src/ndp.c

   1 /**
   2  * Copyright (C) 2012-2013 Steven Barth <steven@midlink.org>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License v2 as published by
   6  * the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  *
  13  */
  14
  15 #include <stdio.h>
  16 #include <stdlib.h>
  17 #include <signal.h>
  18 #include <errno.h>
  19
  20 #include <arpa/inet.h>
  21 #include <sys/socket.h>
  22 #include <net/ethernet.h>
  23 #include <netinet/ip6.h>
  24 #include <netinet/icmp6.h>
  25 #include <netpacket/packet.h>
  26
  27 #include <linux/rtnetlink.h>
  28 #include <linux/filter.h>
  29 #include "router.h"
  30 #include "ndp.h"
  31
  32
  33
  34 static void handle_solicit(void *addr, void *data, size_t len,
  35                 struct interface *iface);
  36 static void handle_rtnetlink(void *addr, void *data, size_t len,
  37                 struct interface *iface);
  38 static struct ndp_neighbor* find_neighbor(struct in6_addr *addr, bool strict);
  39 static void modify_neighbor(struct in6_addr *addr, struct interface *iface,
  40                 bool add);
  41 static ssize_t ping6(struct in6_addr *addr,
  42                 const struct interface *iface);
  43
  44 static struct list_head neighbors = LIST_HEAD_INIT(neighbors);
  45 static size_t neighbor_count = 0;
  46 static uint32_t rtnl_seqid = 0;
  47
  48 static int ping_socket = -1;
  49 static struct odhcpd_event ndp_event = {{.fd = -1}, handle_solicit};
  50 static struct odhcpd_event rtnl_event = {{.fd = -1}, handle_rtnetlink};
  51
  52
  53 // Filter ICMPv6 messages of type neighbor soliciation
  54 static struct sock_filter bpf[] = {
  55         BPF_STMT(BPF_LD | BPF_B | BPF_ABS, offsetof(struct ip6_hdr, ip6_nxt)),
  56         BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, IPPROTO_ICMPV6, 0, 3),
  57         BPF_STMT(BPF_LD | BPF_B | BPF_ABS, sizeof(struct ip6_hdr) +
  58                         offsetof(struct icmp6_hdr, icmp6_type)),
  59         BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, ND_NEIGHBOR_SOLICIT, 0, 1),
  60         BPF_STMT(BPF_RET | BPF_K, 0xffffffff),
  61         BPF_STMT(BPF_RET | BPF_K, 0),
  62 };
  63 static const struct sock_fprog bpf_prog = {sizeof(bpf) / sizeof(*bpf), bpf};
  64
  65
  66 // Initialize NDP-proxy
  67 int init_ndp(void)
  68 {
  69         // Setup netlink socket
  70         if ((rtnl_event.uloop.fd = odhcpd_open_rtnl()) < 0)
  71                 return -1;
  72
  73         // Receive netlink neighbor and ip-address events
  74         uint32_t group = RTNLGRP_IPV6_IFADDR;
  75         setsockopt(rtnl_event.uloop.fd, SOL_NETLINK,
  76                         NETLINK_ADD_MEMBERSHIP, &group, sizeof(group));
  77         group = RTNLGRP_IPV6_ROUTE;
  78         setsockopt(rtnl_event.uloop.fd, SOL_NETLINK,
  79                         NETLINK_ADD_MEMBERSHIP, &group, sizeof(group));
  80
  81         // Synthesize initial address events
  82         struct {
  83                 struct nlmsghdr nh;
  84                 struct ifaddrmsg ifa;
  85         } req2 = {
  86                 {sizeof(req2), RTM_GETADDR, NLM_F_REQUEST | NLM_F_DUMP,
  87                                 ++rtnl_seqid, 0},
  88                 {.ifa_family = AF_INET6}
  89         };
  90         send(rtnl_event.uloop.fd, &req2, sizeof(req2), MSG_DONTWAIT);
  91         odhcpd_register(&rtnl_event);
  92
  93
  94         // Create socket for intercepting NDP
  95         int sock = socket(AF_PACKET, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK,
  96                         htons(ETH_P_ALL)); // ETH_P_ALL for ingress + egress
  97         if (sock < 0) {
  98                 syslog(LOG_ERR, "Unable to open packet socket: %s",
  99                                 strerror(errno));
 100                 return -1;
 101         }
 102
 103         if (setsockopt(sock, SOL_SOCKET, SO_ATTACH_FILTER,
 104                         &bpf_prog, sizeof(bpf_prog))) {
 105                 syslog(LOG_ERR, "Failed to set BPF: %s", strerror(errno));
 106                 return -1;
 107         }
 108
 109         ndp_event.uloop.fd = sock;
 110         odhcpd_register(&ndp_event);
 111
 112         // Open ICMPv6 socket
 113         ping_socket = socket(AF_INET6, SOCK_RAW | SOCK_CLOEXEC, IPPROTO_ICMPV6);
