src/ra.c

   1 /**
   2  * Copyright (C) 2012-2014 Steven Barth <steven@midlink.org>
   3  * Copyright (C) 2017 Hans Dedecker <dedeckeh@gmail.com>
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License v2 as published by
   7  * the Free Software Foundation.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  */
  15
  16 #include <fcntl.h>
  17 #include <stdio.h>
  18 #include <signal.h>
  19 #include <string.h>
  20 #include <stddef.h>
  21 #include <stdbool.h>
  22 #include <syslog.h>
  23 #include <unistd.h>
  24 #include <resolv.h>
  25 #include <alloca.h>
  26
  27 #include <net/if.h>
  28 #include <arpa/inet.h>
  29 #include <sys/socket.h>
  30 #include <sys/types.h>
  31 #include <netinet/in.h>
  32 #include <netinet/icmp6.h>
  33
  34 #include <linux/rtnetlink.h>
  35
  36 #ifndef SOL_NETLINK
  37 #define SOL_NETLINK 270
  38 #endif
  39
  40 #ifndef NETLINK_ADD_MEMBERSHIP
  41 #define NETLINK_ADD_MEMBERSHIP 1
  42 #endif
  43
  44 #ifndef IFF_LOWER_UP
  45 #define IFF_LOWER_UP 0x10000
  46 #endif
  47
  48 #include "odhcp6c.h"
  49 #include "ra.h"
  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 static unsigned int ra_options = 0;
  59 static unsigned int ra_holdoff_interval = 0;
  60
  61 struct {
  62         struct icmp6_hdr hdr;
  63         struct icmpv6_opt lladdr;
  64 } rs = {
  65         .hdr = {ND_ROUTER_SOLICIT, 0, 0, {{0}}},
  66         .lladdr = {ND_OPT_SOURCE_LINKADDR, 1, {0}},
  67 };
  68
  69 static void ra_send_rs(int signal __attribute__((unused)));
  70
  71 int ra_init(const char *ifname, const struct in6_addr *ifid,
  72                 unsigned int options, unsigned int holdoff_interval)
  73 {
  74         ra_options = options;
  75         ra_holdoff_interval = holdoff_interval;
  76
  77         const pid_t ourpid = getpid();
  78         sock = socket(AF_INET6, SOCK_RAW | SOCK_CLOEXEC, IPPROTO_ICMPV6);
  79         if (sock < 0)
  80                 return -1;
  81
  82         if_index = if_nametoindex(ifname);
  83         if (!if_index)
  84                 return -1;
  85
  86         strncpy(if_name, ifname, sizeof(if_name) - 1);
  87         lladdr = *ifid;
  88
  89         rtnl = socket(AF_NETLINK, SOCK_DGRAM | SOCK_CLOEXEC, NETLINK_ROUTE);
  90         if (rtnl < 0)
  91                 return -1;
  92
  93         struct sockaddr_nl rtnl_kernel = { .nl_family = AF_NETLINK };
  94         if (connect(rtnl, (const struct sockaddr*)&rtnl_kernel, sizeof(rtnl_kernel)) < 0)
  95                 return -1;
  96
  97         int val = RTNLGRP_LINK;
  98         setsockopt(rtnl, SOL_NETLINK, NETLINK_ADD_MEMBERSHIP, &val, sizeof(val));
  99         fcntl(rtnl, F_SETOWN, ourpid);
 100         fcntl(rtnl, F_SETFL, fcntl(sock, F_GETFL) | O_ASYNC);
 101
 102         struct {
 103                 struct nlmsghdr hdr;
 104                 struct ifinfomsg ifi;
 105         } req = {
 106                 .hdr = {sizeof(req), RTM_GETLINK, NLM_F_REQUEST, 1, 0},
 107                 .ifi = {.ifi_index = if_index}
 108         };
 109         send(rtnl, &req, sizeof(req), 0);
 110         ra_link_up();
 111
 112         // Filter ICMPv6 package types
 113         struct icmp6_filter filt;
 114         ICMP6_FILTER_SETBLOCKALL(&filt);
 115         ICMP6_FILTER_SETPASS(ND_ROUTER_ADVERT, &filt);
 116         setsockopt(sock, IPPROTO_ICMPV6, ICMP6_FILTER, &filt, sizeof(filt));
 117
 118         // Bind to all-nodes
 119         struct ipv6_mreq an = {ALL_IPV6_NODES, if_index};
 120         setsockopt(sock, IPPROTO_IPV6, IPV6_ADD_MEMBERSHIP, &an, sizeof(an));
 121
 122         // Let the kernel compute our checksums
 123         val = 2;
 124         setsockopt(sock, IPPROTO_RAW, IPV6_CHECKSUM, &val, sizeof(val));
 125
 126         // This is required by RFC 4861
 127         val = 255;
 128         setsockopt(sock, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &val, sizeof(val));
 129
 130         // Receive multicast hops
 131         val = 1;
 132         setsockopt(sock, IPPROTO_IPV6, IPV6_RECVHOPLIMIT, &val, sizeof(val));
