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         if (ping_socket < 0) {
 115                 syslog(LOG_ERR, "Unable to open raw socket: %s", strerror(errno));
 116                         return -1;
 117         }
 118
 119         int val = 2;
 120         setsockopt(ping_socket, IPPROTO_RAW, IPV6_CHECKSUM, &val, sizeof(val));
 121
 122         // This is required by RFC 4861
 123         val = 255;
 124         setsockopt(ping_socket, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &val, sizeof(val));
 125         setsockopt(ping_socket, IPPROTO_IPV6, IPV6_UNICAST_HOPS, &val, sizeof(val));
 126
 127         // Filter all packages, we only want to send
 128         struct icmp6_filter filt;
 129         ICMP6_FILTER_SETBLOCKALL(&filt);
 130         setsockopt(ping_socket, IPPROTO_ICMPV6, ICMP6_FILTER, &filt, sizeof(filt));
 131
 132
 133         // Netlink socket, continued...
 134         group = RTNLGRP_NEIGH;
 135         setsockopt(rtnl_event.uloop.fd, SOL_NETLINK, NETLINK_ADD_MEMBERSHIP, &group, sizeof(group));
 136
 137         // Synthesize initial neighbor events
 138         struct {
 139                 struct nlmsghdr nh;
 140                 struct ndmsg ndm;
 141         } req = {
 142                 {sizeof(req), RTM_GETNEIGH, NLM_F_REQUEST | NLM_F_DUMP,
 143                                 ++rtnl_seqid, 0},
 144                 {.ndm_family = AF_INET6}
 145         };
 146         send(rtnl_event.uloop.fd, &req, sizeof(req), MSG_DONTWAIT);
 147
 148         return 0;
 149 }
 150
 151
 152 int setup_ndp_interface(struct interface *iface, bool enable)
 153 {
 154         struct packet_mreq mreq = {iface->ifindex, PACKET_MR_ALLMULTI, ETH_ALEN, {0}};
 155         setsockopt(ndp_event.uloop.fd, SOL_PACKET, PACKET_DROP_MEMBERSHIP, &mreq, sizeof(mreq));
 156
 157         struct ndp_neighbor *c, *n;
 158         list_for_each_entry_safe(c, n, &neighbors, head)
 159                 if (c->iface == iface && (c->timeout == 0 || iface->ndp != RELAYD_RELAY || !enable))
 160                         modify_neighbor(&c->addr, c->iface, false);
 161
 162         if (enable && iface->ndp == RELAYD_RELAY) {
 163                 setsockopt(ndp_event.uloop.fd, SOL_PACKET, PACKET_ADD_MEMBERSHIP, &mreq, sizeof(mreq));
 164
 165                 if (iface->static_ndp_len) {
 166                         char *entry = alloca(iface->static_ndp_len), *saveptr;
 167                         if (!entry) {
 168                                 syslog(LOG_ERR, "Alloca failed for static NDP list");
 169                                 return -1;
 170                         }
 171                         memcpy(entry, iface->static_ndp, iface->static_ndp_len);
 172
 173                         for (entry = strtok_r(entry, " ", &saveptr); entry; entry = strtok_r(NULL, " ", &saveptr)) {
 174                                 char *sep;
 175                                 struct ndp_neighbor *n = malloc(sizeof(*n));
 176                                 if (!n) {
 177                                         syslog(LOG_ERR, "Malloc failed for static NDP-prefix %s", entry);
 178                                         return -1;
 179                                 }
 180
 181                                 n->iface = iface;
 182                                 n->timeout = 0;
 183
 184                                 sep = strchr(entry, '/');
 185                                 if (!sep) {
 186                                         free(n);
 187                                         syslog(LOG_ERR, "Invalid static NDP-prefix %s", entry);
 188                                         return -1;
 189                                 }
 190
 191                                 *sep = 0;
 192                                 n->len = atoi(sep + 1);
 193                                 if (inet_pton(AF_INET6, entry, &n->addr) != 1 || n->len > 128) {
 194                                         free(n);
 195                                         syslog(LOG_ERR, "Invalid static NDP-prefix %s/%s", entry, sep + 1);
 196                                         return -1;
 197                                 }
 198
 199                                 list_add(&n->head, &neighbors);
 200                         }
 201                 }
 202         }
 203
 204         return 0;
 205 }
 206
 207
 208 // Send an ICMP-ECHO. This is less for actually pinging but for the
 209 // neighbor cache to be kept up-to-date.
