled %s",
  				   "in your kernel");
  			log_fatal ("configuration!");
  		}
  		log_fatal ("Open a socket for LPF: %m");
  	}
  
  	/* Bind to the interface name */
  	memset (&sa, 0, sizeof sa);
  	sa.sa_family = AF_PACKET;
  	strncpy (sa.sa_data, (const char *)info -> ifp, sizeof sa.sa_data);
  	if (bind (sock, &sa, sizeof sa)) {
  		if (errno == ENOPROTOOPT || errno == EPROTONOSUPPORT ||
  		    errno == ESOCKTNOSUPPORT || errno == EPFNOSUPPORT ||
  		    errno == EAFNOSUPPORT || errno == EINVAL) {
  			log_error ("socket: %m - make sure");
  			log_error ("CONFIG_PACKET (Packet socket) %s",
  				   "and CONFIG_FILTER");
  			log_error ("(Socket Filtering) are enabled %s",
  				   "in your kernel");
  			log_fatal ("configuration!");
  		}
  		log_fatal ("Bind socket to interface: %m");
  	}
  
  	get_hw_addr(info->name, &info->hw_address);
  
  	return sock;
  }
  #endif /* USE_LPF_SEND || USE_LPF_RECEIVE */
  
  #ifdef USE_LPF_SEND
  void if_register_send (info)
  	struct interface_info *info;
  {
  	/* If we're using the lpf API for sending and receiving,
  	   we don't need to register this interface twice. */
  #ifndef USE_LPF_RECEIVE
  	info -> wfdesc = if_register_lpf (info);
  #else
  	info -> wfdesc = info -> rfdesc;
  #endif
  	if (!quiet_interface_discovery)
  		log_info ("Sending on   LPF/%s/%s%s%s",
  		      info -> name,
  		      print_hw_addr (info -> hw_address.hbuf [0],
  				     info -> hw_address.hlen - 1,
  				     &info -> hw_address.hbuf [1]),
  		      (info -> shared_network ? "/" : ""),
  		      (info -> shared_network ?
  		       info -> shared_network -> name : ""));
  }
  
  void if_deregister_send (info)
  	struct interface_info *info;
  {
  	/* don't need to close twice if we are using lpf for sending and
  	   receiving */
  #ifndef USE_LPF_RECEIVE
  	/* for LPF this is simple, packet filters are removed when sockets
  	   are closed */
  	close (info -> wfdesc);
  #endif
  	info -> wfdesc = -1;
  	if (!quiet_interface_discovery)
  		log_info ("Disabling output on LPF/%s/%s%s%s",
  		      info -> name,
  		      print_hw_addr (info -> hw_address.hbuf [0],
  				     info -> hw_address.hlen - 1,
  				     &info -> hw_address.hbuf [1]),
  		      (info -> shared_network ? "/" : ""),
  		      (info -> shared_network ?
  		       info -> shared_network -> name : ""));
  }
  #endif /* USE_LPF_SEND */
  
  #ifdef USE_LPF_RECEIVE
  /* Defined in bpf.c.   We can't extern these in dhcpd.h without pulling
     in bpf includes... */
  extern struct sock_filter dhcp_bpf_filter [];
  extern int dhcp_bpf_filter_len;
  
  #if defined (HAVE_TR_SUPPORT)
  extern struct sock_filter dhcp_bpf_tr_filter [];
  extern int dhcp_bpf_tr_filter_len;
  static void lpf_tr_filter_setup (struct interface_info *);
  #endif
  
  static void lpf_gen_filter_setup (struct interface_info *);
  
  void if_register_receive (info)
  	struct interface_info *info;
  {
  	/* Open a LPF device and hang it on this interface... */
  	info -> rfdesc = if_register_lpf (info);
  
  #if defined (HAVE_TR_SUPPORT)
  	if (info -> hw_address.hbuf [0] == HTYPE_IEEE802)
  		lpf_tr_filter_setup (info);
  	else
  #endif
  		lpf_gen_filter_setup (info);
  
  	if (!quiet_interface_discovery)
  		log_info ("Listening on LPF/%s/%s%s%s",
  			  info -> name,
  			  print_hw_addr (info -> hw_address.hbuf [0],
  					 info -> hw_address.hlen - 1,
  					 &info -> hw_address.hbuf [1]),
  			  (info -> shared_network ? "/" : ""),
  			  (info -> shared_network ?
  			   info -> shared_network -> name : ""));
  }
  
  void if_deregister_receive (info)
  	struct interface_info *info;
  {
  	/* for LPF this is simple, packet filters are removed when sockets
  	   are closed */
  	close (info -> rfdesc);
  	info -> rfdesc = -1;
  	if (!quiet_interface_discovery)
  		log_info ("Disabling input on LPF/%s/%s%s%s",
  			  info -> name,
  			  print_hw_addr (info -> hw_address.hbuf [0],
  					 info -> hw_address.hlen - 1,
  					 &info -> hw_address.hbuf [1]),
  			  (info -> shared_network ? "/" : ""),
  			  (info -> shared_network ?
  			   info -> shared_network -> name : ""));
  }
  
  static void lpf_gen_filter_setup (info)
  	struct interface_info *info;
  {
  	struct sock_fprog p;
  
  	memset(&p, 0, sizeof(p));
  
