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
  60 struct {
  61         struct icmp6_hdr hdr;
  62         struct icmpv6_opt lladdr;
  63 } rs = {
  64         .hdr = {ND_ROUTER_SOLICIT, 0, 0, {{0}}},
  65         .lladdr = {ND_OPT_SOURCE_LINKADDR, 1, {0}},
  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, unsigned int options)
  71 {
  72         ra_options = options;
  73
  74         const pid_t ourpid = getpid();
  75         sock = socket(AF_INET6, SOCK_RAW | SOCK_CLOEXEC, IPPROTO_ICMPV6);
  76         if (sock < 0)
  77                 return -1;
  78
  79         if_index = if_nametoindex(ifname);
  80         if (!if_index)
  81                 return -1;
  82
  83         strncpy(if_name, ifname, sizeof(if_name) - 1);
  84         lladdr = *ifid;
  85
  86         rtnl = socket(AF_NETLINK, SOCK_DGRAM | SOCK_CLOEXEC, NETLINK_ROUTE);
  87         if (rtnl < 0)
  88                 return -1;
  89
  90         struct sockaddr_nl rtnl_kernel = { .nl_family = AF_NETLINK };
  91         if (connect(rtnl, (const struct sockaddr*)&rtnl_kernel, sizeof(rtnl_kernel)) < 0)
  92                 return -1;
  93
  94         int val = RTNLGRP_LINK;
  95         setsockopt(rtnl, SOL_NETLINK, NETLINK_ADD_MEMBERSHIP, &val, sizeof(val));
  96         fcntl(rtnl, F_SETOWN, ourpid);
  97         fcntl(rtnl, F_SETFL, fcntl(sock, F_GETFL) | O_ASYNC);
  98
  99         struct {
 100                 struct nlmsghdr hdr;
 101                 struct ifinfomsg ifi;
 102         } req = {
 103                 .hdr = {sizeof(req), RTM_GETLINK, NLM_F_REQUEST, 1, 0},
 104                 .ifi = {.ifi_index = if_index}
 105         };
 106         send(rtnl, &req, sizeof(req), 0);
 107         ra_link_up();
 108
 109         // Filter ICMPv6 package types
 110         struct icmp6_filter filt;
 111         ICMP6_FILTER_SETBLOCKALL(&filt);
 112         ICMP6_FILTER_SETPASS(ND_ROUTER_ADVERT, &filt);
 113         setsockopt(sock, IPPROTO_ICMPV6, ICMP6_FILTER, &filt, sizeof(filt));
 114
 115         // Bind to all-nodes
 116         struct ipv6_mreq an = {ALL_IPV6_NODES, if_index};
 117         setsockopt(sock, IPPROTO_IPV6, IPV6_ADD_MEMBERSHIP, &an, sizeof(an));
 118
 119         // Let the kernel compute our checksums
 120         val = 2;
 121         setsockopt(sock, IPPROTO_RAW, IPV6_CHECKSUM, &val, sizeof(val));
 122
 123         // This is required by RFC 4861
 124         val = 255;
 125         setsockopt(sock, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &val, sizeof(val));
 126
 127         // Receive multicast hops
 128         val = 1;
 129         setsockopt(sock, IPPROTO_IPV6, IPV6_RECVHOPLIMIT, &val, sizeof(val));
 130
 131         // Bind to one device
 132         setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE, ifname, strlen(ifname));
 133
 134         // Add async-mode
 135         fcntl(sock, F_SETOWN, ourpid);
 136         fcntl(sock, F_SETFL, fcntl(sock, F_GETFL) | O_ASYNC);
 137
 138         // Send RS
 139         signal(SIGALRM, ra_send_rs);
 140         ra_send_rs(SIGALRM);
 141
 142         return 0;
 143 }
 144
 145 static void ra_send_rs(int signal __attribute__((unused)))
 146 {
 147         const struct sockaddr_in6 dest = {AF_INET6, 0, 0, ALL_IPV6_ROUTERS, if_index};
 148         const struct icmpv6_opt llnull = {ND_OPT_SOURCE_LINKADDR, 1, {0}};
 149         size_t len;
 150
 151         if ((rs_attempt % 2 == 0) && memcmp(&rs.lladdr, &llnull, sizeof(llnull)))
 152                 len = sizeof(rs);
 153         else
 154                 len = sizeof(struct icmp6_hdr);
 155
 156         sendto(sock, &rs, len, MSG_DONTWAIT, (struct sockaddr*)&dest, sizeof(dest));
 157
 158         if (++rs_attempt <= 3)
 159                 alarm(4);
 160 }
 161
 162 static int16_t pref_to_priority(uint8_t flags)
 163 {
 164         flags = (flags >> 3) & 0x03;
 165
 166         return (flags == 0x0) ? 512 : (flags == 0x1) ? 384 :
