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 <fcntl.h>
  21 #include <unistd.h>
  22 #include <arpa/inet.h>
  23 #include <sys/socket.h>
  24 #include <net/ethernet.h>
  25 #include <netinet/ip6.h>
  26 #include <netinet/icmp6.h>
  27 #include <netpacket/packet.h>
  28
  29 #include <linux/rtnetlink.h>
  30 #include <linux/filter.h>
  31
  32 #include <netlink/msg.h>
  33 #include <netlink/socket.h>
  34 #include <netlink/attr.h>
  35
  36 #include "dhcpv6.h"
  37 #include "odhcpd.h"
  38
  39 struct event_socket {
  40         struct odhcpd_event ev;
  41         struct nl_sock *sock;
  42         int sock_bufsize;
  43 };
  44
  45 static void handle_solicit(void *addr, void *data, size_t len,
  46                 struct interface *iface, void *dest);
  47 static void handle_rtnl_event(struct odhcpd_event *ev);
  48 static int cb_rtnl_valid(struct nl_msg *msg, void *arg);
  49 static void catch_rtnl_err(struct odhcpd_event *e, int error);
  50
  51 static int ping_socket = -1;
  52 static struct event_socket rtnl_event = {
  53         .ev = {
  54                 .uloop = {.fd = - 1, },
  55                 .handle_dgram = NULL,
  56                 .handle_error = catch_rtnl_err,
  57                 .recv_msgs = handle_rtnl_event,
  58         },
  59         .sock = NULL,
  60         .sock_bufsize = 133120,
  61 };
  62
  63 // Filter ICMPv6 messages of type neighbor soliciation
  64 static struct sock_filter bpf[] = {
  65         BPF_STMT(BPF_LD | BPF_B | BPF_ABS, offsetof(struct ip6_hdr, ip6_nxt)),
  66         BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, IPPROTO_ICMPV6, 0, 3),
  67         BPF_STMT(BPF_LD | BPF_B | BPF_ABS, sizeof(struct ip6_hdr) +
  68                         offsetof(struct icmp6_hdr, icmp6_type)),
  69         BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, ND_NEIGHBOR_SOLICIT, 0, 1),
  70         BPF_STMT(BPF_RET | BPF_K, 0xffffffff),
  71         BPF_STMT(BPF_RET | BPF_K, 0),
  72 };
  73 static const struct sock_fprog bpf_prog = {sizeof(bpf) / sizeof(*bpf), bpf};
  74
  75
  76 // Initialize NDP-proxy
  77 int init_ndp(void)
  78 {
  79         int val = 2;
  80
  81         rtnl_event.sock = odhcpd_create_nl_socket(NETLINK_ROUTE);
  82         if (!rtnl_event.sock)
  83                 goto err;
  84
  85         rtnl_event.ev.uloop.fd = nl_socket_get_fd(rtnl_event.sock);
  86
  87         if (nl_socket_set_buffer_size(rtnl_event.sock, rtnl_event.sock_bufsize, 0))
  88                 goto err;
  89
  90         nl_socket_disable_seq_check(rtnl_event.sock);
  91
  92         nl_socket_modify_cb(rtnl_event.sock, NL_CB_VALID, NL_CB_CUSTOM,
  93                         cb_rtnl_valid, NULL);
  94
  95         // Receive IPv4 address, IPv6 address, IPv6 routes and neighbor events
  96         if (nl_socket_add_memberships(rtnl_event.sock, RTNLGRP_IPV4_IFADDR,
  97                                 RTNLGRP_IPV6_IFADDR, RTNLGRP_IPV6_ROUTE,
  98                                 RTNLGRP_NEIGH, 0))
  99                 goto err;
 100
 101         odhcpd_register(&rtnl_event.ev);
 102
 103         // Open ICMPv6 socket
 104         ping_socket = socket(AF_INET6, SOCK_RAW | SOCK_CLOEXEC, IPPROTO_ICMPV6);
 105         if (ping_socket < 0) {
 106                 syslog(LOG_ERR, "Unable to open raw socket: %s", strerror(errno));
 107                         return -1;
 108         }
 109
 110         setsockopt(ping_socket, IPPROTO_RAW, IPV6_CHECKSUM, &val, sizeof(val));
 111
 112         // This is required by RFC 4861
 113         val = 255;
