text: /*
   * Copyright (c) 2000-2016 Apple Inc. All rights reserved.
   *
   * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
   *
   * This file contains Original Code and/or Modifications of Original Code
   * as defined in and that are subject to the Apple Public Source License
   * Version 2.0 (the 'License'). You may not use this file except in
   * compliance with the License. The rights granted to you under the License
   * may not be used to create, or enable the creation or redistribution of,
   * unlawful or unlicensed copies of an Apple operating system, or to
   * circumvent, violate, or enable the circumvention or violation of, any
   * terms of an Apple operating system software license agreement.
   *
   * Please obtain a copy of the License at
   * http://www.opensource.apple.com/apsl/ and read it before using this file.
   *
   * The Original Code and all software distributed under the License are
   * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
   * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
   * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
   * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
   * Please see the License for the specific language governing rights and
   * limitations under the License.
   *
   * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
   */
  /*
   * Copyright (c) 1982, 1986, 1988, 1993
   *	The Regents of the University of California.  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. All advertising materials mentioning features or use of this software
   *    must display the following acknowledgement:
   *	This product includes software developed by the University of
   *	California, Berkeley and its contributors.
   * 4. Neither the name of the University nor the names of its contributors
   *    may be used to endorse or promote products derived from this software
   *    without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``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 REGENTS OR CONTRIBUTORS 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.
   *
   *	@(#)ip_input.c	8.2 (Berkeley) 1/4/94
   */
  /*
   * NOTICE: This file was modified by SPARTA, Inc. in 2007 to introduce
   * support for mandatory and extensible security protections.  This notice
   * is included in support of clause 2.2 (b) of the Apple Public License,
   * Version 2.0.
   */
  
  #define	_IP_VHL
  
  #include <sys/param.h>
  #include <sys/systm.h>
  #include <sys/mbuf.h>
  #include <sys/malloc.h>
  #include <sys/domain.h>
  #include <sys/protosw.h>
  #include <sys/socket.h>
  #include <sys/time.h>
  #include <sys/kernel.h>
  #include <sys/syslog.h>
  #include <sys/sysctl.h>
  #include <sys/mcache.h>
  #include <sys/socketvar.h>
  #include <sys/kdebug.h>
  #include <mach/mach_time.h>
  #include <mach/sdt.h>
  
  #include <machine/endian.h>
  #include <dev/random/randomdev.h>
  
  #include <kern/queue.h>
  #include <kern/locks.h>
  #include <libkern/OSAtomic.h>
  
  #include <pexpert/pexpert.h>
  
  #include <net/if.h>
  #include <net/if_var.h>
  #include <net/if_dl.h>
  #include <net/route.h>
  #include <net/kpi_protocol.h>
  #include <net/ntstat.h>
  #include <net/dlil.h>
  #include <net/classq/classq.h>
  #include <net/net_perf.h>
  #include <net/init.h>
  #if PF
  #include <net/pfvar.h>
  #endif /* PF */
  
  #include <netinet/in.h>
  #include <netinet/in_systm.h>
  #include <netinet/in_var.h>
  #include <netinet/in_arp.h>
  #include <netinet/ip.h>
  #include <netinet/in_pcb.h>
  #include <netinet/ip_var.h>
  #include <netinet/ip_icmp.h>
  #include <netinet/ip_fw.h>
  #include <netinet/ip_divert.h>
  #include <netinet/kpi_ipfilter_var.h>
  #include <netinet/udp.h>
  #include <netinet/udp_var.h>
  #include <netinet/bootp.h>
  #include <netinet/lro_ext.h>
  
  #if DUMMYNET
  #include <netinet/ip_dummynet.h>
  #endif /* DUMMYNET */
  
  #if CONFIG_MACF_NET
  #include <security/mac_framework.h>
  #endif /* CONFIG_MACF_NET */
  
  #if IPSEC
  #include <netinet6/ipsec.h>
  #include <netkey/key.h>
  #endif /* IPSEC */
  
  #define	DBG_LAYER_BEG		NETDBG_CODE(DBG_NETIP, 0)
  #define	DBG_LAYER_END		NETDBG_CODE(DBG_NETIP, 2)
  #define	DBG_FNC_IP_INPUT	NETDBG_CODE(DBG_NETIP, (2 << 8))
  
  #if IPSEC
  extern int ipsec_bypass;
  extern lck_mtx_t *sadb_mutex;
  
  lck_grp_t	*sadb_stat_mutex_grp;
  lck_grp_attr_t	*sadb_stat_mutex_grp_attr;
  lck_attr_t	*sadb_stat_mutex_attr;
  decl_lck_mtx_data(, sadb_stat_mutex_data);
  lck_mtx_t	*sadb_stat_mutex = &sadb_stat_mutex_data;
  #endif /* IPSEC */
  
  MBUFQ_HEAD(fq_head);
  
  static int frag_timeout_run;		/* frag timer is scheduled to run */
  static void frag_timeout(void *);
  static void frag_sched_timeout(void);
  
  static struct ipq *ipq_alloc(int);
  static void ipq_free(struct ipq *);
  static void ipq_updateparams(void);
  static void ip_input_second_pass(struct mbuf *, struct ifnet *,
      u_int32_t, int, int, struct ip_fw_in_args *, int);
  
  decl_lck_mtx_data(static, ipqlock);
  static lck_attr_t	*ipqlock_attr;
  static lck_grp_t	*ipqlock_grp;
  static lck_grp_attr_t	*ipqlock_grp_attr;
  
  /* Packet reassembly stuff */
  #define	IPREASS_NHASH_LOG2	6
  #define	IPREASS_NHASH		(1 << IPREASS_NHASH_LOG2)
  #define	IPREASS_HMASK		(IPREASS_NHASH - 1)
  #define	IPREASS_HASH(x, y) \
  	(((((x) & 0xF) | ((((x) >> 8) & 0xF) << 4)) ^ (y)) & IPREASS_HMASK)
  
  /* IP fragment reassembly queues (protected by ipqlock) */
  static TAILQ_HEAD(ipqhead, ipq) ipq[IPREASS_NHASH]; /* ip reassembly queues */
  static int maxnipq;			/* max packets in reass queues */
  static u_int32_t maxfragsperpacket;	/* max frags/packet in reass queues */
  static u_int32_t nipq;			/* # of packets in reass queues */
  static u_int32_t ipq_limit;		/* ipq allocation limit */
  static u_int32_t ipq_count;		/* current # of allocated ipq's */
  
  static int sysctl_ipforwarding SYSCTL_HANDLER_ARGS;
  static int sysctl_maxnipq SYSCTL_HANDLER_ARGS;
  static int sysctl_maxfragsperpacket SYSCTL_HANDLER_ARGS;
  
  #if (DEBUG || DEVELOPMENT)
  static int sysctl_reset_ip_input_stats SYSCTL_HANDLER_ARGS;
  static int sysctl_ip_input_measure_bins SYSCTL_HANDLER_ARGS;
  static int sysctl_ip_input_getperf SYSCTL_HANDLER_ARGS;
  #endif /* (DEBUG || DEVELOPMENT) */
  
  int ipforwarding = 0;
  SYSCTL_PROC(_net_inet_ip, IPCTL_FORWARDING, forwarding,
  	CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_LOCKED, &ipforwarding, 0,
  	sysctl_ipforwarding, "I", "Enable IP forwarding between interfaces");
  
  static int ipsendredirects = 1; /* XXX */
  SYSCTL_INT(_net_inet_ip, IPCTL_SENDREDIRECTS, redirect,
  	CTLFLAG_RW | CTLFLAG_LOCKED, &ipsendredirects, 0,
  	"Enable sending IP redirects");
  
  int ip_defttl = IPDEFTTL;
  SYSCTL_INT(_net_inet_ip, IPCTL_DEFTTL, ttl, CTLFLAG_RW | CTLFLAG_LOCKED,
  	&ip_defttl, 0, "Maximum TTL on IP packets");
  
  static int ip_dosourceroute = 0;
  SYSCTL_INT(_net_inet_ip, IPCTL_SOURCEROUTE, sourceroute,
  	CTLFLAG_RW | CTLFLAG_LOCKED, &ip_dosourceroute, 0,
  	"Enable forwarding source routed IP packets");
  
  static int ip_acceptsourceroute = 0;
  SYSCTL_INT(_net_inet_ip, IPCTL_ACCEPTSOURCEROUTE, accept_sourceroute,
  	CTLFLAG_RW | CTLFLAG_LOCKED, &ip_acceptsourceroute, 0,
  	"Enable accepting source routed IP packets");
  
  static int ip_sendsourcequench = 0;
  SYSCTL_INT(_net_inet_ip, OID_AUTO, sendsourcequench,
  	CTLFLAG_RW | CTLFLAG_LOCKED, &ip_sendsourcequench, 0,
  	"Enable the transmission of source quench packets");
  
  SYSCTL_PROC(_net_inet_ip, OID_AUTO, maxfragpackets,
  	CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_LOCKED, &maxnipq, 0, sysctl_maxnipq,
  	"I", "Maximum number of IPv4 fragment reassembly queue entries");
  
  SYSCTL_UINT(_net_inet_ip, OID_AUTO, fragpackets, CTLFLAG_RD | CTLFLAG_LOCKED,
  	&nipq, 0, "Current number of IPv4 fragment reassembly queue entries");
  
  SYSCTL_PROC(_net_inet_ip, OID_AUTO, maxfragsperpacket,
  	CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_LOCKED, &maxfragsperpacket, 0,
  	sysctl_maxfragsperpacket, "I",
  	"Maximum number of IPv4 fragments allowed per packet");
  
  static uint32_t ip_adj_clear_hwcksum = 0;
  SYSCTL_UINT(_net_inet_ip, OID_AUTO, adj_clear_hwcksum,
  	CTLFLAG_RW | CTLFLAG_LOCKED, &ip_adj_clear_hwcksum, 0,
  	"Invalidate hwcksum info when adjusting length");
  
  /*
   * XXX - Setting ip_checkinterface mostly implements the receive side of
   * the Strong ES model described in RFC 1122, but since the routing table
   * and transmit implementation do not implement the Strong ES model,
   * setting this to 1 results in an odd hybrid.
   *
   * XXX - ip_checkinterface currently must be disabled if you use ipnat
   * to translate the destination address to another local interface.
   *
   * XXX - ip_checkinterface must be disabled if you add IP aliases
   * to the loopback interface instead of the interface where the
   * packets for those addresses are received.
   */
  static int ip_checkinterface = 0;
  SYSCTL_INT(_net_inet_ip, OID_AUTO, check_interface, CTLFLAG_RW | CTLFLAG_LOCKED,
  	&ip_checkinterface, 0, "Verify packet arrives on correct interface");
  
  static int ip_chaining = 1;
  SYSCTL_INT(_net_inet_ip, OID_AUTO, rx_chaining, CTLFLAG_RW | CTLFLAG_LOCKED,
  	&ip_chaining, 1, "Do receive side ip address based chaining");
  
  static int ip_chainsz = 6;
  SYSCTL_INT(_net_inet_ip, OID_AUTO, rx_chainsz, CTLFLAG_RW | CTLFLAG_LOCKED,
  	&ip_chainsz, 1, "IP receive side max chaining");
  
  #if (DEBUG || DEVELOPMENT)
  static int ip_input_measure = 0;
  SYSCTL_PROC(_net_inet_ip, OID_AUTO, input_perf,
  	CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_LOCKED,
  	&ip_input_measure, 0, sysctl_reset_ip_input_stats, "I", "Do time measurement");
  
  static uint64_t ip_input_measure_bins = 0;
  SYSCTL_PROC(_net_inet_ip, OID_AUTO, input_perf_bins,
  	CTLTYPE_QUAD | CTLFLAG_RW | CTLFLAG_LOCKED, &ip_input_measure_bins, 0,
  	sysctl_ip_input_measure_bins, "I",
  	"bins for chaining performance data histogram");
  
  static net_perf_t net_perf;
  SYSCTL_PROC(_net_inet_ip, OID_AUTO, input_perf_data,
  	CTLTYPE_STRUCT | CTLFLAG_RD | CTLFLAG_LOCKED,
  	0, 0, sysctl_ip_input_getperf, "S,net_perf",
  	"IP input performance data (struct net_perf, net/net_perf.h)");
  #endif /* (DEBUG || DEVELOPMENT) */
  
  #if DIAGNOSTIC
  static int ipprintfs = 0;
  #endif
  
  struct protosw *ip_protox[IPPROTO_MAX];
  
  static lck_grp_attr_t	*in_ifaddr_rwlock_grp_attr;
  static lck_grp_t	*in_ifaddr_rwlock_grp;
  static lck_attr_t	*in_ifaddr_rwlock_attr;
  decl_lck_rw_data(, in_ifaddr_rwlock_data);
  lck_rw_t		*in_ifaddr_rwlock = &in_ifaddr_rwlock_data;
  
  /* Protected by in_ifaddr_rwlock */
  struct in_ifaddrhead in_ifaddrhead;		/* first inet address */
  struct in_ifaddrhashhead *in_ifaddrhashtbl;	/* inet addr hash table  */
  
  #define	INADDR_NHASH	61
  static u_int32_t inaddr_nhash;			/* hash table size */
  static u_int32_t inaddr_hashp;			/* next largest prime */
  
  static int ip_getstat SYSCTL_HANDLER_ARGS;
  struct ipstat ipstat;
  SYSCTL_PROC(_net_inet_ip, IPCTL_STATS, stats,
  	CTLTYPE_STRUCT | CTLFLAG_RD | CTLFLAG_LOCKED,
  	0, 0, ip_getstat, "S,ipstat",
  	"IP statistics (struct ipstat, netinet/ip_var.h)");
  
  #if IPCTL_DEFMTU
  SYSCTL_INT(_net_inet_ip, IPCTL_DEFMTU, mtu, CTLFLAG_RW | CTLFLAG_LOCKED,
  	&ip_mtu, 0, "Default MTU");
  #endif /* IPCTL_DEFMTU */
  
  #if IPSTEALTH
  static int	ipstealth = 0;
  SYSCTL_INT(_net_inet_ip, OID_AUTO, stealth, CTLFLAG_RW | CTLFLAG_LOCKED,
  	&ipstealth, 0, "");
  #endif /* IPSTEALTH */
  
  /* Firewall hooks */
  #if IPFIREWALL
  ip_fw_chk_t *ip_fw_chk_ptr;
  int fw_enable = 1;
  int fw_bypass = 1;
  int fw_one_pass = 0;
  #endif /* IPFIREWALL */
  
  #if DUMMYNET
  ip_dn_io_t *ip_dn_io_ptr;
  #endif /* DUMMYNET */
  
  SYSCTL_NODE(_net_inet_ip, OID_AUTO, linklocal,
  	CTLFLAG_RW | CTLFLAG_LOCKED, 0, "link local");
  
  struct ip_linklocal_stat ip_linklocal_stat;
  SYSCTL_STRUCT(_net_inet_ip_linklocal, OID_AUTO, stat,
  	CTLFLAG_RD | CTLFLAG_LOCKED, &ip_linklocal_stat, ip_linklocal_stat,
  	"Number of link local packets with TTL less than 255");
  
  SYSCTL_NODE(_net_inet_ip_linklocal, OID_AUTO, in,
  	CTLFLAG_RW | CTLFLAG_LOCKED, 0, "link local input");
  
  int ip_linklocal_in_allowbadttl = 1;
  SYSCTL_INT(_net_inet_ip_linklocal_in, OID_AUTO, allowbadttl,
  	CTLFLAG_RW | CTLFLAG_LOCKED, &ip_linklocal_in_allowbadttl, 0,
  	"Allow incoming link local packets with TTL less than 255");
  
  
  /*
   * We need to save the IP options in case a protocol wants to respond
   * to an incoming packet over the same route if the packet got here
   * using IP source routing.  This allows connection establishment and
   * maintenance when the remote end is on a network that is not known
   * to us.
   */
  static int	ip_nhops = 0;
  static	struct ip_srcrt {
  	struct	in_addr dst;			/* final destination */
  	char	nop;				/* one NOP to align */
  	char	srcopt[IPOPT_OFFSET + 1];	/* OPTVAL, OLEN and OFFSET */
  	struct	in_addr route[MAX_IPOPTLEN / sizeof (struct in_addr)];
  } ip_srcrt;
  
  static void in_ifaddrhashtbl_init(void);
  static void save_rte(u_char *, struct in_addr);
  static int ip_dooptions(struct mbuf *, int, struct sockaddr_in *);
  static void ip_forward(struct mbuf *, int, struct sockaddr_in *);
  static void frag_freef(struct ipqhead *, struct ipq *);
  #if IPDIVERT
  #ifdef IPDIVERT_44
  static struct mbuf *ip_reass(struct mbuf *, u_int32_t *, u_int16_t *);
  #else /* !IPDIVERT_44 */
  static struct mbuf *ip_reass(struct mbuf *, u_int16_t *, u_int16_t *);
  #endif /* !IPDIVERT_44 */
  #else /* !IPDIVERT */
  static struct mbuf *ip_reass(struct mbuf *);
  #endif /* !IPDIVERT */
  static void ip_fwd_route_copyout(struct ifnet *, struct route *);
  static void ip_fwd_route_copyin(struct ifnet *, struct route *);
  static inline u_short ip_cksum(struct mbuf *, int);
  
  int ip_use_randomid = 1;
  SYSCTL_INT(_net_inet_ip, OID_AUTO, random_id, CTLFLAG_RW | CTLFLAG_LOCKED,
  	&ip_use_randomid, 0, "Randomize IP packets IDs");
  
  /*
   * On platforms which require strict alignment (currently for anything but
   * i386 or x86_64), check if the IP header pointer is 32-bit aligned; if not,
   * copy the contents of the mbuf chain into a new chain, and free the original
   * one.  Create some head room in the first mbuf of the new chain, in case
   * it's needed later on.
   */
  #if defined(__i386__) || defined(__x86_64__)
  #define	IP_HDR_ALIGNMENT_FIXUP(_m, _ifp, _action) do { } while (0)
  #else /* !__i386__ && !__x86_64__ */
  #define	IP_HDR_ALIGNMENT_FIXUP(_m, _ifp, _action) do {			\
  	if (!IP_HDR_ALIGNED_P(mtod(_m, caddr_t))) {			\
  		struct mbuf *_n;					\
  		struct ifnet *__ifp = (_ifp);				\
  		atomic_add_64(&(__ifp)->if_alignerrs, 1);		\
  		if (((_m)->m_flags & M_PKTHDR) &&			\
  		    (_m)->m_pkthdr.pkt_hdr != NULL)			\
  			(_m)->m_pkthdr.pkt_hdr = NULL;			\
  		_n = m_defrag_offset(_m, max_linkhdr, M_NOWAIT);	\
  		if (_n == NULL) {					\
  			atomic_add_32(&ipstat.ips_toosmall, 1);		\
  			m_freem(_m);					\
  			(_m) = NULL;					\
  			_action;					\
  		} else {						\
  			VERIFY(_n != (_m));				\
  			(_m) = _n;					\
  		}							\
  	}								\
  } while (0)
  #endif /* !__i386__ && !__x86_64__ */
  
  /*
   * GRE input handler function, settable via ip_gre_register_input() for PPTP.
   */
  static gre_input_func_t gre_input_func;
  
  static void
  ip_init_delayed(void)
  {
  	struct ifreq ifr;
  	int error;
  	struct sockaddr_in *sin;
  
  	bzero(&ifr, sizeof(ifr));
  	strlcpy(ifr.ifr_name, "lo0", sizeof(ifr.ifr_name));
  	sin = (struct sockaddr_in *)(void *)&ifr.ifr_addr;
  	sin->sin_len = sizeof(struct sockaddr_in);
  	sin->sin_family = AF_INET;
  	sin->sin_addr.s_addr = htonl(INADDR_LOOPBACK);
  	error = in_control(NULL, SIOCSIFADDR, (caddr_t)&ifr, lo_ifp, kernproc);
  	if (error)
  		printf("%s: failed to initialise lo0's address, error=%d\n",
  		    __func__, error);
  }
  
  /*
   * IP initialization: fill in IP protocol switch table.
   * All protocols not implemented in kernel go to raw IP protocol handler.
   */
  void
  ip_init(struct protosw *pp, struct domain *dp)
  {
  	static int ip_initialized = 0;
  	struct protosw *pr;
  	struct timeval tv;
  	int i;
  
  	domain_proto_mtx_lock_assert_held();
  	VERIFY((pp->pr_flags & (PR_INITIALIZED|PR_ATTACHED)) == PR_ATTACHED);
  
  	/* ipq_alloc() uses mbufs for IP fragment queue structures */
  	_CASSERT(sizeof (struct ipq) <= _MLEN);
  
  	/*
  	 * Some ioctls (e.g. SIOCAIFADDR) use ifaliasreq struct, which is
  	 * interchangeable with in_aliasreq; they must have the same size.
  	 */
  	_CASSERT(sizeof (struct ifaliasreq) == sizeof (struct in_aliasreq));
  
  	if (ip_initialized)
  		return;
  	ip_initialized = 1;
  
  	in_ifaddr_init();
  
  	in_ifaddr_rwlock_grp_attr = lck_grp_attr_alloc_init();
  	in_ifaddr_rwlock_grp = lck_grp_alloc_init("in_ifaddr_rwlock",
  	    in_ifaddr_rwlock_grp_attr);
  	in_ifaddr_rwlock_attr = lck_attr_alloc_init();
  	lck_rw_init(in_ifaddr_rwlock, in_ifaddr_rwlock_grp,
  	    in_ifaddr_rwlock_attr);
  
