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 <unistd.h>
  21 #include <arpa/inet.h>
  22 #include <sys/socket.h>
  23 #include <net/ethernet.h>
  24 #include <netinet/ip6.h>
  25 #include <netinet/icmp6.h>
  26 #include <netpacket/packet.h>
  27
  28 #include <linux/rtnetlink.h>
  29 #include <linux/filter.h>
  30 #include "router.h"
  31 #include "ndp.h"
  32
  33
  34
  35 static void handle_solicit(void *addr, void *data, size_t len,
  36                 struct interface *iface, void *dest);
  37 static void handle_rtnetlink(void *addr, void *data, size_t len,
  38                 struct interface *iface, void *dest);
  39 static struct ndp_neighbor* find_neighbor(struct in6_addr *addr, bool strict);
  40 static void modify_neighbor(struct in6_addr *addr, struct interface *iface,
  41                 bool add);
  42 static ssize_t ping6(struct in6_addr *addr,
  43                 const struct interface *iface);
  44
  45 static struct list_head neighbors = LIST_HEAD_INIT(neighbors);
  46 static size_t neighbor_count = 0;
  47 static uint32_t rtnl_seqid = 0;
  48
  49 static int ping_socket = -1;
  50 static struct odhcpd_event ndp_event = {{.fd = -1}, handle_solicit};
  51 static struct odhcpd_event rtnl_event = {{.fd = -1}, handle_rtnetlink};
  52
  53
  54 // Filter ICMPv6 messages of type neighbor soliciation
  55 static struct sock_filter bpf[] = {
  56         BPF_STMT(BPF_LD | BPF_B | BPF_ABS, offsetof(struct ip6_hdr, ip6_nxt)),
  57         BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, IPPROTO_ICMPV6, 0, 3),
  58         BPF_STMT(BPF_LD | BPF_B | BPF_ABS, sizeof(struct ip6_hdr) +
  59                         offsetof(struct icmp6_hdr, icmp6_type)),
  60         BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, ND_NEIGHBOR_SOLICIT, 0, 1),
  61         BPF_STMT(BPF_RET | BPF_K, 0xffffffff),
  62         BPF_STMT(BPF_RET | BPF_K, 0),
  63 };
  64 static const struct sock_fprog bpf_prog = {sizeof(bpf) / sizeof(*bpf), bpf};
  65
  66
  67 // Initialize NDP-proxy
  68 int init_ndp(void)
  69 {
  70         // Setup netlink socket
  71         if ((rtnl_event.uloop.fd = odhcpd_open_rtnl()) < 0)
  72                 return -1;
  73
  74         // Receive netlink neighbor and ip-address events
  75         uint32_t group = RTNLGRP_IPV6_IFADDR;
  76         setsockopt(rtnl_event.uloop.fd, SOL_NETLINK,
  77                         NETLINK_ADD_MEMBERSHIP, &group, sizeof(group));
  78         group = RTNLGRP_IPV6_ROUTE;
  79         setsockopt(rtnl_event.uloop.fd, SOL_NETLINK,
  80                         NETLINK_ADD_MEMBERSHIP, &group, sizeof(group));
  81
  82         // Synthesize initial address events
  83         struct {
  84                 struct nlmsghdr nh;
  85                 struct ifaddrmsg ifa;
  86         } req2 = {
  87                 {sizeof(req2), RTM_GETADDR, NLM_F_REQUEST | NLM_F_DUMP,
  88                                 ++rtnl_seqid, 0},
  89                 {.ifa_family = AF_INET6}
  90         };
  91         send(rtnl_event.uloop.fd, &req2, sizeof(req2), MSG_DONTWAIT);
  92         odhcpd_register(&rtnl_event);
  93
  94         // Open ICMPv6 socket
  95         ping_socket = socket(AF_INET6, SOCK_RAW | SOCK_CLOEXEC, IPPROTO_ICMPV6);
  96         if (ping_socket < 0) {
  97                 syslog(LOG_ERR, "Unable to open raw socket: %s", strerror(errno));
  98                         return -1;
  99         }
 100
 101         int val = 2;
 102         setsockopt(ping_socket, IPPROTO_RAW, IPV6_CHECKSUM, &val, sizeof(val));
 103
 104         // This is required by RFC 4861
 105         val = 255;
 106         setsockopt(ping_socket, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &val, sizeof(val));
 107         setsockopt(ping_socket, IPPROTO_IPV6, IPV6_UNICAST_HOPS, &val, sizeof(val));
 108
 109         // Filter all packages, we only want to send
 110         struct icmp6_filter filt;
 111         ICMP6_FILTER_SETBLOCKALL(&filt);
 112         setsockopt(ping_socket, IPPROTO_ICMPV6, ICMP6_FILTER, &filt, sizeof(filt));
 113
 114
 115         // Netlink socket, continued...
