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 "ndp.h"
  33
  34
  35
  36 static void handle_solicit(void *addr, void *data, size_t len,
  37                 struct interface *iface, void *dest);
  38 static void handle_rtnetlink(void *addr, void *data, size_t len,
  39                 struct interface *iface, void *dest);
  40 static ssize_t ping6(struct in6_addr *addr,
  41                 const struct interface *iface);
  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};
  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         // Setup netlink socket
  65         if ((rtnl_event.uloop.fd = odhcpd_open_rtnl()) < 0)
  66                 return -1;
  67
  68         // Receive netlink neighbor and ip-address events
  69         uint32_t group = RTNLGRP_IPV6_IFADDR;
  70         setsockopt(rtnl_event.uloop.fd, SOL_NETLINK,
  71                         NETLINK_ADD_MEMBERSHIP, &group, sizeof(group));
  72         group = RTNLGRP_IPV6_ROUTE;
  73         setsockopt(rtnl_event.uloop.fd, SOL_NETLINK,
  74                         NETLINK_ADD_MEMBERSHIP, &group, sizeof(group));
  75
  76         odhcpd_register(&rtnl_event);
  77
  78         // Open ICMPv6 socket
  79         ping_socket = socket(AF_INET6, SOCK_RAW | SOCK_CLOEXEC, IPPROTO_ICMPV6);
  80         if (ping_socket < 0) {
  81                 syslog(LOG_ERR, "Unable to open raw socket: %s", strerror(errno));
  82                         return -1;
  83         }
  84
  85         int val = 2;
  86         setsockopt(ping_socket, IPPROTO_RAW, IPV6_CHECKSUM, &val, sizeof(val));
  87
  88         // This is required by RFC 4861
  89         val = 255;
  90         setsockopt(ping_socket, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &val, sizeof(val));
  91         setsockopt(ping_socket, IPPROTO_IPV6, IPV6_UNICAST_HOPS, &val, sizeof(val));
  92
  93         // Filter all packages, we only want to send
  94         struct icmp6_filter filt;
  95         ICMP6_FILTER_SETBLOCKALL(&filt);
  96         setsockopt(ping_socket, IPPROTO_ICMPV6, ICMP6_FILTER, &filt, sizeof(filt));
  97
  98
  99         // Netlink socket, continued...
 100         group = RTNLGRP_NEIGH;
 101         setsockopt(rtnl_event.uloop.fd, SOL_NETLINK, NETLINK_ADD_MEMBERSHIP, &group, sizeof(group));
 102
 103         return 0;
 104 }
 105
 106
 107 static void dump_neigh_table(bool proxy)
 108 {
 109         struct {
 110                 struct nlmsghdr nh;
 111                 struct ndmsg ndm;
 112         } req = {
 113                 {sizeof(req), RTM_GETNEIGH, NLM_F_REQUEST | NLM_F_DUMP,
 114                                 ++rtnl_seqid, 0},
 115                 {.ndm_family = AF_INET6, .ndm_flags = (proxy) ? NTF_PROXY : 0}
 116         };
 117         send(rtnl_event.uloop.fd, &req, sizeof(req), MSG_DONTWAIT);
 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                         write(procfd, "0\n", 2);
 135
 136                 dump_neigh = true;
 137         }
 138
 139         if (enable && (iface->ra == RELAYD_SERVER || iface->dhcpv6 == RELAYD_SERVER)) {
 140                 // Synthesize initial address events
 141                 struct {
 142                         struct nlmsghdr nh;
 143                         struct ifaddrmsg ifa;
 144                 } req2 = {
 145                         {sizeof(req2), RTM_GETADDR, NLM_F_REQUEST | NLM_F_DUMP,
 146                                         ++rtnl_seqid, 0},
 147                         {.ifa_family = AF_INET6, .ifa_index = iface->ifindex}
 148                 };
 149                 send(rtnl_event.uloop.fd, &req2, sizeof(req2), MSG_DONTWAIT);
 150         }
 151
 152         if (enable && iface->ndp == RELAYD_RELAY) {
 153                 write(procfd, "1\n", 2);
 154                 close(procfd);
 155
 156                 int sock = socket(AF_PACKET, SOCK_DGRAM | SOCK_CLOEXEC, htons(ETH_P_IPV6));
 157                 if (sock < 0) {
 158                         syslog(LOG_ERR, "Unable to open packet socket: %s",
 159                                         strerror(errno));
 160                         return -1;
 161                 }
 162
 163 #ifdef PACKET_RECV_TYPE
 164                 int pktt = 1 << PACKET_MULTICAST;
 165                 setsockopt(sock, SOL_PACKET, PACKET_RECV_TYPE, &pktt, sizeof(pktt));
 166 #endif
 167
 168                 if (setsockopt(sock, SOL_SOCKET, SO_ATTACH_FILTER,
 169                                 &bpf_prog, sizeof(bpf_prog))) {
 170                         syslog(LOG_ERR, "Failed to set BPF: %s", strerror(errno));
 171                         return -1;
 172                 }
 173
 174                 struct sockaddr_ll ll = {
 175                         .sll_family = AF_PACKET,
 176                         .sll_ifindex = iface->ifindex,
