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 <ifaddrs.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
  25 #include <net/if.h>
  26 #include <arpa/inet.h>
  27 #include <sys/socket.h>
  28 #include <sys/types.h>
  29 #include <sys/ioctl.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 static void ra_send_rs(int signal __attribute__((unused)));
  60
  61 int ra_init(const char *ifname, const struct in6_addr *ifid)
  62 {
  63         const pid_t ourpid = getpid();
  64         sock = socket(AF_INET6, SOCK_RAW | SOCK_CLOEXEC, IPPROTO_ICMPV6);
  65         if (sock < 0)
  66                 return -1;
  67
  68         if_index = if_nametoindex(ifname);
  69         if (!if_index)
  70                 return -1;
  71
  72         strncpy(if_name, ifname, sizeof(if_name) - 1);
  73         lladdr = *ifid;
  74
  75         rtnl = socket(AF_NETLINK, SOCK_DGRAM | SOCK_CLOEXEC, NETLINK_ROUTE);
  76         if (rtnl < 0)
  77                 return -1;
  78
  79         struct sockaddr_nl rtnl_kernel = { .nl_family = AF_NETLINK };
  80         if (connect(rtnl, (const struct sockaddr*)&rtnl_kernel, sizeof(rtnl_kernel)) < 0)
  81                 return -1;
  82
  83         int val = RTNLGRP_LINK;
  84         setsockopt(rtnl, SOL_NETLINK, NETLINK_ADD_MEMBERSHIP, &val, sizeof(val));
  85         fcntl(rtnl, F_SETOWN, ourpid);
  86         fcntl(rtnl, F_SETFL, fcntl(sock, F_GETFL) | O_ASYNC);
  87
  88         struct {
  89                 struct nlmsghdr hdr;
  90                 struct ifinfomsg ifi;
  91         } req = {
  92                 .hdr = {sizeof(req), RTM_GETLINK, NLM_F_REQUEST, 1, 0},
  93                 .ifi = {.ifi_index = if_index}
  94         };
  95         send(rtnl, &req, sizeof(req), 0);
  96
  97         // Filter ICMPv6 package types
  98         struct icmp6_filter filt;
  99         ICMP6_FILTER_SETBLOCKALL(&filt);
 100         ICMP6_FILTER_SETPASS(ND_ROUTER_ADVERT, &filt);
 101         setsockopt(sock, IPPROTO_ICMPV6, ICMP6_FILTER, &filt, sizeof(filt));
 102
 103         // Bind to all-nodes
 104         struct ipv6_mreq an = {ALL_IPV6_NODES, if_index};
 105         setsockopt(sock, IPPROTO_IPV6, IPV6_ADD_MEMBERSHIP, &an, sizeof(an));
 106
 107         // Let the kernel compute our checksums
 108         val = 2;
 109         setsockopt(sock, IPPROTO_RAW, IPV6_CHECKSUM, &val, sizeof(val));
 110
 111         // This is required by RFC 4861
 112         val = 255;
 113         setsockopt(sock, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &val, sizeof(val));
 114
 115         // Receive multicast hops
 116         val = 1;
 117         setsockopt(sock, IPPROTO_IPV6, IPV6_RECVHOPLIMIT, &val, sizeof(val));
 118
 119         // Bind to one device
 120         setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE, ifname, strlen(ifname));
 121
 122         // Add async-mode
 123         fcntl(sock, F_SETOWN, ourpid);
 124         fcntl(sock, F_SETFL, fcntl(sock, F_GETFL) | O_ASYNC);
 125
 126         // Send RS
 127         signal(SIGALRM, ra_send_rs);
 128         ra_send_rs(SIGALRM);
 129
 130         return 0;
 131 }
 132
 133
 134 static void ra_send_rs(int signal __attribute__((unused)))
 135 {
 136         struct {
 137                 struct icmp6_hdr hdr;
 138                 struct icmpv6_opt lladdr;
 139         } rs = {
 140                 .hdr = {ND_ROUTER_SOLICIT, 0, 0, {{0}}},
 141                 .lladdr = {ND_OPT_SOURCE_LINKADDR, 1, {0}},
 142         };
 143         const struct sockaddr_in6 dest = {AF_INET6, 0, 0, ALL_IPV6_ROUTERS, if_index};
 144         size_t len = sizeof(rs);
 145
 146         struct ifreq ifr;
 147         memset(&ifr, 0, sizeof(ifr));
 148         strncpy(ifr.ifr_name, if_name, sizeof(ifr.ifr_name));
 149         if ((rs_attempt % 2 == 0) && !ioctl(sock, SIOCGIFHWADDR, &ifr)
 150                         && memcmp(rs.lladdr.data, ifr.ifr_hwaddr.sa_data, 6))
 151                 memcpy(rs.lladdr.data, ifr.ifr_hwaddr.sa_data, 6);
 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) ? 1024 : (flags == 0x1) ? 512 :
 166                         (flags == 0x3) ? 2048 : -1;
 167 }
 168
 169
 170 static void update_proc(const char *sect, const char *opt, uint32_t value)
 171 {
 172         char buf[64];
 173         snprintf(buf, sizeof(buf), "/proc/sys/net/ipv6/%s/%s/%s", sect, if_name, opt);
 174
 175         int fd = open(buf, O_WRONLY);
 176         write(fd, buf, snprintf(buf, sizeof(buf), "%u", value));
 177         close(fd);
 178 }
 179
 180
 181 bool ra_link_up(void)
 182 {
 183         static bool firstcall = true;
 184         struct {
 185                 struct nlmsghdr hdr;
 186                 struct ifinfomsg msg;
 187                 uint8_t pad[4000];
 188         } resp;
 189
 190         bool ret = false;
 191         ssize_t read;
 192
 193         do {