 116         group = RTNLGRP_NEIGH;
 117         setsockopt(rtnl_event.uloop.fd, SOL_NETLINK, NETLINK_ADD_MEMBERSHIP, &group, sizeof(group));
 118
 119         // Synthesize initial neighbor events
 120         struct {
 121                 struct nlmsghdr nh;
 122                 struct ndmsg ndm;
 123         } req = {
 124                 {sizeof(req), RTM_GETNEIGH, NLM_F_REQUEST | NLM_F_DUMP,
 125                                 ++rtnl_seqid, 0},
 126                 {.ndm_family = AF_INET6}
 127         };
 128         send(rtnl_event.uloop.fd, &req, sizeof(req), MSG_DONTWAIT);
 129
 130         return 0;
 131 }
 132
 133
 134 int setup_ndp_interface(struct interface *iface, bool enable)
 135 {
 136         struct packet_mreq mreq = {iface->ifindex, PACKET_MR_ALLMULTI, ETH_ALEN, {0}};
 137         setsockopt(ndp_event.uloop.fd, SOL_PACKET, PACKET_DROP_MEMBERSHIP, &mreq, sizeof(mreq));
 138
 139         struct ndp_neighbor *c, *n;
 140         list_for_each_entry_safe(c, n, &neighbors, head)
 141                 if (c->iface == iface && (c->timeout == 0 || iface->ndp != RELAYD_RELAY || !enable))
 142                         modify_neighbor(&c->addr, c->iface, false);
 143
 144         if (enable && iface->ndp == RELAYD_RELAY) {
 145                 setsockopt(ndp_event.uloop.fd, SOL_PACKET, PACKET_ADD_MEMBERSHIP, &mreq, sizeof(mreq));
 146
 147                 if (iface->static_ndp_len) {
 148                         char *entry = alloca(iface->static_ndp_len), *saveptr;
 149                         if (!entry) {
 150                                 syslog(LOG_ERR, "Alloca failed for static NDP list");
 151                                 return -1;
 152                         }
 153                         memcpy(entry, iface->static_ndp, iface->static_ndp_len);
 154
 155                         for (entry = strtok_r(entry, " ", &saveptr); entry; entry = strtok_r(NULL, " ", &saveptr)) {
 156                                 char *sep;
 157                                 struct ndp_neighbor *n = malloc(sizeof(*n));
 158                                 if (!n) {
 159                                         syslog(LOG_ERR, "Malloc failed for static NDP-prefix %s", entry);
 160                                         return -1;
 161                                 }
 162
 163                                 n->iface = iface;
 164                                 n->timeout = 0;
 165
 166                                 sep = strchr(entry, '/');
 167                                 if (!sep) {
 168                                         free(n);
 169                                         syslog(LOG_ERR, "Invalid static NDP-prefix %s", entry);
 170                                         return -1;
 171                                 }
 172
 173                                 *sep = 0;
 174                                 n->len = atoi(sep + 1);
 175                                 if (inet_pton(AF_INET6, entry, &n->addr) != 1 || n->len > 128) {
 176                                         free(n);
 177                                         syslog(LOG_ERR, "Invalid static NDP-prefix %s/%s", entry, sep + 1);
 178                                         return -1;
 179                                 }
 180
 181                                 list_add(&n->head, &neighbors);
 182                         }
 183                 }
 184         }
 185
 186         bool enable_packet = false;
 187         struct interface *i;
 188         list_for_each_entry(i, &interfaces, head) {
 189                 if (i == iface && !enable)
 190                         continue;
 191
 192                 if (i->ndp == RELAYD_RELAY)
 193                         enable_packet = true;
 194         }
 195
 196         if (enable_packet && ndp_event.uloop.fd < 0) {