 177                         .sll_protocol = htons(ETH_P_IPV6),
 178                         .sll_hatype = 0,
 179                         .sll_pkttype = 0,
 180                         .sll_halen = 0,
 181                         .sll_addr = {0},
 182                 };
 183                 bind(sock, (struct sockaddr*)&ll, sizeof(ll));
 184
 185                 struct packet_mreq mreq = {iface->ifindex, PACKET_MR_ALLMULTI, ETH_ALEN, {0}};
 186                 setsockopt(sock, SOL_PACKET, PACKET_ADD_MEMBERSHIP, &mreq, sizeof(mreq));
 187
 188                 iface->ndp_event.uloop.fd = sock;
 189                 iface->ndp_event.handle_dgram = handle_solicit;
 190                 odhcpd_register(&iface->ndp_event);
 191
 192                 // If we already were enabled dump is unnecessary, if not do dump
 193                 if (!dump_neigh)
 194                         dump_neigh_table(false);
 195                 else
 196                         dump_neigh = false;
 197         } else {
 198                 close(procfd);
 199         }
 200
 201         if (dump_neigh)
 202                 dump_neigh_table(true);
 203
 204         return 0;
 205 }
 206
 207
 208 // Send an ICMP-ECHO. This is less for actually pinging but for the
 209 // neighbor cache to be kept up-to-date.
 210 static ssize_t ping6(struct in6_addr *addr,
 211                 const struct interface *iface)
 212 {
 213         struct sockaddr_in6 dest = {AF_INET6, 0, 0, *addr, 0};
 214         struct icmp6_hdr echo = {.icmp6_type = ICMP6_ECHO_REQUEST};
 215         struct iovec iov = {&echo, sizeof(echo)};
 216
 217         // Linux seems to not honor IPV6_PKTINFO on raw-sockets, so work around
 218         setsockopt(ping_socket, SOL_SOCKET, SO_BINDTODEVICE,
 219                         iface->ifname, sizeof(iface->ifname));
 220         return odhcpd_send(ping_socket, &dest, &iov, 1, iface);
 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 == false))
 261                         ping6(&req->nd_ns_target, c);
 262 }
 263
 264
 265 void odhcpd_setup_route(const struct in6_addr *addr, int prefixlen,
 266                 const struct interface *iface, const struct in6_addr *gw, bool add)
 267 {
 268         struct req {
 269                 struct nlmsghdr nh;
 270                 struct rtmsg rtm;
 271                 struct rtattr rta_dst;
 272                 struct in6_addr dst_addr;
 273                 struct rtattr rta_oif;
 274                 uint32_t ifindex;
 275                 struct rtattr rta_table;
 276                 uint32_t table;
 277                 struct rtattr rta_gw;
 278                 struct in6_addr gw;
 279         } req = {
 280                 {sizeof(req), 0, NLM_F_REQUEST, ++rtnl_seqid, 0},
 281                 {AF_INET6, prefixlen, 0, 0, 0, 0, 0, 0, 0},
 282                 {sizeof(struct rtattr) + sizeof(struct in6_addr), RTA_DST},
 283                 *addr,
 284                 {sizeof(struct rtattr) + sizeof(uint32_t), RTA_OIF},
 285                 iface->ifindex,
 286                 {sizeof(struct rtattr) + sizeof(uint32_t), RTA_TABLE},
 287                 RT_TABLE_MAIN,
 288                 {sizeof(struct rtattr) + sizeof(struct in6_addr), RTA_GATEWAY},
 289                 IN6ADDR_ANY_INIT,
 290         };
 291
 292         if (gw)
 293                 req.gw = *gw;
 294
 295         if (add) {
 296                 req.nh.nlmsg_type = RTM_NEWROUTE;
 297                 req.nh.nlmsg_flags |= (NLM_F_CREATE | NLM_F_REPLACE);
 298                 req.rtm.rtm_protocol = RTPROT_BOOT;
 299                 req.rtm.rtm_scope = (gw) ? RT_SCOPE_UNIVERSE : RT_SCOPE_LINK;
 300                 req.rtm.rtm_type = RTN_UNICAST;
 301         } else {
 302                 req.nh.nlmsg_type = RTM_DELROUTE;
 303                 req.rtm.rtm_scope = RT_SCOPE_NOWHERE;
 304         }
 305
 306         size_t reqlen = (gw) ? sizeof(req) : offsetof(struct req, rta_gw);
 307         send(rtnl_event.uloop.fd, &req, reqlen, MSG_DONTWAIT);
 308 }
 309
 310 // Use rtnetlink to modify kernel routes
 311 static void setup_route(struct in6_addr *addr, struct interface *iface,
 312                 bool add)
 313 {
 314         char namebuf[INET6_ADDRSTRLEN];
 315         inet_ntop(AF_INET6, addr, namebuf, sizeof(namebuf));
 316         syslog(LOG_NOTICE, "%s about %s on %s", (add) ? "Learned" : "Forgot",
 317                         namebuf, (iface) ? iface->ifname : "<pending>");
 318
 319         if (!iface || !iface->learn_routes)
 320                 return;
 321
 322         odhcpd_setup_route(addr, 128, iface, NULL, add);
 323 }
 324
 325
 326 // Handler for neighbor cache entries from the kernel. This is our source
 327 // to learn and unlearn hosts on interfaces.