 114         setsockopt(ping_socket, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &val, sizeof(val));
 115         setsockopt(ping_socket, IPPROTO_IPV6, IPV6_UNICAST_HOPS, &val, sizeof(val));
 116
 117         // Filter all packages, we only want to send
 118         struct icmp6_filter filt;
 119         ICMP6_FILTER_SETBLOCKALL(&filt);
 120         setsockopt(ping_socket, IPPROTO_ICMPV6, ICMP6_FILTER, &filt, sizeof(filt));
 121
 122         return 0;
 123
 124 err:
 125         if (rtnl_event.sock) {
 126                 nl_socket_free(rtnl_event.sock);
 127                 rtnl_event.sock = NULL;
 128                 rtnl_event.ev.uloop.fd = -1;
 129         }
 130
 131         return -1;
 132 }
 133
 134 static void dump_neigh_table(const bool proxy)
 135 {
 136         struct nl_msg *msg;
 137         struct ndmsg ndm = {
 138                 .ndm_family = AF_INET6,
 139                 .ndm_flags = proxy ? NTF_PROXY : 0,
 140         };
 141
 142         msg = nlmsg_alloc_simple(RTM_GETNEIGH, NLM_F_REQUEST | NLM_F_DUMP);
 143         if (!msg)
 144                 return;
 145
 146         nlmsg_append(msg, &ndm, sizeof(ndm), 0);
 147
 148         nl_send_auto_complete(rtnl_event.sock, msg);
 149
 150         nlmsg_free(msg);
 151 }
 152
 153 static void dump_addr_table(bool v6)
 154 {
 155         struct nl_msg *msg;
 156         struct ifaddrmsg ifa = {
 157                 .ifa_family = v6 ? AF_INET6 : AF_INET,
 158         };
 159
 160         msg = nlmsg_alloc_simple(RTM_GETADDR, NLM_F_REQUEST | NLM_F_DUMP);
 161         if (!msg)
 162                 return;
 163
 164         nlmsg_append(msg, &ifa, sizeof(ifa), 0);
 165
 166         nl_send_auto_complete(rtnl_event.sock, msg);
 167
 168         nlmsg_free(msg);
 169 }
 170
 171 int setup_ndp_interface(struct interface *iface, bool enable)
 172 {
 173         int ret = 0, procfd;
 174         bool dump_neigh = false;
 175         char procbuf[64];
 176
 177         snprintf(procbuf, sizeof(procbuf), "/proc/sys/net/ipv6/conf/%s/proxy_ndp", iface->ifname);
 178         procfd = open(procbuf, O_WRONLY);
 179
 180         if (procfd < 0) {
 181                 ret = -1;
 182                 goto out;
 183         }
 184
 185         if (iface->ndp_event.uloop.fd > 0) {
 186                 uloop_fd_delete(&iface->ndp_event.uloop);
 187                 close(iface->ndp_event.uloop.fd);
 188                 iface->ndp_event.uloop.fd = -1;
 189
 190                 if (!enable || iface->ndp != RELAYD_RELAY)
 191                         if (write(procfd, "0\n", 2) < 0) {}
 192
 193                 dump_neigh = true;
 194         }
 195
 196         if (enable && iface->ndp == RELAYD_RELAY) {
 197                 if (write(procfd, "1\n", 2) < 0) {}
 198
 199                 int sock = socket(AF_PACKET, SOCK_DGRAM | SOCK_CLOEXEC, htons(ETH_P_IPV6));
 200                 if (sock < 0) {
 201                         syslog(LOG_ERR, "Unable to open packet socket: %s",
 202                                         strerror(errno));
 203                         ret = -1;
 204                         goto out;
 205                 }
 206
 207 #ifdef PACKET_RECV_TYPE
 208                 int pktt = 1 << PACKET_MULTICAST;
 209                 setsockopt(sock, SOL_PACKET, PACKET_RECV_TYPE, &pktt, sizeof(pktt));
 210 #endif
 211
 212                 if (setsockopt(sock, SOL_SOCKET, SO_ATTACH_FILTER,
 213                                 &bpf_prog, sizeof(bpf_prog))) {
 214                         syslog(LOG_ERR, "Failed to set BPF: %s", strerror(errno));
 215                         ret = -1;
