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 IPv6 address, IPv6 routes and neighbor events
  96         if (nl_socket_add_memberships(rtnl_event.sock, RTNLGRP_IPV6_IFADDR,
  97                                 RTNLGRP_IPV6_ROUTE, RTNLGRP_NEIGH, 0))
  98                 goto err;
  99
 100         odhcpd_register(&rtnl_event.ev);
 101
 102         // Open ICMPv6 socket
 103         ping_socket = socket(AF_INET6, SOCK_RAW | SOCK_CLOEXEC, IPPROTO_ICMPV6);
 104         if (ping_socket < 0) {
 105                 syslog(LOG_ERR, "Unable to open raw socket: %s", strerror(errno));
 106                         return -1;
 107         }
 108
 109         setsockopt(ping_socket, IPPROTO_RAW, IPV6_CHECKSUM, &val, sizeof(val));
 110
 111         // This is required by RFC 4861
 112         val = 255;
 113         setsockopt(ping_socket, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &val, sizeof(val));
 114         setsockopt(ping_socket, IPPROTO_IPV6, IPV6_UNICAST_HOPS, &val, sizeof(val));
 115
 116         // Filter all packages, we only want to send
 117         struct icmp6_filter filt;
 118         ICMP6_FILTER_SETBLOCKALL(&filt);
 119         setsockopt(ping_socket, IPPROTO_ICMPV6, ICMP6_FILTER, &filt, sizeof(filt));
 120
 121         return 0;
 122
 123 err:
 124         if (rtnl_event.sock) {
 125                 nl_socket_free(rtnl_event.sock);
 126                 rtnl_event.sock = NULL;
 127                 rtnl_event.ev.uloop.fd = -1;
 128         }
 129
 130         return -1;
 131 }
 132
 133 static void dump_neigh_table(const bool proxy)
 134 {
 135         struct nl_msg *msg;
 136         struct ndmsg ndm = {
 137                 .ndm_family = AF_INET6,
 138                 .ndm_flags = proxy ? NTF_PROXY : 0,
 139         };
 140
 141         msg = nlmsg_alloc_simple(RTM_GETNEIGH, NLM_F_REQUEST | NLM_F_DUMP);
 142         if (!msg)
 143                 return;
 144
 145         nlmsg_append(msg, &ndm, sizeof(ndm), 0);
 146
 147         nl_send_auto_complete(rtnl_event.sock, msg);
 148
 149         nlmsg_free(msg);
 150 }
 151
 152 static void dump_addr_table(bool v6)
 153 {
 154         struct nl_msg *msg;
 155         struct ifaddrmsg ifa = {
 156                 .ifa_family = v6 ? AF_INET6 : AF_INET,
 157         };
 158
 159         msg = nlmsg_alloc_simple(RTM_GETADDR, NLM_F_REQUEST | NLM_F_DUMP);
 160         if (!msg)
 161                 return;
 162
 163         nlmsg_append(msg, &ifa, sizeof(ifa), 0);
 164
 165         nl_send_auto_complete(rtnl_event.sock, msg);
 166
 167         nlmsg_free(msg);
 168 }
 169
 170 int setup_ndp_interface(struct interface *iface, bool enable)
 171 {
 172         int ret = 0, procfd;
 173         bool dump_neigh = false;
 174         char procbuf[64];
 175
 176         snprintf(procbuf, sizeof(procbuf), "/proc/sys/net/ipv6/conf/%s/proxy_ndp", iface->ifname);
 177         procfd = open(procbuf, O_WRONLY);
 178
 179         if (procfd < 0) {
 180                 ret = -1;
 181                 goto out;
 182         }
 183
 184         if (iface->ndp_event.uloop.fd > 0) {
 185                 uloop_fd_delete(&iface->ndp_event.uloop);
 186                 close(iface->ndp_event.uloop.fd);
 187                 iface->ndp_event.uloop.fd = -1;
 188
 189                 if (!enable || iface->ndp != RELAYD_RELAY)
 190                         if (write(procfd, "0\n", 2) < 0) {}
 191
 192                 dump_neigh = true;
 193         }
 194
 195         if (enable && iface->ndp == RELAYD_RELAY) {
 196                 if (write(procfd, "1\n", 2) < 0) {}
 197
 198                 int sock = socket(AF_PACKET, SOCK_DGRAM | SOCK_CLOEXEC, htons(ETH_P_IPV6));
