src/ra.c

   1 /**
   2  * Copyright (C) 2012-2014 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 <fcntl.h>
  16 #include <stdio.h>
  17 #include <signal.h>
  18 #include <string.h>
  19 #include <stddef.h>
  20 #include <stdbool.h>
  21 #include <syslog.h>
  22 #include <unistd.h>
  23 #include <resolv.h>
  24 #include <alloca.h>
  25
  26 #include <net/if.h>
  27 #include <arpa/inet.h>
  28 #include <sys/socket.h>
  29 #include <sys/types.h>
  30 #include <netinet/in.h>
  31 #include <netinet/icmp6.h>
  32
  33 #include <linux/rtnetlink.h>
  34
  35 #ifndef SOL_NETLINK
  36 #define SOL_NETLINK 270
  37 #endif
  38
  39 #ifndef NETLINK_ADD_MEMBERSHIP
  40 #define NETLINK_ADD_MEMBERSHIP 1
  41 #endif
  42
  43 #ifndef IFF_LOWER_UP
  44 #define IFF_LOWER_UP 0x10000
  45 #endif
  46
  47 #include "odhcp6c.h"
  48 #include "ra.h"
  49
  50
  51 static bool nocarrier = false;
  52
  53 static int sock = -1, rtnl = -1;
  54 static int if_index = 0;
  55 static char if_name[IF_NAMESIZE] = {0};
  56 static volatile int rs_attempt = 0;
  57 static struct in6_addr lladdr = IN6ADDR_ANY_INIT;
  58
  59 struct {
  60         struct icmp6_hdr hdr;
  61         struct icmpv6_opt lladdr;
  62 } rs = {
  63         .hdr = {ND_ROUTER_SOLICIT, 0, 0, {{0}}},
  64         .lladdr = {ND_OPT_SOURCE_LINKADDR, 1, {0}},
  65 };
  66
  67
  68 static void ra_send_rs(int signal __attribute__((unused)));
  69
  70 int ra_init(const char *ifname, const struct in6_addr *ifid)
  71 {
  72         const pid_t ourpid = getpid();
  73         sock = socket(AF_INET6, SOCK_RAW | SOCK_CLOEXEC, IPPROTO_ICMPV6);
  74         if (sock < 0)
  75                 return -1;
  76
  77         if_index = if_nametoindex(ifname);
  78         if (!if_index)
  79                 return -1;
  80
  81         strncpy(if_name, ifname, sizeof(if_name) - 1);
  82         lladdr = *ifid;
  83
  84         rtnl = socket(AF_NETLINK, SOCK_DGRAM | SOCK_CLOEXEC, NETLINK_ROUTE);
  85         if (rtnl < 0)
  86                 return -1;
  87
  88         struct sockaddr_nl rtnl_kernel = { .nl_family = AF_NETLINK };
  89         if (connect(rtnl, (const struct sockaddr*)&rtnl_kernel, sizeof(rtnl_kernel)) < 0)
  90                 return -1;
  91
  92         int val = RTNLGRP_LINK;
  93         setsockopt(rtnl, SOL_NETLINK, NETLINK_ADD_MEMBERSHIP, &val, sizeof(val));
  94         fcntl(rtnl, F_SETOWN, ourpid);
  95         fcntl(rtnl, F_SETFL, fcntl(sock, F_GETFL) | O_ASYNC);
  96
  97         struct {
  98                 struct nlmsghdr hdr;
  99                 struct ifinfomsg ifi;
 100         } req = {
 101                 .hdr = {sizeof(req), RTM_GETLINK, NLM_F_REQUEST, 1, 0},
 102                 .ifi = {.ifi_index = if_index}
 103         };
 104         send(rtnl, &req, sizeof(req), 0);
 105         ra_link_up();
 106
 107         // Filter ICMPv6 package types
 108         struct icmp6_filter filt;
 109         ICMP6_FILTER_SETBLOCKALL(&filt);
 110         ICMP6_FILTER_SETPASS(ND_ROUTER_ADVERT, &filt);
 111         setsockopt(sock, IPPROTO_ICMPV6, ICMP6_FILTER, &filt, sizeof(filt));
 112
 113         // Bind to all-nodes
 114         struct ipv6_mreq an = {ALL_IPV6_NODES, if_index};
 115         setsockopt(sock, IPPROTO_IPV6, IPV6_ADD_MEMBERSHIP, &an, sizeof(an));
 116
 117         // Let the kernel compute our checksums
 118         val = 2;
 119         setsockopt(sock, IPPROTO_RAW, IPV6_CHECKSUM, &val, sizeof(val));
 120
 121         // This is required by RFC 4861
 122         val = 255;
 123         setsockopt(sock, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &val, sizeof(val));
 124
 125         // Receive multicast hops
 126         val = 1;
 127         setsockopt(sock, IPPROTO_IPV6, IPV6_RECVHOPLIMIT, &val, sizeof(val));
 128
 129         // Bind to one device
