/** * Copyright (C) 2012-2013 Steven Barth * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License v2 as published by * the Free Software Foundation. * * 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. * */ #include #include #include #include #include #include #include #include #include #include #include #include #include "router.h" #include "ndp.h" static void handle_solicit(void *addr, void *data, size_t len, struct interface *iface); static void handle_rtnetlink(void *addr, void *data, size_t len, struct interface *iface); static struct ndp_neighbor* find_neighbor(struct in6_addr *addr, bool strict); static void modify_neighbor(struct in6_addr *addr, struct interface *iface, bool add); static ssize_t ping6(struct in6_addr *addr, const struct interface *iface); static struct list_head neighbors = LIST_HEAD_INIT(neighbors); static size_t neighbor_count = 0; static uint32_t rtnl_seqid = 0; static int ping_socket = -1; static struct odhcpd_event ndp_event = {{.fd = -1}, handle_solicit}; static struct odhcpd_event rtnl_event = {{.fd = -1}, handle_rtnetlink}; // Filter ICMPv6 messages of type neighbor soliciation static struct sock_filter bpf[] = { BPF_STMT(BPF_LD | BPF_B | BPF_ABS, offsetof(struct ip6_hdr, ip6_nxt)), BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, IPPROTO_ICMPV6, 0, 3), BPF_STMT(BPF_LD | BPF_B | BPF_ABS, sizeof(struct ip6_hdr) + offsetof(struct icmp6_hdr, icmp6_type)), BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, ND_NEIGHBOR_SOLICIT, 0, 1), BPF_STMT(BPF_RET | BPF_K, 0xffffffff), BPF_STMT(BPF_RET | BPF_K, 0), }; static const struct sock_fprog bpf_prog = {sizeof(bpf) / sizeof(*bpf), bpf}; // Initialize NDP-proxy int init_ndp(void) { // Setup netlink socket if ((rtnl_event.uloop.fd = odhcpd_open_rtnl()) < 0) return -1; // Receive netlink neighbor and ip-address events uint32_t group = RTNLGRP_IPV6_IFADDR; setsockopt(rtnl_event.uloop.fd, SOL_NETLINK, NETLINK_ADD_MEMBERSHIP, &group, sizeof(group)); group = RTNLGRP_IPV6_ROUTE; setsockopt(rtnl_event.uloop.fd, SOL_NETLINK, NETLINK_ADD_MEMBERSHIP, &group, sizeof(group)); // Synthesize initial address events struct { struct nlmsghdr nh; struct ifaddrmsg ifa; } req2 = { {sizeof(req2), RTM_GETADDR, NLM_F_REQUEST | NLM_F_DUMP, ++rtnl_seqid, 0}, {.ifa_family = AF_INET6} }; send(rtnl_event.uloop.fd, &req2, sizeof(req2), MSG_DONTWAIT); odhcpd_register(&rtnl_event); // Create socket for intercepting NDP int sock = socket(AF_PACKET, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, htons(ETH_P_ALL)); // ETH_P_ALL for ingress + egress if (sock < 0) { syslog(LOG_ERR, "Unable to open packet socket: %s", strerror(errno)); return -1; } if (setsockopt(sock, SOL_SOCKET, SO_ATTACH_FILTER, &bpf_prog, sizeof(bpf_prog))) { syslog(LOG_ERR, "Failed to set BPF: %s", strerror(errno)); return -1; } ndp_event.uloop.fd = sock; odhcpd_register(&ndp_event); // Open ICMPv6 socket ping_socket = socket(AF_INET6, SOCK_RAW | SOCK_CLOEXEC, IPPROTO_ICMPV6); int val = 