 197                 // Create socket for intercepting NDP
 198                 int sock = socket(AF_PACKET, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK,
 199                                 htons(ETH_P_ALL)); // ETH_P_ALL for ingress + egress
 200                 if (sock < 0) {
 201                         syslog(LOG_ERR, "Unable to open packet socket: %s",
 202                                         strerror(errno));
 203                         return -1;
 204                 }
 205
 206                 if (setsockopt(sock, SOL_SOCKET, SO_ATTACH_FILTER,
 207                                 &bpf_prog, sizeof(bpf_prog))) {
 208                         syslog(LOG_ERR, "Failed to set BPF: %s", strerror(errno));
 209                         return -1;
 210                 }
 211
 212                 ndp_event.uloop.fd = sock;
 213                 odhcpd_register(&ndp_event);
 214         } else if (!enable_packet && ndp_event.uloop.fd >= 0) {
 215                 close(ndp_event.uloop.fd);
 216                 ndp_event.uloop.fd = -1;
 217         }
 218
 219         return 0;
 220 }
 221
 222
 223 // Send an ICMP-ECHO. This is less for actually pinging but for the
 224 // neighbor cache to be kept up-to-date.
 225 static ssize_t ping6(struct in6_addr *addr,
 226                 const struct interface *iface)
 227 {
 228         struct sockaddr_in6 dest = {AF_INET6, 0, 0, *addr, 0};
 229         struct icmp6_hdr echo = {.icmp6_type = ICMP6_ECHO_REQUEST};
 230         struct iovec iov = {&echo, sizeof(echo)};
 231
 232         // Linux seems to not honor IPV6_PKTINFO on raw-sockets, so work around
 233         setsockopt(ping_socket, SOL_SOCKET, SO_BINDTODEVICE,
 234                         iface->ifname, sizeof(iface->ifname));
 235         return odhcpd_send(ping_socket, &dest, &iov, 1, iface);
 236 }
 237
 238
 239 // Handle solicitations
 240 static void handle_solicit(void *addr, void *data, size_t len,
 241                 struct interface *iface, _unused void *dest)
 242 {
 243         struct ip6_hdr *ip6 = data;
 244         struct nd_neighbor_solicit *req = (struct nd_neighbor_solicit*)&ip6[1];
 245         struct sockaddr_ll *ll = addr;
 246
 247         // Solicitation is for duplicate address detection
 248         bool ns_is_dad = IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src);
 249
 250         // Don't forward any non-DAD solicitation for external ifaces
 251         // TODO: check if we should even forward DADs for them
 252         if (iface->external && !ns_is_dad)
 253                 return;
 254
 255         if (len < sizeof(*ip6) + sizeof(*req))
 256                 return; // Invalid reqicitation
 257
 258         if (IN6_IS_ADDR_LINKLOCAL(&req->nd_ns_target) ||
 259                         IN6_IS_ADDR_LOOPBACK(&req->nd_ns_target) ||
 260                         IN6_IS_ADDR_MULTICAST(&req->nd_ns_target))
 261                 return; // Invalid target
 262
 263         char ipbuf[INET6_ADDRSTRLEN];
 264         inet_ntop(AF_INET6, &req->nd_ns_target, ipbuf, sizeof(ipbuf));
 265         syslog(LOG_DEBUG, "Got a NS for %s", ipbuf);
 266
 267         uint8_t mac[6];
 268         odhcpd_get_mac(iface, mac);
 269         if (!memcmp(ll->sll_addr, mac, sizeof(mac)) &&
 270                         ll->sll_pkttype != PACKET_OUTGOING)
 271                 return; // Looped back
 272
 273         time_t now = time(NULL);
 274
 275         struct ndp_neighbor *n = find_neighbor(&req->nd_ns_target, false);
 276         if (n && (n->iface || abs(n->timeout - now) < 5)) {
 277                 syslog(LOG_DEBUG, "%s is on %s", ipbuf,
 278                                 (n->iface) ? n->iface->ifname : "<pending>");
 279                 if (!n->iface || n->iface == iface)
