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         // Synthesize initial address events
  77         struct {
  78                 struct nlmsghdr nh;
  79                 struct ifaddrmsg ifa;
  80         } req2 = {
  81                 {sizeof(req2), RTM_GETADDR, NLM_F_REQUEST | NLM_F_DUMP,
  82                                 ++rtnl_seqid, 0},
  83                 {.ifa_family = AF_INET6}
  84         };
  85         send(rtnl_event.uloop.fd, &req2, sizeof(req2), MSG_DONTWAIT);
  86         odhcpd_register(&rtnl_event);
  87
  88         // Open ICMPv6 socket
  89         ping_socket = socket(AF_INET6, SOCK_RAW | SOCK_CLOEXEC, IPPROTO_ICMPV6);
  90         if (ping_socket < 0) {
  91                 syslog(LOG_ERR, "Unable to open raw socket: %s", strerror(errno));
  92                         return -1;
  93         }
  94
  95         int val = 2;
  96         setsockopt(ping_socket, IPPROTO_RAW, IPV6_CHECKSUM, &val, sizeof(val));
  97
  98         // This is required by RFC 4861
  99         val = 255;
 100         setsockopt(ping_socket, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &val, sizeof(val));
 101         setsockopt(ping_socket, IPPROTO_IPV6, IPV6_UNICAST_HOPS, &val, sizeof(val));
 102
 103         // Filter all packages, we only want to send
 104         struct icmp6_filter filt;
 105         ICMP6_FILTER_SETBLOCKALL(&filt);
 106         setsockopt(ping_socket, IPPROTO_ICMPV6, ICMP6_FILTER, &filt, sizeof(filt));
 107
 108
 109         // Netlink socket, continued...
 110         group = RTNLGRP_NEIGH;
 111         setsockopt(rtnl_event.uloop.fd, SOL_NETLINK, NETLINK_ADD_MEMBERSHIP, &group, sizeof(group));
 112
 113         return 0;
 114 }
 115
 116
 117 int setup_ndp_interface(struct interface *iface, bool enable)
 118 {
 119         char procbuf[64];
 120         snprintf(procbuf, sizeof(procbuf), "/proc/sys/net/ipv6/conf/%s/proxy_ndp", iface->ifname);
 121         int procfd = open(procbuf, O_WRONLY);
 122
 123         if (iface->ndp_event.uloop.fd >= 0) {
 124                 uloop_fd_delete(&iface->ndp_event.uloop);
 125                 close(iface->ndp_event.uloop.fd);
 126                 iface->ndp_event.uloop.fd = -1;
 127
 128                 write(procfd, "0\n", 2);
 129         }
 130
 131         if (enable && iface->ndp == RELAYD_RELAY) {
 132                 write(procfd, "1\n", 2);
 133
 134                 int sock = socket(AF_PACKET, SOCK_DGRAM | SOCK_CLOEXEC, htons(ETH_P_IPV6));
 135                 if (sock < 0) {
 136                         syslog(LOG_ERR, "Unable to open packet socket: %s",
 137                                         strerror(errno));
 138                         return -1;
 139                 }
 140
 141 #ifdef PACKET_RECV_TYPE
 142                 int pktt = 1 << PACKET_MULTICAST;
 143                 setsockopt(sock, SOL_PACKET, PACKET_RECV_TYPE, &pktt, sizeof(pktt));
 144 #endif
 145
 146                 if (setsockopt(sock, SOL_SOCKET, SO_ATTACH_FILTER,
 147                                 &bpf_prog, sizeof(bpf_prog))) {
 148                         syslog(LOG_ERR, "Failed to set BPF: %s", strerror(errno));
 149                         return -1;
 150                 }
 151
 152                 struct sockaddr_ll ll = {
 153                         .sll_family = AF_PACKET,
 154                         .sll_ifindex = iface->ifindex,
 155                         .sll_protocol = htons(ETH_P_IPV6),
 156                 };
 157                 bind(sock, (struct sockaddr*)&ll, sizeof(ll));
 158
 159                 struct packet_mreq mreq = {iface->ifindex, PACKET_MR_ALLMULTI, ETH_ALEN, {0}};
 160                 setsockopt(sock, SOL_PACKET, PACKET_ADD_MEMBERSHIP, &mreq, sizeof(mreq));
 161
 162                 iface->ndp_event.uloop.fd = sock;
 163                 iface->ndp_event.handle_dgram = handle_solicit;
 164                 odhcpd_register(&iface->ndp_event);
 165
 166                 // Dump neighbor events
 167                 struct {
 168                         struct nlmsghdr nh;
 169                         struct ndmsg ndm;
 170                 } req = {
 171                         {sizeof(req), RTM_GETNEIGH, NLM_F_REQUEST | NLM_F_DUMP,
 172                                         ++rtnl_seqid, 0},
 173                         {.ndm_family = AF_INET6}
 174                 };
 175                 send(rtnl_event.uloop.fd, &req, sizeof(req), MSG_DONTWAIT);
 176         }
 177         close(procfd);
 178
 179         return 0;
 180 }
 181
 182
 183 // Send an ICMP-ECHO. This is less for actually pinging but for the
 184 // neighbor cache to be kept up-to-date.
