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 <netinet/in.h>
  30 #include <netinet/icmp6.h>
  31
  32 #include <linux/rtnetlink.h>
  33
  34 #ifndef SOL_NETLINK
  35 #define SOL_NETLINK 270
  36 #endif
  37
  38 #ifndef NETLINK_ADD_MEMBERSHIP
  39 #define NETLINK_ADD_MEMBERSHIP 1
  40 #endif
  41
  42 #ifndef IFF_LOWER_UP
  43 #define IFF_LOWER_UP 0x10000
  44 #endif
  45
  46 #include "odhcp6c.h"
  47 #include "ra.h"
  48
  49
  50 static bool nocarrier = false;
  51
  52 static int sock = -1, rtnl = -1;
  53 static int if_index = 0;
  54 static char if_name[IF_NAMESIZE] = {0};
  55 static volatile int rs_attempt = 0;
  56 static struct in6_addr lladdr = IN6ADDR_ANY_INIT;
  57
  58 static void ra_send_rs(int signal __attribute__((unused)));
  59
  60 int ra_init(const char *ifname, const struct in6_addr *ifid)
  61 {
  62         const pid_t ourpid = getpid();
  63         sock = socket(AF_INET6, SOCK_RAW | SOCK_CLOEXEC, IPPROTO_ICMPV6);
  64         if (sock < 0)
  65                 return -1;
  66
  67         if_index = if_nametoindex(ifname);
  68         if (!if_index)
  69                 return -1;
  70
  71         strncpy(if_name, ifname, sizeof(if_name) - 1);
  72         lladdr = *ifid;
  73
  74         rtnl = socket(AF_NETLINK, SOCK_DGRAM | SOCK_CLOEXEC, NETLINK_ROUTE);
  75         if (rtnl < 0)
  76                 return -1;
  77
  78         struct sockaddr_nl rtnl_kernel = { .nl_family = AF_NETLINK };
  79         if (connect(rtnl, (const struct sockaddr*)&rtnl_kernel, sizeof(rtnl_kernel)) < 0)
  80                 return -1;
  81
  82         int val = RTNLGRP_LINK;
  83         setsockopt(rtnl, SOL_NETLINK, NETLINK_ADD_MEMBERSHIP, &val, sizeof(val));
  84         fcntl(rtnl, F_SETOWN, ourpid);
  85         fcntl(rtnl, F_SETFL, fcntl(sock, F_GETFL) | O_ASYNC);
  86
  87         struct {
  88                 struct nlmsghdr hdr;
  89                 struct ifinfomsg ifi;
  90         } req = {
  91                 .hdr = {sizeof(req), RTM_GETLINK, NLM_F_REQUEST, 1, 0},
  92                 .ifi = {.ifi_index = if_index}
  93         };
  94         send(rtnl, &req, sizeof(req), 0);
  95
  96         // Filter ICMPv6 package types
  97         struct icmp6_filter filt;
  98         ICMP6_FILTER_SETBLOCKALL(&filt);
  99         ICMP6_FILTER_SETPASS(ND_ROUTER_ADVERT, &filt);
 100         setsockopt(sock, IPPROTO_ICMPV6, ICMP6_FILTER, &filt, sizeof(filt));
 101
 102         // Bind to all-nodes
 103         struct ipv6_mreq an = {ALL_IPV6_NODES, if_index};
 104         setsockopt(sock, IPPROTO_IPV6, IPV6_ADD_MEMBERSHIP, &an, sizeof(an));
 105
 106         // Let the kernel compute our checksums
 107         val = 2;
 108         setsockopt(sock, IPPROTO_RAW, IPV6_CHECKSUM, &val, sizeof(val));
 109
 110         // This is required by RFC 4861
 111         val = 255;
 112         setsockopt(sock, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &val, sizeof(val));
 113
 114         // Receive multicast hops
 115         val = 1;
 116         setsockopt(sock, IPPROTO_IPV6, IPV6_RECVHOPLIMIT, &val, sizeof(val));
 117
 118         // Bind to one device
 119         setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE, ifname, strlen(ifname));
 120
 121         // Add async-mode
 122         fcntl(sock, F_SETOWN, ourpid);
 123         fcntl(sock, F_SETFL, fcntl(sock, F_GETFL) | O_ASYNC);
 124
 125         // Send RS
 126         signal(SIGALRM, ra_send_rs);
 127         ra_send_rs(SIGALRM);
 128
 129         return 0;
 130 }
 131
 132
 133 static void ra_send_rs(int signal __attribute__((unused)))
 134 {
 135         const struct icmp6_hdr rs = {ND_ROUTER_SOLICIT, 0, 0, {{0}}};
 136         const struct sockaddr_in6 dest = {AF_INET6, 0, 0, ALL_IPV6_ROUTERS, if_index};
 137         sendto(sock, &rs, sizeof(rs), MSG_DONTWAIT, (struct sockaddr*)&dest, sizeof(dest));