 216                         goto out;
 217                 }
 218
 219                 struct sockaddr_ll ll = {
 220                         .sll_family = AF_PACKET,
 221                         .sll_ifindex = iface->ifindex,
 222                         .sll_protocol = htons(ETH_P_IPV6),
 223                         .sll_hatype = 0,
 224                         .sll_pkttype = 0,
 225                         .sll_halen = 0,
 226                         .sll_addr = {0},
 227                 };
 228                 bind(sock, (struct sockaddr*)&ll, sizeof(ll));
 229
 230                 struct packet_mreq mreq = {iface->ifindex, PACKET_MR_ALLMULTI, ETH_ALEN, {0}};
 231                 setsockopt(sock, SOL_PACKET, PACKET_ADD_MEMBERSHIP, &mreq, sizeof(mreq));
 232
 233                 iface->ndp_event.uloop.fd = sock;
 234                 iface->ndp_event.handle_dgram = handle_solicit;
 235                 odhcpd_register(&iface->ndp_event);
 236
 237                 // If we already were enabled dump is unnecessary, if not do dump
 238                 if (!dump_neigh)
 239                         dump_neigh_table(false);
 240                 else
 241                         dump_neigh = false;
 242         }
 243
 244         if (dump_neigh)
 245                 dump_neigh_table(true);
 246
 247 out:
 248         if (procfd >= 0)
 249                 close(procfd);
 250
 251         return ret;
 252 }
 253
 254
 255 // Send an ICMP-ECHO. This is less for actually pinging but for the
 256 // neighbor cache to be kept up-to-date.
 257 static void ping6(struct in6_addr *addr,
 258                 const struct interface *iface)
 259 {
 260         struct sockaddr_in6 dest = { .sin6_family = AF_INET6, .sin6_addr = *addr, .sin6_scope_id = iface->ifindex, };
 261         struct icmp6_hdr echo = { .icmp6_type = ICMP6_ECHO_REQUEST };
 262         struct iovec iov = { .iov_base = &echo, .iov_len = sizeof(echo) };
 263         char ipbuf[INET6_ADDRSTRLEN];
 264
 265         inet_ntop(AF_INET6, addr, ipbuf, sizeof(ipbuf));
 266         syslog(LOG_NOTICE, "Pinging for %s%%%s", ipbuf, iface->ifname);
 267
 268         odhcpd_setup_route(addr, 128, iface, NULL, 128, true);
 269         odhcpd_send(ping_socket, &dest, &iov, 1, iface);
 270         odhcpd_setup_route(addr, 128, iface, NULL, 128, false);
 271 }
 272
 273 // Handle solicitations
 274 static void handle_solicit(void *addr, void *data, size_t len,
 275                 struct interface *iface, _unused void *dest)
 276 {
 277         struct ip6_hdr *ip6 = data;
 278         struct nd_neighbor_solicit *req = (struct nd_neighbor_solicit*)&ip6[1];
 279         struct sockaddr_ll *ll = addr;
 280         char ipbuf[INET6_ADDRSTRLEN];
 281         uint8_t mac[6];
 282
 283         // Solicitation is for duplicate address detection
 284         bool ns_is_dad = IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src);
 285
 286         // Don't process solicit messages on non relay interfaces
 287         // Don't forward any non-DAD solicitation for external ifaces
 288         // TODO: check if we should even forward DADs for them
 289         if (iface->ndp != RELAYD_RELAY || (iface->external && !ns_is_dad))
 290                 return;
 291
 292         if (len < sizeof(*ip6) + sizeof(*req))
 293                 return; // Invalid reqicitation
 294
 295         if (IN6_IS_ADDR_LINKLOCAL(&req->nd_ns_target) ||
 296                         IN6_IS_ADDR_LOOPBACK(&req->nd_ns_target) ||
 297                         IN6_IS_ADDR_MULTICAST(&req->nd_ns_target))