 130         setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE, ifname, strlen(ifname));
 131
 132         // Add async-mode
 133         fcntl(sock, F_SETOWN, ourpid);
 134         fcntl(sock, F_SETFL, fcntl(sock, F_GETFL) | O_ASYNC);
 135
 136         // Send RS
 137         signal(SIGALRM, ra_send_rs);
 138         ra_send_rs(SIGALRM);
 139
 140         return 0;
 141 }
 142
 143
 144 static void ra_send_rs(int signal __attribute__((unused)))
 145 {
 146         const struct sockaddr_in6 dest = {AF_INET6, 0, 0, ALL_IPV6_ROUTERS, if_index};
 147         const struct icmpv6_opt llnull = {ND_OPT_SOURCE_LINKADDR, 1, {0}};
 148         size_t len;
 149
 150         if ((rs_attempt % 2 == 0) && memcmp(&rs.lladdr, &llnull, sizeof(llnull)))
 151                 len = sizeof(rs);
 152         else
 153                 len = sizeof(struct icmp6_hdr);
 154
 155         sendto(sock, &rs, len, MSG_DONTWAIT, (struct sockaddr*)&dest, sizeof(dest));
 156
 157         if (++rs_attempt <= 3)
 158                 alarm(4);
 159 }
 160
 161
 162 static int16_t pref_to_priority(uint8_t flags)
 163 {
 164         flags = (flags >> 3) & 0x03;
 165         return (flags == 0x0) ? 512 : (flags == 0x1) ? 384 :
 166                         (flags == 0x3) ? 640 : -1;
 167 }
 168
 169
 170 bool ra_link_up(void)
 171 {
 172         static bool firstcall = true;
 173         struct {
 174                 struct nlmsghdr hdr;
 175                 struct ifinfomsg msg;
 176                 uint8_t pad[4000];
 177         } resp;
 178
 179         bool ret = false;
 180         ssize_t read;
 181
 182         do {
 183                 read = recv(rtnl, &resp, sizeof(resp), MSG_DONTWAIT);
 184                 if (read < 0 || !NLMSG_OK(&resp.hdr, (size_t)read) ||
 185                                 resp.hdr.nlmsg_type != RTM_NEWLINK ||
 186                                 resp.msg.ifi_index != if_index)
 187                         continue;
 188
 189                 ssize_t alen = NLMSG_PAYLOAD(&resp.hdr, sizeof(resp.msg));
 190                 for (struct rtattr *rta = (struct rtattr*)(resp.pad);
 191                                 RTA_OK(rta, alen); rta = RTA_NEXT(rta, alen)) {
 192                         if (rta->rta_type == IFLA_ADDRESS &&
 193                                         RTA_PAYLOAD(rta) >= sizeof(rs.lladdr.data))
 194                                 memcpy(rs.lladdr.data, RTA_DATA(rta), sizeof(rs.lladdr.data));
 195                 }
 196
 197                 bool hascarrier = resp.msg.ifi_flags & IFF_LOWER_UP;
 198                 if (!firstcall && nocarrier != !hascarrier)
 199                         ret = true;
 200
 201                 nocarrier = !hascarrier;
 202                 firstcall = false;
 203         } while (read > 0);
 204
 205         if (ret) {
 206                 syslog(LOG_NOTICE, "carrier => %i event on %s", (int)!nocarrier, if_name);
 207
 208                 rs_attempt = 0;
 209                 ra_send_rs(SIGALRM);
 210         }
 211
 212         return ret;
 213 }
 214
 215 static bool ra_icmpv6_valid(struct sockaddr_in6 *source, int hlim, uint8_t *data, size_t len)
 216 {
 217         struct icmp6_hdr *hdr = (struct icmp6_hdr*)data;
 218         struct icmpv6_opt *opt, *end = (struct icmpv6_opt*)&data[len];
 219
 220         if (hlim != 255 || len < sizeof(*hdr) || hdr->icmp6_code)
 221                 return false;
 222
 223         switch (hdr->icmp6_type) {
 224         case ND_ROUTER_ADVERT:
 225                 if (!IN6_IS_ADDR_LINKLOCAL(&source->sin6_addr))
 226                         return false;
 227
 228                 opt = (struct icmpv6_opt*)((struct nd_router_advert*)data + 1);
 229                 break;
 230
 231         default:
 232                 return false;