 185 static ssize_t ping6(struct in6_addr *addr,
 186                 const struct interface *iface)
 187 {
 188         struct sockaddr_in6 dest = {AF_INET6, 0, 0, *addr, 0};
 189         struct icmp6_hdr echo = {.icmp6_type = ICMP6_ECHO_REQUEST};
 190         struct iovec iov = {&echo, sizeof(echo)};
 191
 192         // Linux seems to not honor IPV6_PKTINFO on raw-sockets, so work around
 193         setsockopt(ping_socket, SOL_SOCKET, SO_BINDTODEVICE,
 194                         iface->ifname, sizeof(iface->ifname));
 195         return odhcpd_send(ping_socket, &dest, &iov, 1, iface);
 196 }
 197
 198
 199 // Handle solicitations
 200 static void handle_solicit(void *addr, void *data, size_t len,
 201                 struct interface *iface, _unused void *dest)
 202 {
 203         struct ip6_hdr *ip6 = data;
 204         struct nd_neighbor_solicit *req = (struct nd_neighbor_solicit*)&ip6[1];
 205         struct sockaddr_ll *ll = addr;
 206
 207         // Solicitation is for duplicate address detection
 208         bool ns_is_dad = IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src);
 209
 210         // Don't forward any non-DAD solicitation for external ifaces
 211         // TODO: check if we should even forward DADs for them
 212         if (iface->external && !ns_is_dad)
 213                 return;
 214
 215         if (len < sizeof(*ip6) + sizeof(*req))
 216                 return; // Invalid reqicitation
 217
 218         if (IN6_IS_ADDR_LINKLOCAL(&req->nd_ns_target) ||
 219                         IN6_IS_ADDR_LOOPBACK(&req->nd_ns_target) ||
 220                         IN6_IS_ADDR_MULTICAST(&req->nd_ns_target))
 221                 return; // Invalid target
 222
 223         char ipbuf[INET6_ADDRSTRLEN];
 224         inet_ntop(AF_INET6, &req->nd_ns_target, ipbuf, sizeof(ipbuf));
 225         syslog(LOG_DEBUG, "Got a NS for %s", ipbuf);
 226
 227         uint8_t mac[6];
 228         odhcpd_get_mac(iface, mac);
 229         if (!memcmp(ll->sll_addr, mac, sizeof(mac)))
 230                 return; // Looped back
 231
 232         struct interface *c;
 233         list_for_each_entry(c, &interfaces, head)
 234                 if (iface->ndp == RELAYD_RELAY && iface != c &&
 235                                 (!ns_is_dad || !c->external == false))
 236                         ping6(&req->nd_ns_target, c);
 237 }
 238
 239
 240 void odhcpd_setup_route(const struct in6_addr *addr, int prefixlen,
 241                 const struct interface *iface, const struct in6_addr *gw, bool add)
 242 {
 243         struct req {
 244                 struct nlmsghdr nh;
 245                 struct rtmsg rtm;
 246                 struct rtattr rta_dst;
 247                 struct in6_addr dst_addr;
 248                 struct rtattr rta_oif;
 249                 uint32_t ifindex;
 250                 struct rtattr rta_table;
 251                 uint32_t table;
 252                 struct rtattr rta_gw;
 253                 struct in6_addr gw;
 254         } req = {
 255                 {sizeof(req), 0, NLM_F_REQUEST, ++rtnl_seqid, 0},
 256                 {AF_INET6, prefixlen, 0, 0, 0, 0, 0, 0, 0},
 257                 {sizeof(struct rtattr) + sizeof(struct in6_addr), RTA_DST},
 258                 *addr,
 259                 {sizeof(struct rtattr) + sizeof(uint32_t), RTA_OIF},
 260                 iface->ifindex,
 261                 {sizeof(struct rtattr) + sizeof(uint32_t), RTA_TABLE},
 262                 RT_TABLE_MAIN,
 263                 {sizeof(struct rtattr) + sizeof(struct in6_addr), RTA_GATEWAY},
 264                 IN6ADDR_ANY_INIT,
 265         };
 266
 267         if (gw)
 268                 req.gw = *gw;
 269
 270         if (add) {
 271                 req.nh.nlmsg_type = RTM_NEWROUTE;
 272                 req.nh.nlmsg_flags |= (NLM_F_CREATE | NLM_F_REPLACE);
 273                 req.rtm.rtm_protocol = RTPROT_BOOT;
 274                 req.rtm.rtm_scope = (gw) ? RT_SCOPE_UNIVERSE : RT_SCOPE_LINK;
 275                 req.rtm.rtm_type = RTN_UNICAST;
 276         } else {
 277                 req.nh.nlmsg_type = RTM_DELROUTE;
 278                 req.rtm.rtm_scope = RT_SCOPE_NOWHERE;
 279         }
 280
 281         size_t reqlen = (gw) ? sizeof(req) : offsetof(struct req, rta_gw);
 282         send(rtnl_event.uloop.fd, &req, reqlen, MSG_DONTWAIT);
 283 }
 284
 285 // Use rtnetlink to modify kernel routes
 286 static void setup_route(struct in6_addr *addr, struct interface *iface,