 138
 139         if (++rs_attempt <= 3)
 140                 alarm(4);
 141 }
 142
 143
 144 static int16_t pref_to_priority(uint8_t flags)
 145 {
 146         flags = (flags >> 3) & 0x03;
 147         return (flags == 0x0) ? 1024 : (flags == 0x1) ? 512 :
 148                         (flags == 0x3) ? 2048 : -1;
 149 }
 150
 151
 152 static void update_proc(const char *sect, const char *opt, uint32_t value)
 153 {
 154         char buf[64];
 155         snprintf(buf, sizeof(buf), "/proc/sys/net/ipv6/%s/%s/%s", sect, if_name, opt);
 156
 157         int fd = open(buf, O_WRONLY);
 158         write(fd, buf, snprintf(buf, sizeof(buf), "%u", value));
 159         close(fd);
 160 }
 161
 162
 163 bool ra_link_up(void)
 164 {
 165         static bool firstcall = true;
 166         struct {
 167                 struct nlmsghdr hdr;
 168                 struct ifinfomsg msg;
 169                 uint8_t pad[4000];
 170         } resp;
 171
 172         bool ret = false;
 173         ssize_t read;
 174
 175         do {
 176                 read = recv(rtnl, &resp, sizeof(resp), MSG_DONTWAIT);
 177                 if (read < 0 || !NLMSG_OK(&resp.hdr, (size_t)read) ||
 178                                 resp.hdr.nlmsg_type != RTM_NEWLINK ||
 179                                 resp.msg.ifi_index != if_index)
 180                         continue;
 181
 182                 bool hascarrier = resp.msg.ifi_flags & IFF_LOWER_UP;
 183                 if (!firstcall && nocarrier != !hascarrier)
 184                         ret = true;
 185
 186                 nocarrier = !hascarrier;
 187                 firstcall = false;
 188         } while (read > 0);
 189
 190         if (ret) {
 191                 syslog(LOG_NOTICE, "carrier => %i event on %s", (int)!nocarrier, if_name);
 192
 193                 rs_attempt = 0;
 194                 ra_send_rs(SIGALRM);
 195         }
 196
 197         return ret;
 198 }
 199
 200 static bool ra_icmpv6_valid(struct sockaddr_in6 *source, int hlim, uint8_t *data, size_t len)
 201 {
 202         struct icmp6_hdr *hdr = (struct icmp6_hdr*)data;
 203         struct icmpv6_opt *opt, *end = (struct icmpv6_opt*)&data[len];
 204
 205         if (hlim != 255 || len < sizeof(*hdr) || hdr->icmp6_code)
 206                 return false;
 207
 208         switch (hdr->icmp6_type) {
 209         case ND_ROUTER_ADVERT:
 210                 if (!IN6_IS_ADDR_LINKLOCAL(&source->sin6_addr))
 211                         return false;
 212
 213                 opt = (struct icmpv6_opt*)((struct nd_router_advert*)data + 1);
 214                 break;
 215
 216         default:
 217                 return false;
 218         }
 219
 220         icmpv6_for_each_option(opt, opt, end)
 221                 ;
 222
 223         return opt == end;
 224 }
 225
 226 bool ra_process(void)
 227 {
 228         bool found = false;
 229         bool changed = false;
 230         bool has_lladdr = !IN6_IS_ADDR_UNSPECIFIED(&lladdr);
 231         uint8_t buf[1500], cmsg_buf[128];
 232         struct nd_router_advert *adv = (struct nd_router_advert*)buf;
 233         struct odhcp6c_entry entry = {IN6ADDR_ANY_INIT, 0, 0, IN6ADDR_ANY_INIT, 0, 0, 0, 0, 0, 0};
 234         const struct in6_addr any = IN6ADDR_ANY_INIT;
 235
 236         if (!has_lladdr) {
 237                 // Autodetect interface-id if not specified
 238                 struct ifaddrs *ifaddr, *ifa;
 239
 240                 if (getifaddrs(&ifaddr) == 0) {
 241                         for (ifa = ifaddr; ifa != NULL; ifa = ifa->ifa_next) {
 242                                 struct sockaddr_in6 *addr;
 243
 244                                 if (ifa->ifa_addr == NULL || ifa->ifa_addr->sa_family != AF_INET6)
 245                                         continue;
 246
 247                                 addr = (struct sockaddr_in6*)ifa->ifa_addr;
