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 #include "router.h"
  32 #include "dhcpv6.h"
  33 #include "ndp.h"
  34
  35
  36
  37 static void handle_solicit(void *addr, void *data, size_t len,
  38                 struct interface *iface, void *dest);
  39 static void handle_rtnetlink(void *addr, void *data, size_t len,
  40                 struct interface *iface, void *dest);
  41 static void catch_rtnetlink(int error);
  42
  43 static uint32_t rtnl_seqid = 0;
  44 static int ping_socket = -1;
  45 static struct odhcpd_event rtnl_event = {{.fd = -1}, handle_rtnetlink, catch_rtnetlink};
  46
  47
  48 // Filter ICMPv6 messages of type neighbor soliciation
  49 static struct sock_filter bpf[] = {
  50         BPF_STMT(BPF_LD | BPF_B | BPF_ABS, offsetof(struct ip6_hdr, ip6_nxt)),
  51         BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, IPPROTO_ICMPV6, 0, 3),
  52         BPF_STMT(BPF_LD | BPF_B | BPF_ABS, sizeof(struct ip6_hdr) +
  53                         offsetof(struct icmp6_hdr, icmp6_type)),
  54         BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, ND_NEIGHBOR_SOLICIT, 0, 1),
  55         BPF_STMT(BPF_RET | BPF_K, 0xffffffff),
  56         BPF_STMT(BPF_RET | BPF_K, 0),
  57 };
  58 static const struct sock_fprog bpf_prog = {sizeof(bpf) / sizeof(*bpf), bpf};
  59
  60
  61 // Initialize NDP-proxy
  62 int init_ndp(void)
  63 {
  64         int val = 256 * 1024;
  65
  66         // Setup netlink socket
  67         if ((rtnl_event.uloop.fd = socket(AF_NETLINK, SOCK_RAW | SOCK_CLOEXEC, NETLINK_ROUTE)) < 0)
  68                 return -1;
  69
  70         struct sockaddr_nl nl = {.nl_family = AF_NETLINK};
  71         if (connect(rtnl_event.uloop.fd, (struct sockaddr*)&nl, sizeof(nl)) < 0)
  72                 return -1;
  73
  74         if (setsockopt(rtnl_event.uloop.fd, SOL_SOCKET, SO_RCVBUF, &val, sizeof(val)))
  75                 setsockopt(rtnl_event.uloop.fd, SOL_SOCKET, SO_RCVBUFFORCE, &val, sizeof(val));
  76
  77         // Receive netlink neighbor and ip-address events
  78         uint32_t group = RTNLGRP_IPV6_IFADDR;
  79         setsockopt(rtnl_event.uloop.fd, SOL_NETLINK,
  80                         NETLINK_ADD_MEMBERSHIP, &group, sizeof(group));
  81         group = RTNLGRP_IPV6_ROUTE;
  82         setsockopt(rtnl_event.uloop.fd, SOL_NETLINK,
  83                         NETLINK_ADD_MEMBERSHIP, &group, sizeof(group));
  84
  85         odhcpd_register(&rtnl_event);
  86
  87         // Open ICMPv6 socket
  88         ping_socket = socket(AF_INET6, SOCK_RAW | SOCK_CLOEXEC, IPPROTO_ICMPV6);
  89         if (ping_socket < 0) {
  90                 syslog(LOG_ERR, "Unable to open raw socket: %s", strerror(errno));
  91                         return -1;
  92         }
  93
  94         val = 2;
  95         setsockopt(ping_socket, IPPROTO_RAW, IPV6_CHECKSUM, &val, sizeof(val));
  96
  97         // This is required by RFC 4861
  98         val = 255;
  99         setsockopt(ping_socket, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &val, sizeof(val));
 100         setsockopt(ping_socket, IPPROTO_IPV6, IPV6_UNICAST_HOPS, &val, sizeof(val));
 101
 102         // Filter all packages, we only want to send
 103         struct icmp6_filter filt;
 104         ICMP6_FILTER_SETBLOCKALL(&filt);
 105         setsockopt(ping_socket, IPPROTO_ICMPV6, ICMP6_FILTER, &filt, sizeof(filt));
 106
 107
 108         // Netlink socket, continued...