  	TAILQ_INIT(&in_ifaddrhead);
  	in_ifaddrhashtbl_init();
  
  	ip_moptions_init();
  
  	pr = pffindproto_locked(PF_INET, IPPROTO_RAW, SOCK_RAW);
  	if (pr == NULL) {
  		panic("%s: Unable to find [PF_INET,IPPROTO_RAW,SOCK_RAW]\n",
  		    __func__);
  		/* NOTREACHED */
  	}
  
  	/* Initialize the entire ip_protox[] array to IPPROTO_RAW. */
  	for (i = 0; i < IPPROTO_MAX; i++)
  		ip_protox[i] = pr;
  	/*
  	 * Cycle through IP protocols and put them into the appropriate place
  	 * in ip_protox[], skipping protocols IPPROTO_{IP,RAW}.
  	 */
  	VERIFY(dp == inetdomain && dp->dom_family == PF_INET);
  	TAILQ_FOREACH(pr, &dp->dom_protosw, pr_entry) {
  		VERIFY(pr->pr_domain == dp);
  		if (pr->pr_protocol != 0 && pr->pr_protocol != IPPROTO_RAW) {
  			/* Be careful to only index valid IP protocols. */
  			if (pr->pr_protocol < IPPROTO_MAX)
  				ip_protox[pr->pr_protocol] = pr;
  		}
  	}
  
  	/* IP fragment reassembly queue lock */
  	ipqlock_grp_attr  = lck_grp_attr_alloc_init();
  	ipqlock_grp = lck_grp_alloc_init("ipqlock", ipqlock_grp_attr);
  	ipqlock_attr = lck_attr_alloc_init();
  	lck_mtx_init(&ipqlock, ipqlock_grp, ipqlock_attr);
  
  	lck_mtx_lock(&ipqlock);
  	/* Initialize IP reassembly queue. */
  	for (i = 0; i < IPREASS_NHASH; i++)
  		TAILQ_INIT(&ipq[i]);
  
  	maxnipq = nmbclusters / 32;
  	maxfragsperpacket = 128; /* enough for 64k in 512 byte fragments */
  	ipq_updateparams();
  	lck_mtx_unlock(&ipqlock);
  
  	getmicrotime(&tv);
  	ip_id = RandomULong() ^ tv.tv_usec;
  	ip_initid();
  
  	ipf_init();
  
  #if IPSEC
  	sadb_stat_mutex_grp_attr = lck_grp_attr_alloc_init();
  	sadb_stat_mutex_grp = lck_grp_alloc_init("sadb_stat",
  	    sadb_stat_mutex_grp_attr);
  	sadb_stat_mutex_attr = lck_attr_alloc_init();
  	lck_mtx_init(sadb_stat_mutex, sadb_stat_mutex_grp,
  	    sadb_stat_mutex_attr);
  
  #endif
  	arp_init();
  	net_init_add(ip_init_delayed);
  }
  
  /*
   * Initialize IPv4 source address hash table.
   */
  static void
  in_ifaddrhashtbl_init(void)
  {
  	int i, k, p;
  
  	if (in_ifaddrhashtbl != NULL)
  		return;
  
  	PE_parse_boot_argn("inaddr_nhash", &inaddr_nhash,
  	    sizeof (inaddr_nhash));
  	if (inaddr_nhash == 0)
  		inaddr_nhash = INADDR_NHASH;
  
  	MALLOC(in_ifaddrhashtbl, struct in_ifaddrhashhead *,
  	    inaddr_nhash * sizeof (*in_ifaddrhashtbl),
  	    M_IFADDR, M_WAITOK | M_ZERO);
  	if (in_ifaddrhashtbl == NULL)
  		panic("in_ifaddrhashtbl_init allocation failed");
  
  	/*
  	 * Generate the next largest prime greater than inaddr_nhash.
  	 */
  	k = (inaddr_nhash % 2 == 0) ? inaddr_nhash + 1 : inaddr_nhash + 2;
  	for (;;) {
  		p = 1;
  		for (i = 3; i * i <= k; i += 2) {
  			if (k % i == 0)
  				p = 0;
  		}
  		if (p == 1)
  			break;
  		k += 2;
  	}
  	inaddr_hashp = k;
  }
  
  u_int32_t
  inaddr_hashval(u_int32_t key)
  {
  	/*
  	 * The hash index is the computed prime times the key modulo
  	 * the hash size, as documented in "Introduction to Algorithms"
  	 * (Cormen, Leiserson, Rivest).
  	 */
  	if (inaddr_nhash > 1)
  		return ((key * inaddr_hashp) % inaddr_nhash);
  	else
  		return (0);
  }
  
  void
  ip_proto_dispatch_in_wrapper(struct mbuf *m, int hlen, u_int8_t proto)
  {
  	ip_proto_dispatch_in(m, hlen, proto, 0);
  }
  
  __private_extern__ void
  ip_proto_dispatch_in(struct mbuf *m, int hlen, u_int8_t proto,
      ipfilter_t inject_ipfref)
  {
  	struct ipfilter *filter;
  	int seen = (inject_ipfref == NULL);
  	int	changed_header = 0;
  	struct ip *ip;
  	void (*pr_input)(struct mbuf *, int len);
  
  	if (!TAILQ_EMPTY(&ipv4_filters)) {
  		ipf_ref();
  		TAILQ_FOREACH(filter, &ipv4_filters, ipf_link) {
  			if (seen == 0) {
  				if ((struct ipfilter *)inject_ipfref == filter)
  					seen = 1;
  			} else if (filter->ipf_filter.ipf_input) {
  				errno_t result;
  
  				if (changed_header == 0) {
  					/*
  					 * Perform IP header alignment fixup,
  					 * if needed, before passing packet
  					 * into filter(s).
  					 */
  					IP_HDR_ALIGNMENT_FIXUP(m,
  					    m->m_pkthdr.rcvif, ipf_unref());
  
  					/* ipf_unref() already called */
  					if (m == NULL)
  						return;
  
  					changed_header = 1;
  					ip = mtod(m, struct ip *);
  					ip->ip_len = htons(ip->ip_len + hlen);
  					ip->ip_off = htons(ip->ip_off);
  					ip->ip_sum = 0;
  					ip->ip_sum = ip_cksum_hdr_in(m, hlen);
  				}
  				result = filter->ipf_filter.ipf_input(
  				    filter->ipf_filter.cookie, (mbuf_t *)&m,
  				    hlen, proto);
  				if (result == EJUSTRETURN) {
  					ipf_unref();
  					return;
  				}
  				if (result != 0) {
  					ipf_unref();
  					m_freem(m);
  					return;
  				}
  			}
  		}
  		ipf_unref();
  	}
  
  	/* Perform IP header alignment fixup (post-filters), if needed */
  	IP_HDR_ALIGNMENT_FIXUP(m, m->m_pkthdr.rcvif, return);
  
  	/*
  	 * If there isn't a specific lock for the protocol
  	 * we're about to call, use the generic lock for AF_INET.
  	 * otherwise let the protocol deal with its own locking
  	 */
  	ip = mtod(m, struct ip *);
  
  	if (changed_header) {
  		ip->ip_len = ntohs(ip->ip_len) - hlen;
  		ip->ip_off = ntohs(ip->ip_off);
  	}
  
  	if ((pr_input = ip_protox[ip->ip_p]->pr_input) == NULL) {
  		m_freem(m);
  	} else if (!(ip_protox[ip->ip_p]->pr_flags & PR_PROTOLOCK)) {
  		lck_mtx_lock(inet_domain_mutex);
  		pr_input(m, hlen);
  		lck_mtx_unlock(inet_domain_mutex);
  	} else {
  		pr_input(m, hlen);
  	}
  }
  
  struct pktchain_elm {
  	struct mbuf	*pkte_head;
  	struct mbuf	*pkte_tail;
  	struct in_addr	pkte_saddr;
  	struct in_addr	pkte_daddr;
  	uint16_t	pkte_npkts;
  	uint16_t	pkte_proto;
  	uint32_t	pkte_nbytes;
  };
  
  typedef struct pktchain_elm pktchain_elm_t;
  
  /* Store upto PKTTBL_SZ unique flows on the stack */
  #define PKTTBL_SZ	7
  
  static struct mbuf *
  ip_chain_insert(struct mbuf *packet, pktchain_elm_t *tbl)
  {
  	struct ip*	ip;
  	int		pkttbl_idx = 0;
  
  	ip = mtod(packet, struct ip*);
  
  	/* reusing the hash function from inaddr_hashval */
  	pkttbl_idx = inaddr_hashval(ntohs(ip->ip_src.s_addr)) % PKTTBL_SZ;
  	if (tbl[pkttbl_idx].pkte_head == NULL) {
  		tbl[pkttbl_idx].pkte_head = packet;
  		tbl[pkttbl_idx].pkte_saddr.s_addr = ip->ip_src.s_addr;
  		tbl[pkttbl_idx].pkte_daddr.s_addr = ip->ip_dst.s_addr;
  		tbl[pkttbl_idx].pkte_proto = ip->ip_p;
  	} else {
  		if ((ip->ip_dst.s_addr == tbl[pkttbl_idx].pkte_daddr.s_addr) &&
  		    (ip->ip_src.s_addr == tbl[pkttbl_idx].pkte_saddr.s_addr) &&
  		    (ip->ip_p == tbl[pkttbl_idx].pkte_proto)) {
  		} else {
  			return (packet);
  		}
  	}
  	if (tbl[pkttbl_idx].pkte_tail != NULL)
  		mbuf_setnextpkt(tbl[pkttbl_idx].pkte_tail, packet);
  
  	tbl[pkttbl_idx].pkte_tail = packet;
  	tbl[pkttbl_idx].pkte_npkts += 1;
  	tbl[pkttbl_idx].pkte_nbytes += packet->m_pkthdr.len;
  	return (NULL);
  }
  
  /* args is a dummy variable here for backward compatibility */
  static void
  ip_input_second_pass_loop_tbl(pktchain_elm_t *tbl, struct ip_fw_in_args *args)
  {
  	int i = 0;
  
  	for (i = 0; i < PKTTBL_SZ; i++) {
  		if (tbl[i].pkte_head != NULL) {
  			struct mbuf *m = tbl[i].pkte_head;
  			ip_input_second_pass(m, m->m_pkthdr.rcvif, 0,
  			    tbl[i].pkte_npkts, tbl[i].pkte_nbytes, args, 0);
  
  			if (tbl[i].pkte_npkts > 2)
  				ipstat.ips_rxc_chainsz_gt2++;
  			if (tbl[i].pkte_npkts > 4)
  				ipstat.ips_rxc_chainsz_gt4++;
  #if (DEBUG || DEVELOPMENT)
  			if (ip_input_measure)
  				net_perf_histogram(&net_perf, tbl[i].pkte_npkts);
  #endif /* (DEBUG || DEVELOPMENT) */
  			tbl[i].pkte_head = tbl[i].pkte_tail = NULL;
  			tbl[i].pkte_npkts = 0;
  			tbl[i].pkte_nbytes = 0;
  			/* no need to initialize address and protocol in tbl */
  		}
  	}
  }
  
  static void
  ip_input_cpout_args(struct ip_fw_in_args *args, struct ip_fw_args *args1,
      boolean_t *done_init)
  {
  	if (*done_init == FALSE) {
  		bzero(args1, sizeof(struct ip_fw_args));
  		*done_init = TRUE;
  	}
  	args1->fwa_next_hop = args->fwai_next_hop;
  	args1->fwa_ipfw_rule = args->fwai_ipfw_rule;
  	args1->fwa_pf_rule = args->fwai_pf_rule;
  	args1->fwa_divert_rule = args->fwai_divert_rule;
  }
  
  static void
  ip_input_cpin_args(struct ip_fw_args *args1, struct ip_fw_in_args *args)
  {
  	args->fwai_next_hop = args1->fwa_next_hop;
  	args->fwai_ipfw_rule = args1->fwa_ipfw_rule;
  	args->fwai_pf_rule = args1->fwa_pf_rule;
  	args->fwai_divert_rule = args1->fwa_divert_rule;
  }
  
  typedef enum {
  	IPINPUT_DOCHAIN = 0,
  	IPINPUT_DONTCHAIN,
  	IPINPUT_FREED,
  	IPINPUT_DONE
  } ipinput_chain_ret_t;
  
  static void
  ip_input_update_nstat(struct ifnet *ifp, struct in_addr src_ip,
      u_int32_t packets, u_int32_t bytes)
  {
  	if (nstat_collect) {
  		struct rtentry *rt = ifnet_cached_rtlookup_inet(ifp,
  		    src_ip);
  		if (rt != NULL) {
  			nstat_route_rx(rt, packets, bytes, 0);
  			rtfree(rt);
  		}
  	}
  }
  
  static void
  ip_input_dispatch_chain(struct mbuf *m)
  {
  	struct mbuf *tmp_mbuf = m;
  	struct mbuf *nxt_mbuf = NULL;
  	struct ip *ip = NULL;
  	unsigned int hlen;
  
  	ip = mtod(tmp_mbuf, struct ip *);
  	hlen = IP_VHL_HL(ip->ip_vhl) << 2;
  	while(tmp_mbuf) {
  		nxt_mbuf = mbuf_nextpkt(tmp_mbuf);
  		mbuf_setnextpkt(tmp_mbuf, NULL);
  
  		if ((sw_lro) && (ip->ip_p == IPPROTO_TCP))
  			tmp_mbuf = tcp_lro(tmp_mbuf, hlen);
  		if (tmp_mbuf)
  			ip_proto_dispatch_in(tmp_mbuf, hlen, ip->ip_p, 0);
  		tmp_mbuf = nxt_mbuf;
  		if (tmp_mbuf) {
  			ip = mtod(tmp_mbuf, struct ip *);
  			/* first mbuf of chain already has adjusted ip_len */
  			hlen = IP_VHL_HL(ip->ip_vhl) << 2;
  			ip->ip_len -= hlen;
  		}
  	}
  }
  
  static void
  ip_input_setdst_chain(struct mbuf *m, uint32_t ifindex, struct in_ifaddr *ia)
  {
  	struct mbuf *tmp_mbuf = m;
  
  	while (tmp_mbuf) {
  		ip_setdstifaddr_info(tmp_mbuf, ifindex, ia);
  		tmp_mbuf = mbuf_nextpkt(tmp_mbuf);
  	}
  }
  
  /*
   * First pass does all essential packet validation and places on a per flow
   * queue for doing operations that have same outcome for all packets of a flow.
   * div_info is packet divert/tee info
   */
  static ipinput_chain_ret_t
  ip_input_first_pass(struct mbuf *m, u_int32_t *div_info,
      struct ip_fw_in_args *args, int *ours, struct mbuf **modm)
  {
  	struct ip	*ip;
  	struct ifnet	*inifp;
  	unsigned int	hlen;
  	int		retval = IPINPUT_DOCHAIN;
  	int		len = 0;
  	struct in_addr	src_ip;
  #if IPFIREWALL
  	int		i;
  #endif
  #if IPFIREWALL || DUMMYNET
  	struct m_tag		*copy;
  	struct m_tag		*p;
  	boolean_t		delete = FALSE;
  	struct ip_fw_args	args1;
  	boolean_t		init = FALSE;
  #endif
  	ipfilter_t inject_filter_ref = NULL;
  
  #if !IPFIREWALL
  #pragma unused (args)
  #endif
  
  #if !IPDIVERT
  #pragma unused (div_info)
  #pragma unused (ours)
  #endif
  
  #if !IPFIREWALL_FORWARD
  #pragma unused (ours)
  #endif
  
  	/* Check if the mbuf is still valid after interface filter processing */
  	MBUF_INPUT_CHECK(m, m->m_pkthdr.rcvif);
  	inifp = mbuf_pkthdr_rcvif(m);
  	VERIFY(inifp != NULL);
  
  	/* Perform IP header alignment fixup, if needed */
  	IP_HDR_ALIGNMENT_FIXUP(m, inifp, goto bad);
  
  	m->m_pkthdr.pkt_flags &= ~PKTF_FORWARDED;
  
  #if IPFIREWALL || DUMMYNET
  
  	/*
  	 * Don't bother searching for tag(s) if there's none.
  	 */
  	if (SLIST_EMPTY(&m->m_pkthdr.tags))
  		goto ipfw_tags_done;
  
  	/* Grab info from mtags prepended to the chain */
  	p = m_tag_first(m);
  	while (p) {
  		if (p->m_tag_id == KERNEL_MODULE_TAG_ID) {
  #if DUMMYNET
  			if (p->m_tag_type == KERNEL_TAG_TYPE_DUMMYNET) {
  				struct dn_pkt_tag *dn_tag;
  
  				dn_tag = (struct dn_pkt_tag *)(p+1);
  				args->fwai_ipfw_rule = dn_tag->dn_ipfw_rule;
  				args->fwai_pf_rule = dn_tag->dn_pf_rule;
  				delete = TRUE;
  			}
  #endif
  
  #if IPDIVERT
  			if (p->m_tag_type == KERNEL_TAG_TYPE_DIVERT) {
  				struct divert_tag *div_tag;
  
  				div_tag = (struct divert_tag *)(p+1);
  				args->fwai_divert_rule = div_tag->cookie;
  				delete = TRUE;
  			}
  #endif
  
  			if (p->m_tag_type == KERNEL_TAG_TYPE_IPFORWARD) {
  				struct ip_fwd_tag *ipfwd_tag;
  
  				ipfwd_tag = (struct ip_fwd_tag *)(p+1);
  				args->fwai_next_hop = ipfwd_tag->next_hop;
  				delete = TRUE;
  			}
  
  			if (delete) {
  				copy = p;
  				p = m_tag_next(m, p);
  				m_tag_delete(m, copy);
  			} else	{
  				p = m_tag_next(m, p);
  			}
  		} else {
  			p = m_tag_next(m, p);
  		}
  	}
  
  #if DIAGNOSTIC
  	if (m == NULL || !(m->m_flags & M_PKTHDR))
  		panic("ip_input no HDR");
  #endif
  
  #if DUMMYNET
  	if (args->fwai_ipfw_rule || args->fwai_pf_rule) {
  		/* dummynet already filtered us */
  		ip = mtod(m, struct ip *);
  		hlen = IP_VHL_HL(ip->ip_vhl) << 2;
  		inject_filter_ref = ipf_get_inject_filter(m);
  #if IPFIREWALL
  		if (args->fwai_ipfw_rule)
  			goto iphack;
  #endif /* IPFIREWALL */
  		if (args->fwai_pf_rule)
  			goto check_with_pf;
  	}
  #endif /* DUMMYNET */
  ipfw_tags_done:
  #endif /* IPFIREWALL || DUMMYNET */
  
  	/*
  	 * No need to process packet twice if we've already seen it.
  	 */
  	if (!SLIST_EMPTY(&m->m_pkthdr.tags))
  		inject_filter_ref = ipf_get_inject_filter(m);
  	if (inject_filter_ref != NULL) {
  		ip = mtod(m, struct ip *);
  		hlen = IP_VHL_HL(ip->ip_vhl) << 2;
  
  		DTRACE_IP6(receive, struct mbuf *, m, struct inpcb *, NULL,
  		    struct ip *, ip, struct ifnet *, inifp,
  		    struct ip *, ip, struct ip6_hdr *, NULL);
  
  		ip->ip_len = ntohs(ip->ip_len) - hlen;
  		ip->ip_off = ntohs(ip->ip_off);
  		ip_proto_dispatch_in(m, hlen, ip->ip_p, inject_filter_ref);
  		return (IPINPUT_DONE);
  	}
  
  	if (m->m_pkthdr.len < sizeof (struct ip)) {
  		OSAddAtomic(1, &ipstat.ips_total);
  		OSAddAtomic(1, &ipstat.ips_tooshort);
  		m_freem(m);
  		return (IPINPUT_FREED);
  	}
  
  	if (m->m_len < sizeof (struct ip) &&
  	    (m = m_pullup(m, sizeof (struct ip))) == NULL) {
  		OSAddAtomic(1, &ipstat.ips_total);
  		OSAddAtomic(1, &ipstat.ips_toosmall);
  		return (IPINPUT_FREED);
  	}
  
  	ip = mtod(m, struct ip *);
  	*modm = m;
  
  	KERNEL_DEBUG(DBG_LAYER_BEG, ip->ip_dst.s_addr, ip->ip_src.s_addr,
  	    ip->ip_p, ip->ip_off, ip->ip_len);
  
  	if (IP_VHL_V(ip->ip_vhl) != IPVERSION) {
  		OSAddAtomic(1, &ipstat.ips_total);
  		OSAddAtomic(1, &ipstat.ips_badvers);
  		KERNEL_DEBUG(DBG_LAYER_END, 0, 0, 0, 0, 0);
  		m_freem(m);
  		return (IPINPUT_FREED);
  	}
  
  	hlen = IP_VHL_HL(ip->ip_vhl) << 2;
  	if (hlen < sizeof (struct ip)) {
  		OSAddAtomic(1, &ipstat.ips_total);
  		OSAddAtomic(1, &ipstat.ips_badhlen);
  		KERNEL_DEBUG(DBG_LAYER_END, 0, 0, 0, 0, 0);
  		m_freem(m);
  		return (IPINPUT_FREED);
  	}
  
  	if (hlen > m->m_len) {
  		if ((m = m_pullup(m, hlen)) == NULL) {
  			OSAddAtomic(1, &ipstat.ips_total);
  			OSAddAtomic(1, &ipstat.ips_badhlen);
  			KERNEL_DEBUG(DBG_LAYER_END, 0, 0, 0, 0, 0);
  			return (IPINPUT_FREED);
  		}
  		ip = mtod(m, struct ip *);
  		*modm = m;
  	}
  