 287                 bool add)
 288 {
 289         char namebuf[INET6_ADDRSTRLEN];
 290         inet_ntop(AF_INET6, addr, namebuf, sizeof(namebuf));
 291         syslog(LOG_NOTICE, "%s about %s on %s", (add) ? "Learned" : "Forgot",
 292                         namebuf, (iface) ? iface->ifname : "<pending>");
 293
 294         if (!iface || !iface->learn_routes)
 295                 return;
 296
 297         odhcpd_setup_route(addr, 128, iface, NULL, add);
 298 }
 299
 300
 301 // Handler for neighbor cache entries from the kernel. This is our source
 302 // to learn and unlearn hosts on interfaces.
 303 static void handle_rtnetlink(_unused void *addr, void *data, size_t len,
 304                 _unused struct interface *iface, _unused void *dest)
 305 {
 306         bool dump_neigh = false;
 307         struct in6_addr last_solicited = IN6ADDR_ANY_INIT;
 308
 309         for (struct nlmsghdr *nh = data; NLMSG_OK(nh, len);
 310                         nh = NLMSG_NEXT(nh, len)) {
 311                 struct rtmsg *rtm = NLMSG_DATA(nh);
 312                 if ((nh->nlmsg_type == RTM_NEWROUTE ||
 313                                 nh->nlmsg_type == RTM_DELROUTE) &&
 314                                 rtm->rtm_dst_len == 0)
 315                         raise(SIGUSR1); // Inform about a change in default route
 316
 317                 struct ndmsg *ndm = NLMSG_DATA(nh);
 318                 struct ifaddrmsg *ifa = NLMSG_DATA(nh);
 319                 if (nh->nlmsg_type != RTM_NEWNEIGH
 320                                 && nh->nlmsg_type != RTM_DELNEIGH
 321                                 && nh->nlmsg_type != RTM_NEWADDR
 322                                 && nh->nlmsg_type != RTM_DELADDR)
 323                         continue; // Unrelated message type
 324                 bool is_addr = (nh->nlmsg_type == RTM_NEWADDR
 325                                 || nh->nlmsg_type == RTM_DELADDR);
 326
 327                 // Family and ifindex are on the same offset for NEIGH and ADDR
 328                 if (NLMSG_PAYLOAD(nh, 0) < sizeof(*ndm)
 329                                 || ndm->ndm_family != AF_INET6)
 330                         continue; //
 331
 332                 // Lookup interface
 333                 struct interface *iface;
 334                 if (!(iface = odhcpd_get_interface_by_index(ndm->ndm_ifindex)))
 335                         continue;
 336
 337                 // Data to retrieve
 338                 size_t rta_offset = (is_addr) ? sizeof(*ifa) : sizeof(*ndm);
 339                 uint16_t atype = (is_addr) ? IFA_ADDRESS : NDA_DST;
 340                 ssize_t alen = NLMSG_PAYLOAD(nh, rta_offset);
 341                 struct in6_addr *addr = NULL;
 342
 343                 for (struct rtattr *rta = (void*)(((uint8_t*)ndm) + rta_offset);
 344                                 RTA_OK(rta, alen); rta = RTA_NEXT(rta, alen))
 345                         if (rta->rta_type == atype &&
 346                                         RTA_PAYLOAD(rta) >= sizeof(*addr))
 347                                 addr = RTA_DATA(rta);
 348
 349                 // Address not specified or unrelated
 350                 if (!addr || IN6_IS_ADDR_LINKLOCAL(addr) ||
 351                                 IN6_IS_ADDR_MULTICAST(addr))
 352                         continue;
 353
 354                 // Check for states
 355                 bool add;
 356                 if (is_addr)
 357                         add = (nh->nlmsg_type == RTM_NEWADDR);
 358                 else
 359                         add = (nh->nlmsg_type == RTM_NEWNEIGH && (ndm->ndm_state &
 360                                 (NUD_REACHABLE | NUD_STALE | NUD_DELAY | NUD_PROBE
 361                                                 | NUD_PERMANENT | NUD_NOARP)));
 362
 363                 if (iface->ndp == RELAYD_RELAY) {
 364                         // Replay change to all neighbor cache
 365                         struct {
 366                                 struct nlmsghdr nh;
 367                                 struct ndmsg ndm;
 368                                 struct nlattr nla_dst;
 369                                 struct in6_addr dst;
 370                         } req = {
 371                                 {sizeof(req), RTM_DELNEIGH, NLM_F_REQUEST,
 372                                                 ++rtnl_seqid, 0},
 373                                 {.ndm_family = AF_INET6, .ndm_flags = NTF_PROXY},