  	/* Set up the bpf filter program structure.    This is defined in
  	   bpf.c */
  	p.len = dhcp_bpf_filter_len;
  	p.filter = dhcp_bpf_filter;
  
          /* Patch the server port into the LPF  program...
  	   XXX changes to filter program may require changes
  	   to the insn number(s) used below! XXX */
  	dhcp_bpf_filter [8].k = ntohs ((short)local_port);
  
  	if (setsockopt (info -> rfdesc, SOL_SOCKET, SO_ATTACH_FILTER, &p,
  			sizeof p) < 0) {
  		if (errno == ENOPROTOOPT || errno == EPROTONOSUPPORT ||
  		    errno == ESOCKTNOSUPPORT || errno == EPFNOSUPPORT ||
  		    errno == EAFNOSUPPORT) {
  			log_error ("socket: %m - make sure");
  			log_error ("CONFIG_PACKET (Packet socket) %s",
  				   "and CONFIG_FILTER");
  			log_error ("(Socket Filtering) are enabled %s",
  				   "in your kernel");
  			log_fatal ("configuration!");
  		}
  		log_fatal ("Can't install packet filter program: %m");
  	}
  }
  
  #if defined (HAVE_TR_SUPPORT)
  static void lpf_tr_filter_setup (info)
  	struct interface_info *info;
  {
  	struct sock_fprog p;
  
  	memset(&p, 0, sizeof(p));
  
  	/* Set up the bpf filter program structure.    This is defined in
  	   bpf.c */
  	p.len = dhcp_bpf_tr_filter_len;
  	p.filter = dhcp_bpf_tr_filter;
  
          /* Patch the server port into the LPF  program...
  	   XXX changes to filter program may require changes
  	   XXX to the insn number(s) used below!
  	   XXX Token ring filter is null - when/if we have a filter 
  	   XXX that's not, we'll need this code.
  	   XXX dhcp_bpf_filter [?].k = ntohs (local_port); */
  
  	if (setsockopt (info -> rfdesc, SOL_SOCKET, SO_ATTACH_FILTER, &p,
  			sizeof p) < 0) {
  		if (errno == ENOPROTOOPT || errno == EPROTONOSUPPORT ||
  		    errno == ESOCKTNOSUPPORT || errno == EPFNOSUPPORT ||
  		    errno == EAFNOSUPPORT) {
  			log_error ("socket: %m - make sure");
  			log_error ("CONFIG_PACKET (Packet socket) %s",
  				   "and CONFIG_FILTER");
  			log_error ("(Socket Filtering) are enabled %s",
  				   "in your kernel");
  			log_fatal ("configuration!");
  		}
  		log_fatal ("Can't install packet filter program: %m");
  	}
  }
  #endif /* HAVE_TR_SUPPORT */
  #endif /* USE_LPF_RECEIVE */
  
  #ifdef USE_LPF_SEND
  ssize_t send_packet (interface, packet, raw, len, from, to, hto)
  	struct interface_info *interface;
  	struct packet *packet;
  	struct dhcp_packet *raw;
  	size_t len;
  	struct in_addr from;
  	struct sockaddr_in *to;
  	struct hardware *hto;
  {
  	unsigned hbufp = 0, ibufp = 0;
  	double hh [16];
  	double ih [1536 / sizeof (double)];
  	unsigned char *buf = (unsigned char *)ih;
  	struct sockaddr_pkt sa;
  	int result;
  	int fudge;
  
  	if (!strcmp (interface -> name, "fallback"))
  		return send_fallback (interface, packet, raw,
  				      len, from, to, hto);
  
  	if (hto == NULL && interface->anycast_mac_addr.hlen)
  		hto = &interface->anycast_mac_addr;
  
  	/* Assemble the headers... */
  	assemble_hw_header (interface, (unsigned char *)hh, &hbufp, hto);
  	fudge = hbufp % 4;	/* IP header must be word-aligned. */
  	memcpy (buf + fudge, (unsigned char *)hh, hbufp);
  	ibufp = hbufp + fudge;
  	assemble_udp_ip_header (interface, buf, &ibufp, from.s_addr,
  				to -> sin_addr.s_addr, to -> sin_port,
  				(unsigned char *)raw, len);
  	memcpy (buf + ibufp, raw, len);
  
