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 <arpa/inet.h>
  21 #include <sys/socket.h>
  22 #include <net/ethernet.h>
  23 #include <netinet/ip6.h>
  24 #include <netinet/icmp6.h>
  25 #include <netpacket/packet.h>
  26
  27 #include <linux/rtnetlink.h>
  28 #include <linux/filter.h>
  29 #include "router.h"
  30 #include "ndp.h"
  31
  32
  33
  34 static void handle_solicit(void *addr, void *data, size_t len,
  35                 struct interface *iface);
  36 static void handle_rtnetlink(void *addr, void *data, size_t len,
  37                 struct interface *iface);
  38 static struct ndp_neighbor* find_neighbor(struct in6_addr *addr, bool strict);
  39 static void modify_neighbor(struct in6_addr *addr, struct interface *iface,
  40                 bool add);
  41 static ssize_t ping6(struct in6_addr *addr,
  42                 const struct interface *iface);
  43
  44 static struct list_head neighbors = LIST_HEAD_INIT(neighbors);
  45 static size_t neighbor_count = 0;
  46 static uint32_t rtnl_seqid = 0;
  47
  48 static int ping_socket = -1;
  49 static struct odhcpd_event ndp_event = {{.fd = -1}, handle_solicit};
  50 static struct odhcpd_event rtnl_event = {{.fd = -1}, handle_rtnetlink};
  51
  52
  53 // Filter ICMPv6 messages of type neighbor soliciation
  54 static struct sock_filter bpf[] = {
  55         BPF_STMT(BPF_LD | BPF_B | BPF_ABS, offsetof(struct ip6_hdr, ip6_nxt)),
  56         BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, IPPROTO_ICMPV6, 0, 3),
  57         BPF_STMT(BPF_LD | BPF_B | BPF_ABS, sizeof(struct ip6_hdr) +
  58                         offsetof(struct icmp6_hdr, icmp6_type)),
  59         BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, ND_NEIGHBOR_SOLICIT, 0, 1),
  60         BPF_STMT(BPF_RET | BPF_K, 0xffffffff),
  61         BPF_STMT(BPF_RET | BPF_K, 0),
  62 };
  63 static const struct sock_fprog bpf_prog = {sizeof(bpf) / sizeof(*bpf), bpf};
  64
  65
  66 // Initialize NDP-proxy
  67 int init_ndp(void)
  68 {
  69         // Setup netlink socket
  70         if ((rtnl_event.uloop.fd = odhcpd_open_rtnl()) < 0)
  71                 return -1;
  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         // Synthesize initial address events
  82         struct {
  83                 struct nlmsghdr nh;
  84                 struct ifaddrmsg ifa;
  85         } req2 = {
  86                 {sizeof(req2), RTM_GETADDR, NLM_F_REQUEST | NLM_F_DUMP,
  87                                 ++rtnl_seqid, 0},
  88                 {.ifa_family = AF_INET6}
  89         };
  90         send(rtnl_event.uloop.fd, &req2, sizeof(req2), MSG_DONTWAIT);
  91         odhcpd_register(&rtnl_event);
  92
  93
  94         // Create socket for intercepting NDP
  95         int sock = socket(AF_PACKET, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK,
  96                         htons(ETH_P_ALL)); // ETH_P_ALL for ingress + egress
  97         if (sock < 0) {
  98                 syslog(LOG_ERR, "Unable to open packet socket: %s",
  99                                 strerror(errno));
 100                 return -1;
 101         }
 102
 103         if (setsockopt(sock, SOL_SOCKET, SO_ATTACH_FILTER,
 104                         &bpf_prog, sizeof(bpf_prog))) {
 105                 syslog(LOG_ERR, "Failed to set BPF: %s", strerror(errno));
 106                 return -1;
 107         }
 108
 109         ndp_event.uloop.fd = sock;
 110         odhcpd_register(&ndp_event);
 111
 112         // Open ICMPv6 socket
 113         ping_socket = socket(AF_INET6, SOCK_RAW | SOCK_CLOEXEC, IPPROTO_ICMPV6);
 114
 115         int val = 2;
 116         setsockopt(ping_socket, IPPROTO_RAW, IPV6_CHECKSUM, &val, sizeof(val));
 117
 118         // This is required by RFC 4861
 119         val = 255;
 120         setsockopt(ping_socket, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &val, sizeof(val));
 121         setsockopt(ping_socket, IPPROTO_IPV6, IPV6_UNICAST_HOPS, &val, sizeof(val));
 122
 123         // Filter all packages, we only want to send
 124         struct icmp6_filter filt;
 125         ICMP6_FILTER_SETBLOCKALL(&filt);
 126         setsockopt(ping_socket, IPPROTO_ICMPV6, ICMP6_FILTER, &filt, sizeof(filt));
 127
 128
 129         // Netlink socket, continued...