 133
 134         // Bind to one device
 135         setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE, ifname, strlen(ifname));
 136
 137         // Add async-mode
 138         fcntl(sock, F_SETOWN, ourpid);
 139         fcntl(sock, F_SETFL, fcntl(sock, F_GETFL) | O_ASYNC);
 140
 141         // Send RS
 142         signal(SIGALRM, ra_send_rs);
 143         ra_send_rs(SIGALRM);
 144
 145         return 0;
 146 }
 147
 148 static void ra_send_rs(int signal __attribute__((unused)))
 149 {
 150         const struct sockaddr_in6 dest = {AF_INET6, 0, 0, ALL_IPV6_ROUTERS, if_index};
 151         const struct icmpv6_opt llnull = {ND_OPT_SOURCE_LINKADDR, 1, {0}};
 152         size_t len;
 153
 154         if ((rs_attempt % 2 == 0) && memcmp(&rs.lladdr, &llnull, sizeof(llnull)))
 155                 len = sizeof(rs);
 156         else
 157                 len = sizeof(struct icmp6_hdr);
 158
 159         sendto(sock, &rs, len, MSG_DONTWAIT, (struct sockaddr*)&dest, sizeof(dest));
 160
 161         if (++rs_attempt <= 3)
 162                 alarm(4);
 163 }
 164
 165 static int16_t pref_to_priority(uint8_t flags)
 166 {
 167         flags = (flags >> 3) & 0x03;
 168
 169         return (flags == 0x0) ? 512 : (flags == 0x1) ? 384 :
 170                         (flags == 0x3) ? 640 : -1;
 171 }
 172
 173 bool ra_link_up(void)
 174 {
 175         static bool firstcall = true;
 176         struct {
 177                 struct nlmsghdr hdr;
 178                 struct ifinfomsg msg;
 179                 uint8_t pad[4000];
 180         } resp;
 181         bool ret = false;
 182         ssize_t read;
 183
 184         do {
 185                 read = recv(rtnl, &resp, sizeof(resp), MSG_DONTWAIT);
 186
 187                 if (read < 0 || !NLMSG_OK(&resp.hdr, (size_t)read) ||
 188                                 resp.hdr.nlmsg_type != RTM_NEWLINK ||
 189                                 resp.msg.ifi_index != if_index)
 190                         continue;
 191
 192                 ssize_t alen = NLMSG_PAYLOAD(&resp.hdr, sizeof(resp.msg));
 193                 for (struct rtattr *rta = (struct rtattr*)(resp.pad);
 194                                 RTA_OK(rta, alen); rta = RTA_NEXT(rta, alen)) {
 195                         if (rta->rta_type == IFLA_ADDRESS &&
 196                                         RTA_PAYLOAD(rta) >= sizeof(rs.lladdr.data))
 197                                 memcpy(rs.lladdr.data, RTA_DATA(rta), sizeof(rs.lladdr.data));
 198                 }
 199
 200                 bool hascarrier = resp.msg.ifi_flags & IFF_LOWER_UP;
 201                 if (!firstcall && nocarrier != !hascarrier)
 202                         ret = true;
 203
 204                 nocarrier = !hascarrier;
 205                 firstcall = false;
 206         } while (read > 0);
 207
 208         if (ret) {
 209                 syslog(LOG_NOTICE, "carrier => %i event on %s", (int)!nocarrier, if_name);
 210
 211                 rs_attempt = 0;
 212                 ra_send_rs(SIGALRM);
 213         }
 214
 215         return ret;
 216 }
 217
 218 static bool ra_icmpv6_valid(struct sockaddr_in6 *source, int hlim, uint8_t *data, size_t len)
 219 {
 220         struct icmp6_hdr *hdr = (struct icmp6_hdr*)data;
 221         struct icmpv6_opt *opt, *end = (struct icmpv6_opt*)&data[len];
 222
 223         if (hlim != 255 || len < sizeof(*hdr) || hdr->icmp6_code)
 224                 return false;
 225
 226         switch (hdr->icmp6_type) {
 227         case ND_ROUTER_ADVERT:
 228                 if (!IN6_IS_ADDR_LINKLOCAL(&source->sin6_addr))
 229                         return false;
 230
 231                 opt = (struct icmpv6_opt*)((struct nd_router_advert*)data + 1);
 232                 break;
 233
 234         default:
 235                 return false;
 236         }
 237
 238         icmpv6_for_each_option(opt, opt, end)
 239                 ;
 240
 241         return opt == end;
 242 }
 243