  	/* 127/8 must not appear on wire - RFC1122 */
  	if ((ntohl(ip->ip_dst.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET ||
  	    (ntohl(ip->ip_src.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET) {
  		/*
  		 * Allow for the following exceptions:
  		 *
  		 *   1. If the packet was sent to loopback (i.e. rcvif
  		 *      would have been set earlier at output time.)
  		 *
  		 *   2. If the packet was sent out on loopback from a local
  		 *      source address which belongs to a non-loopback
  		 *      interface (i.e. rcvif may not necessarily be a
  		 *      loopback interface, hence the test for PKTF_LOOP.)
  		 *      Unlike IPv6, there is no interface scope ID, and
  		 *      therefore we don't care so much about PKTF_IFINFO.
  		 */
  		if (!(inifp->if_flags & IFF_LOOPBACK) &&
  		     !(m->m_pkthdr.pkt_flags & PKTF_LOOP)) {
  			OSAddAtomic(1, &ipstat.ips_total);
  			OSAddAtomic(1, &ipstat.ips_badaddr);
  			KERNEL_DEBUG(DBG_LAYER_END, 0, 0, 0, 0, 0);
  			m_freem(m);
  			return (IPINPUT_FREED);
  		}
  	}
  
  	/* IPv4 Link-Local Addresses as defined in RFC3927 */
  	if ((IN_LINKLOCAL(ntohl(ip->ip_dst.s_addr)) ||
  	    IN_LINKLOCAL(ntohl(ip->ip_src.s_addr)))) {
  		ip_linklocal_stat.iplls_in_total++;
  		if (ip->ip_ttl != MAXTTL) {
  			OSAddAtomic(1, &ip_linklocal_stat.iplls_in_badttl);
  			/* Silently drop link local traffic with bad TTL */
  			if (!ip_linklocal_in_allowbadttl) {
  				OSAddAtomic(1, &ipstat.ips_total);
  				KERNEL_DEBUG(DBG_LAYER_END, 0, 0, 0, 0, 0);
  				m_freem(m);
  				return (IPINPUT_FREED);
  			}
  		}
  	}
  
  	if (ip_cksum(m, hlen)) {
  		OSAddAtomic(1, &ipstat.ips_total);
  		KERNEL_DEBUG(DBG_LAYER_END, 0, 0, 0, 0, 0);
  		m_freem(m);
  		return (IPINPUT_FREED);
  	}
  
  	DTRACE_IP6(receive, struct mbuf *, m, struct inpcb *, NULL,
  	    struct ip *, ip, struct ifnet *, inifp,
  	    struct ip *, ip, struct ip6_hdr *, NULL);
  
  	/*
  	 * Convert fields to host representation.
  	 */
  #if BYTE_ORDER != BIG_ENDIAN
  	NTOHS(ip->ip_len);
  #endif
  
  	if (ip->ip_len < hlen) {
  		OSAddAtomic(1, &ipstat.ips_total);
  		OSAddAtomic(1, &ipstat.ips_badlen);
  		KERNEL_DEBUG(DBG_LAYER_END, 0, 0, 0, 0, 0);
  		m_freem(m);
  		return (IPINPUT_FREED);
  	}
  
  #if BYTE_ORDER != BIG_ENDIAN
  	NTOHS(ip->ip_off);
  #endif
  
  	/*
  	 * Check that the amount of data in the buffers
  	 * is as at least much as the IP header would have us expect.
  	 * Trim mbufs if longer than we expect.
  	 * Drop packet if shorter than we expect.
  	 */
  	if (m->m_pkthdr.len < ip->ip_len) {
  		OSAddAtomic(1, &ipstat.ips_total);
  		OSAddAtomic(1, &ipstat.ips_tooshort);
  		KERNEL_DEBUG(DBG_LAYER_END, 0, 0, 0, 0, 0);
  		m_freem(m);
  		return (IPINPUT_FREED);
  	}
  
  	if (m->m_pkthdr.len > ip->ip_len) {
  		/*
  		 * Invalidate hardware checksum info if ip_adj_clear_hwcksum
  		 * is set; useful to handle buggy drivers.  Note that this
  		 * should not be enabled by default, as we may get here due
  		 * to link-layer padding.
  		 */
  		if (ip_adj_clear_hwcksum &&
  		    (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) &&
  		    !(inifp->if_flags & IFF_LOOPBACK) &&
  		    !(m->m_pkthdr.pkt_flags & PKTF_LOOP)) {
  			m->m_pkthdr.csum_flags &= ~CSUM_DATA_VALID;
  			m->m_pkthdr.csum_data = 0;
  			ipstat.ips_adj_hwcsum_clr++;
  		}
  
  		ipstat.ips_adj++;
  		if (m->m_len == m->m_pkthdr.len) {
  			m->m_len = ip->ip_len;
  			m->m_pkthdr.len = ip->ip_len;
  		} else
  			m_adj(m, ip->ip_len - m->m_pkthdr.len);
  	}
  
  	/* for consistency */
  	m->m_pkthdr.pkt_proto = ip->ip_p;
  
  	/* for netstat route statistics */
  	src_ip = ip->ip_src;
  	len = m->m_pkthdr.len;
  
  #if DUMMYNET
  check_with_pf:
  #endif
  #if PF
  	/* Invoke inbound packet filter */
  	if (PF_IS_ENABLED) {
  		int error;
  		ip_input_cpout_args(args, &args1, &init);
  
  #if DUMMYNET
  		error = pf_af_hook(inifp, NULL, &m, AF_INET, TRUE, &args1);
  #else
  		error = pf_af_hook(inifp, NULL, &m, AF_INET, TRUE, NULL);
  #endif /* DUMMYNET */
  		if (error != 0 || m == NULL) {
  			if (m != NULL) {
  				panic("%s: unexpected packet %p\n",
  				    __func__, m);
  				/* NOTREACHED */
  			}
  			/* Already freed by callee */
  			ip_input_update_nstat(inifp, src_ip, 1, len);
  			KERNEL_DEBUG(DBG_LAYER_END, 0, 0, 0, 0, 0);
  			OSAddAtomic(1, &ipstat.ips_total);
  			return (IPINPUT_FREED);
  		}
  		ip = mtod(m, struct ip *);
  		hlen = IP_VHL_HL(ip->ip_vhl) << 2;
  		*modm = m;
  		ip_input_cpin_args(&args1, args);
  	}
  #endif /* PF */
  
  #if IPSEC
  	if (ipsec_bypass == 0 && ipsec_gethist(m, NULL)) {
  		retval = IPINPUT_DONTCHAIN; /* XXX scope for chaining here? */
  		goto pass;
  	}
  #endif
  
  #if IPFIREWALL
  #if DUMMYNET
  iphack:
  #endif /* DUMMYNET */
  	/*
  	 * Check if we want to allow this packet to be processed.
  	 * Consider it to be bad if not.
  	 */
  	if (fw_enable && IPFW_LOADED) {
  #if IPFIREWALL_FORWARD
  		/*
  		 * If we've been forwarded from the output side, then
  		 * skip the firewall a second time
  		 */
  		if (args->fwai_next_hop) {
  			*ours = 1;
  			return (IPINPUT_DONTCHAIN);
  		}
  #endif	/* IPFIREWALL_FORWARD */
  		ip_input_cpout_args(args, &args1, &init);
  		args1.fwa_m = m;
  
  		i = ip_fw_chk_ptr(&args1);
  		m = args1.fwa_m;
  
  		if ((i & IP_FW_PORT_DENY_FLAG) || m == NULL) { /* drop */
  			if (m)
  				m_freem(m);
  			ip_input_update_nstat(inifp, src_ip, 1, len);
  			KERNEL_DEBUG(DBG_LAYER_END, 0, 0, 0, 0, 0);
  			OSAddAtomic(1, &ipstat.ips_total);
  			return (IPINPUT_FREED);
  		}
  		ip = mtod(m, struct ip *); /* just in case m changed */
  		*modm = m;
  		ip_input_cpin_args(&args1, args);
  
  		if (i == 0 && args->fwai_next_hop == NULL) { /* common case */
  			goto pass;
  		}
  #if DUMMYNET
  		if (DUMMYNET_LOADED && (i & IP_FW_PORT_DYNT_FLAG) != 0) {
  			/* Send packet to the appropriate pipe */
  			ip_dn_io_ptr(m, i&0xffff, DN_TO_IP_IN, &args1,
  			    DN_CLIENT_IPFW);
  			ip_input_update_nstat(inifp, src_ip, 1, len);
  			KERNEL_DEBUG(DBG_LAYER_END, 0, 0, 0, 0, 0);
  			OSAddAtomic(1, &ipstat.ips_total);
  			return (IPINPUT_FREED);
  		}
  #endif /* DUMMYNET */
  #if IPDIVERT
  		if (i != 0 && (i & IP_FW_PORT_DYNT_FLAG) == 0) {
  			/* Divert or tee packet */
  			*div_info = i;
  			*ours = 1;
  			return (IPINPUT_DONTCHAIN);
  		}
  #endif
  #if IPFIREWALL_FORWARD
  		if (i == 0 && args->fwai_next_hop != NULL) {
  			retval = IPINPUT_DONTCHAIN;
  			goto pass;
  		}
  #endif
  		/*
  		 * if we get here, the packet must be dropped
  		 */
  		ip_input_update_nstat(inifp, src_ip, 1, len);
  		KERNEL_DEBUG(DBG_LAYER_END, 0, 0, 0, 0, 0);
  		m_freem(m);
  		OSAddAtomic(1, &ipstat.ips_total);
  		return (IPINPUT_FREED);
  	}
  #endif /* IPFIREWALL */
  #if IPSEC | IPFIREWALL
  pass:
  #endif
  	/*
  	 * Process options and, if not destined for us,
  	 * ship it on.  ip_dooptions returns 1 when an
  	 * error was detected (causing an icmp message
  	 * to be sent and the original packet to be freed).
  	 */
  	ip_nhops = 0;		/* for source routed packets */
  #if IPFIREWALL
  	if (hlen > sizeof (struct ip) &&
  	    ip_dooptions(m, 0, args->fwai_next_hop)) {
  #else /* !IPFIREWALL */
  	if (hlen > sizeof (struct ip) && ip_dooptions(m, 0, NULL)) {
  #endif /* !IPFIREWALL */
  		ip_input_update_nstat(inifp, src_ip, 1, len);
  		KERNEL_DEBUG(DBG_LAYER_END, 0, 0, 0, 0, 0);
  		OSAddAtomic(1, &ipstat.ips_total);
  		return (IPINPUT_FREED);
  	}
  
  	/*
  	 * Don't chain fragmented packets as the process of determining
  	 * if it is our fragment or someone else's plus the complexity of
  	 * divert and fw args makes it harder to do chaining.
  	 */
  	if (ip->ip_off & ~(IP_DF | IP_RF))
  		return (IPINPUT_DONTCHAIN);
  
  	/* Allow DHCP/BootP responses through */
  	if ((inifp->if_eflags & IFEF_AUTOCONFIGURING) &&
  	    hlen == sizeof (struct ip) && ip->ip_p == IPPROTO_UDP) {
  		struct udpiphdr *ui;
  
  		if (m->m_len < sizeof (struct udpiphdr) &&
  		    (m = m_pullup(m, sizeof (struct udpiphdr))) == NULL) {
  			OSAddAtomic(1, &udpstat.udps_hdrops);
  			KERNEL_DEBUG(DBG_LAYER_END, 0, 0, 0, 0, 0);
  			OSAddAtomic(1, &ipstat.ips_total);
  			return (IPINPUT_FREED);
  		}
  		*modm = m;
  		ui = mtod(m, struct udpiphdr *);
  		if (ntohs(ui->ui_dport) == IPPORT_BOOTPC) {
  			ip_setdstifaddr_info(m, inifp->if_index, NULL);
  			return (IPINPUT_DONTCHAIN);
  		}
  	}
  
  	/* Avoid chaining raw sockets as ipsec checks occur later for them */
  	if (ip_protox[ip->ip_p]->pr_flags & PR_LASTHDR)
  		return (IPINPUT_DONTCHAIN);
  
  	return (retval);
  #if !defined(__i386__) && !defined(__x86_64__)
  bad:
  	m_freem(m);
  	return (IPINPUT_FREED);
  #endif
  }
  
  static void
  ip_input_second_pass(struct mbuf *m, struct ifnet *inifp, u_int32_t div_info,
      int npkts_in_chain, int bytes_in_chain, struct ip_fw_in_args *args, int ours)
  {
  	unsigned int		checkif;
  	struct mbuf		*tmp_mbuf = NULL;
  	struct in_ifaddr	*ia = NULL;
  	struct in_addr		pkt_dst;
  	unsigned int		hlen;
  
  #if !IPFIREWALL
  #pragma unused (args)
  #endif
  
  #if !IPDIVERT
  #pragma unused (div_info)
  #endif
  
  	struct ip *ip = mtod(m, struct ip *);
  	hlen = IP_VHL_HL(ip->ip_vhl) << 2;
  
  	OSAddAtomic(npkts_in_chain, &ipstat.ips_total);
  
  	/*
  	 * Naively assume we can attribute inbound data to the route we would
  	 * use to send to this destination. Asymmetric routing breaks this
  	 * assumption, but it still allows us to account for traffic from
  	 * a remote node in the routing table.
  	 * this has a very significant performance impact so we bypass
  	 * if nstat_collect is disabled. We may also bypass if the
  	 * protocol is tcp in the future because tcp will have a route that
  	 * we can use to attribute the data to. That does mean we would not
  	 * account for forwarded tcp traffic.
  	 */
  	ip_input_update_nstat(inifp, ip->ip_src, npkts_in_chain,
  	    bytes_in_chain);
  
  	if (ours)
  		goto ours;
  
  	/*
  	 * Check our list of addresses, to see if the packet is for us.
  	 * If we don't have any addresses, assume any unicast packet
  	 * we receive might be for us (and let the upper layers deal
  	 * with it).
  	 */
  	tmp_mbuf = m;
  	if (TAILQ_EMPTY(&in_ifaddrhead)) {
  		while (tmp_mbuf) {
  			if (!(tmp_mbuf->m_flags & (M_MCAST|M_BCAST))) {
  				ip_setdstifaddr_info(tmp_mbuf, inifp->if_index,
  				    NULL);
  			}
  			tmp_mbuf = mbuf_nextpkt(tmp_mbuf);
  		}
  		goto ours;
  	}
  	/*
  	 * Cache the destination address of the packet; this may be
  	 * changed by use of 'ipfw fwd'.
  	 */
  #if IPFIREWALL
  	pkt_dst = args->fwai_next_hop == NULL ?
  	    ip->ip_dst : args->fwai_next_hop->sin_addr;
  #else /* !IPFIREWALL */
  	pkt_dst = ip->ip_dst;
  #endif /* !IPFIREWALL */
  
  	/*
  	 * Enable a consistency check between the destination address
  	 * and the arrival interface for a unicast packet (the RFC 1122
  	 * strong ES model) if IP forwarding is disabled and the packet
  	 * is not locally generated and the packet is not subject to
  	 * 'ipfw fwd'.
  	 *
  	 * XXX - Checking also should be disabled if the destination
  	 * address is ipnat'ed to a different interface.
  	 *
  	 * XXX - Checking is incompatible with IP aliases added
  	 * to the loopback interface instead of the interface where
  	 * the packets are received.
  	 */
  	checkif = ip_checkinterface && (ipforwarding == 0) &&
  	    !(inifp->if_flags & IFF_LOOPBACK) &&
  	    !(m->m_pkthdr.pkt_flags & PKTF_LOOP)
  #if IPFIREWALL
  	    && (args->fwai_next_hop == NULL);
  #else /* !IPFIREWALL */
  		;
  #endif /* !IPFIREWALL */
  
  	/*
  	 * Check for exact addresses in the hash bucket.
  	 */
  	lck_rw_lock_shared(in_ifaddr_rwlock);
  	TAILQ_FOREACH(ia, INADDR_HASH(pkt_dst.s_addr), ia_hash) {
  		/*
  		 * If the address matches, verify that the packet
  		 * arrived via the correct interface if checking is
  		 * enabled.
  		 */
  		if (IA_SIN(ia)->sin_addr.s_addr == pkt_dst.s_addr &&
  		    (!checkif || ia->ia_ifp == inifp)) {
  			ip_input_setdst_chain(m, 0, ia);
  			lck_rw_done(in_ifaddr_rwlock);
  			goto ours;
  		}
  	}
  	lck_rw_done(in_ifaddr_rwlock);
  
  	/*
  	 * Check for broadcast addresses.
  	 *
  	 * Only accept broadcast packets that arrive via the matching
  	 * interface.  Reception of forwarded directed broadcasts would be
  	 * handled via ip_forward() and ether_frameout() with the loopback
  	 * into the stack for SIMPLEX interfaces handled by ether_frameout().
  	 */
  	if (inifp->if_flags & IFF_BROADCAST) {
  		struct ifaddr *ifa;
  
  		ifnet_lock_shared(inifp);
  		TAILQ_FOREACH(ifa, &inifp->if_addrhead, ifa_link) {
  			if (ifa->ifa_addr->sa_family != AF_INET) {
  				continue;
  			}
  			ia = ifatoia(ifa);
  			if (satosin(&ia->ia_broadaddr)->sin_addr.s_addr ==
  			    pkt_dst.s_addr || ia->ia_netbroadcast.s_addr ==
  			    pkt_dst.s_addr) {
  				ip_input_setdst_chain(m, 0, ia);
  				ifnet_lock_done(inifp);
  				goto ours;
  			}
  		}
  		ifnet_lock_done(inifp);
  	}
  
  	if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr))) {
  		struct in_multi *inm;
  		/*
  		 * See if we belong to the destination multicast group on the
  		 * arrival interface.
  		 */
  		in_multihead_lock_shared();
  		IN_LOOKUP_MULTI(&ip->ip_dst, inifp, inm);
  		in_multihead_lock_done();
  		if (inm == NULL) {
  			OSAddAtomic(npkts_in_chain, &ipstat.ips_notmember);
  			m_freem_list(m);
  			KERNEL_DEBUG(DBG_LAYER_END, 0, 0, 0, 0, 0);
  			return;
  		}
  		ip_input_setdst_chain(m, inifp->if_index, NULL);
  		INM_REMREF(inm);
  		goto ours;
  	}
  
  	if (ip->ip_dst.s_addr == (u_int32_t)INADDR_BROADCAST ||
  	    ip->ip_dst.s_addr == INADDR_ANY) {
  		ip_input_setdst_chain(m, inifp->if_index, NULL);
  		goto ours;
  	}
  
  	if (ip->ip_p == IPPROTO_UDP) {
  		struct udpiphdr *ui;
  		ui = mtod(m, struct udpiphdr *);
  		if (ntohs(ui->ui_dport) == IPPORT_BOOTPC) {
  			goto ours;
  		}
  	}
  
  	tmp_mbuf = m;
  	struct mbuf *nxt_mbuf = NULL;
  	while (tmp_mbuf) {
  		nxt_mbuf = mbuf_nextpkt(tmp_mbuf);
  		/*
  		 * Not for us; forward if possible and desirable.
  		 */
  		mbuf_setnextpkt(tmp_mbuf, NULL);
  		if (ipforwarding == 0) {
  			OSAddAtomic(1, &ipstat.ips_cantforward);
  			m_freem(tmp_mbuf);
  		} else {
  #if IPFIREWALL
  			ip_forward(tmp_mbuf, 0, args->fwai_next_hop);
  #else
  			ip_forward(tmp_mbuf, 0, NULL);
  #endif
  		}
  		tmp_mbuf = nxt_mbuf;
  	}
  	KERNEL_DEBUG(DBG_LAYER_END, 0, 0, 0, 0, 0);
  	return;
  ours:
  	/*
  	 * If offset or IP_MF are set, must reassemble.
  	 */
  	if (ip->ip_off & ~(IP_DF | IP_RF)) {
  		VERIFY(npkts_in_chain == 1);
  		/*
  		 * ip_reass() will return a different mbuf, and update
  		 * the divert info in div_info and args->fwai_divert_rule.
  		 */
  #if IPDIVERT
  		m = ip_reass(m, (u_int16_t *)&div_info, &args->fwai_divert_rule);
  #else
  		m = ip_reass(m);
  #endif
  		if (m == NULL)
  			return;
  		ip = mtod(m, struct ip *);
  		/* Get the header length of the reassembled packet */
  		hlen = IP_VHL_HL(ip->ip_vhl) << 2;
  #if IPDIVERT
  		/* Restore original checksum before diverting packet */
  		if (div_info != 0) {
  			VERIFY(npkts_in_chain == 1);
  #if BYTE_ORDER != BIG_ENDIAN
  			HTONS(ip->ip_len);
  			HTONS(ip->ip_off);
  #endif
  			ip->ip_sum = 0;
  			ip->ip_sum = ip_cksum_hdr_in(m, hlen);
  #if BYTE_ORDER != BIG_ENDIAN
  			NTOHS(ip->ip_off);
  			NTOHS(ip->ip_len);
  #endif
  		}
  #endif
  	}
  