 210 static ssize_t ping6(struct in6_addr *addr,
 211                 const struct interface *iface)
 212 {
 213         struct sockaddr_in6 dest = {AF_INET6, 0, 0, *addr, 0};
 214         struct icmp6_hdr echo = {.icmp6_type = ICMP6_ECHO_REQUEST};
 215         struct iovec iov = {&echo, sizeof(echo)};
 216
 217         // Linux seems to not honor IPV6_PKTINFO on raw-sockets, so work around
 218         setsockopt(ping_socket, SOL_SOCKET, SO_BINDTODEVICE,
 219                         iface->ifname, sizeof(iface->ifname));
 220         return odhcpd_send(ping_socket, &dest, &iov, 1, iface);
 221 }
 222
 223
 224 // Handle solicitations
 225 static void handle_solicit(void *addr, void *data, size_t len,
 226                 struct interface *iface)
 227 {
 228         struct ip6_hdr *ip6 = data;
 229         struct nd_neighbor_solicit *req = (struct nd_neighbor_solicit*)&ip6[1];
 230         struct sockaddr_ll *ll = addr;
 231
 232         // Solicitation is for duplicate address detection
 233         bool ns_is_dad = IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src);
 234
 235         // Don't forward any non-DAD solicitation for external ifaces
 236         // TODO: check if we should even forward DADs for them
 237         if (iface->external && !ns_is_dad)
 238                 return;
 239
 240         if (len < sizeof(*ip6) + sizeof(*req))
 241                 return; // Invalid reqicitation
 242
 243         if (IN6_IS_ADDR_LINKLOCAL(&req->nd_ns_target) ||
 244                         IN6_IS_ADDR_LOOPBACK(&req->nd_ns_target) ||
 245                         IN6_IS_ADDR_MULTICAST(&req->nd_ns_target))
 246                 return; // Invalid target
 247
 248         char ipbuf[INET6_ADDRSTRLEN];
 249         inet_ntop(AF_INET6, &req->nd_ns_target, ipbuf, sizeof(ipbuf));
 250         syslog(LOG_DEBUG, "Got a NS for %s", ipbuf);
 251
 252         uint8_t mac[6];
 253         odhcpd_get_mac(iface, mac);
 254         if (!memcmp(ll->sll_addr, mac, sizeof(mac)) &&
 255                         ll->sll_pkttype != PACKET_OUTGOING)
 256                 return; // Looped back
 257
 258         time_t now = time(NULL);
 259
 260         struct ndp_neighbor *n = find_neighbor(&req->nd_ns_target, false);
 261         if (n && (n->iface || abs(n->timeout - now) < 5)) {
 262                 syslog(LOG_DEBUG, "%s is on %s", ipbuf,
 263                                 (n->iface) ? n->iface->ifname : "<pending>");
 264                 if (!n->iface || n->iface == iface)
 265                         return;
 266
 267                 // Found on other interface, answer with advertisement
 268                 struct {
 269                         struct nd_neighbor_advert body;
 270                         struct nd_opt_hdr opt_ll_hdr;
 271                         uint8_t mac[6];
 272                 } advert = {
 273                         .body = {
 274                                 .nd_na_hdr = {ND_NEIGHBOR_ADVERT,
 275                                         0, 0, {{0}}},
 276                                 .nd_na_target = req->nd_ns_target,
 277                         },
 278                         .opt_ll_hdr = {ND_OPT_TARGET_LINKADDR, 1},
 279                 };
 280
 281                 memcpy(advert.mac, mac, sizeof(advert.mac));
 282                 advert.body.nd_na_flags_reserved = ND_NA_FLAG_ROUTER |
 283                                 ND_NA_FLAG_SOLICITED;
 284
 285                 struct sockaddr_in6 dest = {AF_INET6, 0, 0, ALL_IPV6_NODES, 0};
 286                 if (!ns_is_dad) // If not DAD, then unicast to source
 287                         dest.sin6_addr = ip6->ip6_src;
 288
 289                 // Linux seems to not honor IPV6_PKTINFO on raw-sockets, so work around
 290                 setsockopt(ping_socket, SOL_SOCKET, SO_BINDTODEVICE,
 291                                         iface->ifname, sizeof(iface->ifname));
 292                 struct iovec iov = {&advert, sizeof(advert)};
 293                 odhcpd_send(ping_socket, &dest, &iov, 1, iface);
 294         } else {
 295                 // Send echo to all other interfaces to see where target is on
 296                 // This will trigger neighbor discovery which is what we want.