 244 int ra_conf_hoplimit(int newvalue)
 245 {
 246         static int value = 0;
 247
 248         if (newvalue > 0)
 249                 value = newvalue;
 250
 251         return value;
 252 }
 253
 254 int ra_conf_mtu(int newvalue)
 255 {
 256         static int value = 0;
 257
 258         if (newvalue >= 1280 && newvalue <= 65535)
 259                 value = newvalue;
 260
 261         return value;
 262 }
 263
 264 int ra_conf_reachable(int newvalue)
 265 {
 266         static int value = 0;
 267
 268         if (newvalue > 0 && newvalue <= 3600000)
 269                 value = newvalue;
 270
 271         return value;
 272 }
 273
 274 int ra_conf_retransmit(int newvalue)
 275 {
 276         static int value = 0;
 277
 278         if (newvalue > 0 && newvalue <= 60000)
 279                 value = newvalue;
 280
 281         return value;
 282 }
 283
 284 bool ra_process(void)
 285 {
 286         bool found = false;
 287         bool changed = false;
 288         uint8_t buf[1500] _aligned(4);
 289         union {
 290                 struct cmsghdr hdr;
 291                 uint8_t buf[CMSG_SPACE(sizeof(int))];
 292         } cmsg_buf;
 293         struct nd_router_advert *adv = (struct nd_router_advert*)buf;
 294         struct odhcp6c_entry *entry = alloca(sizeof(*entry) + 256);
 295         const struct in6_addr any = IN6ADDR_ANY_INIT;
 296
 297         memset(entry, 0, sizeof(*entry));
 298
 299         if (IN6_IS_ADDR_UNSPECIFIED(&lladdr)) {
 300                 struct sockaddr_in6 addr = {AF_INET6, 0, 0, ALL_IPV6_ROUTERS, if_index};
 301                 socklen_t alen = sizeof(addr);
 302                 int sock = socket(AF_INET6, SOCK_RAW, IPPROTO_ICMPV6);
 303
 304                 if (!connect(sock, (struct sockaddr*)&addr, sizeof(addr)) &&
 305                                 !getsockname(sock, (struct sockaddr*)&addr, &alen))
 306                         lladdr = addr.sin6_addr;
 307
 308                 close(sock);
 309         }
 310
 311         while (true) {
 312                 struct sockaddr_in6 from;
 313                 struct iovec iov = {buf, sizeof(buf)};
 314                 struct msghdr msg = {
 315                         .msg_name = (void *) &from,
 316                         .msg_namelen = sizeof(from),
 317                         .msg_iov = &iov,
 318                         .msg_iovlen = 1,
 319                         .msg_control = cmsg_buf.buf,
 320                         .msg_controllen = sizeof(cmsg_buf),
 321                         .msg_flags = 0
 322                 };
 323
 324                 ssize_t len = recvmsg(sock, &msg, MSG_DONTWAIT);
 325                 if (len <= 0)
 326                         break;
 327
 328                 if (IN6_IS_ADDR_UNSPECIFIED(&lladdr))
 329                         continue;
 330
 331                 int hlim = 0;
 332                 for (struct cmsghdr *ch = CMSG_FIRSTHDR(&msg); ch != NULL;
 333                                 ch = CMSG_NXTHDR(&msg, ch))
 334                         if (ch->cmsg_level == IPPROTO_IPV6 &&
 335                                         ch->cmsg_type == IPV6_HOPLIMIT)
 336                                 memcpy(&hlim, CMSG_DATA(ch), sizeof(hlim));
 337
 338                 if (!ra_icmpv6_valid(&from, hlim, buf, len))
 339                         continue;
 340
 341                 // Stop sending solicits
 342                 if (rs_attempt > 0) {
 343                         alarm(0);
 344                         rs_attempt = 0;
 345                 }
 346
 347                 if (!found) {
 348                         odhcp6c_expire();
 349                         found = true;
 350                 }
 351                 uint32_t router_valid = ntohs(adv->nd_ra_router_lifetime);
 352
 353                 // Parse default route
 354                 entry->target = any;
 355                 entry->length = 0;
 356                 entry->router = from.sin6_addr;
 357                 entry->priority = pref_to_priority(adv->nd_ra_flags_reserved);