 298                 return; // Invalid target
 299
 300         inet_ntop(AF_INET6, &req->nd_ns_target, ipbuf, sizeof(ipbuf));
 301         syslog(LOG_DEBUG, "Got a NS for %s%%%s", ipbuf, iface->ifname);
 302
 303         odhcpd_get_mac(iface, mac);
 304         if (!memcmp(ll->sll_addr, mac, sizeof(mac)))
 305                 return; // Looped back
 306
 307         struct interface *c;
 308         list_for_each_entry(c, &interfaces, head)
 309                 if (iface != c && c->ndp == RELAYD_RELAY &&
 310                                 (ns_is_dad || !c->external))
 311                         ping6(&req->nd_ns_target, c);
 312 }
 313
 314 // Use rtnetlink to modify kernel routes
 315 static void setup_route(struct in6_addr *addr, struct interface *iface, bool add)
 316 {
 317         char ipbuf[INET6_ADDRSTRLEN];
 318
 319         inet_ntop(AF_INET6, addr, ipbuf, sizeof(ipbuf));
 320         syslog(LOG_NOTICE, "%s about %s%%%s",
 321                         (add) ? "Learned" : "Forgot", ipbuf, iface->ifname);
 322
 323         if (iface->learn_routes)
 324                 odhcpd_setup_route(addr, 128, iface, NULL, 1024, add);
 325 }
 326
 327 // Check address update
 328 static void check_addr_updates(struct interface *iface)
 329 {
 330         struct odhcpd_ipaddr *addr = NULL;
 331         ssize_t len = odhcpd_get_interface_addresses(iface->ifindex, false, &addr);
 332
 333         if (len < 0)
 334                 return;
 335
 336         bool change = len != (ssize_t)iface->addr4_len;
 337         for (ssize_t i = 0; !change && i < len; ++i)
 338                 if (addr[i].addr.in.s_addr != iface->addr4[i].addr.in.s_addr)
 339                         change = true;
 340
 341         free(iface->addr4);
 342         iface->addr4 = addr;
 343         iface->addr4_len = len;
 344 }
 345
 346 // Check v6 address update
 347 static void check_addr6_updates(struct interface *iface)
 348 {
 349         struct odhcpd_ipaddr *addr = NULL;
 350         ssize_t len = odhcpd_get_interface_addresses(iface->ifindex, true, &addr);
 351
 352         if (len < 0)
 353                 return;
 354
 355         bool change = len != (ssize_t)iface->ia_addr_len;
 356         for (ssize_t i = 0; !change && i < len; ++i)
 357                 if (!IN6_ARE_ADDR_EQUAL(&addr[i].addr.in6, &iface->ia_addr[i].addr.in6) ||
 358                                 (addr[i].preferred > 0) != (iface->ia_addr[i].preferred > 0) ||
 359                                 addr[i].valid < iface->ia_addr[i].valid ||
 360                                 addr[i].preferred < iface->ia_addr[i].preferred)
 361                         change = true;
 362
 363         if (change)
 364                 dhcpv6_ia_preupdate(iface);
 365
 366         free(iface->ia_addr);
 367         iface->ia_addr = addr;
 368         iface->ia_addr_len = len;
 369
 370         if (change) {
 371                 dhcpv6_ia_postupdate(iface);
 372                 syslog(LOG_INFO, "Raising SIGUSR1 due to address change on %s", iface->ifname);
 373                 raise(SIGUSR1);
 374         }
 375 }
 376
 377 static void setup_addr_for_relaying(struct in6_addr *addr, struct interface *iface, bool add)
 378 {
 379         struct interface *c;
 380         char ipbuf[INET6_ADDRSTRLEN];
 381
 382         inet_ntop(AF_INET6, addr, ipbuf, sizeof(ipbuf));
 383
 384         list_for_each_entry(c, &interfaces, head) {
 385                 if (iface == c || (c->ndp != RELAYD_RELAY && !add))
 386                         continue;
 387
 388                 bool neigh_add = (c->ndp == RELAYD_RELAY ? add : false);