 328 static void handle_rtnetlink(_unused void *addr, void *data, size_t len,
 329                 _unused struct interface *iface, _unused void *dest)
 330 {
 331         bool dump_neigh = false;
 332         struct in6_addr last_solicited = IN6ADDR_ANY_INIT;
 333
 334         for (struct nlmsghdr *nh = data; NLMSG_OK(nh, len);
 335                         nh = NLMSG_NEXT(nh, len)) {
 336                 struct rtmsg *rtm = NLMSG_DATA(nh);
 337                 if ((nh->nlmsg_type == RTM_NEWROUTE ||
 338                                 nh->nlmsg_type == RTM_DELROUTE) &&
 339                                 rtm->rtm_dst_len == 0)
 340                         raise(SIGUSR1); // Inform about a change in default route
 341
 342                 struct ndmsg *ndm = NLMSG_DATA(nh);
 343                 struct ifaddrmsg *ifa = NLMSG_DATA(nh);
 344                 if (nh->nlmsg_type != RTM_NEWNEIGH
 345                                 && nh->nlmsg_type != RTM_DELNEIGH
 346                                 && nh->nlmsg_type != RTM_NEWADDR
 347                                 && nh->nlmsg_type != RTM_DELADDR)
 348                         continue; // Unrelated message type
 349                 bool is_addr = (nh->nlmsg_type == RTM_NEWADDR
 350                                 || nh->nlmsg_type == RTM_DELADDR);
 351
 352                 // Family and ifindex are on the same offset for NEIGH and ADDR
 353                 if (NLMSG_PAYLOAD(nh, 0) < sizeof(*ndm)
 354                                 || ndm->ndm_family != AF_INET6)
 355                         continue; //
 356
 357                 // Lookup interface
 358                 struct interface *iface;
 359                 if (!(iface = odhcpd_get_interface_by_index(ndm->ndm_ifindex)))
 360                         continue;
 361
 362                 // Data to retrieve
 363                 size_t rta_offset = (is_addr) ? sizeof(*ifa) : sizeof(*ndm);
 364                 uint16_t atype = (is_addr) ? IFA_ADDRESS : NDA_DST;
 365                 ssize_t alen = NLMSG_PAYLOAD(nh, rta_offset);
 366                 struct in6_addr *addr = NULL;
 367
 368                 for (struct rtattr *rta = (void*)(((uint8_t*)ndm) + rta_offset);
 369                                 RTA_OK(rta, alen); rta = RTA_NEXT(rta, alen))
 370                         if (rta->rta_type == atype &&
 371                                         RTA_PAYLOAD(rta) >= sizeof(*addr))
 372                                 addr = RTA_DATA(rta);
 373
 374                 // Address not specified or unrelated
 375                 if (!addr || IN6_IS_ADDR_LINKLOCAL(addr) ||
 376                                 IN6_IS_ADDR_MULTICAST(addr))
 377                         continue;
 378
 379                 // Check for states
 380                 bool add;
 381                 if (is_addr)
 382                         add = (nh->nlmsg_type == RTM_NEWADDR);
 383                 else
 384                         add = (nh->nlmsg_type == RTM_NEWNEIGH && (ndm->ndm_state &
 385                                 (NUD_REACHABLE | NUD_STALE | NUD_DELAY | NUD_PROBE
 386                                                 | NUD_PERMANENT | NUD_NOARP)));
 387
 388                 if (iface->ndp == RELAYD_RELAY) {
 389                         // Replay change to all neighbor cache
 390                         struct {
 391                                 struct nlmsghdr nh;
 392                                 struct ndmsg ndm;
 393                                 struct nlattr nla_dst;
 394                                 struct in6_addr dst;
 395                         } req = {
 396                                 {sizeof(req), RTM_DELNEIGH, NLM_F_REQUEST,
 397                                                 ++rtnl_seqid, 0},
 398                                 {.ndm_family = AF_INET6, .ndm_flags = NTF_PROXY},
 399                                 {sizeof(struct nlattr) + sizeof(struct in6_addr), NDA_DST},
 400                                 *addr
 401                         };
 402
 403                         if (ndm->ndm_flags & NTF_PROXY) {
 404                                 // Dump & flush proxy entries
 405                                 if (nh->nlmsg_type == RTM_NEWNEIGH) {
 406                                         req.ndm.ndm_ifindex = iface->ifindex;
 407                                         send(rtnl_event.uloop.fd, &req, sizeof(req), MSG_DONTWAIT);
 408                                         dump_neigh = true;
 409                                 }
 410                         } else if (add) {
 411                                 struct interface *c;