 109         group = RTNLGRP_NEIGH;
 110         setsockopt(rtnl_event.uloop.fd, SOL_NETLINK, NETLINK_ADD_MEMBERSHIP, &group, sizeof(group));
 111
 112         return 0;
 113 }
 114
 115
 116 static void dump_neigh_table(bool proxy)
 117 {
 118         struct {
 119                 struct nlmsghdr nh;
 120                 struct ndmsg ndm;
 121         } req = {
 122                 {sizeof(req), RTM_GETNEIGH, NLM_F_REQUEST | NLM_F_DUMP,
 123                                 ++rtnl_seqid, 0},
 124                 {.ndm_family = AF_INET6, .ndm_flags = (proxy) ? NTF_PROXY : 0}
 125         };
 126         send(rtnl_event.uloop.fd, &req, sizeof(req), MSG_DONTWAIT);
 127         odhcpd_process(&rtnl_event);
 128 }
 129
 130
 131 int setup_ndp_interface(struct interface *iface, bool enable)
 132 {
 133         char procbuf[64];
 134         snprintf(procbuf, sizeof(procbuf), "/proc/sys/net/ipv6/conf/%s/proxy_ndp", iface->ifname);
 135         int procfd = open(procbuf, O_WRONLY);
 136         bool dump_neigh = false;
 137
 138         if (iface->ndp_event.uloop.fd > 0) {
 139                 uloop_fd_delete(&iface->ndp_event.uloop);
 140                 close(iface->ndp_event.uloop.fd);
 141                 iface->ndp_event.uloop.fd = -1;
 142
 143                 if (!enable || iface->ndp != RELAYD_RELAY)
 144                         if (write(procfd, "0\n", 2) < 0) {}
 145
 146                 dump_neigh = true;
 147         }
 148
 149         if (enable && (iface->ra == RELAYD_SERVER ||
 150                         iface->dhcpv6 == RELAYD_SERVER || iface->ndp == RELAYD_RELAY)) {
 151                 // Synthesize initial address events
 152                 struct {
 153                         struct nlmsghdr nh;
 154                         struct ifaddrmsg ifa;
 155                 } req2 = {
 156                         {sizeof(req2), RTM_GETADDR, NLM_F_REQUEST | NLM_F_DUMP,
 157                                         ++rtnl_seqid, 0},
 158                         {.ifa_family = AF_INET6, .ifa_index = iface->ifindex}
 159                 };
 160                 send(rtnl_event.uloop.fd, &req2, sizeof(req2), MSG_DONTWAIT);
 161         }
 162
 163         if (enable && iface->ndp == RELAYD_RELAY) {
 164                 if (write(procfd, "1\n", 2) < 0) {}
 165                 close(procfd);
 166
 167                 int sock = socket(AF_PACKET, SOCK_DGRAM | SOCK_CLOEXEC, htons(ETH_P_IPV6));
 168                 if (sock < 0) {
 169                         syslog(LOG_ERR, "Unable to open packet socket: %s",
 170                                         strerror(errno));
 171                         return -1;
 172                 }
 173
 174 #ifdef PACKET_RECV_TYPE
 175                 int pktt = 1 << PACKET_MULTICAST;
 176                 setsockopt(sock, SOL_PACKET, PACKET_RECV_TYPE, &pktt, sizeof(pktt));
 177 #endif
 178
 179                 if (setsockopt(sock, SOL_SOCKET, SO_ATTACH_FILTER,
 180                                 &bpf_prog, sizeof(bpf_prog))) {
 181                         syslog(LOG_ERR, "Failed to set BPF: %s", strerror(errno));
 182                         return -1;
 183                 }
 184
 185                 struct sockaddr_ll ll = {
 186                         .sll_family = AF_PACKET,