 130         group = RTNLGRP_NEIGH;
 131         setsockopt(rtnl_event.uloop.fd, SOL_NETLINK, NETLINK_ADD_MEMBERSHIP, &group, sizeof(group));
 132
 133         // Synthesize initial neighbor events
 134         struct {
 135                 struct nlmsghdr nh;
 136                 struct ndmsg ndm;
 137         } req = {
 138                 {sizeof(req), RTM_GETNEIGH, NLM_F_REQUEST | NLM_F_DUMP,
 139                                 ++rtnl_seqid, 0},
 140                 {.ndm_family = AF_INET6}
 141         };
 142         send(rtnl_event.uloop.fd, &req, sizeof(req), MSG_DONTWAIT);
 143
 144         return 0;
 145 }
 146
 147
 148 int setup_ndp_interface(struct interface *iface, bool enable)
 149 {
 150         struct packet_mreq mreq = {iface->ifindex, PACKET_MR_ALLMULTI, ETH_ALEN, {0}};
 151         setsockopt(ndp_event.uloop.fd, SOL_PACKET, PACKET_DROP_MEMBERSHIP, &mreq, sizeof(mreq));
 152
 153         struct ndp_neighbor *c, *n;
 154         list_for_each_entry_safe(c, n, &neighbors, head)
 155                 if (c->iface == iface && (c->timeout == 0 || iface->ndp != RELAYD_RELAY || !enable))
 156                         modify_neighbor(&c->addr, c->iface, false);
 157
 158         if (enable && iface->ndp == RELAYD_RELAY) {
 159                 setsockopt(ndp_event.uloop.fd, SOL_PACKET, PACKET_ADD_MEMBERSHIP, &mreq, sizeof(mreq));
 160
 161                 if (iface->static_ndp_len) {
 162                         char *entry = alloca(iface->static_ndp_len), *saveptr;
 163                         memcpy(entry, iface->static_ndp, iface->static_ndp_len);
 164
 165                         for (entry = strtok_r(entry, " ", &saveptr); entry; entry = strtok_r(NULL, " ", &saveptr)) {
 166                                 struct ndp_neighbor *n = malloc(sizeof(*n));
 167                                 n->iface = iface;
 168                                 n->timeout = 0;
 169
 170                                 char ipbuf[INET6_ADDRSTRLEN];
 171                                 if (sscanf(entry, "%45s/%hhu", ipbuf, &n->len) < 2
 172                                                 || n->len > 128 || inet_pton(AF_INET6, ipbuf, &n->addr) != 1) {
 173                                         syslog(LOG_ERR, "Invalid static NDP-prefix %s", entry);
 174                                         return -1;
 175                                 }
 176
 177                                 list_add(&n->head, &neighbors);
 178                         }
 179                 }
 180         }
 181
 182         return 0;
 183 }
 184
 185
 186 // Send an ICMP-ECHO. This is less for actually pinging but for the
 187 // neighbor cache to be kept up-to-date.
