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 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
  69 static void ra_send_rs(int signal __attribute__((unused)));
  70
  71 int ra_init(const char *ifname, const struct in6_addr *ifid, unsigned int options)
  72 {
  73         ra_options = options;
  74
  75         const pid_t ourpid = getpid();
  76         sock = socket(AF_INET6, SOCK_RAW | SOCK_CLOEXEC, IPPROTO_ICMPV6);
  77         if (sock < 0)
  78                 return -1;
  79
  80         if_index = if_nametoindex(ifname);
  81         if (!if_index)
  82                 return -1;
  83
  84         strncpy(if_name, ifname, sizeof(if_name) - 1);
  85         lladdr = *ifid;
  86
  87         rtnl = socket(AF_NETLINK, SOCK_DGRAM | SOCK_CLOEXEC, NETLINK_ROUTE);
  88         if (rtnl < 0)
  89                 return -1;
  90
  91         struct sockaddr_nl rtnl_kernel = { .nl_family = AF_NETLINK };
  92         if (connect(rtnl, (const struct sockaddr*)&rtnl_kernel, sizeof(rtnl_kernel)) < 0)
  93                 return -1;
  94
  95         int val = RTNLGRP_LINK;
  96         setsockopt(rtnl, SOL_NETLINK, NETLINK_ADD_MEMBERSHIP, &val, sizeof(val));
  97         fcntl(rtnl, F_SETOWN, ourpid);
  98         fcntl(rtnl, F_SETFL, fcntl(sock, F_GETFL) | O_ASYNC);
  99
 100         struct {
 101                 struct nlmsghdr hdr;
 102                 struct ifinfomsg ifi;
 103         } req = {
 104                 .hdr = {sizeof(req), RTM_GETLINK, NLM_F_REQUEST, 1, 0},
 105                 .ifi = {.ifi_index = if_index}
 106         };
 107         send(rtnl, &req, sizeof(req), 0);
 108         ra_link_up();
 109
 110         // Filter ICMPv6 package types
 111         struct icmp6_filter filt;
 112         ICMP6_FILTER_SETBLOCKALL(&filt);
 113         ICMP6_FILTER_SETPASS(ND_ROUTER_ADVERT, &filt);
 114         setsockopt(sock, IPPROTO_ICMPV6, ICMP6_FILTER, &filt, sizeof(filt));
 115
 116         // Bind to all-nodes
 117         struct ipv6_mreq an = {ALL_IPV6_NODES, if_index};
 118         setsockopt(sock, IPPROTO_IPV6, IPV6_ADD_MEMBERSHIP, &an, sizeof(an));
 119
 120         // Let the kernel compute our checksums
 121         val = 2;
 122         setsockopt(sock, IPPROTO_RAW, IPV6_CHECKSUM, &val, sizeof(val));
 123
 124         // This is required by RFC 4861
 125         val = 255;
 126         setsockopt(sock, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &val, sizeof(val));
 127
 128         // Receive multicast hops
 129         val = 1;
 130         setsockopt(sock, IPPROTO_IPV6, IPV6_RECVHOPLIMIT, &val, sizeof(val));
 131
 132         // Bind to one device
 133         setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE, ifname, strlen(ifname));
 134
 135         // Add async-mode
 136         fcntl(sock, F_SETOWN, ourpid);
 137         fcntl(sock, F_SETFL, fcntl(sock, F_GETFL) | O_ASYNC);
 138
 139         // Send RS
 140         signal(SIGALRM, ra_send_rs);
 141         ra_send_rs(SIGALRM);
 142
 143         return 0;
 144 }
 145
 146
 147 static void ra_send_rs(int signal __attribute__((unused)))
 148 {
 149         const struct sockaddr_in6 dest = {AF_INET6, 0, 0, ALL_IPV6_ROUTERS, if_index};
 150         const struct icmpv6_opt llnull = {ND_OPT_SOURCE_LINKADDR, 1, {0}};
 151         size_t len;
 152
 153         if ((rs_attempt % 2 == 0) && memcmp(&rs.lladdr, &llnull, sizeof(llnull)))
 154                 len = sizeof(rs);
 155         else
 156                 len = sizeof(struct icmp6_hdr);
 157
 158         sendto(sock, &rs, len, MSG_DONTWAIT, (struct sockaddr*)&dest, sizeof(dest));
 159
 160         if (++rs_attempt <= 3)
 161                 alarm(4);
 162 }
 163
 164
 165 static int16_t pref_to_priority(uint8_t flags)
 166 {
 167         flags = (flags >> 3) & 0x03;
 168         return (flags == 0x0) ? 512 : (flags == 0x1) ? 384 :
 169                         (flags == 0x3) ? 640 : -1;