 233         }
 234
 235         icmpv6_for_each_option(opt, opt, end)
 236                 ;
 237
 238         return opt == end;
 239 }
 240
 241 int ra_conf_hoplimit(int newvalue)
 242 {
 243         static int value = 0;
 244         if (newvalue > 0)
 245                 value = newvalue;
 246         return value;
 247 }
 248
 249 int ra_conf_mtu(int newvalue)
 250 {
 251         static int value = 0;
 252         if (newvalue >= 1280 && newvalue <= 65535)
 253                 value = newvalue;
 254         return value;
 255 }
 256
 257 int ra_conf_reachable(int newvalue)
 258 {
 259         static int value = 0;
 260         if (newvalue > 0 && newvalue <= 3600000)
 261                 value = newvalue;
 262         return value;
 263 }
 264
 265 int ra_conf_retransmit(int newvalue)
 266 {
 267         static int value = 0;
 268         if (newvalue > 0 && newvalue <= 60000)
 269                 value = newvalue;
 270         return value;
 271 }
 272
 273 bool ra_process(void)
 274 {
 275         bool found = false;
 276         bool changed = false;
 277         uint8_t buf[1500] __aligned(4);
 278         union {
 279                 struct cmsghdr hdr;
 280                 uint8_t buf[CMSG_SPACE(sizeof(int))];
 281         } cmsg_buf;
 282         struct nd_router_advert *adv = (struct nd_router_advert*)buf;
 283         struct odhcp6c_entry *entry = alloca(sizeof(*entry) + 256);
 284         const struct in6_addr any = IN6ADDR_ANY_INIT;
 285
 286         memset(entry, 0, sizeof(*entry));
 287
 288         if (IN6_IS_ADDR_UNSPECIFIED(&lladdr)) {
 289                 struct sockaddr_in6 addr = {AF_INET6, 0, 0, ALL_IPV6_ROUTERS, if_index};
 290                 socklen_t alen = sizeof(addr);
 291                 int sock = socket(AF_INET6, SOCK_RAW, IPPROTO_ICMPV6);
 292
 293                 if (!connect(sock, (struct sockaddr*)&addr, sizeof(addr)) &&
 294                                 !getsockname(sock, (struct sockaddr*)&addr, &alen))
 295                         lladdr = addr.sin6_addr;
 296
 297                 close(sock);
 298         }
 299
 300         while (true) {
 301                 struct sockaddr_in6 from;
 302                 struct iovec iov = {buf, sizeof(buf)};
 303                 struct msghdr msg = {
 304                         .msg_name = (void *) &from,
 305                         .msg_namelen = sizeof(from),
 306                         .msg_iov = &iov,
 307                         .msg_iovlen = 1,
 308                         .msg_control = cmsg_buf.buf,
 309                         .msg_controllen = sizeof(cmsg_buf),
 310                         .msg_flags = 0
 311                 };
 312
 313                 ssize_t len = recvmsg(sock, &msg, MSG_DONTWAIT);
 314                 if (len <= 0)
 315                         break;
 316
 317                 if (IN6_IS_ADDR_UNSPECIFIED(&lladdr))
 318                         continue;
 319
 320                 int hlim = 0;
 321                 for (struct cmsghdr *ch = CMSG_FIRSTHDR(&msg); ch != NULL;
 322                                 ch = CMSG_NXTHDR(&msg, ch))
 323                         if (ch->cmsg_level == IPPROTO_IPV6 &&
 324                                         ch->cmsg_type == IPV6_HOPLIMIT)
 325                                 memcpy(&hlim, CMSG_DATA(ch), sizeof(hlim));
 326
 327                 if (!ra_icmpv6_valid(&from, hlim, buf, len))
 328                         continue;
 329
 330                 // Stop sending solicits
 331                 if (rs_attempt > 0) {
 332                         alarm(0);
 333                         rs_attempt = 0;
 334                 }
 335
 336                 if (!found) {
 337                         odhcp6c_expire();
 338                         found = true;
 339                 }