 188 static ssize_t ping6(struct in6_addr *addr,
 189                 const struct interface *iface)
 190 {
 191         struct sockaddr_in6 dest = {AF_INET6, 0, 0, *addr, 0};
 192         struct icmp6_hdr echo = {.icmp6_type = ICMP6_ECHO_REQUEST};
 193         struct iovec iov = {&echo, sizeof(echo)};
 194
 195         // Linux seems to not honor IPV6_PKTINFO on raw-sockets, so work around
 196         setsockopt(ping_socket, SOL_SOCKET, SO_BINDTODEVICE,
 197                         iface->ifname, sizeof(iface->ifname));
 198         return odhcpd_send(ping_socket, &dest, &iov, 1, iface);
 199 }
 200
 201
 202 // Handle solicitations
 203 static void handle_solicit(void *addr, void *data, size_t len,
 204                 struct interface *iface)
 205 {
 206         struct ip6_hdr *ip6 = data;
 207         struct nd_neighbor_solicit *req = (struct nd_neighbor_solicit*)&ip6[1];
 208         struct sockaddr_ll *ll = addr;
 209
 210         // Solicitation is for duplicate address detection
 211         bool ns_is_dad = IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src);
 212
 213         // Don't forward any non-DAD solicitation for external ifaces
 214         // TODO: check if we should even forward DADs for them
 215         if (iface->external && !ns_is_dad)
 216                 return;
 217
 218         if (len < sizeof(*ip6) + sizeof(*req))
 219                 return; // Invalid reqicitation
 220
 221         if (IN6_IS_ADDR_LINKLOCAL(&req->nd_ns_target) ||
 222                         IN6_IS_ADDR_LOOPBACK(&req->nd_ns_target) ||
 223                         IN6_IS_ADDR_MULTICAST(&req->nd_ns_target))
 224                 return; // Invalid target
 225
 226         char ipbuf[INET6_ADDRSTRLEN];
 227         inet_ntop(AF_INET6, &req->nd_ns_target, ipbuf, sizeof(ipbuf));
 228         syslog(LOG_NOTICE, "Got a NS for %s", ipbuf);
 229
 230         uint8_t mac[6];
 231         odhcpd_get_mac(iface, mac);
 232         if (!memcmp(ll->sll_addr, mac, sizeof(mac)) &&
 233                         ll->sll_pkttype != PACKET_OUTGOING)
 234                 return; // Looped back
 235
 236         time_t now = time(NULL);
 237
 238         struct ndp_neighbor *n = find_neighbor(&req->nd_ns_target, false);
 239         if (n && (n->iface || abs(n->timeout - now) < 5)) {
 240                 syslog(LOG_NOTICE, "%s is on %s", ipbuf,
 241                                 (n->iface) ? n->iface->ifname : "<pending>");
 242                 if (!n->iface || n->iface == iface)
 243                         return;
 244
 245                 // Found on other interface, answer with advertisement
 246                 struct {
 247                         struct nd_neighbor_advert body;
 248                         struct nd_opt_hdr opt_ll_hdr;
 249                         uint8_t mac[6];
 250                 } advert = {
 251                         .body = {
 252                                 .nd_na_hdr = {ND_NEIGHBOR_ADVERT,
 253                                         0, 0, {{0}}},
 254                                 .nd_na_target = req->nd_ns_target,
 255                         },
 256                         .opt_ll_hdr = {ND_OPT_TARGET_LINKADDR, 1},
 257                 };
 258
 259                 memcpy(advert.mac, mac, sizeof(advert.mac));
 260                 advert.body.nd_na_flags_reserved = ND_NA_FLAG_ROUTER |
 261                                 ND_NA_FLAG_SOLICITED;
 262
 263                 struct sockaddr_in6 dest = {AF_INET6, 0, 0, ALL_IPV6_NODES, 0};
 264                 if (!ns_is_dad) // If not DAD, then unicast to source
 265                         dest.sin6_addr = ip6->ip6_src;
 266
 267                 // Linux seems to not honor IPV6_PKTINFO on raw-sockets, so work around
 268                 setsockopt(ping_socket, SOL_SOCKET, SO_BINDTODEVICE,
 269                                         iface->ifname, sizeof(iface->ifname));
 270                 struct iovec iov = {&advert, sizeof(advert)};
 271                 odhcpd_send(ping_socket, &dest, &iov, 1, iface);
 272         } else {
 273                 // Send echo to all other interfaces to see where target is on
 274                 // This will trigger neighbor discovery which is what we want.
