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 "router.h"
  37 #include "dhcpv6.h"
  38 #include "ndp.h"
  39
  40 struct event_socket {
  41         struct odhcpd_event ev;
  42         struct nl_sock *sock;
  43         int sock_bufsize;
  44 };
  45
  46 static void handle_solicit(void *addr, void *data, size_t len,
  47                 struct interface *iface, void *dest);
  48 static void handle_rtnl_event(struct odhcpd_event *ev);
  49 static int cb_rtnl_valid(struct nl_msg *msg, void *arg);
  50 static void catch_rtnl_err(struct odhcpd_event *e, int error);
  51
  52 static int ping_socket = -1;
  53 static struct event_socket rtnl_event = {
  54         .ev = {
  55                 .uloop = {.fd = - 1, },
  56                 .handle_dgram = NULL,
  57                 .handle_error = catch_rtnl_err,
  58                 .recv_msgs = handle_rtnl_event,
  59         },
  60         .sock = NULL,
  61         .sock_bufsize = 133120,
  62 };
  63
  64 // Filter ICMPv6 messages of type neighbor soliciation
  65 static struct sock_filter bpf[] = {
  66         BPF_STMT(BPF_LD | BPF_B | BPF_ABS, offsetof(struct ip6_hdr, ip6_nxt)),
  67         BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, IPPROTO_ICMPV6, 0, 3),
  68         BPF_STMT(BPF_LD | BPF_B | BPF_ABS, sizeof(struct ip6_hdr) +
  69                         offsetof(struct icmp6_hdr, icmp6_type)),
  70         BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, ND_NEIGHBOR_SOLICIT, 0, 1),
  71         BPF_STMT(BPF_RET | BPF_K, 0xffffffff),
  72         BPF_STMT(BPF_RET | BPF_K, 0),
  73 };
  74 static const struct sock_fprog bpf_prog = {sizeof(bpf) / sizeof(*bpf), bpf};
  75
  76
  77 // Initialize NDP-proxy
  78 int init_ndp(void)
  79 {
  80         int val = 2;
  81
  82         rtnl_event.sock = odhcpd_create_nl_socket(NETLINK_ROUTE);
  83         if (!rtnl_event.sock)
  84                 goto err;
  85
  86         rtnl_event.ev.uloop.fd = nl_socket_get_fd(rtnl_event.sock);
  87
  88         if (nl_socket_set_buffer_size(rtnl_event.sock, rtnl_event.sock_bufsize, 0))
  89                 goto err;
  90
  91         nl_socket_disable_seq_check(rtnl_event.sock);
  92
  93         nl_socket_modify_cb(rtnl_event.sock, NL_CB_VALID, NL_CB_CUSTOM,
  94                         cb_rtnl_valid, NULL);
  95
  96         // Receive IPv6 address, IPv6 routes and neighbor events
  97         if (nl_socket_add_memberships(rtnl_event.sock, RTNLGRP_IPV6_IFADDR,
  98                                 RTNLGRP_IPV6_ROUTE, 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(void)
 154 {
 155         struct nl_msg *msg;
 156         struct ifaddrmsg ifa = {
 157                 .ifa_family = AF_INET6,
 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->ra == RELAYD_SERVER ||
 197                         iface->dhcpv6 == RELAYD_SERVER || iface->ndp == RELAYD_RELAY))
 198                 dump_addr_table();
 199
 200         if (enable && iface->ndp == RELAYD_RELAY) {
 201                 if (write(procfd, "1\n", 2) < 0) {}
 202
 203                 int sock = socket(AF_PACKET, SOCK_DGRAM | SOCK_CLOEXEC, htons(ETH_P_IPV6));
 204                 if (sock < 0) {
 205                         syslog(LOG_ERR, "Unable to open packet socket: %s",
 206                                         strerror(errno));
 207                         ret = -1;
 208                         goto out;
 209                 }
 210
 211 #ifdef PACKET_RECV_TYPE
 212                 int pktt = 1 << PACKET_MULTICAST;
 213                 setsockopt(sock, SOL_PACKET, PACKET_RECV_TYPE, &pktt, sizeof(pktt));
 214 #endif
 215
 216                 if (setsockopt(sock, SOL_SOCKET, SO_ATTACH_FILTER,
 217                                 &bpf_prog, sizeof(bpf_prog))) {
 218                         syslog(LOG_ERR, "Failed to set BPF: %s", strerror(errno));
 219                         ret = -1;