 280                         return;
 281
 282                 // Found on other interface, answer with advertisement
 283                 struct {
 284                         struct nd_neighbor_advert body;
 285                         struct nd_opt_hdr opt_ll_hdr;
 286                         uint8_t mac[6];
 287                 } advert = {
 288                         .body = {
 289                                 .nd_na_hdr = {ND_NEIGHBOR_ADVERT,
 290                                         0, 0, {{0}}},
 291                                 .nd_na_target = req->nd_ns_target,
 292                         },
 293                         .opt_ll_hdr = {ND_OPT_TARGET_LINKADDR, 1},
 294                 };
 295
 296                 memcpy(advert.mac, mac, sizeof(advert.mac));
 297                 advert.body.nd_na_flags_reserved = ND_NA_FLAG_ROUTER |
 298                                 ND_NA_FLAG_SOLICITED;
 299
 300                 struct sockaddr_in6 dest = {AF_INET6, 0, 0, ALL_IPV6_NODES, 0};
 301                 if (!ns_is_dad) // If not DAD, then unicast to source
 302                         dest.sin6_addr = ip6->ip6_src;
 303
 304                 // Linux seems to not honor IPV6_PKTINFO on raw-sockets, so work around
 305                 setsockopt(ping_socket, SOL_SOCKET, SO_BINDTODEVICE,
 306                                         iface->ifname, sizeof(iface->ifname));
 307                 struct iovec iov = {&advert, sizeof(advert)};
 308                 odhcpd_send(ping_socket, &dest, &iov, 1, iface);
 309         } else {
 310                 // Send echo to all other interfaces to see where target is on
 311                 // This will trigger neighbor discovery which is what we want.
 312                 // We will observe the neighbor cache to see results.
 313
 314                 ssize_t sent = 0;
 315                 struct interface *c;
 316                 list_for_each_entry(c, &interfaces, head)
 317                         if (iface->ndp == RELAYD_RELAY && iface != c &&
 318                                         (!ns_is_dad || !c->external == false))
 319                                 sent += ping6(&req->nd_ns_target, c);
 320
 321                 if (sent > 0) // Sent a ping, add pending neighbor entry
 322                         modify_neighbor(&req->nd_ns_target, NULL, true);
 323         }
 324 }
 325
 326
 327 void odhcpd_setup_route(const struct in6_addr *addr, int prefixlen,
 328                 const struct interface *iface, const struct in6_addr *gw, bool add)
 329 {
 330         struct req {
 331                 struct nlmsghdr nh;
 332                 struct rtmsg rtm;
 333                 struct rtattr rta_dst;
 334                 struct in6_addr dst_addr;
 335                 struct rtattr rta_oif;
 336                 uint32_t ifindex;
 337                 struct rtattr rta_table;
 338                 uint32_t table;
 339                 struct rtattr rta_gw;
 340                 struct in6_addr gw;
 341         } req = {
 342                 {sizeof(req), 0, NLM_F_REQUEST, ++rtnl_seqid, 0},
 343                 {AF_INET6, prefixlen, 0, 0, 0, 0, 0, 0, 0},
 344                 {sizeof(struct rtattr) + sizeof(struct in6_addr), RTA_DST},
 345                 *addr,
 346                 {sizeof(struct rtattr) + sizeof(uint32_t), RTA_OIF},
 347                 iface->ifindex,
 348                 {sizeof(struct rtattr) + sizeof(uint32_t), RTA_TABLE},
 349                 RT_TABLE_MAIN,
 350                 {sizeof(struct rtattr) + sizeof(struct in6_addr), RTA_GATEWAY},
 351                 IN6ADDR_ANY_INIT,
 352         };
 353
 354         if (gw)
 355                 req.gw = *gw;
 356
 357         if (add) {
 358                 req.nh.nlmsg_type = RTM_NEWROUTE;