 275                 // We will observe the neighbor cache to see results.
 276
 277                 ssize_t sent = 0;
 278                 struct interface *c;
 279                 list_for_each_entry(c, &interfaces, head)
 280                         if (iface->ndp == RELAYD_RELAY && iface != c &&
 281                                         (!ns_is_dad || !c->external == false))
 282                                 sent += ping6(&req->nd_ns_target, c);
 283
 284                 if (sent > 0) // Sent a ping, add pending neighbor entry
 285                         modify_neighbor(&req->nd_ns_target, NULL, true);
 286         }
 287 }
 288
 289
 290 void odhcpd_setup_route(const struct in6_addr *addr, int prefixlen,
 291                 const struct interface *iface, const struct in6_addr *gw, bool add)
 292 {
 293         struct req {
 294                 struct nlmsghdr nh;
 295                 struct rtmsg rtm;
 296                 struct rtattr rta_dst;
 297                 struct in6_addr dst_addr;
 298                 struct rtattr rta_oif;
 299                 uint32_t ifindex;
 300                 struct rtattr rta_table;
 301                 uint32_t table;
 302                 struct rtattr rta_gw;
 303                 struct in6_addr gw;
 304         } req = {
 305                 {sizeof(req), 0, NLM_F_REQUEST, ++rtnl_seqid, 0},
 306                 {AF_INET6, prefixlen, 0, 0, 0, 0, 0, 0, 0},
 307                 {sizeof(struct rtattr) + sizeof(struct in6_addr), RTA_DST},
 308                 *addr,
 309                 {sizeof(struct rtattr) + sizeof(uint32_t), RTA_OIF},
 310                 iface->ifindex,
 311                 {sizeof(struct rtattr) + sizeof(uint32_t), RTA_TABLE},
 312                 RT_TABLE_MAIN,
 313                 {sizeof(struct rtattr) + sizeof(struct in6_addr), RTA_GATEWAY},
 314                 IN6ADDR_ANY_INIT,
 315         };
 316
 317         if (gw)
 318                 req.gw = *gw;
 319
 320         if (add) {
 321                 req.nh.nlmsg_type = RTM_NEWROUTE;
 322                 req.nh.nlmsg_flags |= (NLM_F_CREATE | NLM_F_REPLACE);
 323                 req.rtm.rtm_protocol = RTPROT_BOOT;
 324                 req.rtm.rtm_scope = (gw) ? RT_SCOPE_UNIVERSE : RT_SCOPE_LINK;
 325                 req.rtm.rtm_type = RTN_UNICAST;
 326         } else {
 327                 req.nh.nlmsg_type = RTM_DELROUTE;
 328                 req.rtm.rtm_scope = RT_SCOPE_NOWHERE;
 329         }
 330
 331         size_t reqlen = (gw) ? sizeof(req) : offsetof(struct req, rta_gw);
 332         send(rtnl_event.uloop.fd, &req, reqlen, MSG_DONTWAIT);
 333 }
 334
 335 // Use rtnetlink to modify kernel routes
 336 static void setup_route(struct in6_addr *addr, struct interface *iface,
 337                 bool add)
 338 {
 339         char namebuf[INET6_ADDRSTRLEN];
 340         inet_ntop(AF_INET6, addr, namebuf, sizeof(namebuf));
 341         syslog(LOG_NOTICE, "%s about %s on %s", (add) ? "Learned" : "Forgot",
 342                         namebuf, (iface) ? iface->ifname : "<pending>");
 343
 344         if (!iface || !iface->learn_routes)
 345                 return;
 346
 347         odhcpd_setup_route(addr, 128, iface, NULL, add);
 348 }
 349
 350 static void free_neighbor(struct ndp_neighbor *n)
 351 {
 352         setup_route(&n->addr, n->iface, false);
 353         list_del(&n->head);
 354         free(n);
 355         --neighbor_count;
 356 }
 357
 358
 359 static bool match_neighbor(struct ndp_neighbor *n, struct in6_addr *addr)
