/* route.c -- routing Copyright (C) 2000-2005 Ivo Timmermans, 2000-2017 Guus Sliepen 2015-2016 Vittorio Gambaletta This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. */ #include "system.h" #include "avl_tree.h" #include "connection.h" #include "ethernet.h" #include "ipv4.h" #include "ipv6.h" #include "logger.h" #include "net.h" #include "protocol.h" #include "route.h" #include "subnet.h" #include "utils.h" rmode_t routing_mode = RMODE_ROUTER; fmode_t forwarding_mode = FMODE_INTERNAL; bmode_t broadcast_mode = BMODE_MST; bool decrement_ttl = false; bool directonly = false; bool priorityinheritance = false; int macexpire = 600; bool overwrite_mac = false; mac_t mymac = {{0xFE, 0xFD, 0, 0, 0, 0}}; /* Sizes of various headers */ static const size_t ether_size = sizeof(struct ether_header); static const size_t arp_size = sizeof(struct ether_arp); static const size_t ip_size = sizeof(struct ip); static const size_t icmp_size = sizeof(struct icmp) - sizeof(struct ip); static const size_t ip6_size = sizeof(struct ip6_hdr); static const size_t icmp6_size = sizeof(struct icmp6_hdr); static const size_t ns_size = sizeof(struct nd_neighbor_solicit); static const size_t opt_size = sizeof(struct nd_opt_hdr); #ifndef MAX #define MAX(a, b) ((a) > (b) ? (a) : (b)) #endif /* RFC 1071 */ static uint16_t inet_checksum(void *data, int len, uint16_t prevsum) { uint16_t *p = data; uint32_t checksum = prevsum ^ 0xFFFF; while(len >= 2) { checksum += *p++; len -= 2; } if(len) { checksum += *(uint8_t *)p; } while(checksum >> 16) { checksum = (checksum & 0xFFFF) + (checksum >> 16); } return ~checksum; } static bool ratelimit(int frequency) { static time_t lasttime = 0; static int count = 0; if(lasttime == now) { if(count >= frequency) { return true; } } else { lasttime = now; count = 0; } count++; return false; } static bool checklength(node_t *source, vpn_packet_t *packet, length_t length) { if(packet->len < length) { ifdebug(TRAFFIC) logger(LOG_WARNING, "Got too short packet from %s (%s)", source->name, source->hostname); return false; } else { return true; } } static void swap_mac_addresses(vpn_packet_t *packet) { mac_t tmp; memcpy(&tmp, &packet->data[0], sizeof(tmp)); memcpy(&packet->data[0], &packet->data[6], sizeof(tmp)); memcpy(&packet->data[6], &tmp, sizeof(tmp)); } /* RFC 792 */ static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, length_t ether_size, uint8_t type, uint8_t code) { struct ip ip = {0}; struct icmp icmp = {0}; struct in_addr ip_src; struct in_addr ip_dst; uint32_t oldlen; if(ratelimit(3)) { return; } /* Swap Ethernet source and destination addresses */ swap_mac_addresses(packet); /* Copy headers from packet into properly aligned structs on the stack */ memcpy(&ip, packet->data + ether_size, ip_size); /* Remember original source and destination */ ip_src = ip.ip_src; ip_dst = ip.ip_dst; /* Try to reply with an IP address assigned to the local machine */ if(type == ICMP_TIME_EXCEEDED && code == ICMP_EXC_TTL) { int sockfd = socket(AF_INET, SOCK_DGRAM, 0); if(sockfd != -1) { struct sockaddr_in addr; memset(&addr, 0, sizeof(addr)); addr.sin_family = AF_INET; addr.sin_addr = ip.ip_src; if(!connect(sockfd, (const struct sockaddr *) &addr, sizeof(addr))) { memset(&addr, 0, sizeof(addr)); addr.sin_family = AF_INET; socklen_t addrlen = sizeof(addr); if(!getsockname(sockfd, (struct sockaddr *) &addr, &addrlen) && addrlen <= sizeof(addr)) { ip_dst = addr.sin_addr; } } close(sockfd); } } oldlen = packet->len - ether_size; if(type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) { icmp.icmp_nextmtu = htons(packet->len - ether_size); } if(oldlen >= IP_MSS - ip_size - icmp_size) { oldlen = IP_MSS - ip_size - icmp_size; } /* Copy first part of original contents to ICMP message */ memmove(packet->data + ether_size + ip_size + icmp_size, packet->data + ether_size, oldlen); /* Fill in IPv4 header */ ip.ip_v = 4; ip.ip_hl = ip_size / 4; ip.ip_tos = 0; ip.ip_len = htons(ip_size + icmp_size + oldlen); ip.ip_id = 0; ip.ip_off = 0; ip.ip_ttl = 255; ip.ip_p = IPPROTO_ICMP; ip.ip_sum = 0; ip.ip_src = ip_dst; ip.ip_dst = ip_src; ip.ip_sum = inet_checksum(&ip, ip_size, ~0); /* Fill in ICMP header */ icmp.icmp_type = type; icmp.icmp_code = code; icmp.icmp_cksum = 0; icmp.icmp_cksum = inet_checksum(&icmp, icmp_size, ~0); icmp.icmp_cksum = inet_checksum(packet->data + ether_size + ip_size + icmp_size, oldlen, icmp.icmp_cksum); /* Copy structs on stack back to packet */ memcpy(packet->data + ether_size, &ip, ip_size); memcpy(packet->data + ether_size + ip_size, &icmp, icmp_size); packet->len = ether_size + ip_size + icmp_size + oldlen; send_packet(source, packet); } /* RFC 2463 */ static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, length_t ether_size, uint8_t type, uint8_t code) { struct ip6_hdr ip6; struct icmp6_hdr icmp6 = {0}; uint16_t checksum; struct { struct in6_addr ip6_src; /* source address */ struct in6_addr ip6_dst; /* destination address */ uint32_t length; uint32_t next; } pseudo; if(ratelimit(3)) { return; } /* Swap Ethernet source and destination addresses */ swap_mac_addresses(packet); /* Copy headers from packet to structs on the stack */ memcpy(&ip6, packet->data + ether_size, ip6_size); /* Remember original source and destination */ pseudo.ip6_src = ip6.ip6_dst; pseudo.ip6_dst = ip6.ip6_src; /* Try to reply with an IP address assigned to the local machine */ if(type == ICMP6_TIME_EXCEEDED && code == ICMP6_TIME_EXCEED_TRANSIT) { int sockfd = socket(AF_INET6, SOCK_DGRAM, 0); if(sockfd != -1) { struct sockaddr_in6 addr; memset(&addr, 0, sizeof(addr)); addr.sin6_family = AF_INET6; addr.sin6_addr = ip6.ip6_src; if(!connect(sockfd, (const struct sockaddr *) &addr, sizeof(addr))) { memset(&addr, 0, sizeof(addr)); addr.sin6_family = AF_INET6; socklen_t addrlen = sizeof(addr); if(!getsockname(sockfd, (struct sockaddr *) &addr, &addrlen) && addrlen <= sizeof(addr)) { pseudo.ip6_src = addr.sin6_addr; } } close(sockfd); } } pseudo.length = packet->len - ether_size; if(type == ICMP6_PACKET_TOO_BIG) { icmp6.icmp6_mtu = htonl(pseudo.length); } if(pseudo.length >= IP_MSS - ip6_size - icmp6_size) { pseudo.length = IP_MSS - ip6_size - icmp6_size; } /* Copy first part of original contents to ICMP message */ memmove(packet->data + ether_size + ip6_size + icmp6_size, packet->data + ether_size, pseudo.length); /* Fill in IPv6 header */ ip6.ip6_flow = htonl(0x60000000UL); ip6.ip6_plen = htons(icmp6_size + pseudo.length); ip6.ip6_nxt = IPPROTO_ICMPV6; ip6.ip6_hlim = 255; ip6.ip6_src = pseudo.ip6_src; ip6.ip6_dst = pseudo.ip6_dst; /* Fill in ICMP header */ icmp6.icmp6_type = type; icmp6.icmp6_code = code; icmp6.icmp6_cksum = 0; /* Create pseudo header */ pseudo.length = htonl(icmp6_size + pseudo.length); pseudo.next = htonl(IPPROTO_ICMPV6); /* Generate checksum */ checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0); checksum = inet_checksum(&icmp6, icmp6_size, checksum); checksum = inet_checksum(packet->data + ether_size + ip6_size + icmp6_size, ntohl(pseudo.length) - icmp6_size, checksum); icmp6.icmp6_cksum = checksum; /* Copy structs on stack back to packet */ memcpy(packet->data + ether_size, &ip6, ip6_size); memcpy(packet->data + ether_size + ip6_size, &icmp6, icmp6_size); packet->len = ether_size + ip6_size + ntohl(pseudo.length); send_packet(source, packet); } static bool do_decrement_ttl(node_t *source, vpn_packet_t *packet) { uint16_t type = packet->data[12] << 8 | packet->data[13]; length_t ethlen = ether_size; if(type == ETH_P_8021Q) { type = packet->data[16] << 8 | packet->data[17]; ethlen += 4; } switch(type) { case ETH_P_IP: if(!checklength(source, packet, ethlen + ip_size)) { return false; } if(packet->data[ethlen + 8] <= 1) { if(packet->data[ethlen + 11] != IPPROTO_ICMP || packet->data[ethlen + 