 167                         (flags == 0x3) ? 640 : -1;
 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         bool ret = false;
 179         ssize_t read;
 180
 181         do {
 182                 read = recv(rtnl, &resp, sizeof(resp), MSG_DONTWAIT);
 183
 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
 245         if (newvalue > 0)
 246                 value = newvalue;
 247
 248         return value;
 249 }
 250
 251 int ra_conf_mtu(int newvalue)
 252 {
 253         static int value = 0;
 254
 255         if (newvalue >= 1280 && newvalue <= 65535)
 256                 value = newvalue;
 257
 258         return value;
 259 }
 260
 261 int ra_conf_reachable(int newvalue)
 262 {
 263         static int value = 0;
 264
 265         if (newvalue > 0 && newvalue <= 3600000)
 266                 value = newvalue;
 267
 268         return value;
 269 }
 270
 271 int ra_conf_retransmit(int newvalue)
 272 {
 273         static int value = 0;
 274
 275         if (newvalue > 0 && newvalue <= 60000)
 276                 value = newvalue;
 277
 278         return value;
 279 }
 280
 281 bool ra_process(void)
 282 {
 283         bool found = false;
 284         bool changed = false;
 285         uint8_t buf[1500] _aligned(4);
 286         union {
 287                 struct cmsghdr hdr;
 288                 uint8_t buf[CMSG_SPACE(sizeof(int))];
 289         } cmsg_buf;
 290         struct nd_router_advert *adv = (struct nd_router_advert*)buf;
 291         struct odhcp6c_entry *entry = alloca(sizeof(*entry) + 256);
 292         const struct in6_addr any = IN6ADDR_ANY_INIT;
 293
 294         memset(entry, 0, sizeof(*entry));
 295
 296         if (IN6_IS_ADDR_UNSPECIFIED(&lladdr)) {
 297                 struct sockaddr_in6 addr = {AF_INET6, 0, 0, ALL_IPV6_ROUTERS, if_index};
 298                 socklen_t alen = sizeof(addr);
 299                 int sock = socket(AF_INET6, SOCK_RAW, IPPROTO_ICMPV6);
 300
 301                 if (!connect(sock, (struct sockaddr*)&addr, sizeof(addr)) &&
 302                                 !getsockname(sock, (struct sockaddr*)&addr, &alen))
 303                         lladdr = addr.sin6_addr;
 304
 305                 close(sock);
 306         }
 307
 308         while (true) {
 309                 struct sockaddr_in6 from;
 310                 struct iovec iov = {buf, sizeof(buf)};
 311                 struct msghdr msg = {
 312                         .msg_name = (void *) &from,
 313                         .msg_namelen = sizeof(from),
 314                         .msg_iov = &iov,
 315                         .msg_iovlen = 1,
 316                         .msg_control = cmsg_buf.buf,
 317                         .msg_controllen = sizeof(cmsg_buf),
 318                         .msg_flags = 0
 319                 };
 320
 321                 ssize_t len = recvmsg(sock, &msg, MSG_DONTWAIT);
 322                 if (len <= 0)
 323                         break;
 324
 325                 if (IN6_IS_ADDR_UNSPECIFIED(&lladdr))
 326                         continue;
 327
 328                 int hlim = 0;
 329                 for (struct cmsghdr *ch = CMSG_FIRSTHDR(&msg); ch != NULL;
 330                                 ch = CMSG_NXTHDR(&msg, ch))
 331                         if (ch->cmsg_level == IPPROTO_IPV6 &&
 332                                         ch->cmsg_type == IPV6_HOPLIMIT)
 333                                 memcpy(&hlim, CMSG_DATA(ch), sizeof(hlim));
 334
 335                 if (!ra_icmpv6_valid(&from, hlim, buf, len))
 336                         continue;
 337
 338                 // Stop sending solicits
 339                 if (rs_attempt > 0) {
 340                         alarm(0);
 341                         rs_attempt = 0;
 342                 }
 343
 344                 if (!found) {
 345                         odhcp6c_expire();
 346                         found = true;
 347                 }