 389
 390                 if (odhcpd_setup_proxy_neigh(addr, c, neigh_add))
 391                         syslog(LOG_DEBUG, "Failed to %s proxy neighbour entry %s%%%s",
 392                                 neigh_add ? "add" : "delete", ipbuf, c->ifname);
 393                 else
 394                         syslog(LOG_DEBUG, "%s proxy neighbour entry %s%%%s",
 395                                 neigh_add ? "Added" : "Deleted", ipbuf, c->ifname);
 396         }
 397 }
 398
 399 static void handle_rtnl_event(struct odhcpd_event *e)
 400 {
 401         struct event_socket *ev_sock = container_of(e, struct event_socket, ev);
 402
 403         nl_recvmsgs_default(ev_sock->sock);
 404 }
 405
 406
 407 // Handler for neighbor cache entries from the kernel. This is our source
 408 // to learn and unlearn hosts on interfaces.
 409 static int cb_rtnl_valid(struct nl_msg *msg, _unused void *arg)
 410 {
 411         struct nlmsghdr *hdr = nlmsg_hdr(msg);
 412         struct in6_addr *addr6 = NULL;
 413         struct interface *iface = NULL;
 414         bool add = false;
 415         char ipbuf[INET6_ADDRSTRLEN];
 416
 417         switch (hdr->nlmsg_type) {
 418         case RTM_NEWROUTE:
 419         case RTM_DELROUTE: {
 420                 struct rtmsg *rtm = nlmsg_data(hdr);
 421
 422                 if (!nlmsg_valid_hdr(hdr, sizeof(*rtm)) ||
 423                                 rtm->rtm_family != AF_INET6)
 424                         return NL_SKIP;
 425
 426                 if (rtm->rtm_dst_len == 0) {
 427                         syslog(LOG_INFO, "Raising SIGUSR1 due to default route change");
 428                         raise(SIGUSR1);
 429                 }
 430                 return NL_OK;
 431         }
 432
 433         case RTM_NEWADDR:
 434                 add = true;
 435                 /* fall through */
 436         case RTM_DELADDR: {
 437                 struct ifaddrmsg *ifa = nlmsg_data(hdr);
 438                 struct nlattr *nla[__IFA_MAX];
 439
 440                 if (!nlmsg_valid_hdr(hdr, sizeof(*ifa)) ||
 441                                 (ifa->ifa_family != AF_INET6 &&
 442                                  ifa->ifa_family != AF_INET))
 443                         return NL_SKIP;
 444
 445                 iface = odhcpd_get_interface_by_index(ifa->ifa_index);
 446                 if (!iface)
 447                         return NL_SKIP;
 448
 449                 nlmsg_parse(hdr, sizeof(*ifa), nla, __IFA_MAX - 1, NULL);
 450
 451                 if (ifa->ifa_family == AF_INET6) {
 452                         if (!nla[IFA_ADDRESS])
 453                                 return NL_SKIP;
 454
 455                         addr6 = nla_data(nla[IFA_ADDRESS]);
 456                         if (!addr6 || IN6_IS_ADDR_LINKLOCAL(addr6) ||
 457                                         IN6_IS_ADDR_MULTICAST(addr6))
 458                                 return NL_SKIP;
 459
 460                         inet_ntop(AF_INET6, addr6, ipbuf, sizeof(ipbuf));
 461                         syslog(LOG_DEBUG, "Netlink %s %s%%%s", add ? "newaddr" : "deladdr",
 462                                 ipbuf, iface->ifname);
 463
 464                         check_addr6_updates(iface);
 465
 466                         if (iface->ndp != RELAYD_RELAY)
 467                                 break;
 468
 469                         /* handle the relay logic below */
 470                         setup_addr_for_relaying(addr6, iface, add);
 471
 472                         if (!add)
 473                                 dump_neigh_table(false);