 340                 uint32_t router_valid = ntohs(adv->nd_ra_router_lifetime);
 341
 342                 // Parse default route
 343                 entry->target = any;
 344                 entry->length = 0;
 345                 entry->router = from.sin6_addr;
 346                 entry->priority = pref_to_priority(adv->nd_ra_flags_reserved);
 347                 if (entry->priority < 0)
 348                         entry->priority = pref_to_priority(0);
 349                 entry->valid = router_valid;
 350                 entry->preferred = entry->valid;
 351                 changed |= odhcp6c_update_entry(STATE_RA_ROUTE, entry, 0, true);
 352
 353                 // Parse hoplimit
 354                 ra_conf_hoplimit(adv->nd_ra_curhoplimit);
 355
 356                 // Parse ND parameters
 357                 ra_conf_reachable(ntohl(adv->nd_ra_reachable));
 358                 ra_conf_retransmit(ntohl(adv->nd_ra_retransmit));
 359
 360                 // Evaluate options
 361                 struct icmpv6_opt *opt;
 362                 icmpv6_for_each_option(opt, &adv[1], &buf[len]) {
 363                         if (opt->type == ND_OPT_MTU) {
 364                                 uint32_t *mtu = (uint32_t*)&opt->data[2];
 365                                 ra_conf_mtu(ntohl(*mtu));
 366                         } else if (opt->type == ND_OPT_ROUTE_INFORMATION && opt->len <= 3) {
 367                                 entry->router = from.sin6_addr;
 368                                 entry->target = any;
 369                                 entry->priority = pref_to_priority(opt->data[1]);
 370                                 entry->length = opt->data[0];
 371                                 uint32_t *valid = (uint32_t*)&opt->data[2];
 372                                 entry->valid = ntohl(*valid);
 373                                 memcpy(&entry->target, &opt->data[6], (opt->len - 1) * 8);
 374
 375                                 if (entry->length > 128 || IN6_IS_ADDR_LINKLOCAL(&entry->target)
 376                                                 || IN6_IS_ADDR_LOOPBACK(&entry->target)
 377                                                 || IN6_IS_ADDR_MULTICAST(&entry->target))
 378                                         continue;
 379
 380                                 if (entry->priority > 0)
 381                                         changed |= odhcp6c_update_entry(STATE_RA_ROUTE, entry, 0, true);
 382                         } else if (opt->type == ND_OPT_PREFIX_INFORMATION && opt->len == 4) {
 383                                 struct nd_opt_prefix_info *pinfo = (struct nd_opt_prefix_info*)opt;
 384                                 entry->router = any;
 385                                 entry->target = pinfo->nd_opt_pi_prefix;
 386                                 entry->priority = 256;
 387                                 entry->length = pinfo->nd_opt_pi_prefix_len;
 388                                 entry->valid = ntohl(pinfo->nd_opt_pi_valid_time);
 389                                 entry->preferred = ntohl(pinfo->nd_opt_pi_preferred_time);
 390
 391                                 if (entry->length > 128 || IN6_IS_ADDR_LINKLOCAL(&entry->target)
 392                                                 || IN6_IS_ADDR_LOOPBACK(&entry->target)
 393                                                 || IN6_IS_ADDR_MULTICAST(&entry->target)
 394                                                 || entry->valid < entry->preferred)
 395                                         continue;
 396
 397                                 if (pinfo->nd_opt_pi_flags_reserved & ND_OPT_PI_FLAG_ONLINK)
 398                                         changed |= odhcp6c_update_entry(STATE_RA_ROUTE, entry, 7200, true);
 399