 359                 req.nh.nlmsg_flags |= (NLM_F_CREATE | NLM_F_REPLACE);
 360                 req.rtm.rtm_protocol = RTPROT_BOOT;
 361                 req.rtm.rtm_scope = (gw) ? RT_SCOPE_UNIVERSE : RT_SCOPE_LINK;
 362                 req.rtm.rtm_type = RTN_UNICAST;
 363         } else {
 364                 req.nh.nlmsg_type = RTM_DELROUTE;
 365                 req.rtm.rtm_scope = RT_SCOPE_NOWHERE;
 366         }
 367
 368         size_t reqlen = (gw) ? sizeof(req) : offsetof(struct req, rta_gw);
 369         send(rtnl_event.uloop.fd, &req, reqlen, MSG_DONTWAIT);
 370 }
 371
 372 // Use rtnetlink to modify kernel routes
 373 static void setup_route(struct in6_addr *addr, struct interface *iface,
 374                 bool add)
 375 {
 376         char namebuf[INET6_ADDRSTRLEN];
 377         inet_ntop(AF_INET6, addr, namebuf, sizeof(namebuf));
 378         syslog(LOG_NOTICE, "%s about %s on %s", (add) ? "Learned" : "Forgot",
 379                         namebuf, (iface) ? iface->ifname : "<pending>");
 380
 381         if (!iface || !iface->learn_routes)
 382                 return;
 383
 384         odhcpd_setup_route(addr, 128, iface, NULL, add);
 385 }
 386
 387 static void free_neighbor(struct ndp_neighbor *n)
 388 {
 389         setup_route(&n->addr, n->iface, false);
 390         list_del(&n->head);
 391         free(n);
 392         --neighbor_count;
 393 }
 394
 395 static struct ndp_neighbor* find_neighbor(struct in6_addr *addr, bool strict)
 396 {
 397         time_t now = time(NULL);
 398         struct ndp_neighbor *n, *e;
 399         list_for_each_entry_safe(n, e, &neighbors, head) {
 400                 if ((!strict && !odhcpd_bmemcmp(&n->addr, addr, n->len)) ||
 401                                 (n->len == 128 && IN6_ARE_ADDR_EQUAL(&n->addr, addr)))
 402                         return n;
 403
 404                 if (!n->iface && abs(n->timeout - now) >= 5)
 405                         free_neighbor(n);
 406         }
 407         return NULL;
 408 }
 409
 410
 411 // Modified our own neighbor-entries
 412 static void modify_neighbor(struct in6_addr *addr,
 413                 struct interface *iface, bool add)
 414 {
 415         if (!addr || (void*)addr == (void*)iface)
 416                 return;
 417
 418         struct ndp_neighbor *n = find_neighbor(addr, true);
 419         if (!add) { // Delete action
 420                 if (n && (!n->iface || n->iface == iface))
 421                         free_neighbor(n);
 422         } else if (!n) { // No entry yet, add one if possible
 423                 if (neighbor_count >= NDP_MAX_NEIGHBORS ||
 424                                 !(n = malloc(sizeof(*n))))
 425                         return;
 426
 427                 n->len = 128;
 428                 n->addr = *addr;
 429                 n->iface = iface;
 430                 if (!n->iface)
 431                         time(&n->timeout);
 432                 list_add(&n->head, &neighbors);
 433                 ++neighbor_count;
 434                 setup_route(addr, n->iface, add);
 435         } else if (n->iface == iface) {
 436                 if (!n->iface)
 437                         time(&n->timeout);
 438         } else if (iface && (!n->iface ||
 439                         (!iface->external && n->iface->external))) {
 440                 setup_route(addr, n->iface, false);
 441                 n->iface = iface;
 442                 setup_route(addr, n->iface, add);
 443         }
 444         // TODO: In case a host switches interfaces we might want
 445         // to set its old neighbor entry to NUD_STALE and ping it
 446         // on the old interface to confirm if the MACs match.
 447 }
 448
 449
 450 // Handler for neighbor cache entries from the kernel. This is our source
 451 // to learn and unlearn hosts on interfaces.