2; setsockopt(ping_socket, IPPROTO_RAW, IPV6_CHECKSUM, &val, sizeof(val)); // This is required by RFC 4861 val = 255; setsockopt(ping_socket, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &val, sizeof(val)); setsockopt(ping_socket, IPPROTO_IPV6, IPV6_UNICAST_HOPS, &val, sizeof(val)); // Filter all packages, we only want to send struct icmp6_filter filt; ICMP6_FILTER_SETBLOCKALL(&filt); setsockopt(ping_socket, IPPROTO_ICMPV6, ICMP6_FILTER, &filt, sizeof(filt)); // Netlink socket, continued... group = RTNLGRP_NEIGH; setsockopt(rtnl_event.uloop.fd, SOL_NETLINK, NETLINK_ADD_MEMBERSHIP, &group, sizeof(group)); // Synthesize initial neighbor events struct { struct nlmsghdr nh; struct ndmsg ndm; } req = { {sizeof(req), RTM_GETNEIGH, NLM_F_REQUEST | NLM_F_DUMP, ++rtnl_seqid, 0}, {.ndm_family = AF_INET6} }; send(rtnl_event.uloop.fd, &req, sizeof(req), MSG_DONTWAIT); return 0; } int setup_ndp_interface(struct interface *iface, bool enable) { struct packet_mreq mreq = {iface->ifindex, PACKET_MR_ALLMULTI, ETH_ALEN, {0}}; setsockopt(ndp_event.uloop.fd, SOL_PACKET, PACKET_DROP_MEMBERSHIP, &mreq, sizeof(mreq)); struct ndp_neighbor *c, *n; list_for_each_entry_safe(c, n, &neighbors, head) if (c->iface == iface && (c->timeout == 0 || iface->ndp != RELAYD_RELAY || !enable)) modify_neighbor(&c->addr, c->iface, false); if (enable && iface->ndp == RELAYD_RELAY) { setsockopt(ndp_event.uloop.fd, SOL_PACKET, PACKET_ADD_MEMBERSHIP, &mreq, sizeof(mreq)); if (iface->static_ndp_len) { char *entry = alloca(iface->static_ndp_len), *saveptr; if (!entry) { syslog(LOG_ERR, "Alloca failed for static NDP list"); return -1; } memcpy(entry, iface->static_ndp, iface->static_ndp_len); for (entry = strtok_r(entry, " ", &saveptr); entry; entry = strtok_r(NULL, " ", &saveptr)) { struct ndp_neighbor *n = malloc(sizeof(*n)); if (!n) { syslog(LOG_ERR, "Malloc failed for static NDP-prefix %s", entry); return -1; } n->iface = iface; n->timeout = 0; char ipbuf[INET6_ADDRSTRLEN]; if (sscanf(entry, "%45s/%hhu", ipbuf, &n->len) < 2 || n->len > 128 || inet_pton(AF_INET6, ipbuf, &n->addr) != 1) { syslog(LOG_ERR, "Invalid static NDP-prefix %s", entry); return -1; } list_add(&n->head, &neighbors); } } } return 0; } // Send an ICMP-ECHO. This is less for actually pinging but for the // neighbor cache to be kept up-to-date. static ssize_t ping6(struct in6_addr *addr, const struct interface *iface) { struct sockaddr_in6 dest = {AF_INET6, 0, 0, *addr, 0}; struct icmp6_hdr echo = {.icmp6_type = ICMP6_ECHO_REQUEST}; struct iovec iov = {&echo, sizeof(echo)}; // Linux seems to not honor IPV6_PKTINFO on raw-sockets, so work around setsockopt(ping_socket, SOL_SOCKET, SO_BINDTODEVICE, iface->ifname, sizeof(iface->ifname)); return odhcpd_send(ping_socket, &dest, &iov, 1, iface); } // Handle solicitations static void handle_solicit(void *addr, void *data, size_t len, struct interface *iface) { struct ip6_hdr *ip6 = data; struct nd_neighbor_solicit *req = (struct nd_neighbor_solicit*)&ip6[1]; struct sockaddr_ll *ll = addr; // Solicitation is for duplicate address detection bool ns_is_dad = IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src); // Don't forward any non-DAD solicitation for external ifaces // TODO: check if we should even forward DADs for them if (iface->external && !ns_is_dad) return; if (len < sizeof(*ip6) + sizeof(*req)) return; // Invalid reqicitation if (IN6_IS_ADDR_LINKLOCAL(&req->nd_ns_target) || IN6_IS_ADDR_LOOPBACK(&req->nd_ns_target) || IN6_IS_ADDR_MULTICAST(&req->nd_ns_target)) return; // Invalid target char ipbuf[INET6_ADDRSTRLEN]; inet_ntop(AF_INET6, &req->nd_ns_target, ipbuf, sizeof(ipbuf)); syslog(LOG_NOTICE, "Got a NS for %s", ipbuf); uint8_t mac[6]; odhcpd_get_mac(iface, mac); if (!memcmp(ll->sll_addr, mac, sizeof(mac)) && ll->sll_pkttype != PACKET_OUTGOING) return; // Looped back time_t now = time(NULL); struct ndp_neighbor *n = find_neighbor(&req->nd_ns_target, false); if (n && (n->iface || abs(n->timeout - now) < 5)) { syslog(LOG_NOTICE, "%s is on %s", ipbuf, (n->iface) ? n->iface->ifname : ""); if (!n->iface || n->iface == iface) return; // Found on other interface, answer with advertisement struct { struct nd_neighbor_advert body; struct nd_opt_hdr opt_ll_hdr; uint8_t mac[6]; } advert = { .body = { .nd_na_hdr = {ND_NEIGHBOR_ADVERT, 0, 0, {{0}}}, .nd_na_target = req->nd_ns_target, }, .opt_ll_hdr = {ND_OPT_TARGET_LINKADDR, 1}, }; memcpy(advert.mac, mac, sizeof(advert.mac)); advert.body.nd_na_flags_reserved = ND_NA_FLAG_ROUTER | ND_NA_FLAG_SOLICITED; struct sockaddr_in6 dest = {AF_INET6, 0, 0, ALL_IPV6_NODES, 0}; if (!ns_is_dad) // If not DAD, then unicast to source dest.sin6_addr = ip6->ip6_src; // Linux seems to not honor IPV6_PKTINFO on raw-sockets, so work around setsockopt(ping_socket, SOL_SOCKET, SO_BINDTODEVICE, iface->ifname, sizeof(iface->ifname)); struct iovec iov = {&advert, sizeof(advert)}; odhcpd_send(ping_socket, &dest, &iov, 1, iface); } else { // Send echo to all other interfaces to see where target is on // This will trigger neighbor discovery which is what we want. // We will observe the neighbor cache to see results. ssize_t sent = 0; struct interface *c; list_for_each_entry(c, &interfaces, head) if (iface->ndp == RELAYD_RELAY && iface != c && (!ns_is_dad || !c->external == false)) sent += ping6(&req->nd_ns_target, c); if (sent > 0) // Sent a ping, add pending neighbor entry modify_neighbor(&req->nd_ns_target, NULL, true); } } void odhcpd_setup_route(const struct in6_addr *addr, int prefixlen, const struct interface *iface, const struct in6_addr *gw, bool add) { struct req { struct nlmsghdr nh; struct rtmsg rtm; struct rtattr rta_dst; struct in6_addr dst_addr; struct rtattr rta_oif; uint32_t ifindex; struct rtattr rta_table; uint32_t table; struct rtattr rta_gw; struct in6_addr gw; } req = { {sizeof(req), 0, NLM_F_REQUEST, ++rtnl_seqid, 0}, {AF_INET6, prefixlen, 0, 0, 0, 0, 0, 0, 0}, {sizeof(struct rtattr) + sizeof(struct in6_addr), RTA_DST}, *addr, {sizeof(struct rtattr) + sizeof(uint32_t), RTA_OIF}, iface->ifindex, {sizeof(struct