 170 }
 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
 182         bool ret = false;
 183         ssize_t read;
 184
 185         do {
 186                 read = recv(rtnl, &resp, sizeof(resp), MSG_DONTWAIT);
 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         if (newvalue > 0)
 248                 value = newvalue;
 249         return value;
 250 }
 251
 252 int ra_conf_mtu(int newvalue)
 253 {
 254         static int value = 0;
 255         if (newvalue >= 1280 && newvalue <= 65535)
 256                 value = newvalue;
 257         return value;
 258 }
 259
 260 int ra_conf_reachable(int newvalue)
 261 {
 262         static int value = 0;
 263         if (newvalue > 0 && newvalue <= 3600000)
 264                 value = newvalue;
 265         return value;
 266 }
 267
 268 int ra_conf_retransmit(int newvalue)
 269 {
 270         static int value = 0;
 271         if (newvalue > 0 && newvalue <= 60000)
 272                 value = newvalue;
 273         return value;
 274 }
 275
 276 bool ra_process(void)
 277 {
 278         bool found = false;
 279         bool changed = false;
 280         uint8_t buf[1500] _aligned(4);
 281         union {
 282                 struct cmsghdr hdr;
 283                 uint8_t buf[CMSG_SPACE(sizeof(int))];
 284         } cmsg_buf;
 285         struct nd_router_advert *adv = (struct nd_router_advert*)buf;
 286         struct odhcp6c_entry *entry = alloca(sizeof(*entry) + 256);
 287         const struct in6_addr any = IN6ADDR_ANY_INIT;
 288
 289         memset(entry, 0, sizeof(*entry));
 290
 291         if (IN6_IS_ADDR_UNSPECIFIED(&lladdr)) {
 292                 struct sockaddr_in6 addr = {AF_INET6, 0, 0, ALL_IPV6_ROUTERS, if_index};
 293                 socklen_t alen = sizeof(addr);
 294                 int sock = socket(AF_INET6, SOCK_RAW, IPPROTO_ICMPV6);
 295
 296                 if (!connect(sock, (struct sockaddr*)&addr, sizeof(addr)) &&
 297                                 !getsockname(sock, (struct sockaddr*)&addr, &alen))
 298                         lladdr = addr.sin6_addr;
 299
 300                 close(sock);
 301         }
 302
 303         while (true) {
 304                 struct sockaddr_in6 from;
 305                 struct iovec iov = {buf, sizeof(buf)};
 306                 struct msghdr msg = {
 307                         .msg_name = (void *) &from,
 308                         .msg_namelen = sizeof(from),
 309                         .msg_iov = &iov,
 310                         .msg_iovlen = 1,
 311                         .msg_control = cmsg_buf.buf,
 312                         .msg_controllen = sizeof(cmsg_buf),
 313                         .msg_flags = 0
 314                 };
 315
 316                 ssize_t len = recvmsg(sock, &msg, MSG_DONTWAIT);
 317                 if (len <= 0)
 318                         break;
 319
 320                 if (IN6_IS_ADDR_UNSPECIFIED(&lladdr))
 321                         continue;
 322
 323                 int hlim = 0;
 324                 for (struct cmsghdr *ch = CMSG_FIRSTHDR(&msg); ch != NULL;
 325                                 ch = CMSG_NXTHDR(&msg, ch))
 326                         if (ch->cmsg_level == IPPROTO_IPV6 &&
 327                                         ch->cmsg_type == IPV6_HOPLIMIT)
 328                                 memcpy(&hlim, CMSG_DATA(ch), sizeof(hlim));
 329
 330                 if (!ra_icmpv6_valid(&from, hlim, buf, len))
 331                         continue;
 332
 333                 // Stop sending solicits
 334                 if (rs_attempt > 0) {
 335                         alarm(0);
 336                         rs_attempt = 0;
 337                 }
 338
 339                 if (!found) {
 340                         odhcp6c_expire();
 341                         found = true;
 342                 }
