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
  42 static uint32_t rtnl_seqid = 0;
  43 static int ping_socket = -1;
  44 static struct odhcpd_event rtnl_event = {{.fd = -1}, handle_rtnetlink};
  45
  46
  47 // Filter ICMPv6 messages of type neighbor soliciation
  48 static struct sock_filter bpf[] = {
  49         BPF_STMT(BPF_LD | BPF_B | BPF_ABS, offsetof(struct ip6_hdr, ip6_nxt)),
  50         BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, IPPROTO_ICMPV6, 0, 3),
  51         BPF_STMT(BPF_LD | BPF_B | BPF_ABS, sizeof(struct ip6_hdr) +
  52                         offsetof(struct icmp6_hdr, icmp6_type)),
  53         BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, ND_NEIGHBOR_SOLICIT, 0, 1),
  54         BPF_STMT(BPF_RET | BPF_K, 0xffffffff),
  55         BPF_STMT(BPF_RET | BPF_K, 0),
  56 };
  57 static const struct sock_fprog bpf_prog = {sizeof(bpf) / sizeof(*bpf), bpf};
  58
  59
  60 // Initialize NDP-proxy
  61 int init_ndp(void)
  62 {
  63         // Setup netlink socket
  64         if ((rtnl_event.uloop.fd = odhcpd_open_rtnl()) < 0)
  65                 return -1;
  66
  67         // Receive netlink neighbor and ip-address events
  68         uint32_t group = RTNLGRP_IPV6_IFADDR;
  69         setsockopt(rtnl_event.uloop.fd, SOL_NETLINK,
  70                         NETLINK_ADD_MEMBERSHIP, &group, sizeof(group));
  71         group = RTNLGRP_IPV6_ROUTE;
  72         setsockopt(rtnl_event.uloop.fd, SOL_NETLINK,
  73                         NETLINK_ADD_MEMBERSHIP, &group, sizeof(group));
  74
  75         odhcpd_register(&rtnl_event);
  76
  77         // Open ICMPv6 socket
  78         ping_socket = socket(AF_INET6, SOCK_RAW | SOCK_CLOEXEC, IPPROTO_ICMPV6);
  79         if (ping_socket < 0) {
  80                 syslog(LOG_ERR, "Unable to open raw socket: %s", strerror(errno));
  81                         return -1;
  82         }
  83
  84         int val = 2;
  85         setsockopt(ping_socket, IPPROTO_RAW, IPV6_CHECKSUM, &val, sizeof(val));
  86
  87         // This is required by RFC 4861
  88         val = 255;
  89         setsockopt(ping_socket, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &val, sizeof(val));
  90         setsockopt(ping_socket, IPPROTO_IPV6, IPV6_UNICAST_HOPS, &val, sizeof(val));
  91
  92         // Filter all packages, we only want to send
  93         struct icmp6_filter filt;
  94         ICMP6_FILTER_SETBLOCKALL(&filt);
  95         setsockopt(ping_socket, IPPROTO_ICMPV6, ICMP6_FILTER, &filt, sizeof(filt));
  96
  97
  98         // Netlink socket, continued...