 194                 read = recv(rtnl, &resp, sizeof(resp), MSG_DONTWAIT);
 195                 if (read < 0 || !NLMSG_OK(&resp.hdr, (size_t)read) ||
 196                                 resp.hdr.nlmsg_type != RTM_NEWLINK ||
 197                                 resp.msg.ifi_index != if_index)
 198                         continue;
 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 bool ra_process(void)
 245 {
 246         bool found = false;
 247         bool changed = false;
 248         bool has_lladdr = !IN6_IS_ADDR_UNSPECIFIED(&lladdr);
 249         uint8_t buf[1500], cmsg_buf[128];
 250         struct nd_router_advert *adv = (struct nd_router_advert*)buf;
 251         struct odhcp6c_entry entry = {IN6ADDR_ANY_INIT, 0, 0, IN6ADDR_ANY_INIT, 0, 0, 0, 0, 0, 0};
 252         const struct in6_addr any = IN6ADDR_ANY_INIT;
 253
 254         if (!has_lladdr) {
 255                 // Autodetect interface-id if not specified
 256                 struct ifaddrs *ifaddr, *ifa;
 257
 258                 if (getifaddrs(&ifaddr) == 0) {
 259                         for (ifa = ifaddr; ifa != NULL; ifa = ifa->ifa_next) {
 260                                 struct sockaddr_in6 *addr;
 261
 262                                 if (ifa->ifa_addr == NULL || ifa->ifa_addr->sa_family != AF_INET6)
 263                                         continue;
 264
 265                                 addr = (struct sockaddr_in6*)ifa->ifa_addr;
 266
 267                                 if (!IN6_IS_ADDR_LINKLOCAL(&addr->sin6_addr))
 268                                         continue;
 269
 270                                 if (!strcmp(ifa->ifa_name, if_name)) {
 271                                         lladdr = addr->sin6_addr;
 272                                         has_lladdr = true;
 273                                         break;
 274                                 }
 275                         }
 276
 277                         freeifaddrs(ifaddr);
 278                 }
 279         }
 280
 281         while (true) {
 282                 struct sockaddr_in6 from;
 283                 struct iovec iov = {buf, sizeof(buf)};
 284                 struct msghdr msg = {&from, sizeof(from), &iov, 1,
 285                                 cmsg_buf, sizeof(cmsg_buf), 0};
 286
 287                 ssize_t len = recvmsg(sock, &msg, MSG_DONTWAIT);
 288                 if (len <= 0)
 289                         break;
 290
 291                 if (!has_lladdr)
 292                         continue;
 293
 294                 int hlim = 0;
 295                 for (struct cmsghdr *ch = CMSG_FIRSTHDR(&msg); ch != NULL;
 296                                 ch = CMSG_NXTHDR(&msg, ch))
 297                         if (ch->cmsg_level == IPPROTO_IPV6 &&
 298                                         ch->cmsg_type == IPV6_HOPLIMIT)
 299                                 memcpy(&hlim, CMSG_DATA(ch), sizeof(hlim));
 300
 301                 if (!ra_icmpv6_valid(&from, hlim, buf, len))
 302                         continue;
 303
 304                 // Stop sending solicits
 305                 if (rs_attempt > 0) {
 306                         alarm(0);
 307                         rs_attempt = 0;
 308                 }
 309
 310                 if (!found) {
 311                         odhcp6c_expire();
 312                         found = true;
 313                 }
 314                 uint32_t router_valid = ntohs(adv->nd_ra_router_lifetime);
 315
 316                 // Parse default route
 317                 entry.target = any;
 318                 entry.length = 0;
 319                 entry.router = from.sin6_addr;
 320                 entry.priority = pref_to_priority(adv->nd_ra_flags_reserved);
 321                 if (entry.priority < 0)
 322                         entry.priority = pref_to_priority(0);
 323                 entry.valid = router_valid;
 324                 entry.preferred = entry.valid;
 325                 changed |= odhcp6c_update_entry(STATE_RA_ROUTE, &entry);
 326
 327                 // Parse hoplimit
 328                 if (adv->nd_ra_curhoplimit)
 329                         update_proc("conf", "hop_limit", adv->nd_ra_curhoplimit);
 330
 331                 // Parse ND parameters
 332                 uint32_t reachable = ntohl(adv->nd_ra_reachable);
 333                 if (reachable > 0 && reachable <= 3600000)
 334                         update_proc("neigh", "base_reachable_time_ms", reachable);
 335
 336                 uint32_t retransmit = ntohl(adv->nd_ra_retransmit);
 337                 if (retransmit > 0 && retransmit <= 60000)
 338                         update_proc("neigh", "retrans_time_ms", retransmit);
 339
 340
 341                 // Evaluate options
 342                 struct icmpv6_opt *opt;
 343                 icmpv6_for_each_option(opt, &adv[1], &buf[len]) {