rtattr) + sizeof(uint32_t), RTA_TABLE}, RT_TABLE_MAIN, {sizeof(struct rtattr) + sizeof(struct in6_addr), RTA_GATEWAY}, IN6ADDR_ANY_INIT, }; if (gw) req.gw = *gw; if (add) { req.nh.nlmsg_type = RTM_NEWROUTE; req.nh.nlmsg_flags |= (NLM_F_CREATE | NLM_F_REPLACE); req.rtm.rtm_protocol = RTPROT_BOOT; req.rtm.rtm_scope = (gw) ? RT_SCOPE_UNIVERSE : RT_SCOPE_LINK; req.rtm.rtm_type = RTN_UNICAST; } else { req.nh.nlmsg_type = RTM_DELROUTE; req.rtm.rtm_scope = RT_SCOPE_NOWHERE; } size_t reqlen = (gw) ? sizeof(req) : offsetof(struct req, rta_gw); send(rtnl_event.uloop.fd, &req, reqlen, MSG_DONTWAIT); } // Use rtnetlink to modify kernel routes static void setup_route(struct in6_addr *addr, struct interface *iface, bool add) { char namebuf[INET6_ADDRSTRLEN]; inet_ntop(AF_INET6, addr, namebuf, sizeof(namebuf)); syslog(LOG_NOTICE, "%s about %s on %s", (add) ? "Learned" : "Forgot", namebuf, (iface) ? iface->ifname : ""); if (!iface || !iface->learn_routes) return; odhcpd_setup_route(addr, 128, iface, NULL, add); } static void free_neighbor(struct ndp_neighbor *n) { setup_route(&n->addr, n->iface, false); list_del(&n->head); free(n); --neighbor_count; } static bool match_neighbor(struct ndp_neighbor *n, struct in6_addr *addr) { if (n->len <= 32) return ntohl(n->addr.s6_addr32[0]) >> (32 - n->len) == ntohl(addr->s6_addr32[0]) >> (32 - n->len); if (n->addr.s6_addr32[0] != addr->s6_addr32[0]) return false; if (n->len <= 64) return ntohl(n->addr.s6_addr32[1]) >> (64 - n->len) == ntohl(addr->s6_addr32[1]) >> (64 - n->len); if (n->addr.s6_addr32[1] != addr->s6_addr32[1]) return false; if (n->len <= 96) return ntohl(n->addr.s6_addr32[2]) >> (96 - n->len) == ntohl(addr->s6_addr32[2]) >> (96 - n->len); if (n->addr.s6_addr32[2] != addr->s6_addr32[2]) return false; return ntohl(n->addr.s6_addr32[3]) >> (128 - n->len) == ntohl(addr->s6_addr32[3]) >> (128 - n->len); } static struct ndp_neighbor* find_neighbor(struct in6_addr *addr, bool strict) { time_t now = time(NULL); struct ndp_neighbor *n, *e; list_for_each_entry_safe(n, e, &neighbors, head) { if ((!strict && match_neighbor(n, addr)) || (n->len == 128 && IN6_ARE_ADDR_EQUAL(&n->addr, addr))) return n; if (!n->iface && abs(n->timeout - now) >= 5) free_neighbor(n); } return NULL; } // Modified our own neighbor-entries static void modify_neighbor(struct in6_addr *addr, struct interface *iface, bool add) { if (!addr || (void*)addr == (void*)iface) return; struct ndp_neighbor *n = find_neighbor(addr, true); if (!add) { // Delete action if (n && (!n->iface || n->iface == iface)) free_neighbor(n); } else if (!n) { // No entry yet, add one if possible if (neighbor_count >= NDP_MAX_NEIGHBORS || !