32] != ICMP_TIME_EXCEEDED) { route_ipv4_unreachable(source, packet, ethlen, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL); } return false; } uint16_t old = packet->data[ethlen + 8] << 8 | packet->data[ethlen + 9]; packet->data[ethlen + 8]--; uint16_t new = packet->data[ethlen + 8] << 8 | packet->data[ethlen + 9]; uint32_t checksum = packet->data[ethlen + 10] << 8 | packet->data[ethlen + 11]; checksum += old + (~new & 0xFFFF); while(checksum >> 16) { checksum = (checksum & 0xFFFF) + (checksum >> 16); } packet->data[ethlen + 10] = checksum >> 8; packet->data[ethlen + 11] = checksum & 0xff; return true; case ETH_P_IPV6: if(!checklength(source, packet, ethlen + ip6_size)) { return false; } if(packet->data[ethlen + 7] <= 1) { if(packet->data[ethlen + 6] != IPPROTO_ICMPV6 || packet->data[ethlen + 40] != ICMP6_TIME_EXCEEDED) { route_ipv6_unreachable(source, packet, ethlen, ICMP6_TIME_EXCEEDED, ICMP6_TIME_EXCEED_TRANSIT); } return false; } packet->data[ethlen + 7]--; return true; default: return true; } } static void clamp_mss(const node_t *source, const node_t *via, vpn_packet_t *packet) { if(!source || !via || !(via->options & OPTION_CLAMP_MSS)) { return; } uint16_t mtu = source->mtu; if(via != myself && via->mtu < mtu) { mtu = via->mtu; } /* Find TCP header */ int start = ether_size; uint16_t type = packet->data[12] << 8 | packet->data[13]; if(type == ETH_P_8021Q) { start += 4; type = packet->data[16] << 8 | packet->data[17]; } if(type == ETH_P_IP && packet->data[start + 9] == 6) { start += (packet->data[start] & 0xf) * 4; } else if(type == ETH_P_IPV6 && packet->data[start + 6] == 6) { start += 40; } else { return; } if(packet->len <= start + 20) { return; } /* Use data offset field to calculate length of options field */ int len = ((packet->data[start + 12] >> 4) - 5) * 4; if(packet->len < start + 20 + len) { return; } /* Search for MSS option header */ for(int i = 0; i < len;) { if(packet->data[start + 20 + i] == 0) { break; } if(packet->data[start + 20 + i] == 1) { i++; continue; } if(i > len - 2 || i > len - packet->data[start + 21 + i]) { break; } if(packet->data[start + 20 + i] != 2) { if(packet->data[start + 21 + i] < 2) { break; } i += packet->data[start + 21 + i]; continue; } if(packet->data[start + 21] != 4) { break; } /* Found it */ uint16_t oldmss = packet->data[start + 22 + i] << 8 | packet->data[start + 23 + i]; uint16_t newmss = mtu - start - 20; uint32_t csum = packet->data[start + 16] << 8 | packet->data[start + 17]; if(oldmss <= newmss) { break; } ifdebug(TRAFFIC) logger(LOG_INFO, "Clamping MSS of packet from %s to %s to %d", source->name, via->name, newmss); /* Update the MSS value and the checksum */ packet->data[start + 22 + i] = newmss >> 8; packet->data[start + 23 + i] = newmss & 0xff; csum ^= 0xffff; csum += oldmss ^ 0xffff; csum += newmss; csum = (csum & 0xffff) + (csum >> 16); csum += csum >> 16; csum ^= 0xffff; packet->data[start + 16] = csum >> 8; packet->data[start + 17] = csum; break; } } static void learn_mac(mac_t *address) { subnet_t *subnet; avl_node_t *node; connection_t *c; subnet = lookup_subnet_mac(myself, address); /* If we don't know this MAC address yet, store it */ if(!subnet) { ifdebug(TRAFFIC) logger(LOG_INFO, "Learned new MAC address %x:%x:%x:%x:%x:%x", address->x[0], address->x[1], address->x[2], address->x[3], address->x[4], address->x[5]); subnet = new_subnet(); subnet->type = SUBNET_MAC; subnet->expires = now + macexpire; subnet->net.mac.address = *address; subnet->weight = 10; subnet_add(myself, subnet); subnet_update(myself, subnet, true); /* And tell all other tinc daemons it's our MAC */ for(node = connection_tree->head; node; node = node->next) { c = node->data; if(c->status.active) { send_add_subnet(c, subnet); } } } if(subnet->expires) { subnet->expires = now + macexpire; } } void age_subnets(void) { subnet_t *s; connection_t *c; avl_node_t *node, *next, *node2; for(node = myself->subnet_tree->head; node; node = next) { next = node->next; s = node->data; if(s->expires && s->expires <= now) { ifdebug(TRAFFIC) { char netstr[MAXNETSTR]; if(net2str(netstr, sizeof(netstr), s)) { logger(LOG_INFO, "Subnet %s expired", netstr); } } for(node2 = connection_tree->head; node2; node2 = node2->next) { c = node2->data; if(c->status.active) { send_del_subnet(c, s); } } subnet_update(myself, s, false); subnet_del(myself, s); } } } static void route_broadcast(node_t *source, vpn_packet_t *packet) { if(decrement_ttl && source != myself) if(!do_decrement_ttl(source, packet)) { return; } broadcast_packet(source, packet); } /* RFC 791 */ static void fragment_ipv4_packet(node_t *dest, vpn_packet_t *packet, length_t ether_size) { struct ip ip; vpn_packet_t fragment; int len, maxlen, todo; uint8_t *offset; uint16_t ip_off, origf; memcpy(&ip, packet->data + ether_size, ip_size); fragment.priority = packet->priority; if(ip.ip_hl != ip_size / 4) { return; } todo = ntohs(ip.ip_len) - ip_size; if(ether_size + ip_size + todo != packet->len) { ifdebug(TRAFFIC) logger(LOG_WARNING, "Length of packet (%d) doesn't match length in IPv4 header (%d)", packet->len, (int)(ether_size + ip_size + todo)); return; } ifdebug(TRAFFIC) logger(LOG_INFO, "Fragmenting packet of %d bytes to %s (%s)", packet->len, dest->name, dest->hostname); offset = packet->data + ether_size + ip_size; maxlen = (MAX(dest->mtu, 590) - ether_size - ip_size) & ~0x7; ip_off = ntohs(ip.ip_off); origf = ip_off & ~IP_OFFMASK; ip_off &= IP_OFFMASK; while(todo) { len = todo > maxlen ? maxlen : todo; memcpy(fragment.data + ether_size + ip_size, offset, len); todo -= len; offset += len; ip.ip_len = htons(ip_size + len); ip.ip_off = htons(ip_off | origf | (todo ? IP_MF : 0)); ip.ip_sum = 0; ip.ip_sum = inet_checksum(&ip, ip_size, ~0); memcpy(fragment.data, packet->data, ether_size); memcpy(fragment.data + ether_size, &ip, ip_size); fragment.len = ether_size + ip_size + len; send_packet(dest, &fragment); ip_off += len / 8; } } static void route_ipv4_unicast(node_t *source, vpn_packet_t *packet) { subnet_t *subnet; node_t *via; ipv4_t dest; memcpy(&dest, &packet->data[30], sizeof(dest)); subnet = lookup_subnet_ipv4(&dest); if(!subnet) { ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv4 destination address %d.%d.%d.%d", source->name, source->hostname, dest.x[0], dest.x[1], dest.x[2], dest.x[3]); route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_UNKNOWN); return; } if(subnet->owner == source) { ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname); return; } if(!subnet->owner->status.reachable) { route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_UNREACH); return; } if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself) { route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_ANO); return; } if(decrement_ttl && source != myself && subnet->owner != myself) if(!do_decrement_ttl(source, packet)) { return; } if(priorityinheritance) { packet->priority = packet->data[15]; } via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via; if(via == source) { ifdebug(TRAFFIC) logger(LOG_ERR, "Routing loop for packet from %s (%s)!", source->name, source->hostname); return; } if(directonly && subnet->owner != via) { route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_ANO); return; } if(via && packet->len > MAX(via->mtu, 590) && via != myself) { ifdebug(TRAFFIC) logger(LOG_INFO, "Packet for %s (%s) length %d larger than MTU %d", subnet->owner->name, subnet->owner->hostname, packet->len, via->mtu); if(packet->data[20] & 0x40) { packet->len = MAX(via->mtu, 590); route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED); } else { fragment_ipv4_packet(via, packet, ether_size); } return; } clamp_mss(source, via, packet); send_packet(subnet->owner, packet); } static void route_ipv4(node_t *source, vpn_packet_t *packet) { if(!checklength(source, packet, ether_size + ip_size)) { return; } if(broadcast_mode && (((packet->data[30] & 0xf0) == 0xe0) || ( packet->data[30] == 255 && packet->data[31] == 255 && packet->data[32] == 255 && packet->data[33] == 255))) { route_broadcast(source, packet); } else { route_ipv4_unicast(source, packet); } } static void route_ipv6_unicast(node_t *source, vpn_packet_t *packet) { subnet_t *subnet; node_t *via; ipv6_t dest; memcpy(&dest, &packet->data[38], sizeof(dest)); subnet = lookup_subnet_ipv6(&dest); if(!subnet) { ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv6 destination address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx", source->name, source->hostname, ntohs(dest.x[0]), ntohs(dest.x[1]), ntohs(dest.x[2]), ntohs(dest.x[3]), ntohs(dest.x[4]), ntohs(dest.x[5]), ntohs(dest.x[6]), ntohs(dest.x[7])); route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR); return; } if(subnet->owner == source) { ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname); return; } if(!subnet->owner->status.reachable) { route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOROUTE); return; } if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself) { route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN); return; } if(decrement_ttl && source != myself && subnet->owner != myself) { if(!do_decrement_ttl(source, packet)) { return; } } if(priorityinheritance) { packet->priority = ((packet->data[14] & 0x0f) << 4) | (packet->data[15] >> 4); } via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via; if(via == source) { ifdebug(TRAFFIC) logger(LOG_ERR, "Routing loop for packet from %s (%s)!", source->name, source->hostname); return; } if(directonly && subnet->owner != via) { route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN); return; } if(via && packet->len > MAX(via->mtu, 1294) && via != myself) { ifdebug(TRAFFIC) logger(LOG_INFO, "Packet for %s (%s) length %d larger than MTU %d", subnet->owner->name, subnet->owner->hostname, packet->len, via->mtu); packet->len = MAX(via->mtu, 1294); route_ipv6_unreachable(source, packet, ether_size, ICMP6_PACKET_TOO_BIG, 0); return; } clamp_mss(source, via, packet); send_packet(subnet->owner, packet); } /* RFC 2461 */ static void route_neighborsol(node_t *source, vpn_packet_t *packet) { struct ip6_hdr ip6; struct nd_neighbor_solicit ns; struct nd_opt_hdr opt; subnet_t *subnet; uint16_t checksum; bool has_opt; struct { struct in6_addr ip6_src; /* source address */ struct in6_addr ip6_dst; /* destination address */ uint32_t length; uint32_t next; } pseudo; if(!checklength(source, packet, ether_size + ip6_size + ns_size)) { return; } has_opt = packet->len >= ether_size + ip6_size + ns_size + opt_size + ETH_ALEN; if(source != myself) { ifdebug(TRAFFIC) logger(LOG_WARNING, "Got neighbor solicitation request from %s (%s) while in router mode!", source->name, source->hostname); return; } /* Copy headers from packet to structs on the stack */ memcpy(&ip6, packet->data + ether_size, ip6_size); memcpy(&ns, packet->data + ether_size + ip6_size, ns_size); if(has_opt) { memcpy(&opt, packet->data + ether_size + ip6_size + ns_size, opt_size); } /* First, snatch the source address from the neighbor solicitation packet */ if(overwrite_mac) { memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN); } /* Check if this is a valid neighbor solicitation request */ if(ns.nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT || (has_opt && opt.nd_opt_type != ND_OPT_SOURCE_LINKADDR)) { ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: received unknown type neighbor solicitation request"); return; } /* Create pseudo header */ pseudo.ip6_src = ip6.ip6_src; pseudo.ip6_dst = ip6.ip6_dst; if(has_opt) { pseudo.length = htonl(ns_size + opt_size + ETH_ALEN); } else { pseudo.length = htonl(ns_size); } pseudo.next = htonl(IPPROTO_ICMPV6); /* Generate checksum */ checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0); checksum = inet_checksum(&ns, ns_size, checksum); if(has_opt) { checksum = inet_checksum(&opt, opt_size, checksum); checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum); } if(checksum) { ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: checksum error for neighbor solicitation request"); return; } /* Check if the IPv6 address exists on the VPN */ subnet = lookup_subnet_ipv6((ipv6_t *) &ns.nd_ns_target); if(!subnet) { ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: neighbor solicitation request for unknown address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx", ntohs(((uint16_t *) &ns.nd_ns_target)[0]), ntohs(((uint16_t *) &ns.nd_ns_target)[1]), ntohs(((uint16_t *) &ns.nd_ns_target)[2]), ntohs(((uint16_t *) &ns.nd_ns_target)[3]), ntohs(((uint16_t *) &ns.nd_ns_target)[4]), ntohs(((uint16_t *) &ns.nd_ns_target)[5]), ntohs(((uint16_t *) &ns.nd_ns_target)[6]), ntohs(((uint16_t *) &ns.nd_ns_target)[7])); return; } /* Check if it is for our own subnet */ if(subnet->owner == myself) { return; /* silently ignore */ } if(decrement_ttl) if(!do_decrement_ttl(source, packet)) { return; } /* Create neighbor advertation reply */ memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN); /* copy destination address */ packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */ ip6.ip6_dst = ip6.ip6_src; /* swap destination and source protocol address */ ip6.ip6_src = ns.nd_ns_target; if(has_opt) { memcpy(packet->data + ether_size + ip6_size + ns_size + opt_size, packet->data + ETH_ALEN, ETH_ALEN); /* add fake source hard addr */ } ns.nd_ns_cksum = 0; ns.nd_ns_type = ND_NEIGHBOR_ADVERT; ns.nd_ns_reserved = htonl(0x40000000UL); /* Set solicited flag */ opt.nd_opt_type = ND_OPT_TARGET_LINKADDR; /* Create pseudo header */ pseudo.ip6_src = ip6.ip6_src; pseudo.ip6_dst = ip6.ip6_dst; if(has_opt) { pseudo.length = htonl(ns_size + opt_size + ETH_ALEN); } else { pseudo.length = htonl(ns_size); } pseudo.next = htonl(IPPROTO_ICMPV6); /* Generate checksum */ checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0); checksum = inet_checksum(&ns, ns_size, checksum); if(has_opt) { checksum = inet_checksum(&opt, opt_size, checksum); checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum); } ns.nd_ns_hdr.icmp6_cksum = checksum; /* Copy structs on stack back to packet */ memcpy(packet->data + ether_size, &ip6, ip6_size); memcpy(packet->data + ether_size + ip6_size, &ns, ns_size); if(has_opt) { memcpy(packet->data + ether_size + ip6_size + ns_size, &opt, opt_size); } send_packet(source, packet); } static void route_ipv6(node_t *source, vpn_packet_t *packet) { if(!checklength(source, packet, ether_size + ip6_size)) { return; } if(packet->data[20] == IPPROTO_ICMPV6 && checklength(source, packet, ether_size + ip6_size + icmp6_size) && packet->data[54] == ND_NEIGHBOR_SOLICIT) { route_neighborsol(source, packet); return; } if(broadcast_mode && packet->data[38] == 255) { route_broadcast(source, packet); } else { route_ipv6_unicast(source, packet); } } /* RFC 826 */ static void route_arp(node_t *source, vpn_packet_t *packet) { struct ether_arp arp; subnet_t *subnet; struct in_addr addr; if(!checklength(source, packet, ether_size + arp_size)) { return; } if(source != myself) { ifdebug(TRAFFIC) logger(LOG_WARNING, "Got ARP request from %s (%s) while in router mode!", source->name, source->hostname); return; } /* First, snatch the source address from the ARP packet */ if(overwrite_mac) { memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN); } /* Copy headers from packet to structs on the stack */ memcpy(&arp, packet->data + ether_size, arp_size); /* Check if this is a valid ARP request */ if(ntohs(arp.arp_hrd) != ARPHRD_ETHER || ntohs(arp.arp_pro) != ETH_P_IP || arp.arp_hln != ETH_ALEN || arp.arp_pln != sizeof(addr) || ntohs(arp.arp_op) != ARPOP_REQUEST) { ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: received unknown type ARP request"); return; } /* Check if the IPv4 address exists on the VPN */ subnet = lookup_subnet_ipv4((ipv4_t *) &arp.arp_tpa); if(!subnet) { ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: ARP request for unknown address %d.