 297                 // We will observe the neighbor cache to see results.
 298
 299                 ssize_t sent = 0;
 300                 struct interface *c;
 301                 list_for_each_entry(c, &interfaces, head)
 302                         if (iface->ndp == RELAYD_RELAY && iface != c &&
 303                                         (!ns_is_dad || !c->external == false))
 304                                 sent += ping6(&req->nd_ns_target, c);
 305
 306                 if (sent > 0) // Sent a ping, add pending neighbor entry
 307                         modify_neighbor(&req->nd_ns_target, NULL, true);
 308         }
 309 }
 310
 311
 312 void odhcpd_setup_route(const struct in6_addr *addr, int prefixlen,
 313                 const struct interface *iface, const struct in6_addr *gw, bool add)
 314 {
 315         struct req {
 316                 struct nlmsghdr nh;
 317                 struct rtmsg rtm;
 318                 struct rtattr rta_dst;
 319                 struct in6_addr dst_addr;
 320                 struct rtattr rta_oif;
 321                 uint32_t ifindex;
 322                 struct rtattr rta_table;
 323                 uint32_t table;
 324                 struct rtattr rta_gw;
 325                 struct in6_addr gw;
 326         } req = {
 327                 {sizeof(req), 0, NLM_F_REQUEST, ++rtnl_seqid, 0},
 328                 {AF_INET6, prefixlen, 0, 0, 0, 0, 0, 0, 0},
 329                 {sizeof(struct rtattr) + sizeof(struct in6_addr), RTA_DST},
 330                 *addr,
 331                 {sizeof(struct rtattr) + sizeof(uint32_t), RTA_OIF},
 332                 iface->ifindex,
 333                 {sizeof(struct rtattr) + sizeof(uint32_t), RTA_TABLE},
 334                 RT_TABLE_MAIN,
 335                 {sizeof(struct rtattr) + sizeof(struct in6_addr), RTA_GATEWAY},
 336                 IN6ADDR_ANY_INIT,
 337         };
 338
 339         if (gw)
 340                 req.gw = *gw;
 341
 342         if (add) {
 343                 req.nh.nlmsg_type = RTM_NEWROUTE;
 344                 req.nh.nlmsg_flags |= (NLM_F_CREATE | NLM_F_REPLACE);
 345                 req.rtm.rtm_protocol = RTPROT_BOOT;
 346                 req.rtm.rtm_scope = (gw) ? RT_SCOPE_UNIVERSE : RT_SCOPE_LINK;
 347                 req.rtm.rtm_type = RTN_UNICAST;
 348         } else {
 349                 req.nh.nlmsg_type = RTM_DELROUTE;
 350                 req.rtm.rtm_scope = RT_SCOPE_NOWHERE;
 351         }
 352
 353         size_t reqlen = (gw) ? sizeof(req) : offsetof(struct req, rta_gw);
 354         send(rtnl_event.uloop.fd, &req, reqlen, MSG_DONTWAIT);
 355 }
 356
 357 // Use rtnetlink to modify kernel routes
 358 static void setup_route(struct in6_addr *addr, struct interface *iface,
 359                 bool add)
 360 {
 361         char namebuf[INET6_ADDRSTRLEN];
 362         inet_ntop(AF_INET6, addr, namebuf, sizeof(namebuf));