  	/* For some reason, SOCK_PACKET sockets can't be connected,
  	   so we have to do a sentdo every time. */
  	memset (&sa, 0, sizeof sa);
  	sa.spkt_family = AF_PACKET;
  	strncpy ((char *)sa.spkt_device,
  		 (const char *)interface -> ifp, sizeof sa.spkt_device);
  	sa.spkt_protocol = htons(ETH_P_IP);
  
  	result = sendto (interface -> wfdesc,
  			 buf + fudge, ibufp + len - fudge, 0, 
  			 (const struct sockaddr *)&sa, sizeof sa);
  	if (result < 0)
  		log_error ("send_packet: %m");
  	return result;
  }
  #endif /* USE_LPF_SEND */
  
  #ifdef USE_LPF_RECEIVE
  ssize_t receive_packet (interface, buf, len, from, hfrom)
  	struct interface_info *interface;
  	unsigned char *buf;
  	size_t len;
  	struct sockaddr_in *from;
  	struct hardware *hfrom;
  {
  	int length = 0;
  	int offset = 0;
  	unsigned char ibuf [1536];
  	unsigned bufix = 0;
  	unsigned paylen;
  
  	length = read (interface -> rfdesc, ibuf, sizeof ibuf);
  	if (length <= 0)
  		return length;
  
  	bufix = 0;
  	/* Decode the physical header... */
  	offset = decode_hw_header (interface, ibuf, bufix, hfrom);
  
  	/* If a physical layer checksum failed (dunno of any
  	   physical layer that supports this, but WTH), skip this
  	   packet. */
  	if (offset < 0) {
  		return 0;
  	}
  
  	bufix += offset;
  	length -= offset;
  
  	/* Decode the IP and UDP headers... */
  	offset = decode_udp_ip_header (interface, ibuf, bufix, from,
  				       (unsigned)length, &paylen);
  
  	/* If the IP or UDP checksum was bad, skip the packet... */
  	if (offset < 0)
  		return 0;
  
  	bufix += offset;
  	length -= offset;
  
  	if (length < paylen)
  		log_fatal("Internal inconsistency at %s:%d.", MDL);
  
  	/* Copy out the data in the packet... */
  	memcpy(buf, &ibuf[bufix], paylen);
  	return paylen;
  }
  
  int can_unicast_without_arp (ip)
  	struct interface_info *ip;
  {
  	return 1;
  }
  
  int can_receive_unicast_unconfigured (ip)
  	struct interface_info *ip;
  {
  	return 1;
  }
  
  int supports_multiple_interfaces (ip)
  	struct interface_info *ip;
  {
  	return 1;
  }
  
  void maybe_setup_fallback ()
  {
  	isc_result_t status;
  	struct interface_info *fbi = (struct interface_info *)0;
  	if (setup_fallback (&fbi, MDL)) {
  		if_register_fallback (fbi);
  		status = omapi_register_io_object ((omapi_object_t *)fbi,
  						   if_readsocket, 0,
  						   fallback_discard, 0, 0);
  		if (status != ISC_R_SUCCESS)
  			log_fatal ("Can't register I/O handle for \"%s\": %s",
  				   fbi -> name, isc_result_totext (status));
  		interface_dereference (&fbi, MDL);
  	}
  }
  
  void
  get_hw_addr(const char *name, struct hardware *hw) {
  	int sock;
  	struct ifreq tmp;
  	struct sockaddr *sa;
  
  	if (strlen(name) >= sizeof(tmp.ifr_name)) {
  		log_fatal("Device name too long: \"%s\"", name);
  	}
  
  	sock = socket(AF_INET, SOCK_DGRAM, 0);
  	if (sock < 0) {
  		log_fatal("Can't create socket for \"%s\": %m", name);
  	}
  
  	memset(&tmp, 0, sizeof(tmp));
  	strcpy(tmp.ifr_name, name);
  	if (ioctl(sock, SIOCGIFHWADDR, &tmp) < 0) {
  		log_fatal("Error getting hardware address for \"%s\": %m", 
  			  name);
  	}
  
  	sa = &tmp.ifr_hwaddr;
  	switch (sa->sa_family) {
  		case ARPHRD_ETHER:
  			hw->hlen = 7;
  			hw->hbuf[0] = HTYPE_ETHER;
  			memcpy(&hw->hbuf[1], sa->sa_data, 6);
  			break;
  		case ARPHRD_IEEE802:
  #ifdef ARPHRD_IEEE802_TR
  		case ARPHRD_IEEE802_TR:
  #endif /* ARPHRD_IEEE802_TR */
  			hw->hlen = 7;
  			hw->hbuf[0] = HTYPE_IEEE802;
  			memcpy(&hw->hbuf[1], sa->sa_data, 6);
  			break;
  		case ARPHRD_FDDI:
  			hw->hlen = 7;
  			hw->hbuf[0] = HTYPE_FDDI;
  			memcpy(&hw->hbuf[1], sa->sa_data, 6);
  			break;
  		default:
  			log_fatal("Unsupported device type %ld for \"%s\"",
  				  (long int)sa->sa_family, name);
  	}
  
  	close(sock);
  }
  #endif
  