 452 static void handle_rtnetlink(_unused void *addr, void *data, size_t len,
 453                 _unused struct interface *iface, _unused void *dest)
 454 {
 455         for (struct nlmsghdr *nh = data; NLMSG_OK(nh, len);
 456                         nh = NLMSG_NEXT(nh, len)) {
 457                 struct rtmsg *rtm = NLMSG_DATA(nh);
 458                 if ((nh->nlmsg_type == RTM_NEWROUTE ||
 459                                 nh->nlmsg_type == RTM_DELROUTE) &&
 460                                 rtm->rtm_dst_len == 0)
 461                         raise(SIGUSR1); // Inform about a change in default route
 462
 463                 struct ndmsg *ndm = NLMSG_DATA(nh);
 464                 struct ifaddrmsg *ifa = NLMSG_DATA(nh);
 465                 if (nh->nlmsg_type != RTM_NEWNEIGH
 466                                 && nh->nlmsg_type != RTM_DELNEIGH
 467                                 && nh->nlmsg_type != RTM_NEWADDR
 468                                 && nh->nlmsg_type != RTM_DELADDR)
 469                         continue; // Unrelated message type
 470                 bool is_addr = (nh->nlmsg_type == RTM_NEWADDR
 471                                 || nh->nlmsg_type == RTM_DELADDR);
 472
 473                 // Family and ifindex are on the same offset for NEIGH and ADDR
 474                 if (NLMSG_PAYLOAD(nh, 0) < sizeof(*ndm)
 475                                 || ndm->ndm_family != AF_INET6)
 476                         continue; //
 477
 478                 // Lookup interface
 479                 struct interface *iface;
 480                 if (!(iface = odhcpd_get_interface_by_index(ndm->ndm_ifindex)))
 481                         continue;
 482
 483                 // Data to retrieve
 484                 size_t rta_offset = (is_addr) ? sizeof(*ifa) : sizeof(*ndm);
 485                 uint16_t atype = (is_addr) ? IFA_ADDRESS : NDA_DST;
 486                 ssize_t alen = NLMSG_PAYLOAD(nh, rta_offset);
 487                 struct in6_addr *addr = NULL;
 488
 489                 for (struct rtattr *rta = (void*)(((uint8_t*)ndm) + rta_offset);
 490                                 RTA_OK(rta, alen); rta = RTA_NEXT(rta, alen))
 491                         if (rta->rta_type == atype &&
 492                                         RTA_PAYLOAD(rta) >= sizeof(*addr))
 493                                 addr = RTA_DATA(rta);
 494
 495                 // Address not specified or unrelated
 496                 if (!addr || IN6_IS_ADDR_LINKLOCAL(addr) ||
 497                                 IN6_IS_ADDR_MULTICAST(addr))
 498                         continue;
 499
 500                 // Check for states
 501                 bool add;
 502                 if (is_addr)
 503                         add = (nh->nlmsg_type == RTM_NEWADDR);
 504                 else
 505                         add = (nh->nlmsg_type == RTM_NEWNEIGH && (ndm->ndm_state &
 506                                 (NUD_REACHABLE | NUD_STALE | NUD_DELAY | NUD_PROBE
 507                                                 | NUD_PERMANENT | NUD_NOARP)));
 508
 509                 if (iface->ndp == RELAYD_RELAY)
 510                         modify_neighbor(addr, iface, add);
 511
 512                 if (is_addr && iface->ra == RELAYD_SERVER)
 513                         raise(SIGUSR1); // Inform about a change in addresses
 514
 515                 if (is_addr && iface->dhcpv6 == RELAYD_SERVER)
 516                         iface->ia_reconf = true;
 517
 518                 if (iface->ndp == RELAYD_RELAY && is_addr && iface->master) {
 519                         // Replay address changes on all slave interfaces
 520                         nh->nlmsg_flags = NLM_F_REQUEST;
 521
 522                         if (nh->nlmsg_type == RTM_NEWADDR)
 523                                 nh->nlmsg_flags |= NLM_F_CREATE | NLM_F_REPLACE;
 524
 525                         struct interface *c;
 526                         list_for_each_entry(c, &interfaces, head) {
 527                                 if (c->ndp == RELAYD_RELAY && !c->master) {
 528                                         ifa->ifa_index = c->ifindex;
 529                                         send(rtnl_event.uloop.fd, nh, nh->nlmsg_len, MSG_DONTWAIT);
 530                                 }
 531                         }
 532                 }
 533
 534                 /* TODO: See if this is required for optimal operation
 535                 // Keep neighbor entries alive so we don't loose routes
 536                  */
 537                 if (add && (ndm->ndm_state & NUD_STALE))
 538                         ping6(addr, iface);
 539         }
 540 }