 220                         goto out;
 221                 }
 222
 223                 struct sockaddr_ll ll = {
 224                         .sll_family = AF_PACKET,
 225                         .sll_ifindex = iface->ifindex,
 226                         .sll_protocol = htons(ETH_P_IPV6),
 227                         .sll_hatype = 0,
 228                         .sll_pkttype = 0,
 229                         .sll_halen = 0,
 230                         .sll_addr = {0},
 231                 };
 232                 bind(sock, (struct sockaddr*)&ll, sizeof(ll));
 233
 234                 struct packet_mreq mreq = {iface->ifindex, PACKET_MR_ALLMULTI, ETH_ALEN, {0}};
 235                 setsockopt(sock, SOL_PACKET, PACKET_ADD_MEMBERSHIP, &mreq, sizeof(mreq));
 236
 237                 iface->ndp_event.uloop.fd = sock;
 238                 iface->ndp_event.handle_dgram = handle_solicit;
 239                 odhcpd_register(&iface->ndp_event);
 240
 241                 // If we already were enabled dump is unnecessary, if not do dump
 242                 if (!dump_neigh)
 243                         dump_neigh_table(false);
 244                 else
 245                         dump_neigh = false;
 246         }
 247
 248         if (dump_neigh)
 249                 dump_neigh_table(true);
 250
 251 out:
 252         if (procfd >= 0)
 253                 close(procfd);
 254
 255         return ret;
 256 }
 257
 258
 259 // Send an ICMP-ECHO. This is less for actually pinging but for the
 260 // neighbor cache to be kept up-to-date.
 261 static void ping6(struct in6_addr *addr,
 262                 const struct interface *iface)
 263 {
 264         struct sockaddr_in6 dest = { .sin6_family = AF_INET6, .sin6_addr = *addr, .sin6_scope_id = iface->ifindex, };
 265         struct icmp6_hdr echo = { .icmp6_type = ICMP6_ECHO_REQUEST };
 266         struct iovec iov = { .iov_base = &echo, .iov_len = sizeof(echo) };
 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
 274 // Handle solicitations
 275 static void handle_solicit(void *addr, void *data, size_t len,
 276                 struct interface *iface, _unused void *dest)
 277 {
 278         struct ip6_hdr *ip6 = data;
 279         struct nd_neighbor_solicit *req = (struct nd_neighbor_solicit*)&ip6[1];
 280         struct sockaddr_ll *ll = addr;
 281
 282         // Solicitation is for duplicate address detection
 283         bool ns_is_dad = IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src);
 284
 285         // Don't process solicit messages on non relay interfaces
 286         // Don't forward any non-DAD solicitation for external ifaces
 287         // TODO: check if we should even forward DADs for them
 288         if (iface->ndp != RELAYD_RELAY || (iface->external && !ns_is_dad))
 289                 return;
 290
 291         if (len < sizeof(*ip6) + sizeof(*req))
 292                 return; // Invalid reqicitation
 293
 294         if (IN6_IS_ADDR_LINKLOCAL(&req->nd_ns_target) ||
 295                         IN6_IS_ADDR_LOOPBACK(&req->nd_ns_target) ||
 296                         IN6_IS_ADDR_MULTICAST(&req->nd_ns_target))
 297                 return; // Invalid target
 298
 299         char ipbuf[INET6_ADDRSTRLEN];
 300         inet_ntop(AF_INET6, &req->nd_ns_target, ipbuf, sizeof(ipbuf));
 301         syslog(LOG_DEBUG, "Got a NS for %s", ipbuf);
 302
 303         uint8_t mac[6];
 304         odhcpd_get_mac(iface, mac);
 305         if (!memcmp(ll->sll_addr, mac, sizeof(mac)))
 306                 return; // Looped back
 307
 308         struct interface *c;
 309         list_for_each_entry(c, &interfaces, head)
 310                 if (iface != c && c->ndp == RELAYD_RELAY &&
 311                                 (ns_is_dad || !c->external))
 312                         ping6(&req->nd_ns_target, c);
 313 }
 314
 315 // Use rtnetlink to modify kernel routes