  	/*
  	 * Further protocols expect the packet length to be w/o the
  	 * IP header.
  	 */
  	ip->ip_len -= hlen;
  
  #if IPDIVERT
  	/*
  	 * Divert or tee packet to the divert protocol if required.
  	 *
  	 * If div_info is zero then cookie should be too, so we shouldn't
  	 * need to clear them here.  Assume divert_packet() does so also.
  	 */
  	if (div_info != 0) {
  		struct mbuf *clone = NULL;
  		VERIFY(npkts_in_chain == 1);
  
  		/* Clone packet if we're doing a 'tee' */
  		if (div_info & IP_FW_PORT_TEE_FLAG)
  			clone = m_dup(m, M_DONTWAIT);
  
  		/* Restore packet header fields to original values */
  		ip->ip_len += hlen;
  
  #if BYTE_ORDER != BIG_ENDIAN
  		HTONS(ip->ip_len);
  		HTONS(ip->ip_off);
  #endif
  		/* Deliver packet to divert input routine */
  		OSAddAtomic(1, &ipstat.ips_delivered);
  		divert_packet(m, 1, div_info & 0xffff, args->fwai_divert_rule);
  
  		/* If 'tee', continue with original packet */
  		if (clone == NULL) {
  			return;
  		}
  		m = clone;
  		ip = mtod(m, struct ip *);
  	}
  #endif
  
  #if IPSEC
  	/*
  	 * enforce IPsec policy checking if we are seeing last header.
  	 * note that we do not visit this with protocols with pcb layer
  	 * code - like udp/tcp/raw ip.
  	 */
  	if (ipsec_bypass == 0 && (ip_protox[ip->ip_p]->pr_flags & PR_LASTHDR)) {
  		VERIFY(npkts_in_chain == 1);
  		if (ipsec4_in_reject(m, NULL)) {
  			IPSEC_STAT_INCREMENT(ipsecstat.in_polvio);
  			goto bad;
  		}
  	}
  #endif /* IPSEC */
  
  	/*
  	 * Switch out to protocol's input routine.
  	 */
  	OSAddAtomic(npkts_in_chain, &ipstat.ips_delivered);
  
  #if IPFIREWALL
  	if (args->fwai_next_hop && ip->ip_p == IPPROTO_TCP) {
  		/* TCP needs IPFORWARD info if available */
  		struct m_tag *fwd_tag;
  		struct ip_fwd_tag *ipfwd_tag;
  
  		VERIFY(npkts_in_chain == 1);
  		fwd_tag = m_tag_create(KERNEL_MODULE_TAG_ID,
  		    KERNEL_TAG_TYPE_IPFORWARD, sizeof (*ipfwd_tag),
  		    M_NOWAIT, m);
  		if (fwd_tag == NULL)
  			goto bad;
  
  		ipfwd_tag = (struct ip_fwd_tag *)(fwd_tag+1);
  		ipfwd_tag->next_hop = args->fwai_next_hop;
  
  		m_tag_prepend(m, fwd_tag);
  
  		KERNEL_DEBUG(DBG_LAYER_END, ip->ip_dst.s_addr,
  		    ip->ip_src.s_addr, ip->ip_p, ip->ip_off, ip->ip_len);
  
  		/* TCP deals with its own locking */
  		ip_proto_dispatch_in(m, hlen, ip->ip_p, 0);
  	} else {
  		KERNEL_DEBUG(DBG_LAYER_END, ip->ip_dst.s_addr,
  		    ip->ip_src.s_addr, ip->ip_p, ip->ip_off, ip->ip_len);
  
  		ip_input_dispatch_chain(m);
  
  	}
  #else /* !IPFIREWALL */
  	ip_input_dispatch_chain(m);
  
  #endif /* !IPFIREWALL */
  	KERNEL_DEBUG(DBG_LAYER_END, 0, 0, 0, 0, 0);
  	return;
  bad:
  	KERNEL_DEBUG(DBG_LAYER_END, 0, 0, 0, 0, 0);
  	m_freem(m);
  }
  
  void
  ip_input_process_list(struct mbuf *packet_list)
  {
  	pktchain_elm_t	pktchain_tbl[PKTTBL_SZ];
  
  	struct mbuf	*packet = NULL;
  	struct mbuf	*modm = NULL; /* modified mbuf */
  	int		retval = 0;
  	u_int32_t	div_info = 0;
  	int		ours = 0;
  #if (DEBUG || DEVELOPMENT)
  	struct timeval start_tv;
  #endif /* (DEBUG || DEVELOPMENT) */
  	int	num_pkts = 0;
  	int chain = 0;
  	struct ip_fw_in_args       args;
  
  	if (ip_chaining == 0) {
  		struct mbuf *m = packet_list;
  #if (DEBUG || DEVELOPMENT)
  		if (ip_input_measure)
  			net_perf_start_time(&net_perf, &start_tv);
  #endif /* (DEBUG || DEVELOPMENT) */
  
  		while (m) {
  			packet_list = mbuf_nextpkt(m);
  			mbuf_setnextpkt(m, NULL);
  			ip_input(m);
  			m = packet_list;
  			num_pkts++;
  		}
  #if (DEBUG || DEVELOPMENT)
  		if (ip_input_measure)
  			net_perf_measure_time(&net_perf, &start_tv, num_pkts);
  #endif /* (DEBUG || DEVELOPMENT) */
  		return;
  	}
  #if (DEBUG || DEVELOPMENT)
  	if (ip_input_measure)
  		net_perf_start_time(&net_perf, &start_tv);
  #endif /* (DEBUG || DEVELOPMENT) */
  
  	bzero(&pktchain_tbl, sizeof(pktchain_tbl));
  restart_list_process:
  	chain = 0;
  	for (packet = packet_list; packet; packet = packet_list) {
  		packet_list = mbuf_nextpkt(packet);
  		mbuf_setnextpkt(packet, NULL);
  
  		num_pkts++;
  		modm = NULL;
  		div_info = 0;
  		bzero(&args, sizeof (args));
  
  		retval = ip_input_first_pass(packet, &div_info, &args,
  		    &ours, &modm);
  
  		if (retval == IPINPUT_DOCHAIN) {
  			if (modm)
  				packet = modm;
  			packet = ip_chain_insert(packet, &pktchain_tbl[0]);
  			if (packet == NULL) {
  				ipstat.ips_rxc_chained++;
  				chain++;
  				if (chain > ip_chainsz)
  					break;
  			} else {
  				ipstat.ips_rxc_collisions++;
  				break;
  			}
  		} else if (retval == IPINPUT_DONTCHAIN) {
  			/* in order to preserve order, exit from chaining */
  			if (modm)
  				packet = modm;
  			ipstat.ips_rxc_notchain++;
  			break;
  		} else {
  			/* packet was freed or delivered, do nothing. */
  		}
  	}
  
  	/* do second pass here for pktchain_tbl */
  	if (chain)
  		ip_input_second_pass_loop_tbl(&pktchain_tbl[0], &args);
  
  	if (packet) {
  		/*
  		 * equivalent update in chaining case if performed in
  		 * ip_input_second_pass_loop_tbl().
  		 */
  #if (DEBUG || DEVELOPMENT)
  		if (ip_input_measure)
  			net_perf_histogram(&net_perf, 1);
  #endif /* (DEBUG || DEVELOPMENT) */
  		ip_input_second_pass(packet, packet->m_pkthdr.rcvif, div_info,
  		    1, packet->m_pkthdr.len, &args, ours);
  	}
  
  	if (packet_list)
  		goto restart_list_process;
  
  #if (DEBUG || DEVELOPMENT)
  	if (ip_input_measure)
  		net_perf_measure_time(&net_perf, &start_tv, num_pkts);
  #endif /* (DEBUG || DEVELOPMENT) */
  }
  /*
   * Ip input routine.  Checksum and byte swap header.  If fragmented
   * try to reassemble.  Process options.  Pass to next level.
   */
  void
  ip_input(struct mbuf *m)
  {
  	struct ip *ip;
  	struct in_ifaddr *ia = NULL;
  	unsigned int hlen, checkif;
  	u_short sum = 0;
  	struct in_addr pkt_dst;
  #if IPFIREWALL
  	int i;
  	u_int32_t div_info = 0;		/* packet divert/tee info */
  #endif
  #if IPFIREWALL || DUMMYNET
  	struct ip_fw_args args;
  	struct m_tag	*tag;
  #endif
  	ipfilter_t inject_filter_ref = NULL;
  	struct ifnet *inifp;
  
  	/* Check if the mbuf is still valid after interface filter processing */
  	MBUF_INPUT_CHECK(m, m->m_pkthdr.rcvif);
  	inifp = m->m_pkthdr.rcvif;
  	VERIFY(inifp != NULL);
  
  	ipstat.ips_rxc_notlist++;
  
  	/* Perform IP header alignment fixup, if needed */
  	IP_HDR_ALIGNMENT_FIXUP(m, inifp, goto bad);
  
  	m->m_pkthdr.pkt_flags &= ~PKTF_FORWARDED;
  
  #if IPFIREWALL || DUMMYNET
  	bzero(&args, sizeof (struct ip_fw_args));
  
  	/*
  	 * Don't bother searching for tag(s) if there's none.
  	 */
  	if (SLIST_EMPTY(&m->m_pkthdr.tags))
  		goto ipfw_tags_done;
  
  	/* Grab info from mtags prepended to the chain */
  #if DUMMYNET
  	if ((tag = m_tag_locate(m, KERNEL_MODULE_TAG_ID,
  	    KERNEL_TAG_TYPE_DUMMYNET, NULL)) != NULL) {
  		struct dn_pkt_tag *dn_tag;
  
  		dn_tag = (struct dn_pkt_tag *)(tag+1);
  		args.fwa_ipfw_rule = dn_tag->dn_ipfw_rule;
  		args.fwa_pf_rule = dn_tag->dn_pf_rule;
  
  		m_tag_delete(m, tag);
  	}
  #endif /* DUMMYNET */
  
  #if IPDIVERT
  	if ((tag = m_tag_locate(m, KERNEL_MODULE_TAG_ID,
  	    KERNEL_TAG_TYPE_DIVERT, NULL)) != NULL) {
  		struct divert_tag *div_tag;
  
  		div_tag = (struct divert_tag *)(tag+1);
  		args.fwa_divert_rule = div_tag->cookie;
  
  		m_tag_delete(m, tag);
  	}
  #endif
  
  	if ((tag = m_tag_locate(m, KERNEL_MODULE_TAG_ID,
  	    KERNEL_TAG_TYPE_IPFORWARD, NULL)) != NULL) {
  		struct ip_fwd_tag *ipfwd_tag;
  
  		ipfwd_tag = (struct ip_fwd_tag *)(tag+1);
  		args.fwa_next_hop = ipfwd_tag->next_hop;
  
  		m_tag_delete(m, tag);
  	}
  
  #if	DIAGNOSTIC
  	if (m == NULL || !(m->m_flags & M_PKTHDR))
  		panic("ip_input no HDR");
  #endif
  
  #if DUMMYNET
  	if (args.fwa_ipfw_rule || args.fwa_pf_rule) {
  		/* dummynet already filtered us */
  		ip = mtod(m, struct ip *);
  		hlen = IP_VHL_HL(ip->ip_vhl) << 2;
  		inject_filter_ref = ipf_get_inject_filter(m);
  #if IPFIREWALL
  		if (args.fwa_ipfw_rule)
  			goto iphack;
  #endif /* IPFIREWALL */
  		if (args.fwa_pf_rule)
  			goto check_with_pf;
  	}
  #endif /* DUMMYNET */
  ipfw_tags_done:
  #endif /* IPFIREWALL || DUMMYNET */
  
  	/*
  	 * No need to process packet twice if we've already seen it.
  	 */
  	if (!SLIST_EMPTY(&m->m_pkthdr.tags))
  		inject_filter_ref = ipf_get_inject_filter(m);
  	if (inject_filter_ref != NULL) {
  		ip = mtod(m, struct ip *);
  		hlen = IP_VHL_HL(ip->ip_vhl) << 2;
  
  		DTRACE_IP6(receive, struct mbuf *, m, struct inpcb *, NULL,
  		    struct ip *, ip, struct ifnet *, inifp,
  		    struct ip *, ip, struct ip6_hdr *, NULL);
  
  		ip->ip_len = ntohs(ip->ip_len) - hlen;
  		ip->ip_off = ntohs(ip->ip_off);
  		ip_proto_dispatch_in(m, hlen, ip->ip_p, inject_filter_ref);
  		return;
  	}
  
  	OSAddAtomic(1, &ipstat.ips_total);
  	if (m->m_pkthdr.len < sizeof (struct ip))
  		goto tooshort;
  
  	if (m->m_len < sizeof (struct ip) &&
  	    (m = m_pullup(m, sizeof (struct ip))) == NULL) {
  		OSAddAtomic(1, &ipstat.ips_toosmall);
  		return;
  	}
  	ip = mtod(m, struct ip *);
  
  	KERNEL_DEBUG(DBG_LAYER_BEG, ip->ip_dst.s_addr, ip->ip_src.s_addr,
  	    ip->ip_p, ip->ip_off, ip->ip_len);
  
  	if (IP_VHL_V(ip->ip_vhl) != IPVERSION) {
  		OSAddAtomic(1, &ipstat.ips_badvers);
  		goto bad;
  	}
  
  	hlen = IP_VHL_HL(ip->ip_vhl) << 2;
  	if (hlen < sizeof (struct ip)) {	/* minimum header length */
  		OSAddAtomic(1, &ipstat.ips_badhlen);
  		goto bad;
  	}
  	if (hlen > m->m_len) {
  		if ((m = m_pullup(m, hlen)) == NULL) {
  			OSAddAtomic(1, &ipstat.ips_badhlen);
  			return;
  		}
  		ip = mtod(m, struct ip *);
  	}
  
  	/* 127/8 must not appear on wire - RFC1122 */
  	if ((ntohl(ip->ip_dst.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET ||
  	    (ntohl(ip->ip_src.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET) {
  		/*
  		 * Allow for the following exceptions:
  		 *
  		 *   1. If the packet was sent to loopback (i.e. rcvif
  		 *	would have been set earlier at output time.)
  		 *
  		 *   2. If the packet was sent out on loopback from a local
  		 *	source address which belongs to a non-loopback
  		 *	interface (i.e. rcvif may not necessarily be a
  		 *	loopback interface, hence the test for PKTF_LOOP.)
  		 *	Unlike IPv6, there is no interface scope ID, and
  		 *	therefore we don't care so much about PKTF_IFINFO.
  		 */
  		if (!(inifp->if_flags & IFF_LOOPBACK) &&
  		    !(m->m_pkthdr.pkt_flags & PKTF_LOOP)) {
  			OSAddAtomic(1, &ipstat.ips_badaddr);
  			goto bad;
  		}
  	}
  
  	/* IPv4 Link-Local Addresses as defined in RFC3927 */
  	if ((IN_LINKLOCAL(ntohl(ip->ip_dst.s_addr)) ||
  	    IN_LINKLOCAL(ntohl(ip->ip_src.s_addr)))) {
  		ip_linklocal_stat.iplls_in_total++;
  		if (ip->ip_ttl != MAXTTL) {
  			OSAddAtomic(1, &ip_linklocal_stat.iplls_in_badttl);
  			/* Silently drop link local traffic with bad TTL */
  			if (!ip_linklocal_in_allowbadttl)
  				goto bad;
  		}
  	}
  
  	sum = ip_cksum(m, hlen);
  	if (sum) {
  		goto bad;
  	}
  
  	DTRACE_IP6(receive, struct mbuf *, m, struct inpcb *, NULL,
  	    struct ip *, ip, struct ifnet *, inifp,
  	    struct ip *, ip, struct ip6_hdr *, NULL);
  
  	/*
  	 * Naively assume we can attribute inbound data to the route we would
  	 * use to send to this destination. Asymmetric routing breaks this
  	 * assumption, but it still allows us to account for traffic from
  	 * a remote node in the routing table.
  	 * this has a very significant performance impact so we bypass
  	 * if nstat_collect is disabled. We may also bypass if the
  	 * protocol is tcp in the future because tcp will have a route that
  	 * we can use to attribute the data to. That does mean we would not
  	 * account for forwarded tcp traffic.
  	 */
  	if (nstat_collect) {
  		struct rtentry *rt =
  		    ifnet_cached_rtlookup_inet(inifp, ip->ip_src);
  		if (rt != NULL) {
  			nstat_route_rx(rt, 1, m->m_pkthdr.len, 0);
  			rtfree(rt);
  		}
  	}
  
  	/*
  	 * Convert fields to host representation.
  	 */
  #if BYTE_ORDER != BIG_ENDIAN
  	NTOHS(ip->ip_len);
  #endif
  
  	if (ip->ip_len < hlen) {
  		OSAddAtomic(1, &ipstat.ips_badlen);
  		goto bad;
  	}
  
  #if BYTE_ORDER != BIG_ENDIAN
  	NTOHS(ip->ip_off);
  #endif
  	/*
  	 * Check that the amount of data in the buffers
  	 * is as at least much as the IP header would have us expect.
  	 * Trim mbufs if longer than we expect.
  	 * Drop packet if shorter than we expect.
  	 */
  	if (m->m_pkthdr.len < ip->ip_len) {
  tooshort:
  		OSAddAtomic(1, &ipstat.ips_tooshort);
  		goto bad;
  	}
  	if (m->m_pkthdr.len > ip->ip_len) {
  		/*
  		 * Invalidate hardware checksum info if ip_adj_clear_hwcksum
  		 * is set; useful to handle buggy drivers.  Note that this
  		 * should not be enabled by default, as we may get here due
  		 * to link-layer padding.
  		 */
  		if (ip_adj_clear_hwcksum &&
  		    (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) &&
  		    !(inifp->if_flags & IFF_LOOPBACK) &&
  		    !(m->m_pkthdr.pkt_flags & PKTF_LOOP)) {
  			m->m_pkthdr.csum_flags &= ~CSUM_DATA_VALID;
  			m->m_pkthdr.csum_data = 0;
  			ipstat.ips_adj_hwcsum_clr++;
  		}
  
  		ipstat.ips_adj++;
  		if (m->m_len == m->m_pkthdr.len) {
  			m->m_len = ip->ip_len;
  			m->m_pkthdr.len = ip->ip_len;
  		} else
  			m_adj(m, ip->ip_len - m->m_pkthdr.len);
  	}
  
  	/* for consistency */
  	m->m_pkthdr.pkt_proto = ip->ip_p;
  
  #if DUMMYNET
  check_with_pf:
  #endif
  #if PF
  	/* Invoke inbound packet filter */
  	if (PF_IS_ENABLED) {
  		int error;
  #if DUMMYNET
  		error = pf_af_hook(inifp, NULL, &m, AF_INET, TRUE, &args);
  #else
  		error = pf_af_hook(inifp, NULL, &m, AF_INET, TRUE, NULL);
  #endif /* DUMMYNET */
  		if (error != 0 || m == NULL) {
  			if (m != NULL) {
  				panic("%s: unexpected packet %p\n",
  				    __func__, m);
  				/* NOTREACHED */
  			}
  			/* Already freed by callee */
  			return;
  		}
  		ip = mtod(m, struct ip *);
  		hlen = IP_VHL_HL(ip->ip_vhl) << 2;
  	}
  #endif /* PF */
  
  #if IPSEC
  	if (ipsec_bypass == 0 && ipsec_gethist(m, NULL))
  		goto pass;
  #endif
  
  #if IPFIREWALL
  #if DUMMYNET
  iphack:
  #endif /* DUMMYNET */
  	/*
  	 * Check if we want to allow this packet to be processed.
  	 * Consider it to be bad if not.
  	 */
  	if (fw_enable && IPFW_LOADED) {
  #if IPFIREWALL_FORWARD
  		/*
  		 * If we've been forwarded from the output side, then
  		 * skip the firewall a second time
  		 */
  		if (args.fwa_next_hop)
  			goto ours;
  #endif	/* IPFIREWALL_FORWARD */
  
  		args.fwa_m = m;
  
  		i = ip_fw_chk_ptr(&args);
  		m = args.fwa_m;
  
  		if ((i & IP_FW_PORT_DENY_FLAG) || m == NULL) { /* drop */
  			if (m)
  				m_freem(m);
  			return;
  		}
  		ip = mtod(m, struct ip *); /* just in case m changed */
  
  		if (i == 0 && args.fwa_next_hop == NULL) { /* common case */
  			goto pass;
  		}
  #if DUMMYNET
  		if (DUMMYNET_LOADED && (i & IP_FW_PORT_DYNT_FLAG) != 0) {
  			/* Send packet to the appropriate pipe */
  			ip_dn_io_ptr(m, i&0xffff, DN_TO_IP_IN, &args,
  			    DN_CLIENT_IPFW);
  			return;
  		}
  #endif /* DUMMYNET */
  #if IPDIVERT
  		if (i != 0 && (i & IP_FW_PORT_DYNT_FLAG) == 0) {
  			/* Divert or tee packet */
  			div_info = i;
  			goto ours;
  		}
  #endif
  #if IPFIREWALL_FORWARD
  		if (i == 0 && args.fwa_next_hop != NULL) {
  			goto pass;
  		}
  #endif
  		/*
  		 * if we get here, the packet must be dropped
  		 */
  		m_freem(m);
  		return;
  	}
  #endif /* IPFIREWALL */
  #if IPSEC | IPFIREWALL
  pass:
  #endif
  	/*
  	 * Process options and, if not destined for us,
  	 * ship it on.  ip_dooptions returns 1 when an
  	 * error was detected (causing an icmp message
  	 * to be sent and the original packet to be freed).
  	 */
  	ip_nhops = 0;		/* for source routed packets */
  #if IPFIREWALL
  	if (hlen > sizeof (struct ip) &&
  	    ip_dooptions(m, 0, args.fwa_next_hop)) {
  #else /* !IPFIREWALL */
  	if (hlen > sizeof (struct ip) && ip_dooptions(m, 0, NULL)) {
  #endif /* !IPFIREWALL */
  		return;
  	}
  
