436 lines
12 KiB
C
436 lines
12 KiB
C
/*-
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* Copyright (c) 2003 Andre Oppermann, Internet Business Solutions AG
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. The name of the author may not be used to endorse or promote
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* products derived from this software without specific prior written
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* permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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/*
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* ip_fastforward gets its speed from processing the forwarded packet to
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* completion (if_output on the other side) without any queues or netisr's.
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* The receiving interface DMAs the packet into memory, the upper half of
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* driver calls ip_fastforward, we do our routing table lookup and directly
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* send it off to the outgoing interface, which DMAs the packet to the
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* network card. The only part of the packet we touch with the CPU is the
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* IP header (unless there are complex firewall rules touching other parts
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* of the packet, but that is up to you). We are essentially limited by bus
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* bandwidth and how fast the network card/driver can set up receives and
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* transmits.
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*
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* We handle basic errors, IP header errors, checksum errors,
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* destination unreachable, fragmentation and fragmentation needed and
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* report them via ICMP to the sender.
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*
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* Else if something is not pure IPv4 unicast forwarding we fall back to
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* the normal ip_input processing path. We should only be called from
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* interfaces connected to the outside world.
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*
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* Firewalling is fully supported including divert, ipfw fwd and ipfilter
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* ipnat and address rewrite.
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*
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* IPSEC is not supported if this host is a tunnel broker. IPSEC is
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* supported for connections to/from local host.
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*
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* We try to do the least expensive (in CPU ops) checks and operations
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* first to catch junk with as little overhead as possible.
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*
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* We take full advantage of hardware support for IP checksum and
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* fragmentation offloading.
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*
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* We don't do ICMP redirect in the fast forwarding path. I have had my own
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* cases where two core routers with Zebra routing suite would send millions
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* ICMP redirects to connected hosts if the destination router was not the
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* default gateway. In one case it was filling the routing table of a host
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* with approximately 300.000 cloned redirect entries until it ran out of
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* kernel memory. However the networking code proved very robust and it didn't
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* crash or fail in other ways.
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*/
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/*
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* Many thanks to Matt Thomas of NetBSD for basic structure of ip_flow.c which
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* is being followed here.
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include "opt_ipstealth.h"
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/kernel.h>
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#include <sys/malloc.h>
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#include <sys/mbuf.h>
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#include <sys/protosw.h>
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#include <sys/sdt.h>
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#include <sys/socket.h>
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#include <sys/sysctl.h>
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#include <net/pfil.h>
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#include <net/if.h>
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#include <net/if_types.h>
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#include <net/if_var.h>
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#include <net/if_dl.h>
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#include <net/route.h>
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#include <net/vnet.h>
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#include <netinet/in.h>
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#include <netinet/in_fib.h>
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#include <netinet/in_kdtrace.h>
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#include <netinet/in_systm.h>
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#include <netinet/in_var.h>
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#include <netinet/ip.h>
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#include <netinet/ip_var.h>
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#include <netinet/ip_icmp.h>
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#include <netinet/ip_options.h>
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#include <machine/in_cksum.h>
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static int
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ip_findroute(struct nhop4_basic *pnh, struct in_addr dest, struct mbuf *m)
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{
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bzero(pnh, sizeof(*pnh));
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if (fib4_lookup_nh_basic(M_GETFIB(m), dest, 0, 0, pnh) != 0) {
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IPSTAT_INC(ips_noroute);
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IPSTAT_INC(ips_cantforward);
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icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, 0, 0);
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return (EHOSTUNREACH);
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}
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/*
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* Drop blackholed traffic and directed broadcasts.
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*/
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if ((pnh->nh_flags & (NHF_BLACKHOLE | NHF_BROADCAST)) != 0) {
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IPSTAT_INC(ips_cantforward);
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m_freem(m);
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return (EHOSTUNREACH);
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}
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if (pnh->nh_flags & NHF_REJECT) {
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IPSTAT_INC(ips_cantforward);
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icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, 0, 0);
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return (EHOSTUNREACH);
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}
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return (0);
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}
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/*
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* Try to forward a packet based on the destination address.
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* This is a fast path optimized for the plain forwarding case.
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* If the packet is handled (and consumed) here then we return NULL;
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* otherwise mbuf is returned and the packet should be delivered
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* to ip_input for full processing.