 248
 249                                 if (!IN6_IS_ADDR_LINKLOCAL(&addr->sin6_addr))
 250                                         continue;
 251
 252                                 if (!strcmp(ifa->ifa_name, if_name)) {
 253                                         lladdr = addr->sin6_addr;
 254                                         has_lladdr = true;
 255                                         break;
 256                                 }
 257                         }
 258
 259                         freeifaddrs(ifaddr);
 260                 }
 261         }
 262
 263         while (true) {
 264                 struct sockaddr_in6 from;
 265                 struct iovec iov = {buf, sizeof(buf)};
 266                 struct msghdr msg = {&from, sizeof(from), &iov, 1,
 267                                 cmsg_buf, sizeof(cmsg_buf), 0};
 268
 269                 ssize_t len = recvmsg(sock, &msg, MSG_DONTWAIT);
 270                 if (len <= 0)
 271                         break;
 272
 273                 if (!has_lladdr)
 274                         continue;
 275
 276                 int hlim = 0;
 277                 for (struct cmsghdr *ch = CMSG_FIRSTHDR(&msg); ch != NULL;
 278                                 ch = CMSG_NXTHDR(&msg, ch))
 279                         if (ch->cmsg_level == IPPROTO_IPV6 &&
 280                                         ch->cmsg_type == IPV6_HOPLIMIT)
 281                                 memcpy(&hlim, CMSG_DATA(ch), sizeof(hlim));
 282
 283                 if (!ra_icmpv6_valid(&from, hlim, buf, len))
 284                         continue;
 285
 286                 // Stop sending solicits
 287                 if (rs_attempt > 0) {
 288                         alarm(0);
 289                         rs_attempt = 0;
 290                 }
 291
 292                 if (!found) {
 293                         odhcp6c_expire();
 294                         found = true;
 295                 }
 296                 uint32_t router_valid = ntohs(adv->nd_ra_router_lifetime);
 297
 298                 // Parse default route
 299                 entry.target = any;
 300                 entry.length = 0;
 301                 entry.router = from.sin6_addr;
 302                 entry.priority = pref_to_priority(adv->nd_ra_flags_reserved);
 303                 if (entry.priority < 0)
 304                         entry.priority = pref_to_priority(0);
 305                 entry.valid = router_valid;
 306                 entry.preferred = entry.valid;
 307                 changed |= odhcp6c_update_entry(STATE_RA_ROUTE, &entry);
 308
 309                 // Parse hoplimit
 310                 if (adv->nd_ra_curhoplimit)
 311                         update_proc("conf", "hop_limit", adv->nd_ra_curhoplimit);
 312
 313                 // Parse ND parameters
 314                 uint32_t reachable = ntohl(adv->nd_ra_reachable);
 315                 if (reachable > 0 && reachable <= 3600000)
 316                         update_proc("neigh", "base_reachable_time_ms", reachable);
 317
 318                 uint32_t retransmit = ntohl(adv->nd_ra_retransmit);
 319                 if (retransmit > 0 && retransmit <= 60000)
 320                         update_proc("neigh", "retrans_time_ms", retransmit);
 321
 322
 323                 // Evaluate options
 324                 struct icmpv6_opt *opt;
 325                 icmpv6_for_each_option(opt, &adv[1], &buf[len]) {
 326                         if (opt->type == ND_OPT_MTU) {
 327                                 uint32_t *mtu = (uint32_t*)&opt->data[2];
 328                                 if (ntohl(*mtu) >= 1280 && ntohl(*mtu) <= 65535)
 329                                         update_proc("conf", "mtu", ntohl(*mtu));
 330                         } else if (opt->type == ND_OPT_ROUTE_INFORMATION && opt->len <= 3) {