  	/*
  	 * Check our list of addresses, to see if the packet is for us.
  	 * If we don't have any addresses, assume any unicast packet
  	 * we receive might be for us (and let the upper layers deal
  	 * with it).
  	 */
  	if (TAILQ_EMPTY(&in_ifaddrhead) && !(m->m_flags & (M_MCAST|M_BCAST))) {
  		ip_setdstifaddr_info(m, inifp->if_index, NULL);
  		goto ours;
  	}
  
  	/*
  	 * Cache the destination address of the packet; this may be
  	 * changed by use of 'ipfw fwd'.
  	 */
  #if IPFIREWALL
  	pkt_dst = args.fwa_next_hop == NULL ?
  	    ip->ip_dst : args.fwa_next_hop->sin_addr;
  #else /* !IPFIREWALL */
  	pkt_dst = ip->ip_dst;
  #endif /* !IPFIREWALL */
  
  	/*
  	 * Enable a consistency check between the destination address
  	 * and the arrival interface for a unicast packet (the RFC 1122
  	 * strong ES model) if IP forwarding is disabled and the packet
  	 * is not locally generated and the packet is not subject to
  	 * 'ipfw fwd'.
  	 *
  	 * XXX - Checking also should be disabled if the destination
  	 * address is ipnat'ed to a different interface.
  	 *
  	 * XXX - Checking is incompatible with IP aliases added
  	 * to the loopback interface instead of the interface where
  	 * the packets are received.
  	 */
  	checkif = ip_checkinterface && (ipforwarding == 0) &&
  	    !(inifp->if_flags & IFF_LOOPBACK) &&
  	    !(m->m_pkthdr.pkt_flags & PKTF_LOOP)
  #if IPFIREWALL
  	    && (args.fwa_next_hop == NULL);
  #else /* !IPFIREWALL */
  		;
  #endif /* !IPFIREWALL */
  
  	/*
  	 * Check for exact addresses in the hash bucket.
  	 */
  	lck_rw_lock_shared(in_ifaddr_rwlock);
  	TAILQ_FOREACH(ia, INADDR_HASH(pkt_dst.s_addr), ia_hash) {
  		/*
  		 * If the address matches, verify that the packet
  		 * arrived via the correct interface if checking is
  		 * enabled.
  		 */
  		if (IA_SIN(ia)->sin_addr.s_addr == pkt_dst.s_addr &&
  		    (!checkif || ia->ia_ifp == inifp)) {
  			ip_setdstifaddr_info(m, 0, ia);
  			lck_rw_done(in_ifaddr_rwlock);
  			goto ours;
  		}
  	}
  	lck_rw_done(in_ifaddr_rwlock);
  
  	/*
  	 * Check for broadcast addresses.
  	 *
  	 * Only accept broadcast packets that arrive via the matching
  	 * interface.  Reception of forwarded directed broadcasts would be
  	 * handled via ip_forward() and ether_frameout() with the loopback
  	 * into the stack for SIMPLEX interfaces handled by ether_frameout().
  	 */
  	if (inifp->if_flags & IFF_BROADCAST) {
  		struct ifaddr *ifa;
  
  		ifnet_lock_shared(inifp);
  		TAILQ_FOREACH(ifa, &inifp->if_addrhead, ifa_link) {
  			if (ifa->ifa_addr->sa_family != AF_INET) {
  				continue;
  			}
  			ia = ifatoia(ifa);
  			if (satosin(&ia->ia_broadaddr)->sin_addr.s_addr ==
  			    pkt_dst.s_addr || ia->ia_netbroadcast.s_addr ==
  			    pkt_dst.s_addr) {
  				ip_setdstifaddr_info(m, 0, ia);
  				ifnet_lock_done(inifp);
  				goto ours;
  			}
  		}
  		ifnet_lock_done(inifp);
  	}
  
  	if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr))) {
  		struct in_multi *inm;
  		/*
  		 * See if we belong to the destination multicast group on the
  		 * arrival interface.
  		 */
  		in_multihead_lock_shared();
  		IN_LOOKUP_MULTI(&ip->ip_dst, inifp, inm);
  		in_multihead_lock_done();
  		if (inm == NULL) {
  			OSAddAtomic(1, &ipstat.ips_notmember);
  			m_freem(m);
  			return;
  		}
  		ip_setdstifaddr_info(m, inifp->if_index, NULL);
  		INM_REMREF(inm);
  		goto ours;
  	}
  	if (ip->ip_dst.s_addr == (u_int32_t)INADDR_BROADCAST ||
  	    ip->ip_dst.s_addr == INADDR_ANY) {
  		ip_setdstifaddr_info(m, inifp->if_index, NULL);
  		goto ours;
  	}
  
  	/* Allow DHCP/BootP responses through */
  	if ((inifp->if_eflags & IFEF_AUTOCONFIGURING) &&
  	    hlen == sizeof (struct ip) && ip->ip_p == IPPROTO_UDP) {
  		struct udpiphdr *ui;
  
  		if (m->m_len < sizeof (struct udpiphdr) &&
  		    (m = m_pullup(m, sizeof (struct udpiphdr))) == NULL) {
  			OSAddAtomic(1, &udpstat.udps_hdrops);
  			return;
  		}
  		ui = mtod(m, struct udpiphdr *);
  		if (ntohs(ui->ui_dport) == IPPORT_BOOTPC) {
  			ip_setdstifaddr_info(m, inifp->if_index, NULL);
  			goto ours;
  		}
  		ip = mtod(m, struct ip *); /* in case it changed */
  	}
  
  	/*
  	 * Not for us; forward if possible and desirable.
  	 */
  	if (ipforwarding == 0) {
  		OSAddAtomic(1, &ipstat.ips_cantforward);
  		m_freem(m);
  	} else {
  #if IPFIREWALL
  		ip_forward(m, 0, args.fwa_next_hop);
  #else
  		ip_forward(m, 0, NULL);
  #endif
  	}
  	return;
  
  ours:
  	/*
  	 * If offset or IP_MF are set, must reassemble.
  	 */
  	if (ip->ip_off & ~(IP_DF | IP_RF)) {
  		/*
  		 * ip_reass() will return a different mbuf, and update
  		 * the divert info in div_info and args.fwa_divert_rule.
  		 */
  #if IPDIVERT
  		m = ip_reass(m, (u_int16_t *)&div_info, &args.fwa_divert_rule);
  #else
  		m = ip_reass(m);
  #endif
  		if (m == NULL)
  			return;
  		ip = mtod(m, struct ip *);
  		/* Get the header length of the reassembled packet */
  		hlen = IP_VHL_HL(ip->ip_vhl) << 2;
  #if IPDIVERT
  		/* Restore original checksum before diverting packet */
  		if (div_info != 0) {
  #if BYTE_ORDER != BIG_ENDIAN
  			HTONS(ip->ip_len);
  			HTONS(ip->ip_off);
  #endif
  			ip->ip_sum = 0;
  			ip->ip_sum = ip_cksum_hdr_in(m, hlen);
  #if BYTE_ORDER != BIG_ENDIAN
  			NTOHS(ip->ip_off);
  			NTOHS(ip->ip_len);
  #endif
  		}
  #endif
  	}
  
  	/*
  	 * Further protocols expect the packet length to be w/o the
  	 * IP header.
  	 */
  	ip->ip_len -= hlen;
  
  #if IPDIVERT
  	/*
  	 * Divert or tee packet to the divert protocol if required.
  	 *
  	 * If div_info is zero then cookie should be too, so we shouldn't
  	 * need to clear them here.  Assume divert_packet() does so also.
  	 */
  	if (div_info != 0) {
  		struct mbuf *clone = NULL;
  
  		/* Clone packet if we're doing a 'tee' */
  		if (div_info & IP_FW_PORT_TEE_FLAG)
  			clone = m_dup(m, M_DONTWAIT);
  
  		/* Restore packet header fields to original values */
  		ip->ip_len += hlen;
  
  #if BYTE_ORDER != BIG_ENDIAN
  		HTONS(ip->ip_len);
  		HTONS(ip->ip_off);
  #endif
  		/* Deliver packet to divert input routine */
  		OSAddAtomic(1, &ipstat.ips_delivered);
  		divert_packet(m, 1, div_info & 0xffff, args.fwa_divert_rule);
  
  		/* If 'tee', continue with original packet */
  		if (clone == NULL) {
  			return;
  		}
  		m = clone;
  		ip = mtod(m, struct ip *);
  	}
  #endif
  
  #if IPSEC
  	/*
  	 * enforce IPsec policy checking if we are seeing last header.
  	 * note that we do not visit this with protocols with pcb layer
  	 * code - like udp/tcp/raw ip.
  	 */
  	if (ipsec_bypass == 0 && (ip_protox[ip->ip_p]->pr_flags & PR_LASTHDR)) {
  		if (ipsec4_in_reject(m, NULL)) {
  			IPSEC_STAT_INCREMENT(ipsecstat.in_polvio);
  			goto bad;
  		}
  	}
  #endif /* IPSEC */
  
  	/*
  	 * Switch out to protocol's input routine.
  	 */
  	OSAddAtomic(1, &ipstat.ips_delivered);
  
  #if IPFIREWALL
  	if (args.fwa_next_hop && ip->ip_p == IPPROTO_TCP) {
  		/* TCP needs IPFORWARD info if available */
  		struct m_tag *fwd_tag;
  		struct ip_fwd_tag *ipfwd_tag;
  
  		fwd_tag = m_tag_create(KERNEL_MODULE_TAG_ID,
  		    KERNEL_TAG_TYPE_IPFORWARD, sizeof (*ipfwd_tag),
  		    M_NOWAIT, m);
  		if (fwd_tag == NULL)
  			goto bad;
  
  		ipfwd_tag = (struct ip_fwd_tag *)(fwd_tag+1);
  		ipfwd_tag->next_hop = args.fwa_next_hop;
  
  		m_tag_prepend(m, fwd_tag);
  
  		KERNEL_DEBUG(DBG_LAYER_END, ip->ip_dst.s_addr,
  		    ip->ip_src.s_addr, ip->ip_p, ip->ip_off, ip->ip_len);
  
  		/* TCP deals with its own locking */
  		ip_proto_dispatch_in(m, hlen, ip->ip_p, 0);
  	} else {
  		KERNEL_DEBUG(DBG_LAYER_END, ip->ip_dst.s_addr,
  		    ip->ip_src.s_addr, ip->ip_p, ip->ip_off, ip->ip_len);
  
  		if ((sw_lro) && (ip->ip_p == IPPROTO_TCP)) {
  			m = tcp_lro(m, hlen);
  			if (m == NULL)
  				return;
  		}
  
  		ip_proto_dispatch_in(m, hlen, ip->ip_p, 0);
  	}
  #else /* !IPFIREWALL */
  	if ((sw_lro) && (ip->ip_p == IPPROTO_TCP)) {
  		m = tcp_lro(m, hlen);
  		if (m == NULL)
  			return;
  	}
  	ip_proto_dispatch_in(m, hlen, ip->ip_p, 0);
  #endif /* !IPFIREWALL */
  	return;
  
  bad:
  	KERNEL_DEBUG(DBG_LAYER_END, 0, 0, 0, 0, 0);
  	m_freem(m);
  }
  
  static void
  ipq_updateparams(void)
  {
  	lck_mtx_assert(&ipqlock, LCK_MTX_ASSERT_OWNED);
  	/*
  	 * -1 for unlimited allocation.
  	 */
  	if (maxnipq < 0)
  		ipq_limit = 0;
  	/*
  	 * Positive number for specific bound.
  	 */
  	if (maxnipq > 0)
  		ipq_limit = maxnipq;
  	/*
  	 * Zero specifies no further fragment queue allocation -- set the
  	 * bound very low, but rely on implementation elsewhere to actually
  	 * prevent allocation and reclaim current queues.
  	 */
  	if (maxnipq == 0)
  		ipq_limit = 1;
  	/*
  	 * Arm the purge timer if not already and if there's work to do
  	 */
  	frag_sched_timeout();
  }
  
  static int
  sysctl_maxnipq SYSCTL_HANDLER_ARGS
  {
  #pragma unused(arg1, arg2)
  	int error, i;
  
  	lck_mtx_lock(&ipqlock);
  	i = maxnipq;
  	error = sysctl_handle_int(oidp, &i, 0, req);
  	if (error || req->newptr == USER_ADDR_NULL)
  		goto done;
  	/* impose bounds */
  	if (i < -1 || i > (nmbclusters / 4)) {
  		error = EINVAL;
  		goto done;
  	}
  	maxnipq = i;
  	ipq_updateparams();
  done:
  	lck_mtx_unlock(&ipqlock);
  	return (error);
  }
  
  static int
  sysctl_maxfragsperpacket SYSCTL_HANDLER_ARGS
  {
  #pragma unused(arg1, arg2)
  	int error, i;
  
  	lck_mtx_lock(&ipqlock);
  	i = maxfragsperpacket;
  	error = sysctl_handle_int(oidp, &i, 0, req);
  	if (error || req->newptr == USER_ADDR_NULL)
  		goto done;
  	maxfragsperpacket = i;
  	ipq_updateparams();	/* see if we need to arm timer */
  done:
  	lck_mtx_unlock(&ipqlock);
  	return (error);
  }
  
  /*
   * Take incoming datagram fragment and try to reassemble it into
   * whole datagram.  If a chain for reassembly of this datagram already
   * exists, then it is given as fp; otherwise have to make a chain.
   *
   * When IPDIVERT enabled, keep additional state with each packet that
   * tells us if we need to divert or tee the packet we're building.
   *
   * The IP header is *NOT* adjusted out of iplen.
   */
  static struct mbuf *
  #if IPDIVERT
  ip_reass(struct mbuf *m,
  #ifdef IPDIVERT_44
      u_int32_t *divinfo,
  #else /* IPDIVERT_44 */
      u_int16_t *divinfo,
  #endif /* IPDIVERT_44 */
      u_int16_t *divcookie)
  #else /* IPDIVERT */
  ip_reass(struct mbuf *m)
  #endif /* IPDIVERT */
  {
  	struct ip *ip;
  	struct mbuf *p, *q, *nq, *t;
  	struct ipq *fp = NULL;
  	struct ipqhead *head;
  	int i, hlen, next;
  	u_int8_t ecn, ecn0;
  	uint32_t csum, csum_flags;
  	uint16_t hash;
  	struct fq_head dfq;
  
  	MBUFQ_INIT(&dfq);	/* for deferred frees */
  
  	/* If maxnipq or maxfragsperpacket is 0, never accept fragments. */
  	if (maxnipq == 0 || maxfragsperpacket == 0) {
  		ipstat.ips_fragments++;
  		ipstat.ips_fragdropped++;
  		m_freem(m);
  		if (nipq > 0) {
  			lck_mtx_lock(&ipqlock);
  			frag_sched_timeout();	/* purge stale fragments */
  			lck_mtx_unlock(&ipqlock);
  		}
  		return (NULL);
  	}
  
  	ip = mtod(m, struct ip *);
  	hlen = IP_VHL_HL(ip->ip_vhl) << 2;
  
  	lck_mtx_lock(&ipqlock);
  
  	hash = IPREASS_HASH(ip->ip_src.s_addr, ip->ip_id);
  	head = &ipq[hash];
  
  	/*
  	 * Look for queue of fragments
  	 * of this datagram.
  	 */
  	TAILQ_FOREACH(fp, head, ipq_list) {
  		if (ip->ip_id == fp->ipq_id &&
  		    ip->ip_src.s_addr == fp->ipq_src.s_addr &&
  		    ip->ip_dst.s_addr == fp->ipq_dst.s_addr &&
  #if CONFIG_MACF_NET
  		    mac_ipq_label_compare(m, fp) &&
  #endif
  		    ip->ip_p == fp->ipq_p)
  			goto found;
  	}
  
  	fp = NULL;
  
  	/*
  	 * Attempt to trim the number of allocated fragment queues if it
  	 * exceeds the administrative limit.
  	 */
  	if ((nipq > (unsigned)maxnipq) && (maxnipq > 0)) {
  		/*
  		 * drop something from the tail of the current queue
  		 * before proceeding further
  		 */
  		struct ipq *fq = TAILQ_LAST(head, ipqhead);
  		if (fq == NULL) {   /* gak */
  			for (i = 0; i < IPREASS_NHASH; i++) {
  				struct ipq *r = TAILQ_LAST(&ipq[i], ipqhead);
  				if (r) {
  					ipstat.ips_fragtimeout += r->ipq_nfrags;
  					frag_freef(&ipq[i], r);
  					break;
  				}
  			}
  		} else {
  			ipstat.ips_fragtimeout += fq->ipq_nfrags;
  			frag_freef(head, fq);
  		}
  	}
  
  found:
  	/*
  	 * Leverage partial checksum offload for IP fragments.  Narrow down
  	 * the scope to cover only UDP without IP options, as that is the
  	 * most common case.
  	 *
  	 * Perform 1's complement adjustment of octets that got included/
  	 * excluded in the hardware-calculated checksum value.  Ignore cases
  	 * where the value includes or excludes the IP header span, as the
  	 * sum for those octets would already be 0xffff and thus no-op.
  	 */
  	if (ip->ip_p == IPPROTO_UDP && hlen == sizeof (struct ip) &&
  	    (m->m_pkthdr.csum_flags &
  	    (CSUM_DATA_VALID | CSUM_PARTIAL | CSUM_PSEUDO_HDR)) ==
  	    (CSUM_DATA_VALID | CSUM_PARTIAL)) {
  		uint32_t start;
  
  		start = m->m_pkthdr.csum_rx_start;
  		csum = m->m_pkthdr.csum_rx_val;
  
  		if (start != 0 && start != hlen) {
  #if BYTE_ORDER != BIG_ENDIAN
  			if (start < hlen) {
  				HTONS(ip->ip_len);
  				HTONS(ip->ip_off);
  			}
  #endif
  			/* callee folds in sum */
  			csum = m_adj_sum16(m, start, hlen, csum);
  #if BYTE_ORDER != BIG_ENDIAN
  			if (start < hlen) {
  				NTOHS(ip->ip_off);
  				NTOHS(ip->ip_len);
  			}
  #endif
  		}
  		csum_flags = m->m_pkthdr.csum_flags;
  	} else {
  		csum = 0;
  		csum_flags = 0;
  	}
  
  	/* Invalidate checksum */
  	m->m_pkthdr.csum_flags &= ~CSUM_DATA_VALID;
  
  	ipstat.ips_fragments++;
  
  	/*
  	 * Adjust ip_len to not reflect header,
  	 * convert offset of this to bytes.
  	 */
  	ip->ip_len -= hlen;
  	if (ip->ip_off & IP_MF) {
  		/*
  		 * Make sure that fragments have a data length
  		 * that's a non-zero multiple of 8 bytes.
  		 */
  		if (ip->ip_len == 0 || (ip->ip_len & 0x7) != 0) {
  			OSAddAtomic(1, &ipstat.ips_toosmall);
  			/*
  			 * Reassembly queue may have been found if previous
  			 * fragments were valid; given that this one is bad,
  			 * we need to drop it.  Make sure to set fp to NULL
  			 * if not already, since we don't want to decrement
  			 * ipq_nfrags as it doesn't include this packet.
  			 */
  			fp = NULL;
  			goto dropfrag;
  		}
  		m->m_flags |= M_FRAG;
  	} else {
  		/* Clear the flag in case packet comes from loopback */
  		m->m_flags &= ~M_FRAG;
  	}
  	ip->ip_off <<= 3;
  
  	m->m_pkthdr.pkt_hdr = ip;
  
  	/* Previous ip_reass() started here. */
  	/*
  	 * Presence of header sizes in mbufs
  	 * would confuse code below.
  	 */
  	m->m_data += hlen;
  	m->m_len -= hlen;
  