 343                 uint32_t router_valid = ntohs(adv->nd_ra_router_lifetime);
 344
 345                 // Parse default route
 346                 entry->target = any;
 347                 entry->length = 0;
 348                 entry->router = from.sin6_addr;
 349                 entry->priority = pref_to_priority(adv->nd_ra_flags_reserved);
 350                 if (entry->priority < 0)
 351                         entry->priority = pref_to_priority(0);
 352                 entry->valid = router_valid;
 353                 entry->preferred = entry->valid;
 354                 changed |= odhcp6c_update_entry(STATE_RA_ROUTE, entry, 0, true);
 355
 356                 // Parse hoplimit
 357                 ra_conf_hoplimit(adv->nd_ra_curhoplimit);
 358
 359                 // Parse ND parameters
 360                 ra_conf_reachable(ntohl(adv->nd_ra_reachable));
 361                 ra_conf_retransmit(ntohl(adv->nd_ra_retransmit));
 362
 363                 // Evaluate options
 364                 struct icmpv6_opt *opt;
 365                 icmpv6_for_each_option(opt, &adv[1], &buf[len]) {
 366                         if (opt->type == ND_OPT_MTU) {
 367                                 uint32_t *mtu = (uint32_t*)&opt->data[2];
 368                                 ra_conf_mtu(ntohl(*mtu));
 369                         } else if (opt->type == ND_OPT_ROUTE_INFORMATION && opt->len <= 3) {
 370                                 entry->router = from.sin6_addr;
 371                                 entry->target = any;
 372                                 entry->priority = pref_to_priority(opt->data[1]);
 373                                 entry->length = opt->data[0];
 374                                 uint32_t *valid = (uint32_t*)&opt->data[2];
 375                                 entry->valid = ntohl(*valid);
 376                                 memcpy(&entry->target, &opt->data[6], (opt->len - 1) * 8);
 377
 378                                 if (entry->length > 128 || IN6_IS_ADDR_LINKLOCAL(&entry->target)
 379                                                 || IN6_IS_ADDR_LOOPBACK(&entry->target)
 380                                                 || IN6_IS_ADDR_MULTICAST(&entry->target))
 381                                         continue;
 382
 383                                 if (entry->priority > 0)
 384                                         changed |= odhcp6c_update_entry(STATE_RA_ROUTE, entry, 0, true);
 385                         } else if (opt->type == ND_OPT_PREFIX_INFORMATION && opt->len == 4) {
 386                                 struct nd_opt_prefix_info *pinfo = (struct nd_opt_prefix_info*)opt;
 387                                 entry->router = any;
 388                                 entry->target = pinfo->nd_opt_pi_prefix;
 389                                 entry->priority = 256;
 390                                 entry->length = pinfo->nd_opt_pi_prefix_len;
 391                                 entry->valid = ntohl(pinfo->nd_opt_pi_valid_time);
 392                                 entry->preferred = ntohl(pinfo->nd_opt_pi_preferred_time);
 393
 394                                 if (entry->length > 128 || IN6_IS_ADDR_LINKLOCAL(&entry->target)
 395                                                 || IN6_IS_ADDR_LOOPBACK(&entry->target)
 396                                                 || IN6_IS_ADDR_MULTICAST(&entry->target)
 397                                                 || entry->valid < entry->preferred)
 398                                         continue;
 399
 400                                 if (pinfo->nd_opt_pi_flags_reserved & ND_OPT_PI_FLAG_ONLINK)
 401                                         changed |= odhcp6c_update_entry(STATE_RA_ROUTE, entry, 7200, true);
 402
 403                                 if (!(pinfo->nd_opt_pi_flags_reserved & ND_OPT_PI_FLAG_AUTO) ||
