599 lines
15 KiB
C
599 lines
15 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_ipfw.h"
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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_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 VNET_DEFINE(int, ipfastforward_active);
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#define V_ipfastforward_active VNET(ipfastforward_active)
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SYSCTL_INT(_net_inet_ip, OID_AUTO, fastforwarding, CTLFLAG_VNET | CTLFLAG_RW,
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&VNET_NAME(ipfastforward_active), 0, "Enable fast IP forwarding");
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static struct sockaddr_in *
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ip_findroute(struct route *ro, struct in_addr dest, struct mbuf *m)
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{
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struct sockaddr_in *dst;
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struct rtentry *rt;
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/*
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* Find route to destination.
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*/
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bzero(ro, sizeof(*ro));
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dst = (struct sockaddr_in *)&ro->ro_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.s_addr = dest.s_addr;
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in_rtalloc_ign(ro, 0, M_GETFIB(m));
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/*
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* Route there and interface still up?
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*/
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rt = ro->ro_rt;
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if (rt && (rt->rt_flags & RTF_UP) &&
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(rt->rt_ifp->if_flags & IFF_UP) &&
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(rt->rt_ifp->if_drv_flags & IFF_DRV_RUNNING)) {
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if (rt->rt_flags & RTF_GATEWAY)
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dst = (struct sockaddr_in *)rt->rt_gateway;
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} else {
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IPSTAT_INC(ips_noroute);
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IPSTAT_INC(ips_cantforward);
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if (rt)
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RTFREE(rt);
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icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, 0, 0);
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return NULL;
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}
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return dst;
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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_fastforward(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 route ro;
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struct sockaddr_in *dst = NULL;
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struct ifnet *ifp;
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struct in_addr odest, dest;
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uint16_t sum, ip_len, ip_off;
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int error = 0;
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int hlen, mtu;
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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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if (!V_ipfastforward_active || !V_ipforwarding)
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return m;
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M_ASSERTVALID(m);
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M_ASSERTPKTHDR(m);
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bzero(&ro, sizeof(ro));
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/*
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* Step 1: check for packet drop conditions (and sanity checks)
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*/
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/*
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* Is entire packet big enough?
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*/
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if (m->m_pkthdr.len < sizeof(struct ip)) {
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IPSTAT_INC(ips_tooshort);
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goto drop;
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}
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/*
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* Is first mbuf large enough for ip header and is header present?
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*/
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if (m->m_len < sizeof (struct ip) &&
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(m = m_pullup(m, sizeof (struct ip))) == NULL) {
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IPSTAT_INC(ips_toosmall);
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return NULL; /* mbuf already free'd */
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}
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ip = mtod(m, struct ip *);
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/*
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* Is it IPv4?
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*/
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if (ip->ip_v != IPVERSION) {
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IPSTAT_INC(ips_badvers);
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goto drop;
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}
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/*
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* Is IP header length correct and is it in first mbuf?
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*/
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hlen = ip->ip_hl << 2;
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if (hlen < sizeof(struct ip)) { /* minimum header length */
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IPSTAT_INC(ips_badhlen);
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goto drop;
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}
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if (hlen > m->m_len) {
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if ((m = m_pullup(m, hlen)) == NULL) {
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IPSTAT_INC(ips_badhlen);
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return NULL; /* mbuf already free'd */
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}
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ip = mtod(m, struct ip *);
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}
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/*
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* Checksum correct?
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*/
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if (m->m_pkthdr.csum_flags & CSUM_IP_CHECKED)
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sum = !(m->m_pkthdr.csum_flags & CSUM_IP_VALID);
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else {
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if (hlen == sizeof(struct ip))
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sum = in_cksum_hdr(ip);
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else
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sum = in_cksum(m, hlen);
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}
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if (sum) {
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IPSTAT_INC(ips_badsum);
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goto drop;
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}
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/*
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* Remember that we have checked the IP header and found it valid.
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*/
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m->m_pkthdr.csum_flags |= (CSUM_IP_CHECKED | CSUM_IP_VALID);
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ip_len = ntohs(ip->ip_len);
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/*
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* Is IP length longer than packet we have got?
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*/
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if (m->m_pkthdr.len < ip_len) {
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IPSTAT_INC(ips_tooshort);
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goto drop;
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}
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/*
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* Is packet longer than IP header tells us? If yes, truncate packet.
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*/
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if (m->m_pkthdr.len > ip_len) {
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if (m->m_len == m->m_pkthdr.len) {
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m->m_len = ip_len;
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m->m_pkthdr.len = ip_len;
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} else
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m_adj(m, ip_len - m->m_pkthdr.len);
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}
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/*
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* Is packet from or to 127/8?