 187                         .sll_ifindex = iface->ifindex,
 188                         .sll_protocol = htons(ETH_P_IPV6),
 189                         .sll_hatype = 0,
 190                         .sll_pkttype = 0,
 191                         .sll_halen = 0,
 192                         .sll_addr = {0},
 193                 };
 194                 bind(sock, (struct sockaddr*)&ll, sizeof(ll));
 195
 196                 struct packet_mreq mreq = {iface->ifindex, PACKET_MR_ALLMULTI, ETH_ALEN, {0}};
 197                 setsockopt(sock, SOL_PACKET, PACKET_ADD_MEMBERSHIP, &mreq, sizeof(mreq));
 198
 199                 iface->ndp_event.uloop.fd = sock;
 200                 iface->ndp_event.handle_dgram = handle_solicit;
 201                 odhcpd_register(&iface->ndp_event);
 202
 203                 // If we already were enabled dump is unnecessary, if not do dump
 204                 if (!dump_neigh)
 205                         dump_neigh_table(false);
 206                 else
 207                         dump_neigh = false;
 208         } else {
 209                 close(procfd);
 210         }
 211
 212         if (dump_neigh)
 213                 dump_neigh_table(true);
 214
 215         return 0;
 216 }
 217
 218
 219 // Send an ICMP-ECHO. This is less for actually pinging but for the
 220 // neighbor cache to be kept up-to-date.
 221 static void ping6(struct in6_addr *addr,
 222                 const struct interface *iface)
 223 {
 224         struct sockaddr_in6 dest = {AF_INET6, 0, 0, *addr, iface->ifindex};
 225         struct icmp6_hdr echo = {.icmp6_type = ICMP6_ECHO_REQUEST};
 226         struct iovec iov = {&echo, sizeof(echo)};
 227
 228         odhcpd_setup_route(addr, 128, iface, NULL, 128, true);
 229         odhcpd_send(ping_socket, &dest, &iov, 1, iface);
 230         odhcpd_setup_route(addr, 128, iface, NULL, 128, false);
 231 }
 232
 233
 234 // Handle solicitations
 235 static void handle_solicit(void *addr, void *data, size_t len,
 236                 struct interface *iface, _unused void *dest)
 237 {
 238         struct ip6_hdr *ip6 = data;
 239         struct nd_neighbor_solicit *req = (struct nd_neighbor_solicit*)&ip6[1];
 240         struct sockaddr_ll *ll = addr;
 241
 242         // Solicitation is for duplicate address detection
 243         bool ns_is_dad = IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src);
 244
 245         // Don't forward any non-DAD solicitation for external ifaces
 246         // TODO: check if we should even forward DADs for them
 247         if (iface->external && !ns_is_dad)
 248                 return;
 249
 250         if (len < sizeof(*ip6) + sizeof(*req))
 251                 return; // Invalid reqicitation
 252
 253         if (IN6_IS_ADDR_LINKLOCAL(&req->nd_ns_target) ||
 254                         IN6_IS_ADDR_LOOPBACK(&req->nd_ns_target) ||
 255                         IN6_IS_ADDR_MULTICAST(&req->nd_ns_target))
 256                 return; // Invalid target
 257
 258         char ipbuf[INET6_ADDRSTRLEN];
 259         inet_ntop(AF_INET6, &req->nd_ns_target, ipbuf, sizeof(ipbuf));
 260         syslog(LOG_DEBUG, "Got a NS for %s", ipbuf);
 261
 262         uint8_t mac[6];
 263         odhcpd_get_mac(iface, mac);