 404                                                 pinfo->nd_opt_pi_prefix_len != 64)
 405                                         continue;
 406
 407                                 entry->target.s6_addr32[2] = lladdr.s6_addr32[2];
 408                                 entry->target.s6_addr32[3] = lladdr.s6_addr32[3];
 409
 410                                 changed |= odhcp6c_update_entry(STATE_RA_PREFIX, entry, 7200, true);
 411                         } else if (opt->type == ND_OPT_RECURSIVE_DNS && opt->len > 2) {
 412                                 entry->router = from.sin6_addr;
 413                                 entry->priority = 0;
 414                                 entry->length = 128;
 415                                 uint32_t *valid = (uint32_t*)&opt->data[2];
 416                                 entry->valid = ntohl(*valid);
 417                                 entry->preferred = 0;
 418
 419                                 for (ssize_t i = 0; i < (opt->len - 1) / 2; ++i) {
 420                                         memcpy(&entry->target, &opt->data[6 + i * sizeof(entry->target)],
 421                                                         sizeof(entry->target));
 422                                         changed |= odhcp6c_update_entry(STATE_RA_DNS, entry, 0, true);
 423                                 }
 424                         } else if (opt->type == ND_OPT_DNSSL && opt->len > 1) {
 425                                 uint32_t *valid = (uint32_t*)&opt->data[2];
 426                                 uint8_t *buf = &opt->data[6];
 427                                 uint8_t *end = &buf[(opt->len - 1) * 8];
 428
 429                                 entry->router = from.sin6_addr;
 430                                 entry->valid = ntohl(*valid);
 431
 432                                 while (buf < end) {
 433                                         int len = dn_expand(buf, end, buf, (char*)entry->auxtarget, 256);
 434                                         if (len < 1)
 435                                                 break;
 436
 437                                         buf = &buf[len];
 438                                         entry->auxlen = strlen((char*)entry->auxtarget);
 439
 440                                         if (entry->auxlen == 0)
 441                                                 continue;
 442
 443                                         changed |= odhcp6c_update_entry(STATE_RA_SEARCH, entry, 0, true);
 444                                         entry->auxlen = 0;
 445                                 }
 446                         }
 447                 }
 448
 449                 if (ra_options & RA_RDNSS_DEFAULT_LIFETIME) {
 450                         int states[2] = {STATE_RA_DNS, STATE_RA_SEARCH};
 451                         for (size_t i = 0; i < 2; ++i) {
 452                                 size_t ra_dns_len;
 453                                 uint8_t *start = odhcp6c_get_state(states[i], &ra_dns_len);
 454                                 for (struct odhcp6c_entry *c = (struct odhcp6c_entry*)start;
 455                                                         (uint8_t*)c < &start[ra_dns_len] &&
 456                                                         (uint8_t*)odhcp6c_next_entry(c) <= &start[ra_dns_len];
 457                                                         c = odhcp6c_next_entry(c))
 458                                         if (IN6_ARE_ADDR_EQUAL(&c->router, &from.sin6_addr) &&
 459                                                         c->valid > router_valid)
 460                                                 c->valid = router_valid;
 461                         }
 462                 }
 463         }
 464
 465         if (found)
 466                 odhcp6c_expire();
 467
 468         return found && changed;
 469 }