 363         syslog(LOG_NOTICE, "%s about %s on %s", (add) ? "Learned" : "Forgot",
 364                         namebuf, (iface) ? iface->ifname : "<pending>");
 365
 366         if (!iface || !iface->learn_routes)
 367                 return;
 368
 369         odhcpd_setup_route(addr, 128, iface, NULL, add);
 370 }
 371
 372 static void free_neighbor(struct ndp_neighbor *n)
 373 {
 374         setup_route(&n->addr, n->iface, false);
 375         list_del(&n->head);
 376         free(n);
 377         --neighbor_count;
 378 }
 379
 380 static struct ndp_neighbor* find_neighbor(struct in6_addr *addr, bool strict)
 381 {
 382         time_t now = time(NULL);
 383         struct ndp_neighbor *n, *e;
 384         list_for_each_entry_safe(n, e, &neighbors, head) {
 385                 if ((!strict && !odhcpd_bmemcmp(&n->addr, addr, n->len)) ||
 386                                 (n->len == 128 && IN6_ARE_ADDR_EQUAL(&n->addr, addr)))
 387                         return n;
 388
 389                 if (!n->iface && abs(n->timeout - now) >= 5)
 390                         free_neighbor(n);
 391         }
 392         return NULL;
 393 }
 394
 395
 396 // Modified our own neighbor-entries
 397 static void modify_neighbor(struct in6_addr *addr,
 398                 struct interface *iface, bool add)
 399 {
 400         if (!addr || (void*)addr == (void*)iface)
 401                 return;
 402
 403         struct ndp_neighbor *n = find_neighbor(addr, true);
 404         if (!add) { // Delete action
 405                 if (n && (!n->iface || n->iface == iface))
 406                         free_neighbor(n);
 407         } else if (!n) { // No entry yet, add one if possible
 408                 if (neighbor_count >= NDP_MAX_NEIGHBORS ||
 409                                 !(n = malloc(sizeof(*n))))
 410                         return;
 411
 412                 n->len = 128;
 413                 n->addr = *addr;
 414                 n->iface = iface;
 415                 if (!n->iface)
 416                         time(&n->timeout);
 417                 list_add(&n->head, &neighbors);
 418                 ++neighbor_count;
 419                 setup_route(addr, n->iface, add);
 420         } else if (n->iface == iface) {
 421                 if (!n->iface)
 422                         time(&n->timeout);
 423         } else if (iface && (!n->iface ||
 424                         (!iface->external && n->iface->external))) {
 425                 setup_route(addr, n->iface, false);
 426                 n->iface = iface;
 427                 setup_route(addr, n->iface, add);
 428         }
 429         // TODO: In case a host switches interfaces we might want
 430         // to set its old neighbor entry to NUD_STALE and ping it
 431         // on the old interface to confirm if the MACs match.
 432 }
 433
 434
 435 // Handler for neighbor cache entries from the kernel. This is our source
 436 // to learn and unlearn hosts on interfaces.