 344                         if (opt->type == ND_OPT_MTU) {
 345                                 uint32_t *mtu = (uint32_t*)&opt->data[2];
 346                                 if (ntohl(*mtu) >= 1280 && ntohl(*mtu) <= 65535)
 347                                         update_proc("conf", "mtu", ntohl(*mtu));
 348                         } else if (opt->type == ND_OPT_ROUTE_INFORMATION && opt->len <= 3) {
 349                                 entry.router = from.sin6_addr;
 350                                 entry.target = any;
 351                                 entry.priority = pref_to_priority(opt->data[1]);
 352                                 entry.length = opt->data[0];
 353                                 uint32_t *valid = (uint32_t*)&opt->data[2];
 354                                 entry.valid = ntohl(*valid);
 355                                 memcpy(&entry.target, &opt->data[6], (opt->len - 1) * 8);
 356
 357                                 if (entry.length > 128 || IN6_IS_ADDR_LINKLOCAL(&entry.target)
 358                                                 || IN6_IS_ADDR_LOOPBACK(&entry.target)
 359                                                 || IN6_IS_ADDR_MULTICAST(&entry.target))
 360                                         continue;
 361
 362                                 if (entry.priority > 0)
 363                                         changed |= odhcp6c_update_entry(STATE_RA_ROUTE, &entry);
 364                         } else if (opt->type == ND_OPT_PREFIX_INFORMATION && opt->len == 4) {
 365                                 struct nd_opt_prefix_info *pinfo = (struct nd_opt_prefix_info*)opt;
 366                                 entry.router = any;
 367                                 entry.target = pinfo->nd_opt_pi_prefix;
 368                                 entry.priority = 256;
 369                                 entry.length = pinfo->nd_opt_pi_prefix_len;
 370                                 entry.valid = ntohl(pinfo->nd_opt_pi_valid_time);
 371                                 entry.preferred = ntohl(pinfo->nd_opt_pi_preferred_time);
 372
 373                                 if (entry.length > 128 || IN6_IS_ADDR_LINKLOCAL(&entry.target)
 374                                                 || IN6_IS_ADDR_LOOPBACK(&entry.target)
 375                                                 || IN6_IS_ADDR_MULTICAST(&entry.target)
 376                                                 || entry.valid < entry.preferred)
 377                                         continue;
 378
 379                                 if (pinfo->nd_opt_pi_flags_reserved & ND_OPT_PI_FLAG_ONLINK)
 380                                         changed |= odhcp6c_update_entry_safe(STATE_RA_ROUTE, &entry, 7200);
 381
 382                                 if (!(pinfo->nd_opt_pi_flags_reserved & ND_OPT_PI_FLAG_AUTO) ||
 383                                                 pinfo->nd_opt_pi_prefix_len != 64)
 384                                         continue;
 385
 386                                 entry.target.s6_addr32[2] = lladdr.s6_addr32[2];
 387                                 entry.target.s6_addr32[3] = lladdr.s6_addr32[3];
 388
 389                                 changed |= odhcp6c_update_entry_safe(STATE_RA_PREFIX, &entry, 7200);
 390                         } else if (opt->type == ND_OPT_RECURSIVE_DNS && opt->len > 2) {
 391                                 entry.router = from.sin6_addr;
 392                                 entry.priority = 0;
 393                                 entry.length = 128;
 394                                 uint32_t *valid = (uint32_t*)&opt->data[2];
 395                                 entry.valid = ntohl(*valid);
 396                                 entry.preferred = 0;
 397
 398                                 for (ssize_t i = 0; i < (opt->len - 1) / 2; ++i) {
 399                                         memcpy(&entry.target, &opt->data[6 + i * sizeof(entry.target)],
 400                                                         sizeof(entry.target));
 401                                         changed |= odhcp6c_update_entry(STATE_RA_DNS, &entry);
 402                                 }
 403                         }
 404                 }
 405
 406                 size_t ra_dns_len;
 407                 struct odhcp6c_entry *entry = odhcp6c_get_state(STATE_RA_DNS, &ra_dns_len);
 408                 for (size_t i = 0; i < ra_dns_len / sizeof(*entry); ++i)
 409                         if (IN6_ARE_ADDR_EQUAL(&entry[i].router, &from.sin6_addr) &&
 410                                         entry[i].valid > router_valid)
 411                                 entry[i].valid = router_valid;
 412         }
 413
 414         if (found)
 415                 odhcp6c_expire();
 416
 417         return found && changed;
 418 }