  	/*
  	 * If first fragment to arrive, create a reassembly queue.
  	 */
  	if (fp == NULL) {
  		fp = ipq_alloc(M_DONTWAIT);
  		if (fp == NULL)
  			goto dropfrag;
  #if CONFIG_MACF_NET
  		if (mac_ipq_label_init(fp, M_NOWAIT) != 0) {
  			ipq_free(fp);
  			fp = NULL;
  			goto dropfrag;
  		}
  		mac_ipq_label_associate(m, fp);
  #endif
  		TAILQ_INSERT_HEAD(head, fp, ipq_list);
  		nipq++;
  		fp->ipq_nfrags = 1;
  		fp->ipq_ttl = IPFRAGTTL;
  		fp->ipq_p = ip->ip_p;
  		fp->ipq_id = ip->ip_id;
  		fp->ipq_src = ip->ip_src;
  		fp->ipq_dst = ip->ip_dst;
  		fp->ipq_frags = m;
  		m->m_nextpkt = NULL;
  		/*
  		 * If the first fragment has valid checksum offload
  		 * info, the rest of fragments are eligible as well.
  		 */
  		if (csum_flags != 0) {
  			fp->ipq_csum = csum;
  			fp->ipq_csum_flags = csum_flags;
  		}
  #if IPDIVERT
  		/*
  		 * Transfer firewall instructions to the fragment structure.
  		 * Only trust info in the fragment at offset 0.
  		 */
  		if (ip->ip_off == 0) {
  #ifdef IPDIVERT_44
  			fp->ipq_div_info = *divinfo;
  #else
  			fp->ipq_divert = *divinfo;
  #endif
  			fp->ipq_div_cookie = *divcookie;
  		}
  		*divinfo = 0;
  		*divcookie = 0;
  #endif /* IPDIVERT */
  		m = NULL;	/* nothing to return */
  		goto done;
  	} else {
  		fp->ipq_nfrags++;
  #if CONFIG_MACF_NET
  		mac_ipq_label_update(m, fp);
  #endif
  	}
  
  #define	GETIP(m)	((struct ip *)((m)->m_pkthdr.pkt_hdr))
  
  	/*
  	 * Handle ECN by comparing this segment with the first one;
  	 * if CE is set, do not lose CE.
  	 * drop if CE and not-ECT are mixed for the same packet.
  	 */
  	ecn = ip->ip_tos & IPTOS_ECN_MASK;
  	ecn0 = GETIP(fp->ipq_frags)->ip_tos & IPTOS_ECN_MASK;
  	if (ecn == IPTOS_ECN_CE) {
  		if (ecn0 == IPTOS_ECN_NOTECT)
  			goto dropfrag;
  		if (ecn0 != IPTOS_ECN_CE)
  			GETIP(fp->ipq_frags)->ip_tos |= IPTOS_ECN_CE;
  	}
  	if (ecn == IPTOS_ECN_NOTECT && ecn0 != IPTOS_ECN_NOTECT)
  		goto dropfrag;
  
  	/*
  	 * Find a segment which begins after this one does.
  	 */
  	for (p = NULL, q = fp->ipq_frags; q; p = q, q = q->m_nextpkt)
  		if (GETIP(q)->ip_off > ip->ip_off)
  			break;
  
  	/*
  	 * If there is a preceding segment, it may provide some of
  	 * our data already.  If so, drop the data from the incoming
  	 * segment.  If it provides all of our data, drop us, otherwise
  	 * stick new segment in the proper place.
  	 *
  	 * If some of the data is dropped from the preceding
  	 * segment, then it's checksum is invalidated.
  	 */
  	if (p) {
  		i = GETIP(p)->ip_off + GETIP(p)->ip_len - ip->ip_off;
  		if (i > 0) {
  			if (i >= ip->ip_len)
  				goto dropfrag;
  			m_adj(m, i);
  			fp->ipq_csum_flags = 0;
  			ip->ip_off += i;
  			ip->ip_len -= i;
  		}
  		m->m_nextpkt = p->m_nextpkt;
  		p->m_nextpkt = m;
  	} else {
  		m->m_nextpkt = fp->ipq_frags;
  		fp->ipq_frags = m;
  	}
  
  	/*
  	 * While we overlap succeeding segments trim them or,
  	 * if they are completely covered, dequeue them.
  	 */
  	for (; q != NULL && ip->ip_off + ip->ip_len > GETIP(q)->ip_off;
  	    q = nq) {
  		i = (ip->ip_off + ip->ip_len) - GETIP(q)->ip_off;
  		if (i < GETIP(q)->ip_len) {
  			GETIP(q)->ip_len -= i;
  			GETIP(q)->ip_off += i;
  			m_adj(q, i);
  			fp->ipq_csum_flags = 0;
  			break;
  		}
  		nq = q->m_nextpkt;
  		m->m_nextpkt = nq;
  		ipstat.ips_fragdropped++;
  		fp->ipq_nfrags--;
  		/* defer freeing until after lock is dropped */
  		MBUFQ_ENQUEUE(&dfq, q);
  	}
  
  	/*
  	 * If this fragment contains similar checksum offload info
  	 * as that of the existing ones, accumulate checksum.  Otherwise,
  	 * invalidate checksum offload info for the entire datagram.
  	 */
  	if (csum_flags != 0 && csum_flags == fp->ipq_csum_flags)
  		fp->ipq_csum += csum;
  	else if (fp->ipq_csum_flags != 0)
  		fp->ipq_csum_flags = 0;
  
  #if IPDIVERT
  	/*
  	 * Transfer firewall instructions to the fragment structure.
  	 * Only trust info in the fragment at offset 0.
  	 */
  	if (ip->ip_off == 0) {
  #ifdef IPDIVERT_44
  		fp->ipq_div_info = *divinfo;
  #else
  		fp->ipq_divert = *divinfo;
  #endif
  		fp->ipq_div_cookie = *divcookie;
  	}
  	*divinfo = 0;
  	*divcookie = 0;
  #endif /* IPDIVERT */
  
  	/*
  	 * Check for complete reassembly and perform frag per packet
  	 * limiting.
  	 *
  	 * Frag limiting is performed here so that the nth frag has
  	 * a chance to complete the packet before we drop the packet.
  	 * As a result, n+1 frags are actually allowed per packet, but
  	 * only n will ever be stored. (n = maxfragsperpacket.)
  	 *
  	 */
  	next = 0;
  	for (p = NULL, q = fp->ipq_frags; q; p = q, q = q->m_nextpkt) {
  		if (GETIP(q)->ip_off != next) {
  			if (fp->ipq_nfrags > maxfragsperpacket) {
  				ipstat.ips_fragdropped += fp->ipq_nfrags;
  				frag_freef(head, fp);
  			}
  			m = NULL;	/* nothing to return */
  			goto done;
  		}
  		next += GETIP(q)->ip_len;
  	}
  	/* Make sure the last packet didn't have the IP_MF flag */
  	if (p->m_flags & M_FRAG) {
  		if (fp->ipq_nfrags > maxfragsperpacket) {
  			ipstat.ips_fragdropped += fp->ipq_nfrags;
  			frag_freef(head, fp);
  		}
  		m = NULL;		/* nothing to return */
  		goto done;
  	}
  
  	/*
  	 * Reassembly is complete.  Make sure the packet is a sane size.
  	 */
  	q = fp->ipq_frags;
  	ip = GETIP(q);
  	if (next + (IP_VHL_HL(ip->ip_vhl) << 2) > IP_MAXPACKET) {
  		ipstat.ips_toolong++;
  		ipstat.ips_fragdropped += fp->ipq_nfrags;
  		frag_freef(head, fp);
  		m = NULL;		/* nothing to return */
  		goto done;
  	}
  
  	/*
  	 * Concatenate fragments.
  	 */
  	m = q;
  	t = m->m_next;
  	m->m_next = NULL;
  	m_cat(m, t);
  	nq = q->m_nextpkt;
  	q->m_nextpkt = NULL;
  	for (q = nq; q != NULL; q = nq) {
  		nq = q->m_nextpkt;
  		q->m_nextpkt = NULL;
  		m_cat(m, q);
  	}
  
  	/*
  	 * Store partial hardware checksum info from the fragment queue;
  	 * the receive start offset is set to 20 bytes (see code at the
  	 * top of this routine.)
  	 */
  	if (fp->ipq_csum_flags != 0) {
  		csum = fp->ipq_csum;
  
  		ADDCARRY(csum);
  
  		m->m_pkthdr.csum_rx_val = csum;
  		m->m_pkthdr.csum_rx_start = sizeof (struct ip);
  		m->m_pkthdr.csum_flags = fp->ipq_csum_flags;
  	} else if ((m->m_pkthdr.rcvif->if_flags & IFF_LOOPBACK) ||
  	    (m->m_pkthdr.pkt_flags & PKTF_LOOP)) {
  		/* loopback checksums are always OK */
  		m->m_pkthdr.csum_data = 0xffff;
  		m->m_pkthdr.csum_flags &= ~CSUM_PARTIAL;
  		m->m_pkthdr.csum_flags =
  		    CSUM_DATA_VALID | CSUM_PSEUDO_HDR |
  		    CSUM_IP_CHECKED | CSUM_IP_VALID;
  	}
  
  #if IPDIVERT
  	/*
  	 * Extract firewall instructions from the fragment structure.
  	 */
  #ifdef IPDIVERT_44
  	*divinfo = fp->ipq_div_info;
  #else
  	*divinfo = fp->ipq_divert;
  #endif
  	*divcookie = fp->ipq_div_cookie;
  #endif /* IPDIVERT */
  
  #if CONFIG_MACF_NET
  	mac_mbuf_label_associate_ipq(fp, m);
  	mac_ipq_label_destroy(fp);
  #endif
  	/*
  	 * Create header for new ip packet by modifying header of first
  	 * packet; dequeue and discard fragment reassembly header.
  	 * Make header visible.
  	 */
  	ip->ip_len = (IP_VHL_HL(ip->ip_vhl) << 2) + next;
  	ip->ip_src = fp->ipq_src;
  	ip->ip_dst = fp->ipq_dst;
  
  	fp->ipq_frags = NULL;	/* return to caller as 'm' */
  	frag_freef(head, fp);
  	fp = NULL;
  
  	m->m_len += (IP_VHL_HL(ip->ip_vhl) << 2);
  	m->m_data -= (IP_VHL_HL(ip->ip_vhl) << 2);
  	/* some debugging cruft by sklower, below, will go away soon */
  	if (m->m_flags & M_PKTHDR)	/* XXX this should be done elsewhere */
  		m_fixhdr(m);
  	ipstat.ips_reassembled++;
  
  	/* arm the purge timer if not already and if there's work to do */
  	frag_sched_timeout();
  	lck_mtx_unlock(&ipqlock);
  	/* perform deferred free (if needed) now that lock is dropped */
  	if (!MBUFQ_EMPTY(&dfq))
  		MBUFQ_DRAIN(&dfq);
  	VERIFY(MBUFQ_EMPTY(&dfq));
  	return (m);
  
  done:
  	VERIFY(m == NULL);
  	/* arm the purge timer if not already and if there's work to do */
  	frag_sched_timeout();
  	lck_mtx_unlock(&ipqlock);
  	/* perform deferred free (if needed) */
  	if (!MBUFQ_EMPTY(&dfq))
  		MBUFQ_DRAIN(&dfq);
  	VERIFY(MBUFQ_EMPTY(&dfq));
  	return (NULL);
  
  dropfrag:
  #if IPDIVERT
  	*divinfo = 0;
  	*divcookie = 0;
  #endif /* IPDIVERT */
  	ipstat.ips_fragdropped++;
  	if (fp != NULL)
  		fp->ipq_nfrags--;
  	/* arm the purge timer if not already and if there's work to do */
  	frag_sched_timeout();
  	lck_mtx_unlock(&ipqlock);
  	m_freem(m);
  	/* perform deferred free (if needed) */
  	if (!MBUFQ_EMPTY(&dfq))
  		MBUFQ_DRAIN(&dfq);
  	VERIFY(MBUFQ_EMPTY(&dfq));
  	return (NULL);
  #undef GETIP
  }
  
  /*
   * Free a fragment reassembly header and all
   * associated datagrams.
   */
  static void
  frag_freef(struct ipqhead *fhp, struct ipq *fp)
  {
  	lck_mtx_assert(&ipqlock, LCK_MTX_ASSERT_OWNED);
  
  	fp->ipq_nfrags = 0;
  	if (fp->ipq_frags != NULL) {
  		m_freem_list(fp->ipq_frags);
  		fp->ipq_frags = NULL;
  	}
  	TAILQ_REMOVE(fhp, fp, ipq_list);
  	nipq--;
  	ipq_free(fp);
  }
  
  /*
   * IP reassembly timer processing
   */
  static void
  frag_timeout(void *arg)
  {
  #pragma unused(arg)
  	struct ipq *fp;
  	int i;
  
  	/*
  	 * Update coarse-grained networking timestamp (in sec.); the idea
  	 * is to piggy-back on the timeout callout to update the counter
  	 * returnable via net_uptime().
  	 */
  	net_update_uptime();
  
  	lck_mtx_lock(&ipqlock);
  	for (i = 0; i < IPREASS_NHASH; i++) {
  		for (fp = TAILQ_FIRST(&ipq[i]); fp; ) {
  			struct ipq *fpp;
  
  			fpp = fp;
  			fp = TAILQ_NEXT(fp, ipq_list);
  			if (--fpp->ipq_ttl == 0) {
  				ipstat.ips_fragtimeout += fpp->ipq_nfrags;
  				frag_freef(&ipq[i], fpp);
  			}
  		}
  	}
  	/*
  	 * If we are over the maximum number of fragments
  	 * (due to the limit being lowered), drain off
  	 * enough to get down to the new limit.
  	 */
  	if (maxnipq >= 0 && nipq > (unsigned)maxnipq) {
  		for (i = 0; i < IPREASS_NHASH; i++) {
  			while (nipq > (unsigned)maxnipq &&
  			    !TAILQ_EMPTY(&ipq[i])) {
  				ipstat.ips_fragdropped +=
  				    TAILQ_FIRST(&ipq[i])->ipq_nfrags;
  				frag_freef(&ipq[i], TAILQ_FIRST(&ipq[i]));
  			}
  		}
  	}
  	/* re-arm the purge timer if there's work to do */
  	frag_timeout_run = 0;
  	frag_sched_timeout();
  	lck_mtx_unlock(&ipqlock);
  }
  
  static void
  frag_sched_timeout(void)
  {
  	lck_mtx_assert(&ipqlock, LCK_MTX_ASSERT_OWNED);
  
  	if (!frag_timeout_run && nipq > 0) {
  		frag_timeout_run = 1;
  		timeout(frag_timeout, NULL, hz);
  	}
  }
  
  /*
   * Drain off all datagram fragments.
   */
  static void
  frag_drain(void)
  {
  	int i;
  
  	lck_mtx_lock(&ipqlock);
  	for (i = 0; i < IPREASS_NHASH; i++) {
  		while (!TAILQ_EMPTY(&ipq[i])) {
  			ipstat.ips_fragdropped +=
  			    TAILQ_FIRST(&ipq[i])->ipq_nfrags;
  			frag_freef(&ipq[i], TAILQ_FIRST(&ipq[i]));
  		}
  	}
  	lck_mtx_unlock(&ipqlock);
  }
  
  static struct ipq *
  ipq_alloc(int how)
  {
  	struct mbuf *t;
  	struct ipq *fp;
  
  	/*
  	 * See comments in ipq_updateparams().  Keep the count separate
  	 * from nipq since the latter represents the elements already
  	 * in the reassembly queues.
  	 */
  	if (ipq_limit > 0 && ipq_count > ipq_limit)
  		return (NULL);
  
  	t = m_get(how, MT_FTABLE);
  	if (t != NULL) {
  		atomic_add_32(&ipq_count, 1);
  		fp = mtod(t, struct ipq *);
  		bzero(fp, sizeof (*fp));
  	} else {
  		fp = NULL;
  	}
  	return (fp);
  }
  
  static void
  ipq_free(struct ipq *fp)
  {
  	(void) m_free(dtom(fp));
  	atomic_add_32(&ipq_count, -1);
  }
  
  /*
   * Drain callback
   */
  void
  ip_drain(void)
  {
  	frag_drain();		/* fragments */
  	in_rtqdrain();		/* protocol cloned routes */
  	in_arpdrain(NULL);	/* cloned routes: ARP */
  }
  
  /*
   * Do option processing on a datagram,
   * possibly discarding it if bad options are encountered,
   * or forwarding it if source-routed.
   * The pass argument is used when operating in the IPSTEALTH
   * mode to tell what options to process:
   * [LS]SRR (pass 0) or the others (pass 1).
   * The reason for as many as two passes is that when doing IPSTEALTH,
   * non-routing options should be processed only if the packet is for us.
   * Returns 1 if packet has been forwarded/freed,
   * 0 if the packet should be processed further.
   */
  static int
  ip_dooptions(struct mbuf *m, int pass, struct sockaddr_in *next_hop)
  {
  #pragma unused(pass)
  	struct ip *ip = mtod(m, struct ip *);
  	u_char *cp;
  	struct ip_timestamp *ipt;
  	struct in_ifaddr *ia;
  	int opt, optlen, cnt, off, code, type = ICMP_PARAMPROB, forward = 0;
  	struct in_addr *sin, dst;
  	u_int32_t ntime;
  	struct sockaddr_in ipaddr = {
  	    sizeof (ipaddr), AF_INET, 0, { 0 }, { 0, } };
  
  	/* Expect 32-bit aligned data pointer on strict-align platforms */
  	MBUF_STRICT_DATA_ALIGNMENT_CHECK_32(m);
  
  	dst = ip->ip_dst;
  	cp = (u_char *)(ip + 1);
  	cnt = (IP_VHL_HL(ip->ip_vhl) << 2) - sizeof (struct ip);
  	for (; cnt > 0; cnt -= optlen, cp += optlen) {
  		opt = cp[IPOPT_OPTVAL];
  		if (opt == IPOPT_EOL)
  			break;
  		if (opt == IPOPT_NOP)
  			optlen = 1;
  		else {
  			if (cnt < IPOPT_OLEN + sizeof (*cp)) {
  				code = &cp[IPOPT_OLEN] - (u_char *)ip;
  				goto bad;
  			}
  			optlen = cp[IPOPT_OLEN];
  			if (optlen < IPOPT_OLEN + sizeof (*cp) ||
  			    optlen > cnt) {
  				code = &cp[IPOPT_OLEN] - (u_char *)ip;
  				goto bad;
  			}
  		}
  		switch (opt) {
  
  		default:
  			break;
  
  		/*
  		 * Source routing with record.
  		 * Find interface with current destination address.
  		 * If none on this machine then drop if strictly routed,
  		 * or do nothing if loosely routed.
  		 * Record interface address and bring up next address
  		 * component.  If strictly routed make sure next
  		 * address is on directly accessible net.
  		 */
  		case IPOPT_LSRR:
  		case IPOPT_SSRR:
  			if (optlen < IPOPT_OFFSET + sizeof (*cp)) {
  				code = &cp[IPOPT_OLEN] - (u_char *)ip;
  				goto bad;
  			}
  			if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
  				code = &cp[IPOPT_OFFSET] - (u_char *)ip;
  				goto bad;
  			}
  			ipaddr.sin_addr = ip->ip_dst;
  			ia = (struct in_ifaddr *)ifa_ifwithaddr(SA(&ipaddr));
  			if (ia == NULL) {
  				if (opt == IPOPT_SSRR) {
  					type = ICMP_UNREACH;
  					code = ICMP_UNREACH_SRCFAIL;
  					goto bad;
  				}
  				if (!ip_dosourceroute)
  					goto nosourcerouting;
  				/*
  				 * Loose routing, and not at next destination
  				 * yet; nothing to do except forward.
  				 */
  				break;
  			} else {
  				IFA_REMREF(&ia->ia_ifa);
  				ia = NULL;
  			}
  			off--;			/* 0 origin */
  			if (off > optlen - (int)sizeof (struct in_addr)) {
  				/*
  				 * End of source route.  Should be for us.
  				 */
  				if (!ip_acceptsourceroute)
  					goto nosourcerouting;
  				save_rte(cp, ip->ip_src);
  				break;
  			}
  
  			if (!ip_dosourceroute) {
  				if (ipforwarding) {
  					char buf[MAX_IPv4_STR_LEN];
  					char buf2[MAX_IPv4_STR_LEN];
  					/*
  					 * Acting as a router, so generate ICMP
  					 */
  nosourcerouting:
  					log(LOG_WARNING,
  					    "attempted source route from %s "
  					    "to %s\n",
  					    inet_ntop(AF_INET, &ip->ip_src,
  					    buf, sizeof (buf)),
  					    inet_ntop(AF_INET, &ip->ip_dst,
  					    buf2, sizeof (buf2)));
  					type = ICMP_UNREACH;
  					code = ICMP_UNREACH_SRCFAIL;
  					goto bad;
  				} else {
  					/*
  					 * Not acting as a router,
  					 * so silently drop.
  					 */
  					OSAddAtomic(1, &ipstat.ips_cantforward);
  					m_freem(m);
  					return (1);
  				}
  			}
  
