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