 114
 115         int val = 2;
 116         setsockopt(ping_socket, IPPROTO_RAW, IPV6_CHECKSUM, &val, sizeof(val));
 117
 118         // This is required by RFC 4861
 119         val = 255;
 120         setsockopt(ping_socket, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &val, sizeof(val));
 121         setsockopt(ping_socket, IPPROTO_IPV6, IPV6_UNICAST_HOPS, &val, sizeof(val));
 122
 123         // Filter all packages, we only want to send
 124         struct icmp6_filter filt;
 125         ICMP6_FILTER_SETBLOCKALL(&filt);
 126         setsockopt(ping_socket, IPPROTO_ICMPV6, ICMP6_FILTER, &filt, sizeof(filt));
 127
 128
 129         // Netlink socket, continued...
 130         group = RTNLGRP_NEIGH;
 131         setsockopt(rtnl_event.uloop.fd, SOL_NETLINK, NETLINK_ADD_MEMBERSHIP, &group, sizeof(group));
 132
 133         // Synthesize initial neighbor events
 134         struct {
 135                 struct nlmsghdr nh;
 136                 struct ndmsg ndm;
 137         } req = {
 138                 {sizeof(req), RTM_GETNEIGH, NLM_F_REQUEST | NLM_F_DUMP,
 139                                 ++rtnl_seqid, 0},
 140                 {.ndm_family = AF_INET6}
 141         };
 142         send(rtnl_event.uloop.fd, &req, sizeof(req), MSG_DONTWAIT);
 143
 144         return 0;
 145 }
 146
 147
 148 int setup_ndp_interface(struct interface *iface, bool enable)
 149 {
 150         struct packet_mreq mreq = {iface->ifindex, PACKET_MR_ALLMULTI, ETH_ALEN, {0}};
 151         setsockopt(ndp_event.uloop.fd, SOL_PACKET, PACKET_DROP_MEMBERSHIP, &mreq, sizeof(mreq));
 152
 153         struct ndp_neighbor *c, *n;
 154         list_for_each_entry_safe(c, n, &neighbors, head)
 155                 if (c->iface == iface && (c->timeout == 0 || iface->ndp != RELAYD_RELAY || !enable))
 156                         modify_neighbor(&c->addr, c->iface, false);
 157
 158         if (enable && iface->ndp == RELAYD_RELAY) {
 159                 setsockopt(ndp_event.uloop.fd, SOL_PACKET, PACKET_ADD_MEMBERSHIP, &mreq, sizeof(mreq));
 160
 161                 if (iface->static_ndp_len) {
 162                         char *entry = alloca(iface->static_ndp_len), *saveptr;
 163                         if (!entry) {
 164                                 syslog(LOG_ERR, "Alloca failed for static NDP list");
 165                                 return -1;
 166                         }
 167                         memcpy(entry, iface->static_ndp, iface->static_ndp_len);
 168
 169                         for (entry = strtok_r(entry, " ", &saveptr); entry; entry = strtok_r(NULL, " ", &saveptr)) {
 170                                 char *sep;
 171                                 struct ndp_neighbor *n = malloc(sizeof(*n));
 172                                 if (!n) {
 173                                         syslog(LOG_ERR, "Malloc failed for static NDP-prefix %s", entry);
 174                                         return -1;
 175                                 }
 176
 177                                 n->iface = iface;
 178                                 n->timeout = 0;
 179
 180                                 sep = strchr(entry, '/');
 181                                 if (!sep) {
 182                                         free(n);
 183                                         syslog(LOG_ERR, "Invalid static NDP-prefix %s", entry);
 184                                         return -1;
 185                                 }
 186
 187                                 *sep = 0;
 188                                 n->len = atoi(sep + 1);
 189                                 if (inet_pton(AF_INET6, entry, &n->addr) != 1 || n->len > 128) {
 190                                         free(n);
 191                                         syslog(LOG_ERR, "Invalid static NDP-prefix %s/%s", entry, sep + 1);
 192                                         return -1;
 193                                 }
 194
 195                                 list_add(&n->head, &neighbors);
 196                         }
 197                 }
 198         }
 199
 200         return 0;
 201 }
 202
 203
 204 // Send an ICMP-ECHO. This is less for actually pinging but for the
 205 // neighbor cache to be kept up-to-date.