%d.%d.%d", arp.arp_tpa[0], arp.arp_tpa[1], arp.arp_tpa[2], arp.arp_tpa[3]); return; } /* Check if it is for our own subnet */ if(subnet->owner == myself) { return; /* silently ignore */ } if(decrement_ttl) if(!do_decrement_ttl(source, packet)) { return; } memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN); /* copy destination address */ packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */ memcpy(&addr, arp.arp_tpa, sizeof(addr)); /* save protocol addr */ memcpy(arp.arp_tpa, arp.arp_spa, sizeof(addr)); /* swap destination and source protocol address */ memcpy(arp.arp_spa, &addr, sizeof(addr)); /* ... */ memcpy(arp.arp_tha, arp.arp_sha, ETH_ALEN); /* set target hard/proto addr */ memcpy(arp.arp_sha, packet->data + ETH_ALEN, ETH_ALEN); /* add fake source hard addr */ arp.arp_op = htons(ARPOP_REPLY); /* Copy structs on stack back to packet */ memcpy(packet->data + ether_size, &arp, arp_size); send_packet(source, packet); } static void route_mac(node_t *source, vpn_packet_t *packet) { subnet_t *subnet; mac_t dest; /* Learn source address */ if(source == myself) { mac_t src; memcpy(&src, &packet->data[6], sizeof(src)); learn_mac(&src); } /* Lookup destination address */ memcpy(&dest, &packet->data[0], sizeof(dest)); subnet = lookup_subnet_mac(NULL, &dest); if(!subnet) { route_broadcast(source, packet); return; } if(subnet->owner == source) { ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname); return; } if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself) { return; } if(decrement_ttl && source != myself && subnet->owner != myself) if(!do_decrement_ttl(source, packet)) { return; } uint16_t type = packet->data[12] << 8 | packet->data[13]; if(priorityinheritance) { if(type == ETH_P_IP && packet->len >= ether_size + ip_size) { packet->priority = packet->data[15]; } else if(type == ETH_P_IPV6 && packet->len >= ether_size + ip6_size) { packet->priority = ((packet->data[14] & 0x0f) << 4) | (packet->data[15] >> 4); } } // Handle packets larger than PMTU node_t *via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via; if(directonly && subnet->owner != via) { return; } if(via && packet->len > via->mtu && via != myself) { ifdebug(TRAFFIC) logger(LOG_INFO, "Packet for %s (%s) length %d larger than MTU %d", subnet->owner->name, subnet->owner->hostname, packet->len, via->mtu); length_t ethlen = 14; if(type == ETH_P_8021Q) { type = packet->data[16] << 8 | packet->data[17]; ethlen += 4; } if(type == ETH_P_IP && packet->len > 576 + ethlen) { if(packet->data[6 + ethlen] & 0x40) { packet->len = via->mtu; route_ipv4_unreachable(source, packet, ethlen, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED); } else { fragment_ipv4_packet(via, packet, ethlen); } return; } else if(type == ETH_P_IPV6 && packet->len > 1280 + ethlen) { packet->len = via->mtu; route_ipv6_unreachable(source, packet, ethlen, ICMP6_PACKET_TOO_BIG, 0); return; } } clamp_mss(source, via, packet); send_packet(subnet->owner, packet); } void route(node_t *source, vpn_packet_t *packet) { if(forwarding_mode == FMODE_KERNEL && source != myself) { send_packet(myself, packet); return; } if(!checklength(source, packet, ether_size)) { return; } switch(routing_mode) { case RMODE_ROUTER: { uint16_t type = packet->data[12] << 8 | packet->data[13]; switch(type) { case ETH_P_ARP: route_arp(source, packet); break; case ETH_P_IP: route_ipv4(source, packet); break; case ETH_P_IPV6: route_ipv6(source, packet); break; default: ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown type %hx", source->name, source->hostname, type); break; } } break; case RMODE_SWITCH: route_mac(source, packet); break; case RMODE_HUB: route_broadcast(source, packet); break; } }