 199                 if (sock < 0) {
 200                         syslog(LOG_ERR, "Unable to open packet socket: %s",
 201                                         strerror(errno));
 202                         ret = -1;
 203                         goto out;
 204                 }
 205
 206 #ifdef PACKET_RECV_TYPE
 207                 int pktt = 1 << PACKET_MULTICAST;
 208                 setsockopt(sock, SOL_PACKET, PACKET_RECV_TYPE, &pktt, sizeof(pktt));
 209 #endif
 210
 211                 if (setsockopt(sock, SOL_SOCKET, SO_ATTACH_FILTER,
 212                                 &bpf_prog, sizeof(bpf_prog))) {
 213                         syslog(LOG_ERR, "Failed to set BPF: %s", strerror(errno));
 214                         ret = -1;
 215                         goto out;
 216                 }
 217
 218                 struct sockaddr_ll ll = {
 219                         .sll_family = AF_PACKET,
 220                         .sll_ifindex = iface->ifindex,
 221                         .sll_protocol = htons(ETH_P_IPV6),
 222                         .sll_hatype = 0,
 223                         .sll_pkttype = 0,
 224                         .sll_halen = 0,
 225                         .sll_addr = {0},
 226                 };
 227                 bind(sock, (struct sockaddr*)&ll, sizeof(ll));
 228
 229                 struct packet_mreq mreq = {iface->ifindex, PACKET_MR_ALLMULTI, ETH_ALEN, {0}};
 230                 setsockopt(sock, SOL_PACKET, PACKET_ADD_MEMBERSHIP, &mreq, sizeof(mreq));
 231
 232                 iface->ndp_event.uloop.fd = sock;
 233                 iface->ndp_event.handle_dgram = handle_solicit;
 234                 odhcpd_register(&iface->ndp_event);
 235
 236                 // If we already were enabled dump is unnecessary, if not do dump
 237                 if (!dump_neigh)
 238                         dump_neigh_table(false);
 239                 else
 240                         dump_neigh = false;
 241         }
 242
 243         if (dump_neigh)
 244                 dump_neigh_table(true);
 245
 246 out:
 247         if (procfd >= 0)
 248                 close(procfd);
 249
 250         return ret;
 251 }
 252
 253
 254 // Send an ICMP-ECHO. This is less for actually pinging but for the
 255 // neighbor cache to be kept up-to-date.
 256 static void ping6(struct in6_addr *addr,
 257                 const struct interface *iface)
 258 {
 259         struct sockaddr_in6 dest = { .sin6_family = AF_INET6, .sin6_addr = *addr, .sin6_scope_id = iface->ifindex, };
 260         struct icmp6_hdr echo = { .icmp6_type = ICMP6_ECHO_REQUEST };
 261         struct iovec iov = { .iov_base = &echo, .iov_len = sizeof(echo) };
 262         char ipbuf[INET6_ADDRSTRLEN];
 263
 264         inet_ntop(AF_INET6, addr, ipbuf, sizeof(ipbuf));
 265         syslog(LOG_NOTICE, "Pinging for %s%%%s", ipbuf, iface->ifname);
 266
 267         odhcpd_setup_route(addr, 128, iface, NULL, 128, true);
 268         odhcpd_send(ping_socket, &dest, &iov, 1, iface);
 269         odhcpd_setup_route(addr, 128, iface, NULL, 128, false);
 270 }
 271
 272 // Handle solicitations
 273 static void handle_solicit(void *addr, void *data, size_t len,
 274                 struct interface *iface, _unused void *dest)
 275 {
 276         struct ip6_hdr *ip6 = data;
 277         struct nd_neighbor_solicit *req = (struct nd_neighbor_solicit*)&ip6[1];
 278         struct sockaddr_ll *ll = addr;
 279         char ipbuf[INET6_ADDRSTRLEN];
 280         uint8_t mac[6];
 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         inet_ntop(AF_INET6, &req->nd_ns_target, ipbuf, sizeof(ipbuf));