  99         group = RTNLGRP_NEIGH;
 100         setsockopt(rtnl_event.uloop.fd, SOL_NETLINK, NETLINK_ADD_MEMBERSHIP, &group, sizeof(group));
 101
 102         return 0;
 103 }
 104
 105
 106 static void dump_neigh_table(bool proxy)
 107 {
 108         struct {
 109                 struct nlmsghdr nh;
 110                 struct ndmsg ndm;
 111         } req = {
 112                 {sizeof(req), RTM_GETNEIGH, NLM_F_REQUEST | NLM_F_DUMP,
 113                                 ++rtnl_seqid, 0},
 114                 {.ndm_family = AF_INET6, .ndm_flags = (proxy) ? NTF_PROXY : 0}
 115         };
 116         send(rtnl_event.uloop.fd, &req, sizeof(req), MSG_DONTWAIT);
 117         odhcpd_process(&rtnl_event);
 118 }
 119
 120
 121 int setup_ndp_interface(struct interface *iface, bool enable)
 122 {
 123         char procbuf[64];
 124         snprintf(procbuf, sizeof(procbuf), "/proc/sys/net/ipv6/conf/%s/proxy_ndp", iface->ifname);
 125         int procfd = open(procbuf, O_WRONLY);
 126         bool dump_neigh = false;
 127
 128         if (iface->ndp_event.uloop.fd > 0) {
 129                 uloop_fd_delete(&iface->ndp_event.uloop);
 130                 close(iface->ndp_event.uloop.fd);
 131                 iface->ndp_event.uloop.fd = -1;
 132
 133                 if (!enable || iface->ndp != RELAYD_RELAY)
 134                         if (write(procfd, "0\n", 2) < 0) {}
 135
 136                 dump_neigh = true;
 137         }
 138
 139         if (enable && (iface->ra == RELAYD_SERVER ||
 140                         iface->dhcpv6 == RELAYD_SERVER || iface->ndp == RELAYD_RELAY)) {
 141                 // Synthesize initial address events
 142                 struct {
 143                         struct nlmsghdr nh;
 144                         struct ifaddrmsg ifa;
 145                 } req2 = {
 146                         {sizeof(req2), RTM_GETADDR, NLM_F_REQUEST | NLM_F_DUMP,
 147                                         ++rtnl_seqid, 0},
 148                         {.ifa_family = AF_INET6, .ifa_index = iface->ifindex}
 149                 };
 150                 send(rtnl_event.uloop.fd, &req2, sizeof(req2), MSG_DONTWAIT);
 151         }
 152
 153         if (enable && iface->ndp == RELAYD_RELAY) {
 154                 if (write(procfd, "1\n", 2) < 0) {}
 155                 close(procfd);
 156
 157                 int sock = socket(AF_PACKET, SOCK_DGRAM | SOCK_CLOEXEC, htons(ETH_P_IPV6));
 158                 if (sock < 0) {
 159                         syslog(LOG_ERR, "Unable to open packet socket: %s",
 160                                         strerror(errno));
 161                         return -1;
 162                 }
 163
 164 #ifdef PACKET_RECV_TYPE
 165                 int pktt = 1 << PACKET_MULTICAST;
 166                 setsockopt(sock, SOL_PACKET, PACKET_RECV_TYPE, &pktt, sizeof(pktt));
 167 #endif
 168
 169                 if (setsockopt(sock, SOL_SOCKET, SO_ATTACH_FILTER,
 170                                 &bpf_prog, sizeof(bpf_prog))) {
 171                         syslog(LOG_ERR, "Failed to set BPF: %s", strerror(errno));
 172                         return -1;
 173                 }
 174
 175                 struct sockaddr_ll ll = {
 176                         .sll_family = AF_PACKET,
 177                         .sll_ifindex = iface->ifindex,
 178                         .sll_protocol = htons(ETH_P_IPV6),
 179                         .sll_hatype = 0,
 180                         .sll_pkttype = 0,
 181                         .sll_halen = 0,
 182                         .sll_addr = {0},
 183                 };
 184                 bind(sock, (struct sockaddr*)&ll, sizeof(ll));
 185
 186                 struct packet_mreq mreq = {iface->ifindex, PACKET_MR_ALLMULTI, ETH_ALEN, {0}};
 187                 setsockopt(sock, SOL_PACKET, PACKET_ADD_MEMBERSHIP, &mreq, sizeof(mreq));
 188
 189                 iface->ndp_event.uloop.fd = sock;
 190                 iface->ndp_event.handle_dgram = handle_solicit;
 191                 odhcpd_register(&iface->ndp_event);
 192
 193                 // If we already were enabled dump is unnecessary, if not do dump
 194                 if (!dump_neigh)
 195                         dump_neigh_table(false);
 196                 else
 197                         dump_neigh = false;
 198         } else {
 199                 close(procfd);
 200         }
 201
 202         if (dump_neigh)
 203                 dump_neigh_table(true);
 204
 205         return 0;
 206 }
 207
 208
 209 // Send an ICMP-ECHO. This is less for actually pinging but for the
 210 // neighbor cache to be kept up-to-date.