 360 {
 361         if (n->len <= 32)
 362                 return ntohl(n->addr.s6_addr32[0]) >> (32 - n->len) ==
 363                                 ntohl(addr->s6_addr32[0]) >> (32 - n->len);
 364
 365         if (n->addr.s6_addr32[0] != addr->s6_addr32[0])
 366                 return false;
 367
 368         if (n->len <= 64)
 369                 return ntohl(n->addr.s6_addr32[1]) >> (64 - n->len) ==
 370                                 ntohl(addr->s6_addr32[1]) >> (64 - n->len);
 371
 372         if (n->addr.s6_addr32[1] != addr->s6_addr32[1])
 373                 return false;
 374
 375         if (n->len <= 96)
 376                 return ntohl(n->addr.s6_addr32[2]) >> (96 - n->len) ==
 377                                 ntohl(addr->s6_addr32[2]) >> (96 - n->len);
 378
 379         if (n->addr.s6_addr32[2] != addr->s6_addr32[2])
 380                 return false;
 381
 382         return ntohl(n->addr.s6_addr32[3]) >> (128 - n->len) ==
 383                         ntohl(addr->s6_addr32[3]) >> (128 - n->len);
 384 }
 385
 386
 387 static struct ndp_neighbor* find_neighbor(struct in6_addr *addr, bool strict)
 388 {
 389         time_t now = time(NULL);
 390         struct ndp_neighbor *n, *e;
 391         list_for_each_entry_safe(n, e, &neighbors, head) {
 392                 if ((!strict && match_neighbor(n, addr)) ||
 393                                 (n->len == 128 && IN6_ARE_ADDR_EQUAL(&n->addr, addr)))
 394                         return n;
 395
 396                 if (!n->iface && abs(n->timeout - now) >= 5)
 397                         free_neighbor(n);
 398         }
 399         return NULL;
 400 }
 401
 402
 403 // Modified our own neighbor-entries
 404 static void modify_neighbor(struct in6_addr *addr,
 405                 struct interface *iface, bool add)
 406 {
 407         if (!addr || (void*)addr == (void*)iface)
 408                 return;
 409
 410         struct ndp_neighbor *n = find_neighbor(addr, true);
 411         if (!add) { // Delete action
 412                 if (n && (!n->iface || n->iface == iface))
 413                         free_neighbor(n);
 414         } else if (!n) { // No entry yet, add one if possible
 415                 if (neighbor_count >= NDP_MAX_NEIGHBORS ||
 416                                 !(n = malloc(sizeof(*n))))
 417                         return;
 418
 419                 n->len = 128;
 420                 n->addr = *addr;
 421                 n->iface = iface;
 422                 if (!n->iface)
 423                         time(&n->timeout);
 424                 list_add(&n->head, &neighbors);
 425                 ++neighbor_count;
 426                 setup_route(addr, n->iface, add);
 427         } else if (n->iface == iface) {
 428                 if (!n->iface)
 429                         time(&n->timeout);
 430         } else if (iface && (!n->iface ||
 431                         (!iface->external && n->iface->external))) {
 432                 setup_route(addr, n->iface, false);
 433                 n->iface = iface;
 434                 setup_route(addr, n->iface, add);
 435         }
 436         // TODO: In case a host switches interfaces we might want
 437         // to set its old neighbor entry to NUD_STALE and ping it
 438         // on the old interface to confirm if the MACs match.
 439 }
 440
 441
 442 // Handler for neighbor cache entries from the kernel. This is our source
 443 // to learn and unlearn hosts on interfaces.