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*/
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if ((ntohl(ip->ip_dst.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET ||
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(ntohl(ip->ip_src.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET) {
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IPSTAT_INC(ips_badaddr);
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goto drop;
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}
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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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* Step 2: fallback conditions to normal ip_input path processing
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*/
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/*
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* Only IP packets without options
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*/
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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 neccessary 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 ((dst = ip_findroute(&ro, dest, m)) == NULL)
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return NULL; /* icmp unreach already sent */
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ifp = ro.ro_rt->rt_ifp;
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/*
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* Immediately drop blackholed traffic, and directed broadcasts
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* for either the all-ones or all-zero subnet addresses on
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* locally attached networks.
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*/
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if ((ro.ro_rt->rt_flags & (RTF_BLACKHOLE|RTF_BROADCAST)) != 0)
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goto drop;
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/*
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* Step 5: outgoing firewall packet processing
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*/
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/*
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* Run through list of hooks for output packets.
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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, ifp, PFIL_OUT, NULL) || 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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if (ro.ro_rt)
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RTFREE(ro.ro_rt);
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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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RTFREE(ro.ro_rt);
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if ((dst = ip_findroute(&ro, dest, m)) == NULL)
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return NULL; /* icmp unreach already sent */
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ifp = ro.ro_rt->rt_ifp;
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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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/*
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* Check if route is dampned (when ARP is unable to resolve)
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*/
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if ((ro.ro_rt->rt_flags & RTF_REJECT) &&
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(ro.ro_rt->rt_expire == 0 || time_uptime < ro.ro_rt->rt_expire)) {
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icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, 0, 0);
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goto consumed;
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}
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#ifndef ALTQ
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/*
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* Check if there is enough space in the interface queue
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*/
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if ((ifp->if_snd.ifq_len + ip_len / ifp->if_mtu + 1) >=
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ifp->if_snd.ifq_maxlen) {
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IPSTAT_INC(ips_odropped);
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goto drop;
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}
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#endif
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/*
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* Check if media link state of interface is not down
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*/
|
|
if (ifp->if_link_state == LINK_STATE_DOWN) {
|
|
icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, 0, 0);
|
|
goto consumed;
|
|
}
|
|
|
|
/*
|
|
* Check if packet fits MTU or if hardware will fragment for us
|
|
*/
|
|
if (ro.ro_rt->rt_mtu)
|
|
mtu = min(ro.ro_rt->rt_mtu, ifp->if_mtu);
|
|
else
|
|
mtu = ifp->if_mtu;
|
|
|
|
if (ip_len <= mtu) {
|
|
/*
|
|
* Avoid confusing lower layers.
|
|
*/
|
|
m_clrprotoflags(m);
|
|
/*
|
|
* Send off the packet via outgoing interface
|
|
*/
|
|
IP_PROBE(send, NULL, NULL, ip, ifp, ip, NULL);
|
|
error = (*ifp->if_output)(ifp, m,
|
|
(struct sockaddr *)dst, &ro);
|
|
} else {
|
|
/*
|
|
* Handle EMSGSIZE with icmp reply needfrag for TCP MTU discovery
|
|
*/
|
|
if (ip_off & IP_DF) {
|
|
IPSTAT_INC(ips_cantfrag);
|
|
icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_NEEDFRAG,
|
|
0, mtu);
|
|
goto consumed;
|
|
} else {
|
|
/*
|
|
* We have to fragment the packet
|
|
*/
|
|
m->m_pkthdr.csum_flags |= CSUM_IP;
|
|
if (ip_fragment(ip, &m, mtu, ifp->if_hwassist))
|
|
goto drop;
|
|
KASSERT(m != NULL, ("null mbuf and no error"));
|
|
/*
|
|
* Send off the fragments via outgoing interface
|
|
*/
|
|
error = 0;
|
|
do {
|
|
m0 = m->m_nextpkt;
|
|
m->m_nextpkt = NULL;
|
|
/*
|
|
* Avoid confusing lower layers.
|
|
*/
|
|
m_clrprotoflags(m);
|
|
|
|
IP_PROBE(send, NULL, NULL, ip, ifp, ip, NULL);
|
|
error = (*ifp->if_output)(ifp, m,
|
|
(struct sockaddr *)dst, &ro);
|
|
if (error)
|
|
break;
|
|
} while ((m = m0) != NULL);
|
|
if (error) {
|
|
/* Reclaim remaining fragments */
|
|
for (m = m0; m; m = m0) {
|
|
m0 = m->m_nextpkt;
|
|
m_freem(m);
|
|
}
|
|
} else
|
|
IPSTAT_INC(ips_fragmented);
|
|
}
|
|
}
|
|
|
|
if (error != 0)
|
|
IPSTAT_INC(ips_odropped);
|
|
else {
|
|
counter_u64_add(ro.ro_rt->rt_pksent, 1);
|
|
IPSTAT_INC(ips_forward);
|
|
IPSTAT_INC(ips_fastforward);
|
|
}
|
|
consumed:
|
|
RTFREE(ro.ro_rt);
|
|
return NULL;
|
|
drop:
|
|
if (m)
|
|
m_freem(m);
|
|
if (ro.ro_rt)
|
|
RTFREE(ro.ro_rt);
|
|
return NULL;
|
|
}
|