 211 static void ping6(struct in6_addr *addr,
 212                 const struct interface *iface)
 213 {
 214         struct sockaddr_in6 dest = {AF_INET6, 0, 0, *addr, iface->ifindex};
 215         struct icmp6_hdr echo = {.icmp6_type = ICMP6_ECHO_REQUEST};
 216         struct iovec iov = {&echo, sizeof(echo)};
 217
 218         odhcpd_setup_route(addr, 128, iface, NULL, 128, true);
 219         odhcpd_send(ping_socket, &dest, &iov, 1, iface);
 220         odhcpd_setup_route(addr, 128, iface, NULL, 128, false);
 221 }
 222
 223
 224 // Handle solicitations
 225 static void handle_solicit(void *addr, void *data, size_t len,
 226                 struct interface *iface, _unused void *dest)
 227 {
 228         struct ip6_hdr *ip6 = data;
 229         struct nd_neighbor_solicit *req = (struct nd_neighbor_solicit*)&ip6[1];
 230         struct sockaddr_ll *ll = addr;
 231
 232         // Solicitation is for duplicate address detection
 233         bool ns_is_dad = IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src);
 234
 235         // Don't forward any non-DAD solicitation for external ifaces
 236         // TODO: check if we should even forward DADs for them
 237         if (iface->external && !ns_is_dad)
 238                 return;
 239
 240         if (len < sizeof(*ip6) + sizeof(*req))
 241                 return; // Invalid reqicitation
 242
 243         if (IN6_IS_ADDR_LINKLOCAL(&req->nd_ns_target) ||
 244                         IN6_IS_ADDR_LOOPBACK(&req->nd_ns_target) ||
 245                         IN6_IS_ADDR_MULTICAST(&req->nd_ns_target))
 246                 return; // Invalid target
 247
 248         char ipbuf[INET6_ADDRSTRLEN];
 249         inet_ntop(AF_INET6, &req->nd_ns_target, ipbuf, sizeof(ipbuf));
 250         syslog(LOG_DEBUG, "Got a NS for %s", ipbuf);
 251
 252         uint8_t mac[6];
 253         odhcpd_get_mac(iface, mac);
 254         if (!memcmp(ll->sll_addr, mac, sizeof(mac)))
 255                 return; // Looped back
 256
 257         struct interface *c;
 258         list_for_each_entry(c, &interfaces, head)
 259                 if (iface->ndp == RELAYD_RELAY && iface != c &&
 260                                 (ns_is_dad || !c->external))
 261                         ping6(&req->nd_ns_target, c);
 262 }
 263
 264 // Use rtnetlink to modify kernel routes
 265 static void setup_route(struct in6_addr *addr, struct interface *iface, bool add)
 266 {
 267         char namebuf[INET6_ADDRSTRLEN];
 268         inet_ntop(AF_INET6, addr, namebuf, sizeof(namebuf));
 269         syslog(LOG_NOTICE, "%s about %s on %s",
 270                         (add) ? "Learned" : "Forgot", namebuf, iface->ifname);
 271
 272         if (iface->learn_routes)
 273                 odhcpd_setup_route(addr, 128, iface, NULL, 1024, add);
 274 }
 275
 276 // compare prefixes
 277 static int prefixcmp(const void *va, const void *vb)
 278 {
 279         const struct odhcpd_ipaddr *a = va, *b = vb;
 280         uint32_t a_pref = ((a->addr.s6_addr[0] & 0xfe) != 0xfc) ? a->preferred : 1;
 281         uint32_t b_pref = ((b->addr.s6_addr[0] & 0xfe) != 0xfc) ? b->preferred : 1;
 282         return (a_pref < b_pref) ? 1 : (a_pref > b_pref) ? -1 : 0;
 283 }
 284
 285 // Check address update
 286 static void check_updates(struct interface *iface)
 287 {
 288         struct odhcpd_ipaddr addr[8] = {{IN6ADDR_ANY_INIT, 0, 0, 0, 0}};
 289         time_t now = odhcpd_time();
 290         ssize_t len = odhcpd_get_interface_addresses(iface->ifindex, addr, 8);
 291
 292         if (len < 0)
 293                 return;
 294
 295         qsort(addr, len, sizeof(*addr), prefixcmp);
 296
 297         for (int i = 0; i < len; ++i) {
 298                 addr[i].addr.s6_addr32[3] = 0;
 299
 300                 if (addr[i].preferred < UINT32_MAX - now)
 301                         addr[i].preferred += now;
 302
 303                 if (addr[i].valid < UINT32_MAX - now)
 304                         addr[i].valid += now;
 305         }
 306
 307         bool change = len != (ssize_t)iface->ia_addr_len;
 308         for (ssize_t i = 0; !change && i < len; ++i)
 309                 if (!IN6_ARE_ADDR_EQUAL(&addr[i].addr, &iface->ia_addr[i].addr) ||
 310                                 (addr[i].preferred > 0) != (iface->ia_addr[i].preferred > 0) ||
 311                                 addr[i].valid < iface->ia_addr[i].valid ||
 312                                 addr[i].preferred < iface->ia_addr[i].preferred)
 313                         change = true;
 314
 315         if (change)
 316                 dhcpv6_ia_preupdate(iface);
 317
 318         memcpy(iface->ia_addr, addr, len * sizeof(*addr));
 319         iface->ia_addr_len = len;
 320
 321         if (change)
 322                 dhcpv6_ia_postupdate(iface, now);
 323
 324         if (change)
 325                 raise(SIGUSR1);
 326 }
 327
 328
 329 // Handler for neighbor cache entries from the kernel. This is our source
 330 // to learn and unlearn hosts on interfaces.