 348                 uint32_t router_valid = ntohs(adv->nd_ra_router_lifetime);
 349
 350                 // Parse default route
 351                 entry->target = any;
 352                 entry->length = 0;
 353                 entry->router = from.sin6_addr;
 354                 entry->priority = pref_to_priority(adv->nd_ra_flags_reserved);
 355                 if (entry->priority < 0)
 356                         entry->priority = pref_to_priority(0);
 357
 358                 entry->valid = router_valid;
 359                 entry->preferred = entry->valid;
 360                 changed |= odhcp6c_update_entry(STATE_RA_ROUTE, entry, 0, true);
 361
 362                 // Parse hoplimit
 363                 ra_conf_hoplimit(adv->nd_ra_curhoplimit);
 364
 365                 // Parse ND parameters
 366                 ra_conf_reachable(ntohl(adv->nd_ra_reachable));
 367                 ra_conf_retransmit(ntohl(adv->nd_ra_retransmit));
 368
 369                 // Evaluate options
 370                 struct icmpv6_opt *opt;
 371                 icmpv6_for_each_option(opt, &adv[1], &buf[len]) {
 372                         if (opt->type == ND_OPT_MTU) {
 373                                 uint32_t *mtu = (uint32_t*)&opt->data[2];
 374                                 ra_conf_mtu(ntohl(*mtu));
 375                         } else if (opt->type == ND_OPT_ROUTE_INFORMATION && opt->len <= 3) {
 376                                 entry->router = from.sin6_addr;
 377                                 entry->target = any;
 378                                 entry->priority = pref_to_priority(opt->data[1]);
 379                                 entry->length = opt->data[0];
 380                                 uint32_t *valid = (uint32_t*)&opt->data[2];
 381                                 entry->valid = ntohl(*valid);
 382                                 memcpy(&entry->target, &opt->data[6], (opt->len - 1) * 8);
 383
 384                                 if (entry->length > 128 || IN6_IS_ADDR_LINKLOCAL(&entry->target)
 385                                                 || IN6_IS_ADDR_LOOPBACK(&entry->target)
 386                                                 || IN6_IS_ADDR_MULTICAST(&entry->target))
 387                                         continue;
 388
 389                                 if (entry->priority > 0)
 390                                         changed |= odhcp6c_update_entry(STATE_RA_ROUTE, entry, 0, true);
 391                         } else if (opt->type == ND_OPT_PREFIX_INFORMATION && opt->len == 4) {
 392                                 struct nd_opt_prefix_info *pinfo = (struct nd_opt_prefix_info*)opt;
 393                                 entry->router = any;
 394                                 entry->target = pinfo->nd_opt_pi_prefix;
 395                                 entry->priority = 256;
 396                                 entry->length = pinfo->nd_opt_pi_prefix_len;
 397                                 entry->valid = ntohl(pinfo->nd_opt_pi_valid_time);
 398                                 entry->preferred = ntohl(pinfo->nd_opt_pi_preferred_time);
 399
 400                                 if (entry->length > 128 || IN6_IS_ADDR_LINKLOCAL(&entry->target)
 401                                                 || IN6_IS_ADDR_LOOPBACK(&entry->target)
 402                                                 || IN6_IS_ADDR_MULTICAST(&entry->target)
 403                                                 || entry->valid < entry->preferred)
 404                                         continue;
 405
 406                                 if (pinfo->nd_opt_pi_flags_reserved & ND_OPT_PI_FLAG_ONLINK)
 407                                         changed |= odhcp6c_update_entry(STATE_RA_ROUTE, entry, 7200, true);
 408
 409                                 if (!(pinfo->nd_opt_pi_flags_reserved & ND_OPT_PI_FLAG_AUTO) ||