 300         syslog(LOG_DEBUG, "Got a NS for %s%%%s", ipbuf, iface->ifname);
 301
 302         odhcpd_get_mac(iface, mac);
 303         if (!memcmp(ll->sll_addr, mac, sizeof(mac)))
 304                 return; // Looped back
 305
 306         struct interface *c;
 307         list_for_each_entry(c, &interfaces, head)
 308                 if (iface != c && c->ndp == RELAYD_RELAY &&
 309                                 (ns_is_dad || !c->external))
 310                         ping6(&req->nd_ns_target, c);
 311 }
 312
 313 // Use rtnetlink to modify kernel routes
 314 static void setup_route(struct in6_addr *addr, struct interface *iface, bool add)
 315 {
 316         char ipbuf[INET6_ADDRSTRLEN];
 317
 318         inet_ntop(AF_INET6, addr, ipbuf, sizeof(ipbuf));
 319         syslog(LOG_NOTICE, "%s about %s%%%s",
 320                         (add) ? "Learned" : "Forgot", ipbuf, iface->ifname);
 321
 322         if (iface->learn_routes)
 323                 odhcpd_setup_route(addr, 128, iface, NULL, 1024, add);
 324 }
 325
 326 // Check address update
 327 static void check_addr6_updates(struct interface *iface)
 328 {
 329         struct odhcpd_ipaddr *addr = NULL;
 330         ssize_t len = odhcpd_get_interface_addresses(iface->ifindex, true, &addr);
 331
 332         if (len < 0)
 333                 return;
 334
 335         bool change = len != (ssize_t)iface->ia_addr_len;
 336         for (ssize_t i = 0; !change && i < len; ++i)
 337                 if (!IN6_ARE_ADDR_EQUAL(&addr[i].addr.in6, &iface->ia_addr[i].addr.in6) ||
 338                                 (addr[i].preferred > 0) != (iface->ia_addr[i].preferred > 0) ||
 339                                 addr[i].valid < iface->ia_addr[i].valid ||
 340                                 addr[i].preferred < iface->ia_addr[i].preferred)
 341                         change = true;
 342
 343         if (change)
 344                 dhcpv6_ia_preupdate(iface);
 345
 346         free(iface->ia_addr);
 347         iface->ia_addr = addr;
 348         iface->ia_addr_len = len;
 349
 350         if (change) {
 351                 dhcpv6_ia_postupdate(iface);
 352                 syslog(LOG_INFO, "Raising SIGUSR1 due to address change on %s", iface->ifname);
 353                 raise(SIGUSR1);
 354         }
 355 }
 356
 357 static void setup_addr_for_relaying(struct in6_addr *addr, struct interface *iface, bool add)
 358 {
 359         struct interface *c;
 360         char ipbuf[INET6_ADDRSTRLEN];
 361
 362         inet_ntop(AF_INET6, addr, ipbuf, sizeof(ipbuf));
 363
 364         list_for_each_entry(c, &interfaces, head) {
 365                 if (iface == c || (c->ndp != RELAYD_RELAY && !add))
 366                         continue;
 367
 368                 bool neigh_add = (c->ndp == RELAYD_RELAY ? add : false);
 369
 370                 if (odhcpd_setup_proxy_neigh(addr, c, neigh_add))
 371                         syslog(LOG_DEBUG, "Failed to %s proxy neighbour entry %s%%%s",
 372                                 neigh_add ? "add" : "delete", ipbuf, c->ifname);
 373                 else
 374                         syslog(LOG_DEBUG, "%s proxy neighbour entry %s%%%s",
 375                                 neigh_add ? "Added" : "Deleted", ipbuf, c->ifname);
 376         }
 377 }
 378
 379 static void handle_rtnl_event(struct odhcpd_event *e)
 380 {
 381         struct event_socket *ev_sock = container_of(e, struct event_socket, ev);
 382
 383         nl_recvmsgs_default(ev_sock->sock);
 384 }
 385
 386
 387 // Handler for neighbor cache entries from the kernel. This is our source
 388 // to learn and unlearn hosts on interfaces.