 358                 if (entry->priority < 0)
 359                         entry->priority = pref_to_priority(0);
 360
 361                 entry->valid = router_valid;
 362                 entry->preferred = entry->valid;
 363                 changed |= odhcp6c_update_entry(STATE_RA_ROUTE, entry,
 364                                                 0, ra_holdoff_interval);
 365
 366                 // Parse hoplimit
 367                 ra_conf_hoplimit(adv->nd_ra_curhoplimit);
 368
 369                 // Parse ND parameters
 370                 ra_conf_reachable(ntohl(adv->nd_ra_reachable));
 371                 ra_conf_retransmit(ntohl(adv->nd_ra_retransmit));
 372
 373                 // Evaluate options
 374                 struct icmpv6_opt *opt;
 375                 icmpv6_for_each_option(opt, &adv[1], &buf[len]) {
 376                         if (opt->type == ND_OPT_MTU) {
 377                                 uint32_t *mtu = (uint32_t*)&opt->data[2];
 378                                 ra_conf_mtu(ntohl(*mtu));
 379                         } else if (opt->type == ND_OPT_ROUTE_INFORMATION && opt->len <= 3) {
 380                                 entry->router = from.sin6_addr;
 381                                 entry->target = any;
 382                                 entry->priority = pref_to_priority(opt->data[1]);
 383                                 entry->length = opt->data[0];
 384                                 uint32_t *valid = (uint32_t*)&opt->data[2];
 385                                 entry->valid = ntohl(*valid);
 386                                 memcpy(&entry->target, &opt->data[6], (opt->len - 1) * 8);
 387
 388                                 if (entry->length > 128 || IN6_IS_ADDR_LINKLOCAL(&entry->target)
 389                                                 || IN6_IS_ADDR_LOOPBACK(&entry->target)
 390                                                 || IN6_IS_ADDR_MULTICAST(&entry->target))
 391                                         continue;
 392
 393                                 if (entry->priority > 0)
 394                                         changed |= odhcp6c_update_entry(STATE_RA_ROUTE, entry,
 395                                                                         0, ra_holdoff_interval);
 396                         } else if (opt->type == ND_OPT_PREFIX_INFORMATION && opt->len == 4) {
 397                                 struct nd_opt_prefix_info *pinfo = (struct nd_opt_prefix_info*)opt;
 398                                 entry->router = any;
 399                                 entry->target = pinfo->nd_opt_pi_prefix;
 400                                 entry->priority = 256;
 401                                 entry->length = pinfo->nd_opt_pi_prefix_len;
 402                                 entry->valid = ntohl(pinfo->nd_opt_pi_valid_time);
 403                                 entry->preferred = ntohl(pinfo->nd_opt_pi_preferred_time);
 404
 405                                 if (entry->length > 128 || IN6_IS_ADDR_LINKLOCAL(&entry->target)
 406                                                 || IN6_IS_ADDR_LOOPBACK(&entry->target)
 407                                                 || IN6_IS_ADDR_MULTICAST(&entry->target)
 408                                                 || entry->valid < entry->preferred)
 409                                         continue;
 410
 411                                 if (pinfo->nd_opt_pi_flags_reserved & ND_OPT_PI_FLAG_ONLINK)
 412                                         changed |= odhcp6c_update_entry(STATE_RA_ROUTE, entry,
 413                                                                         7200, ra_holdoff_interval);
 414
 415                                 if (!(pinfo->nd_opt_pi_flags_reserved & ND_OPT_PI_FLAG_AUTO) ||
 416                                                 pinfo->nd_opt_pi_prefix_len != 64)
 417                                         continue;
 418
 419                                 entry->target.s6_addr32[2] = lladdr.s6_addr32[2];