 206 static ssize_t ping6(struct in6_addr *addr,
 207                 const struct interface *iface)
 208 {
 209         struct sockaddr_in6 dest = {AF_INET6, 0, 0, *addr, 0};
 210         struct icmp6_hdr echo = {.icmp6_type = ICMP6_ECHO_REQUEST};
 211         struct iovec iov = {&echo, sizeof(echo)};
 212
 213         // Linux seems to not honor IPV6_PKTINFO on raw-sockets, so work around
 214         setsockopt(ping_socket, SOL_SOCKET, SO_BINDTODEVICE,
 215                         iface->ifname, sizeof(iface->ifname));
 216         return odhcpd_send(ping_socket, &dest, &iov, 1, iface);
 217 }
 218
 219
 220 // Handle solicitations
 221 static void handle_solicit(void *addr, void *data, size_t len,
 222                 struct interface *iface)
 223 {
 224         struct ip6_hdr *ip6 = data;
 225         struct nd_neighbor_solicit *req = (struct nd_neighbor_solicit*)&ip6[1];
 226         struct sockaddr_ll *ll = addr;
 227
 228         // Solicitation is for duplicate address detection
 229         bool ns_is_dad = IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src);
 230
 231         // Don't forward any non-DAD solicitation for external ifaces
 232         // TODO: check if we should even forward DADs for them
 233         if (iface->external && !ns_is_dad)
 234                 return;
 235
 236         if (len < sizeof(*ip6) + sizeof(*req))
 237                 return; // Invalid reqicitation
 238
 239         if (IN6_IS_ADDR_LINKLOCAL(&req->nd_ns_target) ||
 240                         IN6_IS_ADDR_LOOPBACK(&req->nd_ns_target) ||
 241                         IN6_IS_ADDR_MULTICAST(&req->nd_ns_target))
 242                 return; // Invalid target
 243
 244         char ipbuf[INET6_ADDRSTRLEN];
 245         inet_ntop(AF_INET6, &req->nd_ns_target, ipbuf, sizeof(ipbuf));
 246         syslog(LOG_DEBUG, "Got a NS for %s", ipbuf);
 247
 248         uint8_t mac[6];
 249         odhcpd_get_mac(iface, mac);
 250         if (!memcmp(ll->sll_addr, mac, sizeof(mac)) &&
 251                         ll->sll_pkttype != PACKET_OUTGOING)
 252                 return; // Looped back
 253
 254         time_t now = time(NULL);
 255
 256         struct ndp_neighbor *n = find_neighbor(&req->nd_ns_target, false);
 257         if (n && (n->iface || abs(n->timeout - now) < 5)) {
 258                 syslog(LOG_DEBUG, "%s is on %s", ipbuf,
 259                                 (n->iface) ? n->iface->ifname : "<pending>");
 260                 if (!n->iface || n->iface == iface)
 261                         return;
 262
 263                 // Found on other interface, answer with advertisement
 264                 struct {
 265                         struct nd_neighbor_advert body;
 266                         struct nd_opt_hdr opt_ll_hdr;
 267                         uint8_t mac[6];
 268                 } advert = {
 269                         .body = {
 270                                 .nd_na_hdr = {ND_NEIGHBOR_ADVERT,
 271                                         0, 0, {{0}}},
 272                                 .nd_na_target = req->nd_ns_target,
 273                         },
 274                         .opt_ll_hdr = {ND_OPT_TARGET_LINKADDR, 1},
 275                 };
 276
 277                 memcpy(advert.mac, mac, sizeof(advert.mac));
 278                 advert.body.nd_na_flags_reserved = ND_NA_FLAG_ROUTER |