 412                                 list_for_each_entry(c, &interfaces, head) {
 413                                         if (iface == c)
 414                                                 continue;
 415
 416                                         if (c->ndp == RELAYD_RELAY) {
 417                                                 req.nh.nlmsg_type = RTM_NEWNEIGH;
 418                                                 req.nh.nlmsg_flags |= NLM_F_CREATE | NLM_F_REPLACE;
 419
 420                                                 req.ndm.ndm_ifindex = c->ifindex;
 421                                                 send(rtnl_event.uloop.fd, &req, sizeof(req), MSG_DONTWAIT);
 422                                         } else { // Delete NDP cache from interfaces without relay
 423                                                 req.nh.nlmsg_type = RTM_DELNEIGH;
 424                                                 req.nh.nlmsg_flags &= ~(NLM_F_CREATE | NLM_F_REPLACE);
 425
 426                                                 req.ndm.ndm_ifindex = c->ifindex;
 427                                                 send(rtnl_event.uloop.fd, &req, sizeof(req), MSG_DONTWAIT);
 428                                         }
 429                                 }
 430
 431                                 setup_route(addr, iface, true);
 432                         } else {
 433                                 if (nh->nlmsg_type == RTM_NEWNEIGH) {
 434                                         // might be locally originating
 435                                         if (!IN6_ARE_ADDR_EQUAL(&last_solicited, addr)) {
 436                                                 last_solicited = *addr;
 437
 438                                                 struct interface *c;
 439                                                 list_for_each_entry(c, &interfaces, head)
 440                                                         if (iface->ndp == RELAYD_RELAY && iface != c &&
 441                                                                         !c->external == false)
 442                                                                 ping6(addr, c);
 443                                         }
 444                                 } else {
 445                                         struct interface *c;
 446                                         list_for_each_entry(c, &interfaces, head) {
 447                                                 if (c->ndp == RELAYD_RELAY && iface != c) {
 448                                                         req.ndm.ndm_ifindex = c->ifindex;
 449                                                         send(rtnl_event.uloop.fd, &req, sizeof(req), MSG_DONTWAIT);
 450                                                 }
 451                                         }
 452                                         setup_route(addr, iface, false);
 453
 454                                         // also: dump to add proxies back in case it moved elsewhere
 455                                         dump_neigh = true;
 456                                 }
 457                         }
 458                 }
 459
 460                 if (is_addr) {
 461                         if (iface->ra == RELAYD_SERVER)
 462                                 raise(SIGUSR1); // Inform about a change in addresses
 463
 464                         if (iface->dhcpv6 == RELAYD_SERVER)
 465                                 iface->ia_reconf = true;
 466
 467                         if (iface->ndp == RELAYD_RELAY && iface->master) {
 468                                 // Replay address changes on all slave interfaces
 469                                 nh->nlmsg_flags = NLM_F_REQUEST;
 470
 471                                 if (nh->nlmsg_type == RTM_NEWADDR)
 472                                         nh->nlmsg_flags |= NLM_F_CREATE | NLM_F_REPLACE;
 473
 474                                 struct interface *c;
 475                                 list_for_each_entry(c, &interfaces, head) {
 476                                         if (c->ndp == RELAYD_RELAY && !c->master) {
 477                                                 ifa->ifa_index = c->ifindex;
 478                                                 send(rtnl_event.uloop.fd, nh, nh->nlmsg_len, MSG_DONTWAIT);
 479                                         }
 480                                 }
 481                         }
 482                 }
 483         }
 484
 485         if (dump_neigh)
 486                 dump_neigh_table(false);
 487 }