  			/*
  			 * locate outgoing interface
  			 */
  			(void) memcpy(&ipaddr.sin_addr, cp + off,
  			    sizeof (ipaddr.sin_addr));
  
  			if (opt == IPOPT_SSRR) {
  #define	INA	struct in_ifaddr *
  				if ((ia = (INA)ifa_ifwithdstaddr(
  				    SA(&ipaddr))) == NULL) {
  					ia = (INA)ifa_ifwithnet(SA(&ipaddr));
  				}
  			} else {
  				ia = ip_rtaddr(ipaddr.sin_addr);
  			}
  			if (ia == NULL) {
  				type = ICMP_UNREACH;
  				code = ICMP_UNREACH_SRCFAIL;
  				goto bad;
  			}
  			ip->ip_dst = ipaddr.sin_addr;
  			IFA_LOCK(&ia->ia_ifa);
  			(void) memcpy(cp + off, &(IA_SIN(ia)->sin_addr),
  			    sizeof (struct in_addr));
  			IFA_UNLOCK(&ia->ia_ifa);
  			IFA_REMREF(&ia->ia_ifa);
  			ia = NULL;
  			cp[IPOPT_OFFSET] += sizeof (struct in_addr);
  			/*
  			 * Let ip_intr's mcast routing check handle mcast pkts
  			 */
  			forward = !IN_MULTICAST(ntohl(ip->ip_dst.s_addr));
  			break;
  
  		case IPOPT_RR:
  			if (optlen < IPOPT_OFFSET + sizeof (*cp)) {
  				code = &cp[IPOPT_OFFSET] - (u_char *)ip;
  				goto bad;
  			}
  			if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
  				code = &cp[IPOPT_OFFSET] - (u_char *)ip;
  				goto bad;
  			}
  			/*
  			 * If no space remains, ignore.
  			 */
  			off--;			/* 0 origin */
  			if (off > optlen - (int)sizeof (struct in_addr))
  				break;
  			(void) memcpy(&ipaddr.sin_addr, &ip->ip_dst,
  			    sizeof (ipaddr.sin_addr));
  			/*
  			 * locate outgoing interface; if we're the destination,
  			 * use the incoming interface (should be same).
  			 */
  			if ((ia = (INA)ifa_ifwithaddr(SA(&ipaddr))) == NULL) {
  				if ((ia = ip_rtaddr(ipaddr.sin_addr)) == NULL) {
  					type = ICMP_UNREACH;
  					code = ICMP_UNREACH_HOST;
  					goto bad;
  				}
  			}
  			IFA_LOCK(&ia->ia_ifa);
  			(void) memcpy(cp + off, &(IA_SIN(ia)->sin_addr),
  			    sizeof (struct in_addr));
  			IFA_UNLOCK(&ia->ia_ifa);
  			IFA_REMREF(&ia->ia_ifa);
  			ia = NULL;
  			cp[IPOPT_OFFSET] += sizeof (struct in_addr);
  			break;
  
  		case IPOPT_TS:
  			code = cp - (u_char *)ip;
  			ipt = (struct ip_timestamp *)(void *)cp;
  			if (ipt->ipt_len < 4 || ipt->ipt_len > 40) {
  				code = (u_char *)&ipt->ipt_len - (u_char *)ip;
  				goto bad;
  			}
  			if (ipt->ipt_ptr < 5) {
  				code = (u_char *)&ipt->ipt_ptr - (u_char *)ip;
  				goto bad;
  			}
  			if (ipt->ipt_ptr >
  			    ipt->ipt_len - (int)sizeof (int32_t)) {
  				if (++ipt->ipt_oflw == 0) {
  					code = (u_char *)&ipt->ipt_ptr -
  					    (u_char *)ip;
  					goto bad;
  				}
  				break;
  			}
  			sin = (struct in_addr *)(void *)(cp + ipt->ipt_ptr - 1);
  			switch (ipt->ipt_flg) {
  
  			case IPOPT_TS_TSONLY:
  				break;
  
  			case IPOPT_TS_TSANDADDR:
  				if (ipt->ipt_ptr - 1 + sizeof (n_time) +
  				    sizeof (struct in_addr) > ipt->ipt_len) {
  					code = (u_char *)&ipt->ipt_ptr -
  					    (u_char *)ip;
  					goto bad;
  				}
  				ipaddr.sin_addr = dst;
  				ia = (INA)ifaof_ifpforaddr(SA(&ipaddr),
  				    m->m_pkthdr.rcvif);
  				if (ia == NULL)
  					continue;
  				IFA_LOCK(&ia->ia_ifa);
  				(void) memcpy(sin, &IA_SIN(ia)->sin_addr,
  				    sizeof (struct in_addr));
  				IFA_UNLOCK(&ia->ia_ifa);
  				ipt->ipt_ptr += sizeof (struct in_addr);
  				IFA_REMREF(&ia->ia_ifa);
  				ia = NULL;
  				break;
  
  			case IPOPT_TS_PRESPEC:
  				if (ipt->ipt_ptr - 1 + sizeof (n_time) +
  				    sizeof (struct in_addr) > ipt->ipt_len) {
  					code = (u_char *)&ipt->ipt_ptr -
  					    (u_char *)ip;
  					goto bad;
  				}
  				(void) memcpy(&ipaddr.sin_addr, sin,
  				    sizeof (struct in_addr));
  				if ((ia = (struct in_ifaddr *)ifa_ifwithaddr(
  				    SA(&ipaddr))) == NULL)
  					continue;
  				IFA_REMREF(&ia->ia_ifa);
  				ia = NULL;
  				ipt->ipt_ptr += sizeof (struct in_addr);
  				break;
  
  			default:
  				/* XXX can't take &ipt->ipt_flg */
  				code = (u_char *)&ipt->ipt_ptr -
  				    (u_char *)ip + 1;
  				goto bad;
  			}
  			ntime = iptime();
  			(void) memcpy(cp + ipt->ipt_ptr - 1, &ntime,
  			    sizeof (n_time));
  			ipt->ipt_ptr += sizeof (n_time);
  		}
  	}
  	if (forward && ipforwarding) {
  		ip_forward(m, 1, next_hop);
  		return (1);
  	}
  	return (0);
  bad:
  	icmp_error(m, type, code, 0, 0);
  	OSAddAtomic(1, &ipstat.ips_badoptions);
  	return (1);
  }
  
  /*
   * Check for the presence of the IP Router Alert option [RFC2113]
   * in the header of an IPv4 datagram.
   *
   * This call is not intended for use from the forwarding path; it is here
   * so that protocol domains may check for the presence of the option.
   * Given how FreeBSD's IPv4 stack is currently structured, the Router Alert
   * option does not have much relevance to the implementation, though this
   * may change in future.
   * Router alert options SHOULD be passed if running in IPSTEALTH mode and
   * we are not the endpoint.
   * Length checks on individual options should already have been peformed
   * by ip_dooptions() therefore they are folded under DIAGNOSTIC here.
   *
   * Return zero if not present or options are invalid, non-zero if present.
   */
  int
  ip_checkrouteralert(struct mbuf *m)
  {
  	struct ip *ip = mtod(m, struct ip *);
  	u_char *cp;
  	int opt, optlen, cnt, found_ra;
  
  	found_ra = 0;
  	cp = (u_char *)(ip + 1);
  	cnt = (IP_VHL_HL(ip->ip_vhl) << 2) - sizeof (struct ip);
  	for (; cnt > 0; cnt -= optlen, cp += optlen) {
  		opt = cp[IPOPT_OPTVAL];
  		if (opt == IPOPT_EOL)
  			break;
  		if (opt == IPOPT_NOP)
  			optlen = 1;
  		else {
  #ifdef DIAGNOSTIC
  			if (cnt < IPOPT_OLEN + sizeof (*cp))
  				break;
  #endif
  			optlen = cp[IPOPT_OLEN];
  #ifdef DIAGNOSTIC
  			if (optlen < IPOPT_OLEN + sizeof (*cp) || optlen > cnt)
  				break;
  #endif
  		}
  		switch (opt) {
  		case IPOPT_RA:
  #ifdef DIAGNOSTIC
  			if (optlen != IPOPT_OFFSET + sizeof (uint16_t) ||
  			    (*((uint16_t *)(void *)&cp[IPOPT_OFFSET]) != 0))
  				break;
  			else
  #endif
  				found_ra = 1;
  			break;
  		default:
  			break;
  		}
  	}
  
  	return (found_ra);
  }
  
  /*
   * Given address of next destination (final or next hop),
   * return internet address info of interface to be used to get there.
   */
  struct in_ifaddr *
  ip_rtaddr(struct in_addr dst)
  {
  	struct sockaddr_in *sin;
  	struct ifaddr *rt_ifa;
  	struct route ro;
  
  	bzero(&ro, sizeof (ro));
  	sin = SIN(&ro.ro_dst);
  	sin->sin_family = AF_INET;
  	sin->sin_len = sizeof (*sin);
  	sin->sin_addr = dst;
  
  	rtalloc_ign(&ro, RTF_PRCLONING);
  	if (ro.ro_rt == NULL) {
  		ROUTE_RELEASE(&ro);
  		return (NULL);
  	}
  
  	RT_LOCK(ro.ro_rt);
  	if ((rt_ifa = ro.ro_rt->rt_ifa) != NULL)
  		IFA_ADDREF(rt_ifa);
  	RT_UNLOCK(ro.ro_rt);
  	ROUTE_RELEASE(&ro);
  
  	return ((struct in_ifaddr *)rt_ifa);
  }
  
  /*
   * Save incoming source route for use in replies,
   * to be picked up later by ip_srcroute if the receiver is interested.
   */
  void
  save_rte(u_char *option, struct in_addr dst)
  {
  	unsigned olen;
  
  	olen = option[IPOPT_OLEN];
  #if DIAGNOSTIC
  	if (ipprintfs)
  		printf("save_rte: olen %d\n", olen);
  #endif
  	if (olen > sizeof (ip_srcrt) - (1 + sizeof (dst)))
  		return;
  	bcopy(option, ip_srcrt.srcopt, olen);
  	ip_nhops = (olen - IPOPT_OFFSET - 1) / sizeof (struct in_addr);
  	ip_srcrt.dst = dst;
  }
  
  /*
   * Retrieve incoming source route for use in replies,
   * in the same form used by setsockopt.
   * The first hop is placed before the options, will be removed later.
   */
  struct mbuf *
  ip_srcroute(void)
  {
  	struct in_addr *p, *q;
  	struct mbuf *m;
  
  	if (ip_nhops == 0)
  		return (NULL);
  
  	m = m_get(M_DONTWAIT, MT_HEADER);
  	if (m == NULL)
  		return (NULL);
  
  #define	OPTSIZ	(sizeof (ip_srcrt.nop) + sizeof (ip_srcrt.srcopt))
  
  	/* length is (nhops+1)*sizeof(addr) + sizeof(nop + srcrt header) */
  	m->m_len = ip_nhops * sizeof (struct in_addr) +
  	    sizeof (struct in_addr) + OPTSIZ;
  #if DIAGNOSTIC
  	if (ipprintfs)
  		printf("ip_srcroute: nhops %d mlen %d", ip_nhops, m->m_len);
  #endif
  
  	/*
  	 * First save first hop for return route
  	 */
  	p = &ip_srcrt.route[ip_nhops - 1];
  	*(mtod(m, struct in_addr *)) = *p--;
  #if DIAGNOSTIC
  	if (ipprintfs)
  		printf(" hops %lx",
  		    (u_int32_t)ntohl(mtod(m, struct in_addr *)->s_addr));
  #endif
  
  	/*
  	 * Copy option fields and padding (nop) to mbuf.
  	 */
  	ip_srcrt.nop = IPOPT_NOP;
  	ip_srcrt.srcopt[IPOPT_OFFSET] = IPOPT_MINOFF;
  	(void) memcpy(mtod(m, caddr_t) + sizeof (struct in_addr),
  	    &ip_srcrt.nop, OPTSIZ);
  	q = (struct in_addr *)(void *)(mtod(m, caddr_t) +
  	    sizeof (struct in_addr) + OPTSIZ);
  #undef OPTSIZ
  	/*
  	 * Record return path as an IP source route,
  	 * reversing the path (pointers are now aligned).
  	 */
  	while (p >= ip_srcrt.route) {
  #if DIAGNOSTIC
  		if (ipprintfs)
  			printf(" %lx", (u_int32_t)ntohl(q->s_addr));
  #endif
  		*q++ = *p--;
  	}
  	/*
  	 * Last hop goes to final destination.
  	 */
  	*q = ip_srcrt.dst;
  #if DIAGNOSTIC
  	if (ipprintfs)
  		printf(" %lx\n", (u_int32_t)ntohl(q->s_addr));
  #endif
  	return (m);
  }
  
  /*
   * Strip out IP options, at higher
   * level protocol in the kernel.
   * Second argument is buffer to which options
   * will be moved, and return value is their length.
   * XXX should be deleted; last arg currently ignored.
   */
  void
  ip_stripoptions(struct mbuf *m, struct mbuf *mopt)
  {
  #pragma unused(mopt)
  	int i;
  	struct ip *ip = mtod(m, struct ip *);
  	caddr_t opts;
  	int olen;
  
  	/* Expect 32-bit aligned data pointer on strict-align platforms */
  	MBUF_STRICT_DATA_ALIGNMENT_CHECK_32(m);
  
  	olen = (IP_VHL_HL(ip->ip_vhl) << 2) - sizeof (struct ip);
  	opts = (caddr_t)(ip + 1);
  	i = m->m_len - (sizeof (struct ip) + olen);
  	bcopy(opts + olen, opts, (unsigned)i);
  	m->m_len -= olen;
  	if (m->m_flags & M_PKTHDR)
  		m->m_pkthdr.len -= olen;
  	ip->ip_vhl = IP_MAKE_VHL(IPVERSION, sizeof (struct ip) >> 2);
  }
  
  u_char inetctlerrmap[PRC_NCMDS] = {
  	0,		0,		0,		0,
  	0,		EMSGSIZE,	EHOSTDOWN,	EHOSTUNREACH,
  	ENETUNREACH,	EHOSTUNREACH,	ECONNREFUSED,	ECONNREFUSED,
  	EMSGSIZE,	EHOSTUNREACH,	0,		0,
  	0,		0,		0,		0,
  	ENOPROTOOPT,	ECONNREFUSED
  };
  
  static int
  sysctl_ipforwarding SYSCTL_HANDLER_ARGS
  {
  #pragma unused(arg1, arg2)
  	int i, was_ipforwarding = ipforwarding;
  
  	i = sysctl_handle_int(oidp, oidp->oid_arg1, oidp->oid_arg2, req);
  	if (i != 0 || req->newptr == USER_ADDR_NULL)
  		return (i);
  
  	if (was_ipforwarding && !ipforwarding) {
  		/* clean up IPv4 forwarding cached routes */
  		ifnet_head_lock_shared();
  		for (i = 0; i <= if_index; i++) {
  			struct ifnet *ifp = ifindex2ifnet[i];
  			if (ifp != NULL) {
  				lck_mtx_lock(&ifp->if_cached_route_lock);
  				ROUTE_RELEASE(&ifp->if_fwd_route);
  				bzero(&ifp->if_fwd_route,
  				    sizeof (ifp->if_fwd_route));
  				lck_mtx_unlock(&ifp->if_cached_route_lock);
  			}
  		}
  		ifnet_head_done();
  	}
  
  	return (0);
  }
  
  /*
   * Similar to inp_route_{copyout,copyin} routines except that these copy
   * out the cached IPv4 forwarding route from struct ifnet instead of the
   * inpcb.  See comments for those routines for explanations.
   */
  static void
  ip_fwd_route_copyout(struct ifnet *ifp, struct route *dst)
  {
  	struct route *src = &ifp->if_fwd_route;
  
  	lck_mtx_lock_spin(&ifp->if_cached_route_lock);
  	lck_mtx_convert_spin(&ifp->if_cached_route_lock);
  
  	/* Minor sanity check */
  	if (src->ro_rt != NULL && rt_key(src->ro_rt)->sa_family != AF_INET)
  		panic("%s: wrong or corrupted route: %p", __func__, src);
  
  	route_copyout(dst, src, sizeof (*dst));
  
  	lck_mtx_unlock(&ifp->if_cached_route_lock);
  }
  
  static void
  ip_fwd_route_copyin(struct ifnet *ifp, struct route *src)
  {
  	struct route *dst = &ifp->if_fwd_route;
  
  	lck_mtx_lock_spin(&ifp->if_cached_route_lock);
  	lck_mtx_convert_spin(&ifp->if_cached_route_lock);
  
  	/* Minor sanity check */
  	if (src->ro_rt != NULL && rt_key(src->ro_rt)->sa_family != AF_INET)
  		panic("%s: wrong or corrupted route: %p", __func__, src);
  
  	if (ifp->if_fwd_cacheok)
  		route_copyin(src, dst, sizeof (*src));
  
  	lck_mtx_unlock(&ifp->if_cached_route_lock);
  }
  
  /*
   * Forward a packet.  If some error occurs return the sender
   * an icmp packet.  Note we can't always generate a meaningful
   * icmp message because icmp doesn't have a large enough repertoire
   * of codes and types.
   *
   * If not forwarding, just drop the packet.  This could be confusing
   * if ipforwarding was zero but some routing protocol was advancing
   * us as a gateway to somewhere.  However, we must let the routing
   * protocol deal with that.
   *
   * The srcrt parameter indicates whether the packet is being forwarded
   * via a source route.
   */
  static void
  ip_forward(struct mbuf *m, int srcrt, struct sockaddr_in *next_hop)
  {
  #if !IPFIREWALL
  #pragma unused(next_hop)
  #endif
  	struct ip *ip = mtod(m, struct ip *);
  	struct sockaddr_in *sin;
  	struct rtentry *rt;
  	struct route fwd_rt;
  	int error, type = 0, code = 0;
  	struct mbuf *mcopy;
  	n_long dest;
  	struct in_addr pkt_dst;
  	u_int32_t nextmtu = 0, len;
  	struct ip_out_args ipoa = { IFSCOPE_NONE, { 0 }, 0, 0,
  	    SO_TC_UNSPEC, _NET_SERVICE_TYPE_UNSPEC };
  	struct ifnet *rcvifp = m->m_pkthdr.rcvif;
  #if IPSEC
  	struct secpolicy *sp = NULL;
  	int ipsecerror;
  #endif /* IPSEC */
  #if PF
  	struct pf_mtag *pf_mtag;
  #endif /* PF */
  
  	dest = 0;
  #if IPFIREWALL
  	/*
  	 * Cache the destination address of the packet; this may be
  	 * changed by use of 'ipfw fwd'.
  	 */
  	pkt_dst = ((next_hop != NULL) ? next_hop->sin_addr : ip->ip_dst);
  #else /* !IPFIREWALL */
  	pkt_dst = ip->ip_dst;
  #endif /* !IPFIREWALL */
  
  #if DIAGNOSTIC
  	if (ipprintfs)
  		printf("forward: src %lx dst %lx ttl %x\n",
  		    (u_int32_t)ip->ip_src.s_addr, (u_int32_t)pkt_dst.s_addr,
  		    ip->ip_ttl);
  #endif
  
  	if (m->m_flags & (M_BCAST|M_MCAST) || !in_canforward(pkt_dst)) {
  		OSAddAtomic(1, &ipstat.ips_cantforward);
  		m_freem(m);
  		return;
  	}
  #if IPSTEALTH
  	if (!ipstealth) {
  #endif /* IPSTEALTH */
  		if (ip->ip_ttl <= IPTTLDEC) {
  			icmp_error(m, ICMP_TIMXCEED, ICMP_TIMXCEED_INTRANS,
  			    dest, 0);
  			return;
  		}
  #if IPSTEALTH
  	}
  #endif /* IPSTEALTH */
  
  #if PF
  	pf_mtag = pf_find_mtag(m);
  	if (pf_mtag != NULL && pf_mtag->pftag_rtableid != IFSCOPE_NONE) {
  		ipoa.ipoa_boundif = pf_mtag->pftag_rtableid;
  		ipoa.ipoa_flags |= IPOAF_BOUND_IF;
  	}
  #endif /* PF */
  
  	ip_fwd_route_copyout(rcvifp, &fwd_rt);
  
  	sin = SIN(&fwd_rt.ro_dst);
  	if (ROUTE_UNUSABLE(&fwd_rt) || pkt_dst.s_addr != sin->sin_addr.s_addr) {
  		ROUTE_RELEASE(&fwd_rt);
  
  		sin->sin_family = AF_INET;
  		sin->sin_len = sizeof (*sin);
  		sin->sin_addr = pkt_dst;
  
  		rtalloc_scoped_ign(&fwd_rt, RTF_PRCLONING, ipoa.ipoa_boundif);
  		if (fwd_rt.ro_rt == NULL) {
  			icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, dest, 0);
  			goto done;
  		}
  	}
  	rt = fwd_rt.ro_rt;
  
  	/*
  	 * Save the IP header and at most 8 bytes of the payload,
  	 * in case we need to generate an ICMP message to the src.
  	 *
  	 * We don't use m_copy() because it might return a reference
  	 * to a shared cluster. Both this function and ip_output()
  	 * assume exclusive access to the IP header in `m', so any
  	 * data in a cluster may change before we reach icmp_error().
  	 */
  	MGET(mcopy, M_DONTWAIT, m->m_type);
  	if (mcopy != NULL) {
  		M_COPY_PKTHDR(mcopy, m);
  		mcopy->m_len = imin((IP_VHL_HL(ip->ip_vhl) << 2) + 8,
  		    (int)ip->ip_len);
  		m_copydata(m, 0, mcopy->m_len, mtod(mcopy, caddr_t));
  	}
  
  #if IPSTEALTH
  	if (!ipstealth) {
  #endif /* IPSTEALTH */
  		ip->ip_ttl -= IPTTLDEC;
  #if IPSTEALTH
  	}
  #endif /* IPSTEALTH */
  