 279                                 ND_NA_FLAG_SOLICITED;
 280
 281                 struct sockaddr_in6 dest = {AF_INET6, 0, 0, ALL_IPV6_NODES, 0};
 282                 if (!ns_is_dad) // If not DAD, then unicast to source
 283                         dest.sin6_addr = ip6->ip6_src;
 284
 285                 // Linux seems to not honor IPV6_PKTINFO on raw-sockets, so work around
 286                 setsockopt(ping_socket, SOL_SOCKET, SO_BINDTODEVICE,
 287                                         iface->ifname, sizeof(iface->ifname));
 288                 struct iovec iov = {&advert, sizeof(advert)};
 289                 odhcpd_send(ping_socket, &dest, &iov, 1, iface);
 290         } else {
 291                 // Send echo to all other interfaces to see where target is on
 292                 // This will trigger neighbor discovery which is what we want.
 293                 // We will observe the neighbor cache to see results.
 294
 295                 ssize_t sent = 0;
 296                 struct interface *c;
 297                 list_for_each_entry(c, &interfaces, head)
 298                         if (iface->ndp == RELAYD_RELAY && iface != c &&
 299                                         (!ns_is_dad || !c->external == false))
 300                                 sent += ping6(&req->nd_ns_target, c);
 301
 302                 if (sent > 0) // Sent a ping, add pending neighbor entry
 303                         modify_neighbor(&req->nd_ns_target, NULL, true);
 304         }
 305 }
 306
 307
 308 void odhcpd_setup_route(const struct in6_addr *addr, int prefixlen,
 309                 const struct interface *iface, const struct in6_addr *gw, bool add)
 310 {
 311         struct req {
 312                 struct nlmsghdr nh;
 313                 struct rtmsg rtm;
 314                 struct rtattr rta_dst;
 315                 struct in6_addr dst_addr;
 316                 struct rtattr rta_oif;
 317                 uint32_t ifindex;
 318                 struct rtattr rta_table;
 319                 uint32_t table;
 320                 struct rtattr rta_gw;
 321                 struct in6_addr gw;
 322         } req = {
 323                 {sizeof(req), 0, NLM_F_REQUEST, ++rtnl_seqid, 0},
 324                 {AF_INET6, prefixlen, 0, 0, 0, 0, 0, 0, 0},
 325                 {sizeof(struct rtattr) + sizeof(struct in6_addr), RTA_DST},
 326                 *addr,
 327                 {sizeof(struct rtattr) + sizeof(uint32_t), RTA_OIF},
 328                 iface->ifindex,
 329                 {sizeof(struct rtattr) + sizeof(uint32_t), RTA_TABLE},
 330                 RT_TABLE_MAIN,
 331                 {sizeof(struct rtattr) + sizeof(struct in6_addr), RTA_GATEWAY},
 332                 IN6ADDR_ANY_INIT,
 333         };
 334
 335         if (gw)
 336                 req.gw = *gw;
 337
 338         if (add) {
 339                 req.nh.nlmsg_type = RTM_NEWROUTE;
 340                 req.nh.nlmsg_flags |= (NLM_F_CREATE | NLM_F_REPLACE);
 341                 req.rtm.rtm_protocol = RTPROT_BOOT;
 342                 req.rtm.rtm_scope = (gw) ? RT_SCOPE_UNIVERSE : RT_SCOPE_LINK;
 343                 req.rtm.rtm_type = RTN_UNICAST;
 344         } else {
 345                 req.nh.nlmsg_type = RTM_DELROUTE;
 346                 req.rtm.rtm_scope = RT_SCOPE_NOWHERE;
 347         }
 348