 316 static void setup_route(struct in6_addr *addr, struct interface *iface, bool add)
 317 {
 318         char namebuf[INET6_ADDRSTRLEN];
 319         inet_ntop(AF_INET6, addr, namebuf, sizeof(namebuf));
 320         syslog(LOG_NOTICE, "%s about %s on %s",
 321                         (add) ? "Learned" : "Forgot", namebuf, iface->ifname);
 322
 323         if (iface->learn_routes)
 324                 odhcpd_setup_route(addr, 128, iface, NULL, 1024, add);
 325 }
 326
 327 // compare prefixes
 328 static int prefixcmp(const void *va, const void *vb)
 329 {
 330         const struct odhcpd_ipaddr *a = va, *b = vb;
 331         uint32_t a_pref = ((a->addr.s6_addr[0] & 0xfe) != 0xfc) ? a->preferred : 1;
 332         uint32_t b_pref = ((b->addr.s6_addr[0] & 0xfe) != 0xfc) ? b->preferred : 1;
 333         return (a_pref < b_pref) ? 1 : (a_pref > b_pref) ? -1 : 0;
 334 }
 335
 336 // Check address update
 337 static void check_addr_updates(struct interface *iface)
 338 {
 339         struct odhcpd_ipaddr addr[RELAYD_MAX_ADDRS] = {{IN6ADDR_ANY_INIT, 0, 0, 0, 0}};
 340         time_t now = odhcpd_time();
 341         ssize_t len = odhcpd_get_interface_addresses(iface->ifindex, addr, ARRAY_SIZE(addr));
 342
 343         if (len < 0)
 344                 return;
 345
 346         qsort(addr, len, sizeof(*addr), prefixcmp);
 347
 348         for (int i = 0; i < len; ++i) {
 349                 addr[i].addr.s6_addr32[3] = 0;
 350
 351                 if (addr[i].preferred < UINT32_MAX - now)
 352                         addr[i].preferred += now;
 353
 354                 if (addr[i].valid < UINT32_MAX - now)
 355                         addr[i].valid += now;
 356         }
 357
 358         bool change = len != (ssize_t)iface->ia_addr_len;
 359         for (ssize_t i = 0; !change && i < len; ++i)
 360                 if (!IN6_ARE_ADDR_EQUAL(&addr[i].addr, &iface->ia_addr[i].addr) ||
 361                                 (addr[i].preferred > 0) != (iface->ia_addr[i].preferred > 0) ||
 362                                 addr[i].valid < iface->ia_addr[i].valid ||
 363                                 addr[i].preferred < iface->ia_addr[i].preferred)
 364                         change = true;
 365
 366         if (change)
 367                 dhcpv6_ia_preupdate(iface);
 368
 369         memcpy(iface->ia_addr, addr, len * sizeof(*addr));
 370         iface->ia_addr_len = len;
 371
 372         if (change)
 373                 dhcpv6_ia_postupdate(iface, now);
 374
 375         if (change) {
 376                 syslog(LOG_INFO, "Raising SIGUSR1 due to address change on %s", iface->ifname);
 377                 raise(SIGUSR1);
 378         }
 379 }
 380
 381 void setup_addr_for_relaying(struct in6_addr *addr, struct interface *iface, bool add)
 382 {
 383         struct interface *c;
 384
 385         list_for_each_entry(c, &interfaces, head) {
 386                 if (iface == c || (c->ndp != RELAYD_RELAY && !add))
 387                         continue;
 388
 389                 odhcpd_setup_proxy_neigh(addr, c, c->ndp == RELAYD_RELAY ? add : false);
 390         }
 391 }
 392
 393 void setup_ping6(struct in6_addr *addr, struct interface *iface)
 394 {
 395         struct interface *c;
 396
 397         list_for_each_entry(c, &interfaces, head) {
 398                 if (iface == c || c->ndp != RELAYD_RELAY ||
 399                                 c->external == true)
 400                         continue;
 401
 402                 ping6(addr, c);
 403         }
 404 }
 405
 406 static struct in6_addr last_solicited;
 407
 408 static void handle_rtnl_event(struct odhcpd_event *e)
 409 {
 410         struct event_socket *ev_sock = container_of(e, struct event_socket, ev);
 411
 412         nl_recvmsgs_default(ev_sock->sock);
 413 }
 414
 415
 416 // Handler for neighbor cache entries from the kernel. This is our source
 417 // to learn and unlearn hosts on interfaces.