 474                 } else {
 475                         if (!nla[IFA_LOCAL])
 476                                 return NL_SKIP;
 477
 478                         struct in_addr *addr = nla_data(nla[IFA_ADDRESS]);
 479
 480                         inet_ntop(AF_INET, addr, ipbuf, sizeof(ipbuf));
 481                         syslog(LOG_DEBUG, "Netlink %s %s%%%s", add ? "newaddr" : "deladdr",
 482                                 ipbuf, iface->ifname);
 483
 484                         check_addr_updates(iface);
 485                 }
 486                 break;
 487         }
 488
 489         case RTM_NEWNEIGH:
 490                 add = true;
 491                 /* fall through */
 492         case RTM_DELNEIGH: {
 493                 struct ndmsg *ndm = nlmsg_data(hdr);
 494                 struct nlattr *nla[__NDA_MAX];
 495
 496                 if (!nlmsg_valid_hdr(hdr, sizeof(*ndm)) ||
 497                                 ndm->ndm_family != AF_INET6)
 498                         return NL_SKIP;
 499
 500                 iface = odhcpd_get_interface_by_index(ndm->ndm_ifindex);
 501                 if (!iface || iface->ndp != RELAYD_RELAY)
 502                         return (iface ? NL_OK : NL_SKIP);
 503
 504                 nlmsg_parse(hdr, sizeof(*ndm), nla, __NDA_MAX - 1, NULL);
 505                 if (!nla[NDA_DST])
 506                         return NL_SKIP;
 507
 508                 addr6 = nla_data(nla[NDA_DST]);
 509                 if (!addr6 || IN6_IS_ADDR_LINKLOCAL(addr6) ||
 510                                 IN6_IS_ADDR_MULTICAST(addr6))
 511                         return NL_SKIP;
 512
 513                 inet_ntop(AF_INET6, addr6, ipbuf, sizeof(ipbuf));
 514                 syslog(LOG_DEBUG, "Netlink %s %s%%%s", true ? "newneigh" : "delneigh",
 515                         ipbuf, iface->ifname);
 516
 517                 if (ndm->ndm_flags & NTF_PROXY) {
 518                         /* Dump and flush proxy entries */
 519                         if (hdr->nlmsg_type == RTM_NEWNEIGH) {
 520                                 odhcpd_setup_proxy_neigh(addr6, iface, false);
 521                                 setup_route(addr6, iface, false);
 522                                 dump_neigh_table(false);
 523                         }
 524
 525                         return NL_OK;
 526                 }
 527
 528                 if (add && !(ndm->ndm_state &
 529                                 (NUD_REACHABLE | NUD_STALE | NUD_DELAY | NUD_PROBE |
 530                                  NUD_PERMANENT | NUD_NOARP)))
 531                         return NL_OK;
 532
 533                 setup_addr_for_relaying(addr6, iface, add);
 534                 setup_route(addr6, iface, add);
 535
 536                 if (!add)
 537                         dump_neigh_table(false);
 538                 break;
 539         }
 540
 541         default:
 542                 return NL_SKIP;
 543         }
 544
 545         return NL_OK;
 546 }
 547
 548 static void catch_rtnl_err(struct odhcpd_event *e, int error)
 549 {
 550         struct event_socket *ev_sock = container_of(e, struct event_socket, ev);
 551
 552         if (error != ENOBUFS)
 553                 goto err;
 554
 555         /* Double netlink event buffer size */
 556         ev_sock->sock_bufsize *= 2;
 557
 558         if (nl_socket_set_buffer_size(ev_sock->sock, ev_sock->sock_bufsize, 0))
 559                 goto err;
 560
 561         dump_addr_table(true);
 562         return;
 563
 564 err:
 565         odhcpd_deregister(e);
 566 }