 331 static void handle_rtnetlink(_unused void *addr, void *data, size_t len,
 332                 _unused struct interface *iface, _unused void *dest)
 333 {
 334         bool dump_neigh = false;
 335         struct in6_addr last_solicited = IN6ADDR_ANY_INIT;
 336
 337         for (struct nlmsghdr *nh = data; NLMSG_OK(nh, len);
 338                         nh = NLMSG_NEXT(nh, len)) {
 339                 struct ndmsg *ndm = NLMSG_DATA(nh);
 340                 struct rtmsg *rtm = NLMSG_DATA(nh);
 341
 342                 bool is_addr = (nh->nlmsg_type == RTM_NEWADDR
 343                                 || nh->nlmsg_type == RTM_DELADDR);
 344                 bool is_route = (nh->nlmsg_type == RTM_NEWROUTE
 345                                 || nh->nlmsg_type == RTM_DELROUTE);
 346                 bool is_neigh = (nh->nlmsg_type == RTM_NEWNEIGH
 347                                 || nh->nlmsg_type == RTM_DELNEIGH);
 348
 349                 // Family and ifindex are on the same offset for NEIGH and ADDR
 350                 if ((!is_addr && !is_route && !is_neigh)
 351                                 || NLMSG_PAYLOAD(nh, 0) < sizeof(*ndm)
 352                                 || ndm->ndm_family != AF_INET6)
 353                         continue;
 354
 355                 // Inform about a change in default route
 356                 if (is_route && rtm->rtm_dst_len == 0)
 357                         raise(SIGUSR1);
 358                 else if (is_route)
 359                         continue;
 360
 361                 // Data to retrieve
 362                 size_t rta_offset = (is_addr) ? sizeof(struct ifaddrmsg) : sizeof(*ndm);
 363                 uint16_t atype = (is_addr) ? IFA_ADDRESS : NDA_DST;
 364                 ssize_t alen = NLMSG_PAYLOAD(nh, rta_offset);
 365                 struct in6_addr *addr = NULL;
 366
 367                 for (struct rtattr *rta = (void*)(((uint8_t*)ndm) + rta_offset);
 368                                 RTA_OK(rta, alen); rta = RTA_NEXT(rta, alen)) {
 369                         if (rta->rta_type == atype &&
 370                                         RTA_PAYLOAD(rta) >= sizeof(*addr)) {
 371                                 addr = RTA_DATA(rta);
 372                         }
 373                 }
 374
 375                 // Lookup interface
 376                 struct interface *iface = odhcpd_get_interface_by_index(ndm->ndm_ifindex);
 377                 if (!iface)
 378                         continue;
 379
 380                 // Address not specified or unrelated
 381                 if (!addr || IN6_IS_ADDR_LINKLOCAL(addr) ||
 382                                 IN6_IS_ADDR_MULTICAST(addr))
 383                         continue;
 384
 385                 // Check for states
 386                 bool add;
 387                 if (is_addr)
 388                         add = (nh->nlmsg_type == RTM_NEWADDR);
 389                 else
 390                         add = (nh->nlmsg_type == RTM_NEWNEIGH && (ndm->ndm_state &
 391                                 (NUD_REACHABLE | NUD_STALE | NUD_DELAY | NUD_PROBE
 392                                                 | NUD_PERMANENT | NUD_NOARP)));
 393
 394                 if (iface->ndp == RELAYD_RELAY) {
 395                         // Replay change to all neighbor cache
 396                         struct {
 397                                 struct nlmsghdr nh;
 398                                 struct ndmsg ndm;
 399                                 struct nlattr nla_dst;
 400                                 struct in6_addr dst;
 401                         } req = {
 402                                 {sizeof(req), RTM_DELNEIGH, NLM_F_REQUEST,
 403                                                 ++rtnl_seqid, 0},
 404                                 {.ndm_family = AF_INET6, .ndm_flags = NTF_PROXY},
 405                                 {sizeof(struct nlattr) + sizeof(struct in6_addr), NDA_DST},
 406                                 *addr
 407                         };
 408
 409                         if (ndm->ndm_flags & NTF_PROXY) {
 410                                 // Dump & flush proxy entries
 411                                 if (nh->nlmsg_type == RTM_NEWNEIGH) {
 412                                         req.ndm.ndm_ifindex = iface->ifindex;
 413                                         send(rtnl_event.uloop.fd, &req, sizeof(req), MSG_DONTWAIT);
 414                                         setup_route(addr, iface, false);
 415                                         dump_neigh = true;
 416                                 }