(n = malloc(sizeof(*n)))) return; n->len = 128; n->addr = *addr; n->iface = iface; if (!n->iface) time(&n->timeout); list_add(&n->head, &neighbors); ++neighbor_count; setup_route(addr, n->iface, add); } else if (n->iface == iface) { if (!n->iface) time(&n->timeout); } else if (iface && (!n->iface || (!iface->external && n->iface->external))) { setup_route(addr, n->iface, false); n->iface = iface; setup_route(addr, n->iface, add); } // TODO: In case a host switches interfaces we might want // to set its old neighbor entry to NUD_STALE and ping it // on the old interface to confirm if the MACs match. } // Handler for neighbor cache entries from the kernel. This is our source // to learn and unlearn hosts on interfaces. static void handle_rtnetlink(_unused void *addr, void *data, size_t len, _unused struct interface *iface) { for (struct nlmsghdr *nh = data; NLMSG_OK(nh, len); nh = NLMSG_NEXT(nh, len)) { struct rtmsg *rtm = NLMSG_DATA(nh); if ((nh->nlmsg_type == RTM_NEWROUTE || nh->nlmsg_type == RTM_DELROUTE) && rtm->rtm_dst_len == 0) raise(SIGUSR1); // Inform about a change in default route struct ndmsg *ndm = NLMSG_DATA(nh); struct ifaddrmsg *ifa = NLMSG_DATA(nh); if (nh->nlmsg_type != RTM_NEWNEIGH && nh->nlmsg_type != RTM_DELNEIGH && nh->nlmsg_type != RTM_NEWADDR && nh->nlmsg_type != RTM_DELADDR) continue; // Unrelated message type bool is_addr = (nh->nlmsg_type == RTM_NEWADDR || nh->nlmsg_type == RTM_DELADDR); // Family and ifindex are on the same offset for NEIGH and ADDR if (NLMSG_PAYLOAD(nh, 0) < sizeof(*ndm) || ndm->ndm_family != AF_INET6) continue; // // Lookup interface struct interface *iface; if (!(iface = odhcpd_get_interface_by_index(ndm->ndm_ifindex))) continue; // Data to retrieve size_t rta_offset = (is_addr) ? sizeof(*ifa) : sizeof(*ndm); uint16_t atype = (is_addr) ? IFA_ADDRESS : NDA_DST; ssize_t alen = NLMSG_PAYLOAD(nh, rta_offset); struct in6_addr *addr = NULL; for (struct rtattr *rta = (void*)(((uint8_t*)ndm) + rta_offset); RTA_OK(rta, alen); rta = RTA_NEXT(rta, alen)) if (rta->rta_type == atype && RTA_PAYLOAD(rta) >= sizeof(*addr)) addr = RTA_DATA(rta); // Address not specified or unrelated if (!addr || IN6_IS_ADDR_LINKLOCAL(addr) || IN6_IS_ADDR_MULTICAST(addr)) continue; // Check for states bool add; if (is_addr) add = (nh->nlmsg_type == RTM_NEWADDR); else add = (nh->nlmsg_type == RTM_NEWNEIGH && (ndm->ndm_state & (NUD_REACHABLE | NUD_STALE | NUD_DELAY | NUD_PROBE | NUD_PERMANENT | NUD_NOARP))); if (iface->ndp == RELAYD_RELAY) modify_neighbor(addr, iface, add); if (is_addr && iface->ra == RELAYD_SERVER) raise(SIGUSR1); // Inform about a change in addresses if (is_addr && iface->dhcpv6 == RELAYD_SERVER) iface->ia_reconf = true; if (iface->ndp == RELAYD_RELAY && is_addr && iface->master) { // Replay address changes on all slave interfaces nh->nlmsg_flags = NLM_F_REQUEST; if (nh->nlmsg_type == RTM_NEWADDR) nh->nlmsg_flags |= NLM_F_CREATE | NLM_F_REPLACE; struct interface *c; list_for_each_entry(c, &interfaces, head) { if (c->ndp == RELAYD_RELAY && !c->master) { ifa->ifa_index = c->ifindex; send(rtnl_event.uloop.fd, nh, nh->nlmsg_len, MSG_DONTWAIT); } } } /* TODO: See if this is required for optimal operation // Keep neighbor entries alive so we don't loose routes if (add && (ndm->ndm_state & NUD_STALE)) ping6(addr, iface); */ } }