 264         if (!memcmp(ll->sll_addr, mac, sizeof(mac)))
 265                 return; // Looped back
 266
 267         struct interface *c;
 268         list_for_each_entry(c, &interfaces, head)
 269                 if (iface->ndp == RELAYD_RELAY && iface != c &&
 270                                 (ns_is_dad || !c->external))
 271                         ping6(&req->nd_ns_target, c);
 272 }
 273
 274 // Use rtnetlink to modify kernel routes
 275 static void setup_route(struct in6_addr *addr, struct interface *iface, bool add)
 276 {
 277         char namebuf[INET6_ADDRSTRLEN];
 278         inet_ntop(AF_INET6, addr, namebuf, sizeof(namebuf));
 279         syslog(LOG_NOTICE, "%s about %s on %s",
 280                         (add) ? "Learned" : "Forgot", namebuf, iface->ifname);
 281
 282         if (iface->learn_routes)
 283                 odhcpd_setup_route(addr, 128, iface, NULL, 1024, add);
 284 }
 285
 286 // compare prefixes
 287 static int prefixcmp(const void *va, const void *vb)
 288 {
 289         const struct odhcpd_ipaddr *a = va, *b = vb;
 290         uint32_t a_pref = ((a->addr.s6_addr[0] & 0xfe) != 0xfc) ? a->preferred : 1;
 291         uint32_t b_pref = ((b->addr.s6_addr[0] & 0xfe) != 0xfc) ? b->preferred : 1;
 292         return (a_pref < b_pref) ? 1 : (a_pref > b_pref) ? -1 : 0;
 293 }
 294
 295 // Check address update
 296 static void check_updates(struct interface *iface)
 297 {
 298         struct odhcpd_ipaddr addr[RELAYD_MAX_ADDRS] = {{IN6ADDR_ANY_INIT, 0, 0, 0, 0}};
 299         time_t now = odhcpd_time();
 300         ssize_t len = odhcpd_get_interface_addresses(iface->ifindex, addr, ARRAY_SIZE(addr));
 301
 302         if (len < 0)
 303                 return;
 304
 305         qsort(addr, len, sizeof(*addr), prefixcmp);
 306
 307         for (int i = 0; i < len; ++i) {
 308                 addr[i].addr.s6_addr32[3] = 0;
 309
 310                 if (addr[i].preferred < UINT32_MAX - now)
 311                         addr[i].preferred += now;
 312
 313                 if (addr[i].valid < UINT32_MAX - now)
 314                         addr[i].valid += now;
 315         }
 316
 317         bool change = len != (ssize_t)iface->ia_addr_len;
 318         for (ssize_t i = 0; !change && i < len; ++i)
 319                 if (!IN6_ARE_ADDR_EQUAL(&addr[i].addr, &iface->ia_addr[i].addr) ||
 320                                 (addr[i].preferred > 0) != (iface->ia_addr[i].preferred > 0) ||
 321                                 addr[i].valid < iface->ia_addr[i].valid ||
 322                                 addr[i].preferred < iface->ia_addr[i].preferred)
 323                         change = true;
 324
 325         if (change)
 326                 dhcpv6_ia_preupdate(iface);
 327
 328         memcpy(iface->ia_addr, addr, len * sizeof(*addr));
 329         iface->ia_addr_len = len;
 330
 331         if (change)
 332                 dhcpv6_ia_postupdate(iface, now);
 333
 334         if (change) {
 335                 syslog(LOG_INFO, "Raising SIGUSR1 due to address change on %s", iface->ifname);
 336                 raise(SIGUSR1);
 337         }
 338 }
 339
 340
 341 // Handler for neighbor cache entries from the kernel. This is our source
 342 // to learn and unlearn hosts on interfaces.