 410                                                 pinfo->nd_opt_pi_prefix_len != 64)
 411                                         continue;
 412
 413                                 entry->target.s6_addr32[2] = lladdr.s6_addr32[2];
 414                                 entry->target.s6_addr32[3] = lladdr.s6_addr32[3];
 415
 416                                 changed |= odhcp6c_update_entry(STATE_RA_PREFIX, entry, 7200, true);
 417                         } else if (opt->type == ND_OPT_RECURSIVE_DNS && opt->len > 2) {
 418                                 entry->router = from.sin6_addr;
 419                                 entry->priority = 0;
 420                                 entry->length = 128;
 421                                 uint32_t *valid = (uint32_t*)&opt->data[2];
 422                                 entry->valid = ntohl(*valid);
 423                                 entry->preferred = 0;
 424
 425                                 for (ssize_t i = 0; i < (opt->len - 1) / 2; ++i) {
 426                                         memcpy(&entry->target, &opt->data[6 + i * sizeof(entry->target)],
 427                                                         sizeof(entry->target));
 428                                         changed |= odhcp6c_update_entry(STATE_RA_DNS, entry, 0, true);
 429                                 }
 430                         } else if (opt->type == ND_OPT_DNSSL && opt->len > 1) {
 431                                 uint32_t *valid = (uint32_t*)&opt->data[2];
 432                                 uint8_t *buf = &opt->data[6];
 433                                 uint8_t *end = &buf[(opt->len - 1) * 8];
 434
 435                                 entry->router = from.sin6_addr;
 436                                 entry->valid = ntohl(*valid);
 437
 438                                 while (buf < end) {
 439                                         int len = dn_expand(buf, end, buf, (char*)entry->auxtarget, 256);
 440                                         if (len < 1)
 441                                                 break;
 442
 443                                         buf = &buf[len];
 444                                         entry->auxlen = strlen((char*)entry->auxtarget);
 445
 446                                         if (entry->auxlen == 0)
 447                                                 continue;
 448
 449                                         changed |= odhcp6c_update_entry(STATE_RA_SEARCH, entry, 0, true);
 450                                         entry->auxlen = 0;
 451                                 }
 452                         }
 453                 }
 454
 455                 if (ra_options & RA_RDNSS_DEFAULT_LIFETIME) {
 456                         int states[2] = {STATE_RA_DNS, STATE_RA_SEARCH};
 457
 458                         for (size_t i = 0; i < 2; ++i) {
 459                                 size_t ra_dns_len;
 460                                 uint8_t *start = odhcp6c_get_state(states[i], &ra_dns_len);
 461
 462                                 for (struct odhcp6c_entry *c = (struct odhcp6c_entry*)start;
 463                                                         (uint8_t*)c < &start[ra_dns_len] &&
 464                                                         (uint8_t*)odhcp6c_next_entry(c) <= &start[ra_dns_len];
 465                                                         c = odhcp6c_next_entry(c)) {
 466                                         if (IN6_ARE_ADDR_EQUAL(&c->router, &from.sin6_addr) &&
 467                                                         c->valid > router_valid)
 468                                                 c->valid = router_valid;
 469                                 }
 470                         }
 471                 }
 472         }
 473
 474         if (found)
 475                 odhcp6c_expire();
 476
 477         return found && changed;
 478 }