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*/
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struct mbuf *
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ip_tryforward(struct mbuf *m)
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{
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struct ip *ip;
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struct mbuf *m0 = NULL;
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struct nhop4_basic nh;
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struct sockaddr_in dst;
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struct in_addr odest, dest;
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uint16_t ip_len, ip_off;
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int error = 0;
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struct m_tag *fwd_tag = NULL;
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/*
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* Are we active and forwarding packets?
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*/
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M_ASSERTVALID(m);
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M_ASSERTPKTHDR(m);
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#ifdef ALTQ
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/*
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* Is packet dropped by traffic conditioner?
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*/
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if (altq_input != NULL && (*altq_input)(m, AF_INET) == 0)
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goto drop;
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#endif
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/*
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* Only IP packets without options
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*/
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ip = mtod(m, struct ip *);
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if (ip->ip_hl != (sizeof(struct ip) >> 2)) {
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if (V_ip_doopts == 1)
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return m;
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else if (V_ip_doopts == 2) {
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icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_FILTER_PROHIB,
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0, 0);
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return NULL; /* mbuf already free'd */
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}
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/* else ignore IP options and continue */
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}
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/*
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* Only unicast IP, not from loopback, no L2 or IP broadcast,
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* no multicast, no INADDR_ANY
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*
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* XXX: Probably some of these checks could be direct drop
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* conditions. However it is not clear whether there are some
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* hacks or obscure behaviours which make it necessary to
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* let ip_input handle it. We play safe here and let ip_input
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* deal with it until it is proven that we can directly drop it.
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*/
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if ((m->m_flags & (M_BCAST|M_MCAST)) ||
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(m->m_pkthdr.rcvif->if_flags & IFF_LOOPBACK) ||
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ntohl(ip->ip_src.s_addr) == (u_long)INADDR_BROADCAST ||
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ntohl(ip->ip_dst.s_addr) == (u_long)INADDR_BROADCAST ||
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IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
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IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
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IN_LINKLOCAL(ntohl(ip->ip_src.s_addr)) ||
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IN_LINKLOCAL(ntohl(ip->ip_dst.s_addr)) ||
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ip->ip_src.s_addr == INADDR_ANY ||
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ip->ip_dst.s_addr == INADDR_ANY )
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return m;
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/*
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* Is it for a local address on this host?
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*/
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if (in_localip(ip->ip_dst))
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return m;
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IPSTAT_INC(ips_total);
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/*
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* Step 3: incoming packet firewall processing
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*/
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odest.s_addr = dest.s_addr = ip->ip_dst.s_addr;
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/*
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* Run through list of ipfilter hooks for input packets
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*/
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if (!PFIL_HOOKED(&V_inet_pfil_hook))
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goto passin;
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if (pfil_run_hooks(
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&V_inet_pfil_hook, &m, m->m_pkthdr.rcvif, PFIL_IN, NULL) ||
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m == NULL)
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goto drop;
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M_ASSERTVALID(m);
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M_ASSERTPKTHDR(m);
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ip = mtod(m, struct ip *); /* m may have changed by pfil hook */
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dest.s_addr = ip->ip_dst.s_addr;
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/*
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* Destination address changed?
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*/
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if (odest.s_addr != dest.s_addr) {
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/*
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* Is it now for a local address on this host?
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*/
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if (in_localip(dest))
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goto forwardlocal;
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/*
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* Go on with new destination address
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*/
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}
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if (m->m_flags & M_FASTFWD_OURS) {
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/*
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* ipfw changed it for a local address on this host.
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*/
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goto forwardlocal;
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}
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passin:
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/*
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* Step 4: decrement TTL and look up route
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*/
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/*
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* Check TTL
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*/
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#ifdef IPSTEALTH
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if (!V_ipstealth) {
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#endif
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if (ip->ip_ttl <= IPTTLDEC) {
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icmp_error(m, ICMP_TIMXCEED, ICMP_TIMXCEED_INTRANS, 0, 0);
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return NULL; /* mbuf already free'd */
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}
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/*
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* Decrement the TTL and incrementally change the IP header checksum.
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* Don't bother doing this with hw checksum offloading, it's faster
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* doing it right here.
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*/
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ip->ip_ttl -= IPTTLDEC;
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if (ip->ip_sum >= (u_int16_t) ~htons(IPTTLDEC << 8))
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ip->ip_sum -= ~htons(IPTTLDEC << 8);
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else
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ip->ip_sum += htons(IPTTLDEC << 8);
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#ifdef IPSTEALTH
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}
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#endif
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/*
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* Find route to destination.