 437 static void handle_rtnetlink(_unused void *addr, void *data, size_t len,
 438                 _unused struct interface *iface)
 439 {
 440         for (struct nlmsghdr *nh = data; NLMSG_OK(nh, len);
 441                         nh = NLMSG_NEXT(nh, len)) {
 442                 struct rtmsg *rtm = NLMSG_DATA(nh);
 443                 if ((nh->nlmsg_type == RTM_NEWROUTE ||
 444                                 nh->nlmsg_type == RTM_DELROUTE) &&
 445                                 rtm->rtm_dst_len == 0)
 446                         raise(SIGUSR1); // Inform about a change in default route
 447
 448                 struct ndmsg *ndm = NLMSG_DATA(nh);
 449                 struct ifaddrmsg *ifa = NLMSG_DATA(nh);
 450                 if (nh->nlmsg_type != RTM_NEWNEIGH
 451                                 && nh->nlmsg_type != RTM_DELNEIGH
 452                                 && nh->nlmsg_type != RTM_NEWADDR
 453                                 && nh->nlmsg_type != RTM_DELADDR)
 454                         continue; // Unrelated message type
 455                 bool is_addr = (nh->nlmsg_type == RTM_NEWADDR
 456                                 || nh->nlmsg_type == RTM_DELADDR);
 457
 458                 // Family and ifindex are on the same offset for NEIGH and ADDR
 459                 if (NLMSG_PAYLOAD(nh, 0) < sizeof(*ndm)
 460                                 || ndm->ndm_family != AF_INET6)
 461                         continue; //
 462
 463                 // Lookup interface
 464                 struct interface *iface;
 465                 if (!(iface = odhcpd_get_interface_by_index(ndm->ndm_ifindex)))
 466                         continue;
 467
 468                 // Data to retrieve
 469                 size_t rta_offset = (is_addr) ? sizeof(*ifa) : sizeof(*ndm);
 470                 uint16_t atype = (is_addr) ? IFA_ADDRESS : NDA_DST;
 471                 ssize_t alen = NLMSG_PAYLOAD(nh, rta_offset);
 472                 struct in6_addr *addr = NULL;
 473
 474                 for (struct rtattr *rta = (void*)(((uint8_t*)ndm) + rta_offset);
 475                                 RTA_OK(rta, alen); rta = RTA_NEXT(rta, alen))
 476                         if (rta->rta_type == atype &&
 477                                         RTA_PAYLOAD(rta) >= sizeof(*addr))
 478                                 addr = RTA_DATA(rta);
 479
 480                 // Address not specified or unrelated
 481                 if (!addr || IN6_IS_ADDR_LINKLOCAL(addr) ||
 482                                 IN6_IS_ADDR_MULTICAST(addr))
 483                         continue;
 484
 485                 // Check for states
 486                 bool add;
 487                 if (is_addr)
 488                         add = (nh->nlmsg_type == RTM_NEWADDR);
 489                 else
 490                         add = (nh->nlmsg_type == RTM_NEWNEIGH && (ndm->ndm_state &
 491                                 (NUD_REACHABLE | NUD_STALE | NUD_DELAY | NUD_PROBE
 492                                                 | NUD_PERMANENT | NUD_NOARP)));
 493
 494                 if (iface->ndp == RELAYD_RELAY)
 495                         modify_neighbor(addr, iface, add);
 496
 497                 if (is_addr && iface->ra == RELAYD_SERVER)
 498                         raise(SIGUSR1); // Inform about a change in addresses
 499
 500                 if (is_addr && iface->dhcpv6 == RELAYD_SERVER)
 501                         iface->ia_reconf = true;
 502
 503                 if (iface->ndp == RELAYD_RELAY && is_addr && iface->master) {
 504                         // Replay address changes on all slave interfaces
 505                         nh->nlmsg_flags = NLM_F_REQUEST;
 506
 507                         if (nh->nlmsg_type == RTM_NEWADDR)
 508                                 nh->nlmsg_flags |= NLM_F_CREATE | NLM_F_REPLACE;
 509
 510                         struct interface *c;
 511                         list_for_each_entry(c, &interfaces, head) {
 512                                 if (c->ndp == RELAYD_RELAY && !c->master) {
 513                                         ifa->ifa_index = c->ifindex;
 514                                         send(rtnl_event.uloop.fd, nh, nh->nlmsg_len, MSG_DONTWAIT);
 515                                 }
 516                         }
 517                 }
 518
 519                 /* TODO: See if this is required for optimal operation
 520                 // Keep neighbor entries alive so we don't loose routes
 521                  */
 522                 if (add && (ndm->ndm_state & NUD_STALE))
 523                         ping6(addr, iface);
 524         }
 525 }