 417                         } else if (add) {
 418                                 struct interface *c;
 419                                 list_for_each_entry(c, &interfaces, head) {
 420                                         if (iface == c)
 421                                                 continue;
 422
 423                                         if (c->ndp == RELAYD_RELAY) {
 424                                                 req.nh.nlmsg_type = RTM_NEWNEIGH;
 425                                                 req.nh.nlmsg_flags |= NLM_F_CREATE | NLM_F_REPLACE;
 426
 427                                                 req.ndm.ndm_ifindex = c->ifindex;
 428                                                 send(rtnl_event.uloop.fd, &req, sizeof(req), MSG_DONTWAIT);
 429                                         } else { // Delete NDP cache from interfaces without relay
 430                                                 req.nh.nlmsg_type = RTM_DELNEIGH;
 431                                                 req.nh.nlmsg_flags &= ~(NLM_F_CREATE | NLM_F_REPLACE);
 432
 433                                                 req.ndm.ndm_ifindex = c->ifindex;
 434                                                 send(rtnl_event.uloop.fd, &req, sizeof(req), MSG_DONTWAIT);
 435                                         }
 436                                 }
 437
 438                                 setup_route(addr, iface, true);
 439                         } else {
 440                                 if (nh->nlmsg_type == RTM_NEWNEIGH) {
 441                                         // might be locally originating
 442                                         if (!IN6_ARE_ADDR_EQUAL(&last_solicited, addr)) {
 443                                                 last_solicited = *addr;
 444
 445                                                 struct interface *c;
 446                                                 list_for_each_entry(c, &interfaces, head)
 447                                                         if (iface->ndp == RELAYD_RELAY && iface != c &&
 448                                                                         !c->external == false)
 449                                                                 ping6(addr, c);
 450                                         }
 451                                 } else {
 452                                         struct interface *c;
 453                                         list_for_each_entry(c, &interfaces, head) {
 454                                                 if (c->ndp == RELAYD_RELAY && iface != c) {
 455                                                         req.ndm.ndm_ifindex = c->ifindex;
 456                                                         send(rtnl_event.uloop.fd, &req, sizeof(req), MSG_DONTWAIT);
 457                                                 }
 458                                         }
 459                                         setup_route(addr, iface, false);
 460
 461                                         // also: dump to add proxies back in case it moved elsewhere
 462                                         dump_neigh = true;
 463                                 }
 464                         }
 465                 }
 466
 467                 if (is_addr) {
 468                         check_updates(iface);
 469
 470                         if (iface->dhcpv6 == RELAYD_SERVER)
 471                                 iface->ia_reconf = true;
 472
 473                         if (iface->ndp == RELAYD_RELAY && iface->master) {
 474                                 // Replay address changes on all slave interfaces
 475                                 nh->nlmsg_flags = NLM_F_REQUEST;
 476
 477                                 if (nh->nlmsg_type == RTM_NEWADDR)
 478                                         nh->nlmsg_flags |= NLM_F_CREATE | NLM_F_REPLACE;
 479
 480                                 struct interface *c;
 481                                 list_for_each_entry(c, &interfaces, head) {
 482                                         if (c->ndp == RELAYD_RELAY && !c->master) {
 483                                                 ndm->ndm_ifindex = c->ifindex;
 484                                                 send(rtnl_event.uloop.fd, nh, nh->nlmsg_len, MSG_DONTWAIT);
 485                                         }
 486                                 }
 487                         }
 488                 }
 489         }
 490
 491         if (dump_neigh)
 492                 dump_neigh_table(false);
 493 }