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*/
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if (ip_findroute(&nh, dest, m) != 0)
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return (NULL); /* icmp unreach already sent */
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/*
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* Step 5: outgoing firewall packet processing
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*/
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if (!PFIL_HOOKED(&V_inet_pfil_hook))
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goto passout;
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if (pfil_run_hooks(&V_inet_pfil_hook, &m, nh.nh_ifp, PFIL_OUT, NULL) ||
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m == NULL) {
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goto drop;
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}
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M_ASSERTVALID(m);
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M_ASSERTPKTHDR(m);
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ip = mtod(m, struct ip *);
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dest.s_addr = ip->ip_dst.s_addr;
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/*
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* Destination address changed?
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*/
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if (m->m_flags & M_IP_NEXTHOP)
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fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL);
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if (odest.s_addr != dest.s_addr || fwd_tag != NULL) {
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/*
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* Is it now for a local address on this host?
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*/
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if (m->m_flags & M_FASTFWD_OURS || in_localip(dest)) {
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forwardlocal:
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/*
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* Return packet for processing by ip_input().
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*/
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m->m_flags |= M_FASTFWD_OURS;
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return (m);
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}
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/*
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* Redo route lookup with new destination address
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*/
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if (fwd_tag) {
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dest.s_addr = ((struct sockaddr_in *)
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(fwd_tag + 1))->sin_addr.s_addr;
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m_tag_delete(m, fwd_tag);
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m->m_flags &= ~M_IP_NEXTHOP;
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}
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if (ip_findroute(&nh, dest, m) != 0)
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return (NULL); /* icmp unreach already sent */
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}
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passout:
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/*
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* Step 6: send off the packet
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*/
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ip_len = ntohs(ip->ip_len);
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ip_off = ntohs(ip->ip_off);
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bzero(&dst, sizeof(dst));
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dst.sin_family = AF_INET;
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dst.sin_len = sizeof(dst);
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dst.sin_addr = nh.nh_addr;
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/*
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* Check if packet fits MTU or if hardware will fragment for us
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*/
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if (ip_len <= nh.nh_mtu) {
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/*
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* Avoid confusing lower layers.
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*/
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m_clrprotoflags(m);
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/*
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* Send off the packet via outgoing interface
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*/
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IP_PROBE(send, NULL, NULL, ip, nh.nh_ifp, ip, NULL);
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error = (*nh.nh_ifp->if_output)(nh.nh_ifp, m,
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(struct sockaddr *)&dst, NULL);
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} else {
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/*
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* Handle EMSGSIZE with icmp reply needfrag for TCP MTU discovery
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*/
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if (ip_off & IP_DF) {
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IPSTAT_INC(ips_cantfrag);
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icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_NEEDFRAG,
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0, nh.nh_mtu);
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goto consumed;
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} else {
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/*
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* We have to fragment the packet
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*/
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m->m_pkthdr.csum_flags |= CSUM_IP;
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if (ip_fragment(ip, &m, nh.nh_mtu,
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nh.nh_ifp->if_hwassist) != 0)
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goto drop;
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KASSERT(m != NULL, ("null mbuf and no error"));
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/*
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* Send off the fragments via outgoing interface
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*/
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error = 0;
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do {
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m0 = m->m_nextpkt;
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m->m_nextpkt = NULL;
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/*
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* Avoid confusing lower layers.
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*/
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m_clrprotoflags(m);
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IP_PROBE(send, NULL, NULL,
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mtod(m, struct ip *), nh.nh_ifp,
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mtod(m, struct ip *), NULL);
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/* XXX: we can use cached route here */
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error = (*nh.nh_ifp->if_output)(nh.nh_ifp, m,
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(struct sockaddr *)&dst, NULL);
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if (error)
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break;
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} while ((m = m0) != NULL);
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if (error) {
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/* Reclaim remaining fragments */
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for (m = m0; m; m = m0) {
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m0 = m->m_nextpkt;
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m_freem(m);
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}
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} else
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IPSTAT_INC(ips_fragmented);
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}
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}
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if (error != 0)
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IPSTAT_INC(ips_odropped);
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else {
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IPSTAT_INC(ips_forward);
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IPSTAT_INC(ips_fastforward);
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}
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consumed:
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return NULL;
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drop:
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if (m)
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m_freem(m);
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return NULL;
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}
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