 389 static int cb_rtnl_valid(struct nl_msg *msg, _unused void *arg)
 390 {
 391         struct nlmsghdr *hdr = nlmsg_hdr(msg);
 392         struct in6_addr *addr = NULL;
 393         struct interface *iface = NULL;
 394         bool add = false;
 395         char ipbuf[INET6_ADDRSTRLEN];
 396
 397         switch (hdr->nlmsg_type) {
 398         case RTM_NEWROUTE:
 399         case RTM_DELROUTE: {
 400                 struct rtmsg *rtm = nlmsg_data(hdr);
 401
 402                 if (!nlmsg_valid_hdr(hdr, sizeof(*rtm)) ||
 403                                 rtm->rtm_family != AF_INET6)
 404                         return NL_SKIP;
 405
 406                 if (rtm->rtm_dst_len == 0) {
 407                         syslog(LOG_INFO, "Raising SIGUSR1 due to default route change");
 408                         raise(SIGUSR1);
 409                 }
 410                 return NL_OK;
 411         }
 412
 413         case RTM_NEWADDR:
 414                 add = true;
 415                 /* fall through */
 416         case RTM_DELADDR: {
 417                 struct ifaddrmsg *ifa = nlmsg_data(hdr);
 418                 struct nlattr *nla[__IFA_MAX];
 419
 420                 if (!nlmsg_valid_hdr(hdr, sizeof(*ifa)) ||
 421                                 ifa->ifa_family != AF_INET6)
 422                         return NL_SKIP;
 423
 424                 iface = odhcpd_get_interface_by_index(ifa->ifa_index);
 425                 if (!iface)
 426                         return NL_SKIP;
 427
 428                 nlmsg_parse(hdr, sizeof(*ifa), nla, __IFA_MAX - 1, NULL);
 429                 if (!nla[IFA_ADDRESS])
 430                         return NL_SKIP;
 431
 432                 addr = nla_data(nla[IFA_ADDRESS]);
 433                 if (!addr || IN6_IS_ADDR_LINKLOCAL(addr) ||
 434                                 IN6_IS_ADDR_MULTICAST(addr))
 435                         return NL_SKIP;
 436
 437                 inet_ntop(AF_INET6, addr, ipbuf, sizeof(ipbuf));
 438                 syslog(LOG_DEBUG, "Netlink %s %s%%%s", add ? "newaddr" : "deladdr",
 439                         ipbuf, iface->ifname);
 440
 441                 check_addr6_updates(iface);
 442
 443                 if (iface->ndp != RELAYD_RELAY)
 444                         break;
 445
 446                 /* handle the relay logic below */
 447                 setup_addr_for_relaying(addr, iface, add);
 448
 449                 if (!add)
 450                         dump_neigh_table(false);
 451                 break;
 452         }
 453
 454         case RTM_NEWNEIGH:
 455                 add = true;
 456                 /* fall through */
 457         case RTM_DELNEIGH: {
 458                 struct ndmsg *ndm = nlmsg_data(hdr);
 459                 struct nlattr *nla[__NDA_MAX];
 460
 461                 if (!nlmsg_valid_hdr(hdr, sizeof(*ndm)) ||
 462                                 ndm->ndm_family != AF_INET6)
 463                         return NL_SKIP;
 464
 465                 iface = odhcpd_get_interface_by_index(ndm->ndm_ifindex);
 466                 if (!iface || iface->ndp != RELAYD_RELAY)
 467                         return (iface ? NL_OK : NL_SKIP);
 468
 469                 nlmsg_parse(hdr, sizeof(*ndm), nla, __NDA_MAX - 1, NULL);
 470                 if (!nla[NDA_DST])
 471                         return NL_SKIP;
 472
 473                 addr = nla_data(nla[NDA_DST]);
 474                 if (!addr || IN6_IS_ADDR_LINKLOCAL(addr) ||
 475                                 IN6_IS_ADDR_MULTICAST(addr))
 476                         return NL_SKIP;
 477
 478                 inet_ntop(AF_INET6, addr, ipbuf, sizeof(ipbuf));
 479                 syslog(LOG_DEBUG, "Netlink %s %s%%%s", add ? "newneigh" : "delneigh",
 480                         ipbuf, iface->ifname);
 481
 482                 if (ndm->ndm_flags & NTF_PROXY) {
 483                         /* Dump and flush proxy entries */
 484                         if (hdr->nlmsg_type == RTM_NEWNEIGH) {
 485                                 odhcpd_setup_proxy_neigh(addr, iface, false);
 486                                 setup_route(addr, iface, false);
 487                                 dump_neigh_table(false);
 488                         }
 489
 490                         return NL_OK;
 491                 }
 492
 493                 if (add && !(ndm->ndm_state &
 494                                 (NUD_REACHABLE | NUD_STALE | NUD_DELAY | NUD_PROBE |
 495                                  NUD_PERMANENT | NUD_NOARP)))
 496                         return NL_OK;
 497
 498                 setup_addr_for_relaying(addr, iface, add);
 499                 setup_route(addr, iface, add);
 500
 501                 if (!add)
 502                         dump_neigh_table(false);
 503                 break;
 504         }
 505
 506         default:
 507                 return NL_SKIP;
 508         }
 509
 510         return NL_OK;
 511 }
 512
 513 static void catch_rtnl_err(struct odhcpd_event *e, int error)
 514 {
 515         struct event_socket *ev_sock = container_of(e, struct event_socket, ev);
 516
 517         if (error != ENOBUFS)
 518                 goto err;
 519
 520         /* Double netlink event buffer size */
 521         ev_sock->sock_bufsize *= 2;
 522
 523         if (nl_socket_set_buffer_size(ev_sock->sock, ev_sock->sock_bufsize, 0))
 524                 goto err;
 525
 526         dump_addr_table(true);
 527         return;
 528
 529 err:
 530         odhcpd_deregister(e);
 531 }