 420                                 entry->target.s6_addr32[3] = lladdr.s6_addr32[3];
 421
 422                                 changed |= odhcp6c_update_entry(STATE_RA_PREFIX, entry,
 423                                                                 7200, ra_holdoff_interval);
 424                         } else if (opt->type == ND_OPT_RECURSIVE_DNS && opt->len > 2) {
 425                                 entry->router = from.sin6_addr;
 426                                 entry->priority = 0;
 427                                 entry->length = 128;
 428                                 uint32_t *valid = (uint32_t*)&opt->data[2];
 429                                 entry->valid = ntohl(*valid);
 430                                 entry->preferred = 0;
 431
 432                                 for (ssize_t i = 0; i < (opt->len - 1) / 2; ++i) {
 433                                         memcpy(&entry->target, &opt->data[6 + i * sizeof(entry->target)],
 434                                                         sizeof(entry->target));
 435                                         changed |= odhcp6c_update_entry(STATE_RA_DNS, entry,
 436                                                                         0, ra_holdoff_interval);
 437                                 }
 438                         } else if (opt->type == ND_OPT_DNSSL && opt->len > 1) {
 439                                 uint32_t *valid = (uint32_t*)&opt->data[2];
 440                                 uint8_t *buf = &opt->data[6];
 441                                 uint8_t *end = &buf[(opt->len - 1) * 8];
 442
 443                                 entry->router = from.sin6_addr;
 444                                 entry->valid = ntohl(*valid);
 445
 446                                 while (buf < end) {
 447                                         int len = dn_expand(buf, end, buf, (char*)entry->auxtarget, 256);
 448                                         if (len < 1)
 449                                                 break;
 450
 451                                         buf = &buf[len];
 452                                         entry->auxlen = strlen((char*)entry->auxtarget);
 453
 454                                         if (entry->auxlen == 0)
 455                                                 continue;
 456
 457                                         changed |= odhcp6c_update_entry(STATE_RA_SEARCH, entry,
 458                                                                         0, ra_holdoff_interval);
 459                                         entry->auxlen = 0;
 460                                 }
 461                         }
 462                 }
 463
 464                 if (ra_options & RA_RDNSS_DEFAULT_LIFETIME) {
 465                         int states[2] = {STATE_RA_DNS, STATE_RA_SEARCH};
 466
 467                         for (size_t i = 0; i < 2; ++i) {
 468                                 size_t ra_dns_len;
 469                                 uint8_t *start = odhcp6c_get_state(states[i], &ra_dns_len);
 470
 471                                 for (struct odhcp6c_entry *c = (struct odhcp6c_entry*)start;
 472                                                         (uint8_t*)c < &start[ra_dns_len] &&
 473                                                         (uint8_t*)odhcp6c_next_entry(c) <= &start[ra_dns_len];
 474                                                         c = odhcp6c_next_entry(c)) {
 475                                         if (IN6_ARE_ADDR_EQUAL(&c->router, &from.sin6_addr) &&
 476                                                         c->valid > router_valid)
 477                                                 c->valid = router_valid;
 478                                 }
 479                         }
 480                 }
 481         }
 482
 483         if (found)
 484                 odhcp6c_expire();
 485
 486         return found && changed;
 487 }