  	/*
  	 * If forwarding packet using same interface that it came in on,
  	 * perhaps should send a redirect to sender to shortcut a hop.
  	 * Only send redirect if source is sending directly to us,
  	 * and if packet was not source routed (or has any options).
  	 * Also, don't send redirect if forwarding using a default route
  	 * or a route modified by a redirect.
  	 */
  	RT_LOCK_SPIN(rt);
  	if (rt->rt_ifp == m->m_pkthdr.rcvif &&
  	    !(rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) &&
  	    satosin(rt_key(rt))->sin_addr.s_addr != INADDR_ANY &&
  	    ipsendredirects && !srcrt && rt->rt_ifa != NULL) {
  		struct in_ifaddr *ia = (struct in_ifaddr *)rt->rt_ifa;
  		u_int32_t src = ntohl(ip->ip_src.s_addr);
  
  		/* Become a regular mutex */
  		RT_CONVERT_LOCK(rt);
  		IFA_LOCK_SPIN(&ia->ia_ifa);
  		if ((src & ia->ia_subnetmask) == ia->ia_subnet) {
  			if (rt->rt_flags & RTF_GATEWAY)
  				dest = satosin(rt->rt_gateway)->sin_addr.s_addr;
  			else
  				dest = pkt_dst.s_addr;
  			/*
  			 * Router requirements says to only send
  			 * host redirects.
  			 */
  			type = ICMP_REDIRECT;
  			code = ICMP_REDIRECT_HOST;
  #if DIAGNOSTIC
  			if (ipprintfs)
  				printf("redirect (%d) to %lx\n", code,
  				    (u_int32_t)dest);
  #endif
  		}
  		IFA_UNLOCK(&ia->ia_ifa);
  	}
  	RT_UNLOCK(rt);
  
  #if IPFIREWALL
  	if (next_hop != NULL) {
  		/* Pass IPFORWARD info if available */
  		struct m_tag *tag;
  		struct ip_fwd_tag *ipfwd_tag;
  
  		tag = m_tag_create(KERNEL_MODULE_TAG_ID,
  		    KERNEL_TAG_TYPE_IPFORWARD,
  		    sizeof (*ipfwd_tag), M_NOWAIT, m);
  		if (tag == NULL) {
  			error = ENOBUFS;
  			m_freem(m);
  			goto done;
  		}
  
  		ipfwd_tag = (struct ip_fwd_tag *)(tag+1);
  		ipfwd_tag->next_hop = next_hop;
  
  		m_tag_prepend(m, tag);
  	}
  #endif /* IPFIREWALL */
  
  	/* Mark this packet as being forwarded from another interface */
  	m->m_pkthdr.pkt_flags |= PKTF_FORWARDED;
  	len = m_pktlen(m);
  
  	error = ip_output(m, NULL, &fwd_rt, IP_FORWARDING | IP_OUTARGS,
  	    NULL, &ipoa);
  
  	/* Refresh rt since the route could have changed while in IP */
  	rt = fwd_rt.ro_rt;
  
  	if (error != 0) {
  		OSAddAtomic(1, &ipstat.ips_cantforward);
  	} else {
  		/*
  		 * Increment stats on the source interface; the ones
  		 * for destination interface has been taken care of
  		 * during output above by virtue of PKTF_FORWARDED.
  		 */
  		rcvifp->if_fpackets++;
  		rcvifp->if_fbytes += len;
  
  		OSAddAtomic(1, &ipstat.ips_forward);
  		if (type != 0) {
  			OSAddAtomic(1, &ipstat.ips_redirectsent);
  		} else {
  			if (mcopy != NULL) {
  				/*
  				 * If we didn't have to go thru ipflow and
  				 * the packet was successfully consumed by
  				 * ip_output, the mcopy is rather a waste;
  				 * this could be further optimized.
  				 */
  				m_freem(mcopy);
  			}
  			goto done;
  		}
  	}
  	if (mcopy == NULL)
  		goto done;
  
  	switch (error) {
  	case 0:				/* forwarded, but need redirect */
  		/* type, code set above */
  		break;
  
  	case ENETUNREACH:		/* shouldn't happen, checked above */
  	case EHOSTUNREACH:
  	case ENETDOWN:
  	case EHOSTDOWN:
  	default:
  		type = ICMP_UNREACH;
  		code = ICMP_UNREACH_HOST;
  		break;
  
  	case EMSGSIZE:
  		type = ICMP_UNREACH;
  		code = ICMP_UNREACH_NEEDFRAG;
  
  		if (rt == NULL) {
  			break;
  		} else {
  			RT_LOCK_SPIN(rt);
  			if (rt->rt_ifp != NULL)
  				nextmtu = rt->rt_ifp->if_mtu;
  			RT_UNLOCK(rt);
  		}
  #ifdef IPSEC
  		if (ipsec_bypass)
  			break;
  
  		/*
  		 * If the packet is routed over IPsec tunnel, tell the
  		 * originator the tunnel MTU.
  		 *	tunnel MTU = if MTU - sizeof(IP) - ESP/AH hdrsiz
  		 * XXX quickhack!!!
  		 */
  		sp = ipsec4_getpolicybyaddr(mcopy, IPSEC_DIR_OUTBOUND,
  		    IP_FORWARDING, &ipsecerror);
  
  		if (sp == NULL)
  			break;
  
  		/*
  		 * find the correct route for outer IPv4
  		 * header, compute tunnel MTU.
  		 */
  		nextmtu = 0;
  
  		if (sp->req != NULL &&
  		    sp->req->saidx.mode == IPSEC_MODE_TUNNEL) {
  			struct secasindex saidx;
  			struct secasvar *sav;
  			struct route *ro;
  			struct ip *ipm;
  			int ipsechdr;
  
  			/* count IPsec header size */
  			ipsechdr = ipsec_hdrsiz(sp);
  
  			ipm = mtod(mcopy, struct ip *);
  			bcopy(&sp->req->saidx, &saidx, sizeof (saidx));
  			saidx.mode = sp->req->saidx.mode;
  			saidx.reqid = sp->req->saidx.reqid;
  			sin = SIN(&saidx.src);
  			if (sin->sin_len == 0) {
  				sin->sin_len = sizeof (*sin);
  				sin->sin_family = AF_INET;
  				sin->sin_port = IPSEC_PORT_ANY;
  				bcopy(&ipm->ip_src, &sin->sin_addr,
  				    sizeof (sin->sin_addr));
  			}
  			sin = SIN(&saidx.dst);
  			if (sin->sin_len == 0) {
  				sin->sin_len = sizeof (*sin);
  				sin->sin_family = AF_INET;
  				sin->sin_port = IPSEC_PORT_ANY;
  				bcopy(&ipm->ip_dst, &sin->sin_addr,
  				    sizeof (sin->sin_addr));
  			}
  			sav = key_allocsa_policy(&saidx);
  			if (sav != NULL) {
  				lck_mtx_lock(sadb_mutex);
  				if (sav->sah != NULL) {
  					ro = &sav->sah->sa_route;
  					if (ro->ro_rt != NULL) {
  						RT_LOCK(ro->ro_rt);
  						if (ro->ro_rt->rt_ifp != NULL) {
  							nextmtu = ro->ro_rt->
  							    rt_ifp->if_mtu;
  							nextmtu -= ipsechdr;
  						}
  						RT_UNLOCK(ro->ro_rt);
  					}
  				}
  				key_freesav(sav, KEY_SADB_LOCKED);
  				lck_mtx_unlock(sadb_mutex);
  			}
  		}
  		key_freesp(sp, KEY_SADB_UNLOCKED);
  #endif /* IPSEC */
  		break;
  
  	case ENOBUFS:
  		/*
  		 * A router should not generate ICMP_SOURCEQUENCH as
  		 * required in RFC1812 Requirements for IP Version 4 Routers.
  		 * Source quench could be a big problem under DoS attacks,
  		 * or if the underlying interface is rate-limited.
  		 * Those who need source quench packets may re-enable them
  		 * via the net.inet.ip.sendsourcequench sysctl.
  		 */
  		if (ip_sendsourcequench == 0) {
  			m_freem(mcopy);
  			goto done;
  		} else {
  			type = ICMP_SOURCEQUENCH;
  			code = 0;
  		}
  		break;
  
  	case EACCES:			/* ipfw denied packet */
  		m_freem(mcopy);
  		goto done;
  	}
  
  	if (type == ICMP_UNREACH && code == ICMP_UNREACH_NEEDFRAG)
  		OSAddAtomic(1, &ipstat.ips_cantfrag);
  
  	icmp_error(mcopy, type, code, dest, nextmtu);
  done:
  	ip_fwd_route_copyin(rcvifp, &fwd_rt);
  }
  
  int
  ip_savecontrol(struct inpcb *inp, struct mbuf **mp, struct ip *ip,
      struct mbuf *m)
  {
  	*mp = NULL;
  	if (inp->inp_socket->so_options & SO_TIMESTAMP) {
  		struct timeval tv;
  
  		getmicrotime(&tv);
  		mp = sbcreatecontrol_mbuf((caddr_t)&tv, sizeof (tv),
  		    SCM_TIMESTAMP, SOL_SOCKET, mp);
  		if (*mp == NULL) {
  			goto no_mbufs;
  		}
  	}
  	if (inp->inp_socket->so_options & SO_TIMESTAMP_MONOTONIC) {
  		uint64_t time;
  
  		time = mach_absolute_time();
  		mp = sbcreatecontrol_mbuf((caddr_t)&time, sizeof (time),
  		    SCM_TIMESTAMP_MONOTONIC, SOL_SOCKET, mp);
  		if (*mp == NULL) {
  			goto no_mbufs;
  		}
  	}
  	if (inp->inp_flags & INP_RECVDSTADDR) {
  		mp = sbcreatecontrol_mbuf((caddr_t)&ip->ip_dst,
  		    sizeof (struct in_addr), IP_RECVDSTADDR, IPPROTO_IP, mp);
  		if (*mp == NULL) {
  			goto no_mbufs;
  		}
  	}
  #ifdef notyet
  	/*
  	 * XXX
  	 * Moving these out of udp_input() made them even more broken
  	 * than they already were.
  	 */
  	/* options were tossed already */
  	if (inp->inp_flags & INP_RECVOPTS) {
  		mp = sbcreatecontrol_mbuf((caddr_t)opts_deleted_above,
  		    sizeof (struct in_addr), IP_RECVOPTS, IPPROTO_IP, mp);
  		if (*mp == NULL) {
  			goto no_mbufs;
  		}
  	}
  	/* ip_srcroute doesn't do what we want here, need to fix */
  	if (inp->inp_flags & INP_RECVRETOPTS) {
  		mp = sbcreatecontrol_mbuf((caddr_t)ip_srcroute(),
  		    sizeof (struct in_addr), IP_RECVRETOPTS, IPPROTO_IP, mp);
  		if (*mp == NULL) {
  			goto no_mbufs;
  		}
  	}
  #endif /* notyet */
  	if (inp->inp_flags & INP_RECVIF) {
  		struct ifnet *ifp;
  		uint8_t sdlbuf[SOCK_MAXADDRLEN + 1];
  		struct sockaddr_dl *sdl2 = SDL(&sdlbuf);
  
  		/*
  		 * Make sure to accomodate the largest possible
  		 * size of SA(if_lladdr)->sa_len.
  		 */
  		_CASSERT(sizeof (sdlbuf) == (SOCK_MAXADDRLEN + 1));
  
  		ifnet_head_lock_shared();
  		if ((ifp = m->m_pkthdr.rcvif) != NULL &&
  		    ifp->if_index && (ifp->if_index <= if_index)) {
  			struct ifaddr *ifa = ifnet_addrs[ifp->if_index - 1];
  			struct sockaddr_dl *sdp;
  
  			if (!ifa || !ifa->ifa_addr)
  				goto makedummy;
  
  			IFA_LOCK_SPIN(ifa);
  			sdp = SDL(ifa->ifa_addr);
  			/*
  			 * Change our mind and don't try copy.
  			 */
  			if (sdp->sdl_family != AF_LINK) {
  				IFA_UNLOCK(ifa);
  				goto makedummy;
  			}
  			/* the above _CASSERT ensures sdl_len fits in sdlbuf */
  			bcopy(sdp, sdl2, sdp->sdl_len);
  			IFA_UNLOCK(ifa);
  		} else {
  makedummy:
  			sdl2->sdl_len =
  			    offsetof(struct sockaddr_dl, sdl_data[0]);
  			sdl2->sdl_family = AF_LINK;
  			sdl2->sdl_index = 0;
  			sdl2->sdl_nlen = sdl2->sdl_alen = sdl2->sdl_slen = 0;
  		}
  		ifnet_head_done();
  		mp = sbcreatecontrol_mbuf((caddr_t)sdl2, sdl2->sdl_len,
  		    IP_RECVIF, IPPROTO_IP, mp);
  		if (*mp == NULL) {
  			goto no_mbufs;
  		}
  	}
  	if (inp->inp_flags & INP_RECVTTL) {
  		mp = sbcreatecontrol_mbuf((caddr_t)&ip->ip_ttl,
  		    sizeof (ip->ip_ttl), IP_RECVTTL, IPPROTO_IP, mp);
  		if (*mp == NULL) {
  			goto no_mbufs;
  		}
  	}
  	if (inp->inp_socket->so_flags & SOF_RECV_TRAFFIC_CLASS) {
  		int tc = m_get_traffic_class(m);
  
  		mp = sbcreatecontrol_mbuf((caddr_t)&tc, sizeof (tc),
  		    SO_TRAFFIC_CLASS, SOL_SOCKET, mp);
  		if (*mp == NULL) {
  			goto no_mbufs;
  		}
  	}
  	if (inp->inp_flags & INP_PKTINFO) {
  		struct in_pktinfo pi;
  
  		bzero(&pi, sizeof (struct in_pktinfo));
  		bcopy(&ip->ip_dst, &pi.ipi_addr, sizeof (struct in_addr));
  		pi.ipi_ifindex = (m != NULL && m->m_pkthdr.rcvif != NULL) ?
  		    m->m_pkthdr.rcvif->if_index : 0;
  
  		mp = sbcreatecontrol_mbuf((caddr_t)&pi,
  		    sizeof (struct in_pktinfo), IP_RECVPKTINFO, IPPROTO_IP, mp);
  		if (*mp == NULL) {
  			goto no_mbufs;
  		}
  	}
  	return (0);
  
  no_mbufs:
  	ipstat.ips_pktdropcntrl++;
  	return (ENOBUFS);
  }
  
  static inline u_short
  ip_cksum(struct mbuf *m, int hlen)
  {
  	u_short sum;
  
  	if (m->m_pkthdr.csum_flags & CSUM_IP_CHECKED) {
  		sum = !(m->m_pkthdr.csum_flags & CSUM_IP_VALID);
  	} else if (!(m->m_pkthdr.rcvif->if_flags & IFF_LOOPBACK) &&
  	    !(m->m_pkthdr.pkt_flags & PKTF_LOOP)) {
  		/*
  		 * The packet arrived on an interface which isn't capable
  		 * of performing IP header checksum; compute it now.
  		 */
  		sum = ip_cksum_hdr_in(m, hlen);
  	} else {
  		sum = 0;
  		m->m_pkthdr.csum_flags |= (CSUM_DATA_VALID | CSUM_PSEUDO_HDR |
  		    CSUM_IP_CHECKED | CSUM_IP_VALID);
  		m->m_pkthdr.csum_data = 0xffff;
  	}
  
  	if (sum != 0)
  		OSAddAtomic(1, &ipstat.ips_badsum);
  
  	return (sum);
  }
  
  static int
  ip_getstat SYSCTL_HANDLER_ARGS
  {
  #pragma unused(oidp, arg1, arg2)
  	if (req->oldptr == USER_ADDR_NULL)
  		req->oldlen = (size_t)sizeof (struct ipstat);
  
  	return (SYSCTL_OUT(req, &ipstat, MIN(sizeof (ipstat), req->oldlen)));
  }
  
  void
  ip_setsrcifaddr_info(struct mbuf *m, uint32_t src_idx, struct in_ifaddr *ia)
  {
  	VERIFY(m->m_flags & M_PKTHDR);
  
  	/*
  	 * If the source ifaddr is specified, pick up the information
  	 * from there; otherwise just grab the passed-in ifindex as the
  	 * caller may not have the ifaddr available.
  	 */
  	if (ia != NULL) {
  		m->m_pkthdr.pkt_flags |= PKTF_IFAINFO;
  		m->m_pkthdr.src_ifindex = ia->ia_ifp->if_index;
  	} else {
  		m->m_pkthdr.src_ifindex = src_idx;
  		if (src_idx != 0)
  			m->m_pkthdr.pkt_flags |= PKTF_IFAINFO;
  	}
  }
  
  void
  ip_setdstifaddr_info(struct mbuf *m, uint32_t dst_idx, struct in_ifaddr *ia)
  {
  	VERIFY(m->m_flags & M_PKTHDR);
  
  	/*
  	 * If the destination ifaddr is specified, pick up the information
  	 * from there; otherwise just grab the passed-in ifindex as the
  	 * caller may not have the ifaddr available.
  	 */
  	if (ia != NULL) {
  		m->m_pkthdr.pkt_flags |= PKTF_IFAINFO;
  		m->m_pkthdr.dst_ifindex = ia->ia_ifp->if_index;
  	} else {
  		m->m_pkthdr.dst_ifindex = dst_idx;
  		if (dst_idx != 0)
  			m->m_pkthdr.pkt_flags |= PKTF_IFAINFO;
  	}
  }
  
  int
  ip_getsrcifaddr_info(struct mbuf *m, uint32_t *src_idx, uint32_t *iaf)
  {
  	VERIFY(m->m_flags & M_PKTHDR);
  
  	if (!(m->m_pkthdr.pkt_flags & PKTF_IFAINFO))
  		return (-1);
  
  	if (src_idx != NULL)
  		*src_idx = m->m_pkthdr.src_ifindex;
  
  	if (iaf != NULL)
  		*iaf = 0;
  
  	return (0);
  }
  
  int
  ip_getdstifaddr_info(struct mbuf *m, uint32_t *dst_idx, uint32_t *iaf)
  {
  	VERIFY(m->m_flags & M_PKTHDR);
  
  	if (!(m->m_pkthdr.pkt_flags & PKTF_IFAINFO))
  		return (-1);
  
  	if (dst_idx != NULL)
  		*dst_idx = m->m_pkthdr.dst_ifindex;
  
  	if (iaf != NULL)
  		*iaf = 0;
  
  	return (0);
  }
  
  /*
   * Protocol input handler for IPPROTO_GRE.
   */
  void
  gre_input(struct mbuf *m, int off)
  {
  	gre_input_func_t fn = gre_input_func;
  
  	/*
  	 * If there is a registered GRE input handler, pass mbuf to it.
  	 */
  	if (fn != NULL) {
  		lck_mtx_unlock(inet_domain_mutex);
  		m = fn(m, off, (mtod(m, struct ip *))->ip_p);
  		lck_mtx_lock(inet_domain_mutex);
  	}
  
  	/*
  	 * If no matching tunnel that is up is found, we inject
  	 * the mbuf to raw ip socket to see if anyone picks it up.
  	 */
  	if (m != NULL)
  		rip_input(m, off);
  }
  
  /*
   * Private KPI for PPP/PPTP.
   */
  int
  ip_gre_register_input(gre_input_func_t fn)
  {
  	lck_mtx_lock(inet_domain_mutex);
  	gre_input_func = fn;
  	lck_mtx_unlock(inet_domain_mutex);
  
  	return (0);
  }
  
  #if (DEBUG || DEVELOPMENT)
  static int
  sysctl_reset_ip_input_stats SYSCTL_HANDLER_ARGS
  {
  #pragma unused(arg1, arg2)
  	int error, i;
  
  	i = ip_input_measure;
  	error = sysctl_handle_int(oidp, &i, 0, req);
  	if (error || req->newptr == USER_ADDR_NULL)
  		goto done;
  	/* impose bounds */
  	if (i < 0 || i > 1) {
  		error = EINVAL;
  		goto done;
  	}
  	if (ip_input_measure != i && i == 1) {
  		net_perf_initialize(&net_perf, ip_input_measure_bins);
  	}
  	ip_input_measure = i;
  done:
  	return (error);
  }
  
  static int
  sysctl_ip_input_measure_bins SYSCTL_HANDLER_ARGS
  {
  #pragma unused(arg1, arg2)
  	int error;
  	uint64_t i;
  
  	i = ip_input_measure_bins;
  	error = sysctl_handle_quad(oidp, &i, 0, req);
  	if (error || req->newptr == USER_ADDR_NULL)
  		goto done;
  	/* validate data */
  	if (!net_perf_validate_bins(i)) {
  		error = EINVAL;
  		goto done;
  	}
  	ip_input_measure_bins = i;
  done:
  	return (error);
  }
  
  static int
  sysctl_ip_input_getperf SYSCTL_HANDLER_ARGS
  {
  #pragma unused(oidp, arg1, arg2)
  	if (req->oldptr == USER_ADDR_NULL)
  		req->oldlen = (size_t)sizeof (struct ipstat);
  
  	return (SYSCTL_OUT(req, &net_perf, MIN(sizeof (net_perf), req->oldlen)));
  }
  #endif /* (DEBUG || DEVELOPMENT) */
  