 343 static void handle_rtnetlink(_unused void *addr, void *data, size_t len,
 344                 _unused struct interface *iface, _unused void *dest)
 345 {
 346         bool dump_neigh = false;
 347         struct in6_addr last_solicited = IN6ADDR_ANY_INIT;
 348
 349         for (struct nlmsghdr *nh = data; NLMSG_OK(nh, len);
 350                         nh = NLMSG_NEXT(nh, len)) {
 351                 struct ndmsg *ndm = NLMSG_DATA(nh);
 352                 struct rtmsg *rtm = NLMSG_DATA(nh);
 353
 354                 bool is_addr = (nh->nlmsg_type == RTM_NEWADDR
 355                                 || nh->nlmsg_type == RTM_DELADDR);
 356                 bool is_route = (nh->nlmsg_type == RTM_NEWROUTE
 357                                 || nh->nlmsg_type == RTM_DELROUTE);
 358                 bool is_neigh = (nh->nlmsg_type == RTM_NEWNEIGH
 359                                 || nh->nlmsg_type == RTM_DELNEIGH);
 360
 361                 // Family and ifindex are on the same offset for NEIGH and ADDR
 362                 if ((!is_addr && !is_route && !is_neigh)
 363                                 || NLMSG_PAYLOAD(nh, 0) < sizeof(*ndm)
 364                                 || ndm->ndm_family != AF_INET6)
 365                         continue;
 366
 367                 if (is_route) {
 368                         // Inform about a change in default route
 369                         if (rtm->rtm_dst_len == 0) {
 370                                 syslog(LOG_INFO, "Raising SIGUSR1 due to default route change");
 371                                 raise(SIGUSR1);
 372                         }
 373
 374                         continue;
 375                 }
 376
 377                 // Data to retrieve
 378                 size_t rta_offset = (is_addr) ? sizeof(struct ifaddrmsg) : sizeof(*ndm);
 379                 uint16_t atype = (is_addr) ? IFA_ADDRESS : NDA_DST;
 380                 ssize_t alen = NLMSG_PAYLOAD(nh, rta_offset);
 381                 struct in6_addr *addr = NULL;
 382
 383                 for (struct rtattr *rta = (void*)(((uint8_t*)ndm) + rta_offset);
 384                                 RTA_OK(rta, alen); rta = RTA_NEXT(rta, alen)) {
 385                         if (rta->rta_type == atype &&
 386                                         RTA_PAYLOAD(rta) >= sizeof(*addr)) {
 387                                 addr = RTA_DATA(rta);
 388                         }
 389                 }
 390
 391                 // Lookup interface
 392                 struct interface *iface = odhcpd_get_interface_by_index(ndm->ndm_ifindex);
 393                 if (!iface)
 394                         continue;
 395
 396                 // Address not specified or unrelated
 397                 if (!addr || IN6_IS_ADDR_LINKLOCAL(addr) ||
 398                                 IN6_IS_ADDR_MULTICAST(addr))
 399                         continue;
 400
 401                 // Check for states
 402                 bool add;
 403                 if (is_addr)
 404                         add = (nh->nlmsg_type == RTM_NEWADDR);
 405                 else
 406                         add = (nh->nlmsg_type == RTM_NEWNEIGH && (ndm->ndm_state &
 407                                 (NUD_REACHABLE | NUD_STALE | NUD_DELAY | NUD_PROBE
 408                                                 | NUD_PERMANENT | NUD_NOARP)));
 409
 410                 if (iface->ndp == RELAYD_RELAY) {
 411                         // Replay change to all neighbor cache
 412                         struct {
 413                                 struct nlmsghdr nh;
 414                                 struct ndmsg ndm;
 415                                 struct nlattr nla_dst;
 416                                 struct in6_addr dst;
 417                         } req = {
 418                                 {sizeof(req), RTM_DELNEIGH, NLM_F_REQUEST,
 419                                                 ++rtnl_seqid, 0},
 420                                 {.ndm_family = AF_INET6, .ndm_flags = NTF_PROXY},
 421                                 {sizeof(struct nlattr) + sizeof(struct in6_addr), NDA_DST},
 422                                 *addr
 423                         };
 424
 425                         if (ndm->ndm_flags & NTF_PROXY) {
 426                                 // Dump & flush proxy entries
 427                                 if (nh->nlmsg_type == RTM_NEWNEIGH) {
 428                                         req.ndm.ndm_ifindex = iface->ifindex;
 429                                         send(rtnl_event.uloop.fd, &req, sizeof(req), MSG_DONTWAIT);
 430                                         setup_route(addr, iface, false);
 431                                         dump_neigh = true;
 432                                 }
 433                         } else if (add) {
 434                                 struct interface *c;
