/*- * 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. * * $FreeBSD$ */ /* * 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 "opt_ipfw.h" #include "opt_ipstealth.h" #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include static int ipfastforward_active = 0; SYSCTL_INT(_net_inet_ip, OID_AUTO, fastforwarding, CTLFLAG_RW, &ipfastforward_active, 0, "Enable fast IP forwarding"); static struct sockaddr_in * ip_findroute(struct route *ro, struct in_addr dest, struct mbuf *m) { struct sockaddr_in *dst; struct rtentry *rt; /* * Find route to destination. */ bzero(ro, sizeof(*ro)); dst = (struct sockaddr_in *)&ro->ro_dst; dst->sin_family = AF_INET; dst->sin_len = sizeof(*dst); dst->sin_addr.s_addr = dest.s_addr; rtalloc_ign(ro, RTF_CLONING); /* * Route there and interface still up? */ rt = ro->ro_rt; if (rt && (rt->rt_flags & RTF_UP) && (rt->rt_ifp->if_flags & IFF_UP) && (rt->rt_ifp->if_drv_flags & IFF_DRV_RUNNING)) { if (rt->rt_flags & RTF_GATEWAY) dst = (struct sockaddr_in *)rt->rt_gateway; } else { ipstat.ips_noroute++; ipstat.ips_cantforward++; if (rt) RTFREE(rt); icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, 0, 0); return NULL; } return dst; } /* * 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 1; * otherwise 0 is returned and the packet should be delivered * to ip_input for full processing. */ struct mbuf * ip_fastforward(struct mbuf *m) { struct ip *ip; struct mbuf *m0 = NULL; struct route ro; struct sockaddr_in *dst = NULL; struct ifnet *ifp; struct in_addr odest, dest; u_short sum, ip_len; int error = 0; int hlen, mtu; #ifdef IPFIREWALL_FORWARD struct m_tag *fwd_tag; #endif /* * Are we active and forwarding packets? */ if (!ipfastforward_active || !ipforwarding) return m; M_ASSERTVALID(m); M_ASSERTPKTHDR(m); ro.ro_rt = NULL; /* * Step 1: check for packet drop conditions (and sanity checks) */ /* * Is entire packet big enough? */ if (m->m_pkthdr.len < sizeof(struct ip)) { ipstat.ips_tooshort++; goto drop; } /* * Is first mbuf large enough for ip header and is header present? */ if (m->m_len < sizeof (struct ip) && (m = m_pullup(m, sizeof (struct ip))) == NULL) { ipstat.ips_toosmall++; return NULL; /* mbuf already free'd */ } ip = mtod(m, struct ip *); /* * Is it IPv4? */ if (ip->ip_v != IPVERSION) { ipstat.ips_badvers++; goto drop; } /* * Is IP header length correct and is it in first mbuf? */ hlen = ip->ip_hl << 2; if (hlen < sizeof(struct ip)) { /* minimum header length */ ipstat.ips_badlen++; goto drop; } if (hlen > m->m_len) { if ((m = m_pullup(m, hlen)) == NULL) { ipstat.ips_badhlen++; return NULL; /* mbuf already free'd */ } ip = mtod(m, struct ip *); } /* * Checksum correct? */ if (m->m_pkthdr.csum_flags & CSUM_IP_CHECKED) sum = !(m->m_pkthdr.csum_flags & CSUM_IP_VALID); else { if (hlen == sizeof(struct ip)) sum = in_cksum_hdr(ip); else sum = in_cksum(m, hlen); } if (sum) { ipstat.ips_badsum++; goto drop; } /* * Remember that we have checked the IP header and found it valid. */ m->m_pkthdr.csum_flags |= (CSUM_IP_CHECKED | CSUM_IP_VALID); ip_len = ntohs(ip->ip_len); /* * Is IP length longer than packet we have got? */ if (m->m_pkthdr.len < ip_len) { ipstat.ips_tooshort++; goto drop; } /* * Is packet longer than IP header tells us? If yes, truncate packet. */ if (m->m_pkthdr.len > ip_len) { if (m->m_len == m->m_pkthdr.len) { m->m_len = ip_len; m->m_pkthdr.len = ip_len; } else m_adj(m, ip_len - m->m_pkthdr.len); } /* * Is packet from or to 127/8? */ if ((ntohl(ip->ip_dst.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET || (ntohl(ip->ip_src.