 349         size_t reqlen = (gw) ? sizeof(req) : offsetof(struct req, rta_gw);
 350         send(rtnl_event.uloop.fd, &req, reqlen, MSG_DONTWAIT);
 351 }
 352
 353 // Use rtnetlink to modify kernel routes
 354 static void setup_route(struct in6_addr *addr, struct interface *iface,
 355                 bool add)
 356 {
 357         char namebuf[INET6_ADDRSTRLEN];
 358         inet_ntop(AF_INET6, addr, namebuf, sizeof(namebuf));
 359         syslog(LOG_NOTICE, "%s about %s on %s", (add) ? "Learned" : "Forgot",
 360                         namebuf, (iface) ? iface->ifname : "<pending>");
 361
 362         if (!iface || !iface->learn_routes)
 363                 return;
 364
 365         odhcpd_setup_route(addr, 128, iface, NULL, add);
 366 }
 367
 368 static void free_neighbor(struct ndp_neighbor *n)
 369 {
 370         setup_route(&n->addr, n->iface, false);
 371         list_del(&n->head);
 372         free(n);
 373         --neighbor_count;
 374 }
 375
 376 static struct ndp_neighbor* find_neighbor(struct in6_addr *addr, bool strict)
 377 {
 378         time_t now = time(NULL);
 379         struct ndp_neighbor *n, *e;
 380         list_for_each_entry_safe(n, e, &neighbors, head) {
 381                 if ((!strict && !odhcpd_bmemcmp(&n->addr, addr, n->len)) ||
 382                                 (n->len == 128 && IN6_ARE_ADDR_EQUAL(&n->addr, addr)))
 383                         return n;
 384
 385                 if (!n->iface && abs(n->timeout - now) >= 5)
 386                         free_neighbor(n);
 387         }
 388         return NULL;
 389 }
 390
 391
 392 // Modified our own neighbor-entries
 393 static void modify_neighbor(struct in6_addr *addr,
 394                 struct interface *iface, bool add)
 395 {
 396         if (!addr || (void*)addr == (void*)iface)
 397                 return;
 398
 399         struct ndp_neighbor *n = find_neighbor(addr, true);
 400         if (!add) { // Delete action
 401                 if (n && (!n->iface || n->iface == iface))
 402                         free_neighbor(n);
 403         } else if (!n) { // No entry yet, add one if possible
 404                 if (neighbor_count >= NDP_MAX_NEIGHBORS ||
 405                                 !(n = malloc(sizeof(*n))))
 406                         return;
 407
 408                 n->len = 128;
 409                 n->addr = *addr;
 410                 n->iface = iface;
 411                 if (!n->iface)
 412                         time(&n->timeout);
 413                 list_add(&n->head, &neighbors);
 414                 ++neighbor_count;
 415                 setup_route(addr, n->iface, add);
 416         } else if (n->iface == iface) {
 417                 if (!n->iface)
 418                         time(&n->timeout);
 419         } else if (iface && (!n->iface ||
 420                         (!iface->external && n->iface->external))) {
 421                 setup_route(addr, n->iface, false);
 422                 n->iface = iface;
 423                 setup_route(addr, n->iface, add);
 424         }
 425         // TODO: In case a host switches interfaces we might want
 426         // to set its old neighbor entry to NUD_STALE and ping it
 427         // on the old interface to confirm if the MACs match.
 428 }
 429
 430
 431 // Handler for neighbor cache entries from the kernel. This is our source
 432 // to learn and unlearn hosts on interfaces.