 435                                 list_for_each_entry(c, &interfaces, head) {
 436                                         if (iface == c)
 437                                                 continue;
 438
 439                                         if (c->ndp == RELAYD_RELAY) {
 440                                                 req.nh.nlmsg_type = RTM_NEWNEIGH;
 441                                                 req.nh.nlmsg_flags |= NLM_F_CREATE | NLM_F_REPLACE;
 442
 443                                                 req.ndm.ndm_ifindex = c->ifindex;
 444                                                 send(rtnl_event.uloop.fd, &req, sizeof(req), MSG_DONTWAIT);
 445                                         } else { // Delete NDP cache from interfaces without relay
 446                                                 req.nh.nlmsg_type = RTM_DELNEIGH;
 447                                                 req.nh.nlmsg_flags &= ~(NLM_F_CREATE | NLM_F_REPLACE);
 448
 449                                                 req.ndm.ndm_ifindex = c->ifindex;
 450                                                 send(rtnl_event.uloop.fd, &req, sizeof(req), MSG_DONTWAIT);
 451                                         }
 452                                 }
 453
 454                                 setup_route(addr, iface, true);
 455                         } else {
 456                                 if (nh->nlmsg_type == RTM_NEWNEIGH) {
 457                                         // might be locally originating
 458                                         if (!IN6_ARE_ADDR_EQUAL(&last_solicited, addr)) {
 459                                                 last_solicited = *addr;
 460
 461                                                 struct interface *c;
 462                                                 list_for_each_entry(c, &interfaces, head)
 463                                                         if (iface->ndp == RELAYD_RELAY && iface != c &&
 464                                                                         !c->external == false)
 465                                                                 ping6(addr, c);
 466                                         }
 467                                 } else {
 468                                         struct interface *c;
 469                                         list_for_each_entry(c, &interfaces, head) {
 470                                                 if (c->ndp == RELAYD_RELAY && iface != c) {
 471                                                         req.ndm.ndm_ifindex = c->ifindex;
 472                                                         send(rtnl_event.uloop.fd, &req, sizeof(req), MSG_DONTWAIT);
 473                                                 }
 474                                         }
 475                                         setup_route(addr, iface, false);
 476
 477                                         // also: dump to add proxies back in case it moved elsewhere
 478                                         dump_neigh = true;
 479                                 }
 480                         }
 481                 }
 482
 483                 if (is_addr) {
 484                         check_updates(iface);
 485
 486                         if (iface->ndp == RELAYD_RELAY && iface->master) {
 487                                 // Replay address changes on all slave interfaces
 488                                 nh->nlmsg_flags = NLM_F_REQUEST;
 489
 490                                 if (nh->nlmsg_type == RTM_NEWADDR)
 491                                         nh->nlmsg_flags |= NLM_F_CREATE | NLM_F_REPLACE;
 492
 493                                 struct interface *c;
 494                                 list_for_each_entry(c, &interfaces, head) {
 495                                         if (c->ndp == RELAYD_RELAY && !c->master) {
 496                                                 ndm->ndm_ifindex = c->ifindex;
 497                                                 send(rtnl_event.uloop.fd, nh, nh->nlmsg_len, MSG_DONTWAIT);
 498                                         }
 499                                 }
 500                         }
 501                 }
 502         }
 503
 504         if (dump_neigh)
 505                 dump_neigh_table(false);
 506 }
 507
 508 static void catch_rtnetlink(int error)
 509 {
 510         if (error == ENOBUFS) {
 511                 struct {
 512                         struct nlmsghdr nh;
 513                         struct ifaddrmsg ifa;
 514                 } req2 = {
 515                         {sizeof(req2), RTM_GETADDR, NLM_F_REQUEST | NLM_F_DUMP,
 516                                         ++rtnl_seqid, 0},
 517                         {.ifa_family = AF_INET6}
 518                 };
 519                 send(rtnl_event.uloop.fd, &req2, sizeof(req2), MSG_DONTWAIT);
 520         }
 521 }