 418 static int cb_rtnl_valid(struct nl_msg *msg, _unused void *arg)
 419 {
 420         struct nlmsghdr *hdr = nlmsg_hdr(msg);
 421         struct in6_addr *addr = NULL;
 422         struct interface *iface = NULL;
 423         bool add = false;
 424
 425         switch (hdr->nlmsg_type) {
 426         case RTM_NEWROUTE:
 427         case RTM_DELROUTE: {
 428                 struct rtmsg *rtm = nlmsg_data(hdr);
 429
 430                 if (!nlmsg_valid_hdr(hdr, sizeof(*rtm)) ||
 431                                 rtm->rtm_family != AF_INET6)
 432                         return NL_SKIP;
 433
 434                 if (rtm->rtm_dst_len == 0) {
 435                         syslog(LOG_INFO, "Raising SIGUSR1 due to default route change");
 436                         raise(SIGUSR1);
 437                 }
 438                 return NL_OK;
 439         }
 440
 441         case RTM_NEWADDR:
 442                 add = true;
 443         case RTM_DELADDR: {
 444                 struct ifaddrmsg *ifa = nlmsg_data(hdr);
 445                 struct nlattr *nla[__IFA_MAX];
 446
 447                 if (!nlmsg_valid_hdr(hdr, sizeof(*ifa)) ||
 448                                 ifa->ifa_family != AF_INET6)
 449                         return NL_SKIP;
 450
 451                 iface = odhcpd_get_interface_by_index(ifa->ifa_index);
 452                 if (!iface)
 453                         return NL_SKIP;
 454
 455                 nlmsg_parse(hdr, sizeof(*ifa), nla, __IFA_MAX - 1, NULL);
 456                 if (!nla[IFA_ADDRESS])
 457                         return NL_SKIP;
 458
 459                 addr = nla_data(nla[IFA_ADDRESS]);
 460                 if (!addr || IN6_IS_ADDR_LINKLOCAL(addr) ||
 461                                 IN6_IS_ADDR_MULTICAST(addr))
 462                         return NL_SKIP;
 463
 464                 check_addr_updates(iface);
 465
 466                 if (iface->ndp != RELAYD_RELAY)
 467                         break;
 468
 469                 /* handle the relay logic below */
 470                 setup_addr_for_relaying(addr, iface, add);
 471
 472                 if (!add)
 473                         dump_neigh_table(false);
 474                 break;
 475         }
 476
 477         case RTM_NEWNEIGH:
 478                 add = true;
 479         case RTM_DELNEIGH: {
 480                 struct ndmsg *ndm = nlmsg_data(hdr);
 481                 struct nlattr *nla[__NDA_MAX];
 482
 483                 if (!nlmsg_valid_hdr(hdr, sizeof(*ndm)) ||
 484                                 ndm->ndm_family != AF_INET6)
 485                         return NL_SKIP;
 486
 487                 iface = odhcpd_get_interface_by_index(ndm->ndm_ifindex);
 488                 if (!iface || iface->ndp != RELAYD_RELAY)
 489                         return (iface ? NL_OK : NL_SKIP);
 490
 491                 nlmsg_parse(hdr, sizeof(*ndm), nla, __NDA_MAX - 1, NULL);
 492                 if (!nla[NDA_DST])
 493                         return NL_SKIP;
 494
 495                 addr = nla_data(nla[NDA_DST]);
 496                 if (!addr || IN6_IS_ADDR_LINKLOCAL(addr) ||
 497                                 IN6_IS_ADDR_MULTICAST(addr))
 498                         return NL_SKIP;
 499
 500                 if (ndm->ndm_flags & NTF_PROXY) {
 501                         /* Dump and flush proxy entries */
 502                         if (hdr->nlmsg_type == RTM_NEWNEIGH) {
 503                                 odhcpd_setup_proxy_neigh(addr, iface, false);
 504                                 setup_route(addr, iface, false);
 505                                 dump_neigh_table(false);
 506                         }
 507
 508                         return NL_OK;
 509                 }
 510
 511                 if (add && !(ndm->ndm_state &
 512                                 (NUD_REACHABLE | NUD_STALE | NUD_DELAY | NUD_PROBE |
 513                                  NUD_PERMANENT | NUD_NOARP))) {
 514                         if (!IN6_ARE_ADDR_EQUAL(&last_solicited, addr)) {
 515                                 last_solicited = *addr;
 516                                 setup_ping6(addr, iface);
 517                         }
 518
 519                         return NL_OK;
 520                 }
 521
 522                 setup_addr_for_relaying(addr, iface, add);
 523                 setup_route(addr, iface, add);
 524
 525                 if (!add)
 526                         dump_neigh_table(false);
 527                 break;
 528         }
 529
 530         default:
 531                 return NL_SKIP;
 532         }
 533
 534         return NL_OK;
 535 }
 536
 537 static void catch_rtnl_err(struct odhcpd_event *e, int error)
 538 {
 539         struct event_socket *ev_sock = container_of(e, struct event_socket, ev);
 540
 541         if (error != ENOBUFS)
 542                 return;
 543
 544         /* Double netlink event buffer size */
 545         ev_sock->sock_bufsize *= 2;
 546
 547         if (nl_socket_set_buffer_size(ev_sock->sock, ev_sock->sock_bufsize, 0))
 548                 return;
 549
 550         dump_addr_table();
 551 }