 374                                 {sizeof(struct nlattr) + sizeof(struct in6_addr), NDA_DST},
 375                                 *addr
 376                         };
 377
 378                         if (add) {
 379                                 req.nh.nlmsg_type = RTM_NEWNEIGH;
 380                                 req.nh.nlmsg_flags |= NLM_F_CREATE;
 381
 382                                 struct interface *c;
 383                                 list_for_each_entry(c, &interfaces, head) {
 384                                         if (c->ndp == RELAYD_RELAY && iface != c) {
 385                                                 req.ndm.ndm_ifindex = c->ifindex;
 386                                                 send(rtnl_event.uloop.fd, &req, sizeof(req), MSG_DONTWAIT);
 387                                         }
 388                                 }
 389
 390                                 setup_route(addr, iface, true);
 391                         } else {
 392                                 if (nh->nlmsg_type == RTM_NEWNEIGH) {
 393                                         // might be locally originating
 394                                         if (!IN6_ARE_ADDR_EQUAL(&last_solicited, addr)) {
 395                                                 last_solicited = *addr;
 396
 397                                                 struct interface *c;
 398                                                 list_for_each_entry(c, &interfaces, head)
 399                                                         if (iface->ndp == RELAYD_RELAY && iface != c &&
 400                                                                         !c->external == false)
 401                                                                 ping6(addr, c);
 402                                         }
 403                                 } else {
 404                                         struct interface *c;
 405                                         list_for_each_entry(c, &interfaces, head) {
 406                                                 if (c->ndp == RELAYD_RELAY && iface != c) {
 407                                                         req.ndm.ndm_ifindex = c->ifindex;
 408                                                         send(rtnl_event.uloop.fd, &req, sizeof(req), MSG_DONTWAIT);
 409                                                 }
 410                                         }
 411                                         setup_route(addr, iface, false);
 412
 413                                         // also: dump to add proxies back in case it moved elsewhere
 414                                         dump_neigh = true;
 415                                 }
 416                         }
 417                 }
 418
 419                 if (is_addr && iface->ra == RELAYD_SERVER)
 420                         raise(SIGUSR1); // Inform about a change in addresses
 421
 422                 if (is_addr && iface->dhcpv6 == RELAYD_SERVER)
 423                         iface->ia_reconf = true;
 424
 425                 if (iface->ndp == RELAYD_RELAY && is_addr && iface->master) {
 426                         // Replay address changes on all slave interfaces
 427                         nh->nlmsg_flags = NLM_F_REQUEST;
 428
 429                         if (nh->nlmsg_type == RTM_NEWADDR)
 430                                 nh->nlmsg_flags |= NLM_F_CREATE | NLM_F_REPLACE;
 431
 432                         struct interface *c;
 433                         list_for_each_entry(c, &interfaces, head) {
 434                                 if (c->ndp == RELAYD_RELAY && !c->master) {
 435                                         ifa->ifa_index = c->ifindex;
 436                                         send(rtnl_event.uloop.fd, nh, nh->nlmsg_len, MSG_DONTWAIT);
 437                                 }
 438                         }
 439                 }
 440         }
 441
 442         if (dump_neigh) {
 443                 struct {
 444                         struct nlmsghdr nh;
 445                         struct ndmsg ndm;
 446                 } req = {
 447                         {sizeof(req), RTM_GETNEIGH, NLM_F_REQUEST | NLM_F_DUMP,
 448                                         ++rtnl_seqid, 0},
 449                         {.ndm_family = AF_INET6}
 450                 };
 451                 send(rtnl_event.uloop.fd, &req, sizeof(req), MSG_DONTWAIT);
 452         }
 453 }