 400                                 if (!(pinfo->nd_opt_pi_flags_reserved & ND_OPT_PI_FLAG_AUTO) ||
 401                                                 pinfo->nd_opt_pi_prefix_len != 64)
 402                                         continue;
 403
 404                                 entry->target.s6_addr32[2] = lladdr.s6_addr32[2];
 405                                 entry->target.s6_addr32[3] = lladdr.s6_addr32[3];
 406
 407                                 changed |= odhcp6c_update_entry(STATE_RA_PREFIX, entry, 7200, true);
 408                         } else if (opt->type == ND_OPT_RECURSIVE_DNS && opt->len > 2) {
 409                                 entry->router = from.sin6_addr;
 410                                 entry->priority = 0;
 411                                 entry->length = 128;
 412                                 uint32_t *valid = (uint32_t*)&opt->data[2];
 413                                 entry->valid = ntohl(*valid);
 414                                 entry->preferred = 0;
 415
 416                                 for (ssize_t i = 0; i < (opt->len - 1) / 2; ++i) {
 417                                         memcpy(&entry->target, &opt->data[6 + i * sizeof(entry->target)],
 418                                                         sizeof(entry->target));
 419                                         changed |= odhcp6c_update_entry(STATE_RA_DNS, entry, 0, true);
 420                                 }
 421                         } else if (opt->type == ND_OPT_DNSSL && opt->len > 1) {
 422                                 uint32_t *valid = (uint32_t*)&opt->data[2];
 423                                 uint8_t *buf = &opt->data[6];
 424                                 uint8_t *end = &buf[(opt->len - 1) * 8];
 425
 426                                 entry->router = from.sin6_addr;
 427                                 entry->valid = ntohl(*valid);
 428
 429                                 while (buf < end) {
 430                                         int len = dn_expand(buf, end, buf, (char*)entry->auxtarget, 256);
 431                                         if (len < 1)
 432                                                 break;
 433
 434                                         buf = &buf[len];
 435                                         entry->auxlen = strlen((char*)entry->auxtarget);
 436
 437                                         if (entry->auxlen == 0)
 438                                                 continue;
 439
 440                                         changed |= odhcp6c_update_entry(STATE_RA_SEARCH, entry, 0, true);
 441                                         entry->auxlen = 0;
 442                                 }
 443                         }
 444                 }
 445
 446                 int states[2] = {STATE_RA_DNS, STATE_RA_SEARCH};
 447                 for (size_t i = 0; i < 2; ++i) {
 448                         size_t ra_dns_len;
 449                         uint8_t *start = odhcp6c_get_state(states[i], &ra_dns_len);
 450                         for (struct odhcp6c_entry *c = (struct odhcp6c_entry*)start;
 451                                                 (uint8_t*)c < &start[ra_dns_len] &&
 452                                                 (uint8_t*)odhcp6c_next_entry(c) <= &start[ra_dns_len];
 453                                                 c = odhcp6c_next_entry(c))
 454                                 if (IN6_ARE_ADDR_EQUAL(&c->router, &from.sin6_addr) &&
 455                                                 c->valid > router_valid)
 456                                         c->valid = router_valid;
 457                 }
 458         }
 459
 460         if (found)
 461                 odhcp6c_expire();
 462
 463         return found && changed;
 464 }