 444 static void handle_rtnetlink(_unused void *addr, void *data, size_t len,
 445                 _unused struct interface *iface)
 446 {
 447         for (struct nlmsghdr *nh = data; NLMSG_OK(nh, len);
 448                         nh = NLMSG_NEXT(nh, len)) {
 449                 struct rtmsg *rtm = NLMSG_DATA(nh);
 450                 if ((nh->nlmsg_type == RTM_NEWROUTE ||
 451                                 nh->nlmsg_type == RTM_DELROUTE) &&
 452                                 rtm->rtm_dst_len == 0)
 453                         raise(SIGUSR1); // Inform about a change in default route
 454
 455                 struct ndmsg *ndm = NLMSG_DATA(nh);
 456                 struct ifaddrmsg *ifa = NLMSG_DATA(nh);
 457                 if (nh->nlmsg_type != RTM_NEWNEIGH
 458                                 && nh->nlmsg_type != RTM_DELNEIGH
 459                                 && nh->nlmsg_type != RTM_NEWADDR
 460                                 && nh->nlmsg_type != RTM_DELADDR)
 461                         continue; // Unrelated message type
 462                 bool is_addr = (nh->nlmsg_type == RTM_NEWADDR
 463                                 || nh->nlmsg_type == RTM_DELADDR);
 464
 465                 // Family and ifindex are on the same offset for NEIGH and ADDR
 466                 if (NLMSG_PAYLOAD(nh, 0) < sizeof(*ndm)
 467                                 || ndm->ndm_family != AF_INET6)
 468                         continue; //
 469
 470                 // Lookup interface
 471                 struct interface *iface;
 472                 if (!(iface = odhcpd_get_interface_by_index(ndm->ndm_ifindex)))
 473                         continue;
 474
 475                 // Data to retrieve
 476                 size_t rta_offset = (is_addr) ? sizeof(*ifa) : sizeof(*ndm);
 477                 uint16_t atype = (is_addr) ? IFA_ADDRESS : NDA_DST;
 478                 ssize_t alen = NLMSG_PAYLOAD(nh, rta_offset);
 479                 struct in6_addr *addr = NULL;
 480
 481                 for (struct rtattr *rta = (void*)(((uint8_t*)ndm) + rta_offset);
 482                                 RTA_OK(rta, alen); rta = RTA_NEXT(rta, alen))
 483                         if (rta->rta_type == atype &&
 484                                         RTA_PAYLOAD(rta) >= sizeof(*addr))
 485                                 addr = RTA_DATA(rta);
 486
 487                 // Address not specified or unrelated
 488                 if (!addr || IN6_IS_ADDR_LINKLOCAL(addr) ||
 489                                 IN6_IS_ADDR_MULTICAST(addr))
 490                         continue;
 491
 492                 // Check for states
 493                 bool add;
 494                 if (is_addr)
 495                         add = (nh->nlmsg_type == RTM_NEWADDR);
 496                 else
 497                         add = (nh->nlmsg_type == RTM_NEWNEIGH && (ndm->ndm_state &
 498                                 (NUD_REACHABLE | NUD_STALE | NUD_DELAY | NUD_PROBE
 499                                                 | NUD_PERMANENT | NUD_NOARP)));
 500
 501                 if (iface->ndp == RELAYD_RELAY)
 502                         modify_neighbor(addr, iface, add);
 503
 504                 if (is_addr && iface->ra == RELAYD_SERVER)
 505                         raise(SIGUSR1); // Inform about a change in addresses
 506
 507                 if (is_addr && iface->dhcpv6 == RELAYD_SERVER)
 508                         iface->ia_reconf = true;
 509
 510                 if (iface->ndp == RELAYD_RELAY && is_addr && iface->master) {
 511                         // Replay address changes on all slave interfaces
 512                         nh->nlmsg_flags = NLM_F_REQUEST;
 513
 514                         if (nh->nlmsg_type == RTM_NEWADDR)
 515                                 nh->nlmsg_flags |= NLM_F_CREATE | NLM_F_REPLACE;
 516
 517                         struct interface *c;
 518                         list_for_each_entry(c, &interfaces, head) {
 519                                 if (c->ndp == RELAYD_RELAY && !c->master) {
 520                                         ifa->ifa_index = c->ifindex;
 521                                         send(rtnl_event.uloop.fd, nh, nh->nlmsg_len, MSG_DONTWAIT);
 522                                 }
 523                         }
 524                 }
 525
 526                 /* TODO: See if this is required for optimal operation
 527                 // Keep neighbor entries alive so we don't loose routes
 528                 if (add && (ndm->ndm_state & NUD_STALE))
 529                         ping6(addr, iface);
 530                 */
 531         }
 532 }