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET) { ipstat.ips_badaddr++; goto drop; } #ifdef ALTQ /* * Is packet dropped by traffic conditioner? */ if (altq_input != NULL && (*altq_input)(m, AF_INET) == 0) goto drop; #endif /* * Step 2: fallback conditions to normal ip_input path processing */ /* * Only IP packets without options */ if (ip->ip_hl != (sizeof(struct ip) >> 2)) { if (ip_doopts == 1) return m; else if (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 neccessary 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)) || 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.ips_total++; /* * Step 3: incoming packet firewall processing */ /* * Convert to host representation */ ip->ip_len = ntohs(ip->ip_len); ip->ip_off = ntohs(ip->ip_off); odest.s_addr = dest.s_addr = ip->ip_dst.s_addr; /* * Run through list of ipfilter hooks for input packets */ if (inet_pfil_hook.ph_busy_count == -1) goto passin; if (pfil_run_hooks(&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 */ } #ifdef IPFIREWALL_FORWARD if (m->m_flags & M_FASTFWD_OURS) { /* * ipfw changed it for a local address on this host. */ goto forwardlocal; } #endif /* IPFIREWALL_FORWARD */ passin: /* * Step 4: decrement TTL and look up route */ /* * Check TTL */ #ifdef IPSTEALTH if (!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 ((dst = ip_findroute(&ro, dest, m)) == NULL) return NULL; /* icmp unreach already sent */ ifp = ro.ro_rt->rt_ifp; /* * Immediately drop blackholed traffic. */ if (ro.ro_rt->rt_flags & RTF_BLACKHOLE) goto drop; /* * Step 5: outgoing firewall packet processing */ /* * Run through list of hooks for output packets. */ if (inet_pfil_hook.ph_busy_count == -1) goto passout; if (pfil_run_hooks(&inet_pfil_hook, &m, 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? */ #ifndef IPFIREWALL_FORWARD if (odest.s_addr != dest.s_addr) { #else fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); if (odest.s_addr != dest.s_addr || fwd_tag != NULL) { #endif /* IPFIREWALL_FORWARD */ /* * Is it now for a local address on this host? */ #ifndef IPFIREWALL_FORWARD if (in_localip(dest)) { #else if (m->m_flags & M_FASTFWD_OURS || in_localip(dest)) { #endif /* IPFIREWALL_FORWARD */ forwardlocal: /* * Return packet for processing by ip_input(). * Keep host byte order as expected at ip_input's * "ours"-label. */ m->m_flags |= M_FASTFWD_OURS; if (ro.ro_rt) RTFREE(ro.ro_rt); return m; } /* * Redo route lookup with new destination address */ #ifdef IPFIREWALL_FORWARD if (fwd_tag) { if (!in_localip(ip->ip_src) && !in_localaddr(ip->ip_dst)) dest.s_addr = ((struct sockaddr_in *)(fwd_tag+1))->sin_addr.s_addr; m_tag_delete(m, fwd_tag); } #endif /* IPFIREWALL_FORWARD */ RTFREE(ro.ro_rt); if ((dst = ip_findroute(&ro, dest, m)) == NULL) return NULL; /* icmp unreach already sent */ ifp = ro.ro_rt->rt_ifp; } passout: /* * Step 6: send off the packet */ /* * Check if route is dampned (when ARP is unable to resolve) */ if ((ro.ro_rt->rt_flags & RTF_REJECT) && ro.ro_rt->rt_rmx.rmx_expire >= time_uptime) { icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, 0, 0); goto consumed; } #ifndef ALTQ /* * Check if there is enough space in the interface queue */ if ((ifp->if_snd.ifq_len + ip->ip_len / ifp->if_mtu + 1) >= ifp->if_snd.ifq_maxlen) { ipstat.ips_odropped++; /* would send source quench here but that is depreciated */ goto drop; } #endif /* * Check if media link state of interface is not down */ 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_rmx.rmx_mtu) mtu = min(ro.ro_rt->rt_rmx.rmx_mtu, ifp->if_mtu); else mtu = ifp->if_mtu; if (ip->ip_len <= mtu || (ifp->if_hwassist & CSUM_FRAGMENT && (ip->ip_off & IP_DF) == 0)) { /* * Restore packet header fields to original values */ ip->ip_len = htons(ip->ip_len); ip->ip_off = htons(ip->ip_off); /* * Send off the packet via outgoing interface */ error = (*ifp->if_output)(ifp, m, (struct sockaddr *)dst, ro.ro_rt); } else { /* * Handle EMSGSIZE with icmp reply needfrag for TCP MTU discovery */ if (ip->ip_off & IP_DF) { ipstat.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; /* * ip_fragment expects ip_len and ip_off in host byte * order but returns all packets in network byte order */ if (ip_fragment(ip, &m, mtu, ifp->if_hwassist, (~ifp->if_hwassist & CSUM_DELAY_IP))) { 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; error = (*ifp->if_output)(ifp, m, (struct sockaddr *)dst, ro.ro_rt); 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.ips_fragmented++; } } if (error != 0) ipstat.ips_odropped++; else { ro.ro_rt->rt_rmx.rmx_pksent++; ipstat.ips_forward++; ipstat.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; }