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