 433 static void handle_rtnetlink(_unused void *addr, void *data, size_t len,
 434                 _unused struct interface *iface)
 435 {
 436         for (struct nlmsghdr *nh = data; NLMSG_OK(nh, len);
 437                         nh = NLMSG_NEXT(nh, len)) {
 438                 struct rtmsg *rtm = NLMSG_DATA(nh);
 439                 if ((nh->nlmsg_type == RTM_NEWROUTE ||
 440                                 nh->nlmsg_type == RTM_DELROUTE) &&
 441                                 rtm->rtm_dst_len == 0)
 442                         raise(SIGUSR1); // Inform about a change in default route
 443
 444                 struct ndmsg *ndm = NLMSG_DATA(nh);
 445                 struct ifaddrmsg *ifa = NLMSG_DATA(nh);
 446                 if (nh->nlmsg_type != RTM_NEWNEIGH
 447                                 && nh->nlmsg_type != RTM_DELNEIGH
 448                                 && nh->nlmsg_type != RTM_NEWADDR
 449                                 && nh->nlmsg_type != RTM_DELADDR)
 450                         continue; // Unrelated message type
 451                 bool is_addr = (nh->nlmsg_type == RTM_NEWADDR
 452                                 || nh->nlmsg_type == RTM_DELADDR);
 453
 454                 // Family and ifindex are on the same offset for NEIGH and ADDR
 455                 if (NLMSG_PAYLOAD(nh, 0) < sizeof(*ndm)
 456                                 || ndm->ndm_family != AF_INET6)
 457                         continue; //
 458
 459                 // Lookup interface
 460                 struct interface *iface;
 461                 if (!(iface = odhcpd_get_interface_by_index(ndm->ndm_ifindex)))
 462                         continue;
 463
 464                 // Data to retrieve
 465                 size_t rta_offset = (is_addr) ? sizeof(*ifa) : sizeof(*ndm);
 466                 uint16_t atype = (is_addr) ? IFA_ADDRESS : NDA_DST;
 467                 ssize_t alen = NLMSG_PAYLOAD(nh, rta_offset);
 468                 struct in6_addr *addr = NULL;
 469
 470                 for (struct rtattr *rta = (void*)(((uint8_t*)ndm) + rta_offset);
 471                                 RTA_OK(rta, alen); rta = RTA_NEXT(rta, alen))
 472                         if (rta->rta_type == atype &&
 473                                         RTA_PAYLOAD(rta) >= sizeof(*addr))
 474                                 addr = RTA_DATA(rta);
 475
 476                 // Address not specified or unrelated
 477                 if (!addr || IN6_IS_ADDR_LINKLOCAL(addr) ||
 478                                 IN6_IS_ADDR_MULTICAST(addr))
 479                         continue;
 480
 481                 // Check for states
 482                 bool add;
 483                 if (is_addr)
 484                         add = (nh->nlmsg_type == RTM_NEWADDR);
 485                 else
 486                         add = (nh->nlmsg_type == RTM_NEWNEIGH && (ndm->ndm_state &
 487                                 (NUD_REACHABLE | NUD_STALE | NUD_DELAY | NUD_PROBE
 488                                                 | NUD_PERMANENT | NUD_NOARP)));
 489
 490                 if (iface->ndp == RELAYD_RELAY)
 491                         modify_neighbor(addr, iface, add);
 492
 493                 if (is_addr && iface->ra == RELAYD_SERVER)
 494                         raise(SIGUSR1); // Inform about a change in addresses
 495
 496                 if (is_addr && iface->dhcpv6 == RELAYD_SERVER)
 497                         iface->ia_reconf = true;
 498
 499                 if (iface->ndp == RELAYD_RELAY && is_addr && iface->master) {
 500                         // Replay address changes on all slave interfaces
 501                         nh->nlmsg_flags = NLM_F_REQUEST;
 502
 503                         if (nh->nlmsg_type == RTM_NEWADDR)
 504                                 nh->nlmsg_flags |= NLM_F_CREATE | NLM_F_REPLACE;
 505
 506                         struct interface *c;
 507                         list_for_each_entry(c, &interfaces, head) {
 508                                 if (c->ndp == RELAYD_RELAY && !c->master) {
 509                                         ifa->ifa_index = c->ifindex;
 510                                         send(rtnl_event.uloop.fd, nh, nh->nlmsg_len, MSG_DONTWAIT);
 511                                 }
 512                         }
 513                 }
 514
 515                 /* TODO: See if this is required for optimal operation
 516                 // Keep neighbor entries alive so we don't loose routes
 517                  */
 518                 if (add && (ndm->ndm_state & NUD_STALE))
 519                         ping6(addr, iface);
 520         }
 521 }