 331                                 entry.router = from.sin6_addr;
 332                                 entry.target = any;
 333                                 entry.priority = pref_to_priority(opt->data[1]);
 334                                 entry.length = opt->data[0];
 335                                 uint32_t *valid = (uint32_t*)&opt->data[2];
 336                                 entry.valid = ntohl(*valid);
 337                                 memcpy(&entry.target, &opt->data[6], (opt->len - 1) * 8);
 338
 339                                 if (entry.length > 128 || IN6_IS_ADDR_LINKLOCAL(&entry.target)
 340                                                 || IN6_IS_ADDR_LOOPBACK(&entry.target)
 341                                                 || IN6_IS_ADDR_MULTICAST(&entry.target))
 342                                         continue;
 343
 344                                 if (entry.priority > 0)
 345                                         changed |= odhcp6c_update_entry(STATE_RA_ROUTE, &entry);
 346                         } else if (opt->type == ND_OPT_PREFIX_INFORMATION && opt->len == 4) {
 347                                 struct nd_opt_prefix_info *pinfo = (struct nd_opt_prefix_info*)opt;
 348                                 entry.router = any;
 349                                 entry.target = pinfo->nd_opt_pi_prefix;
 350                                 entry.priority = 256;
 351                                 entry.length = pinfo->nd_opt_pi_prefix_len;
 352                                 entry.valid = ntohl(pinfo->nd_opt_pi_valid_time);
 353                                 entry.preferred = ntohl(pinfo->nd_opt_pi_preferred_time);
 354
 355                                 if (entry.length > 128 || IN6_IS_ADDR_LINKLOCAL(&entry.target)
 356                                                 || IN6_IS_ADDR_LOOPBACK(&entry.target)
 357                                                 || IN6_IS_ADDR_MULTICAST(&entry.target)
 358                                                 || entry.valid < entry.preferred)
 359                                         continue;
 360
 361                                 if (pinfo->nd_opt_pi_flags_reserved & ND_OPT_PI_FLAG_ONLINK)
 362                                         changed |= odhcp6c_update_entry_safe(STATE_RA_ROUTE, &entry, 7200);
 363
 364                                 if (!(pinfo->nd_opt_pi_flags_reserved & ND_OPT_PI_FLAG_AUTO) ||
 365                                                 pinfo->nd_opt_pi_prefix_len != 64)
 366                                         continue;
 367
 368                                 entry.target.s6_addr32[2] = lladdr.s6_addr32[2];
 369                                 entry.target.s6_addr32[3] = lladdr.s6_addr32[3];
 370
 371                                 changed |= odhcp6c_update_entry_safe(STATE_RA_PREFIX, &entry, 7200);
 372                         } else if (opt->type == ND_OPT_RECURSIVE_DNS && opt->len > 2) {
 373                                 entry.router = from.sin6_addr;
 374                                 entry.priority = 0;
 375                                 entry.length = 128;
 376                                 uint32_t *valid = (uint32_t*)&opt->data[2];
 377                                 entry.valid = ntohl(*valid);
 378                                 entry.preferred = 0;
 379
 380                                 for (ssize_t i = 0; i < (opt->len - 1) / 2; ++i) {
 381                                         memcpy(&entry.target, &opt->data[6 + i * sizeof(entry.target)],
 382                                                         sizeof(entry.target));
 383                                         changed |= odhcp6c_update_entry(STATE_RA_DNS, &entry);
 384                                 }
 385                         }
 386                 }
 387
 388                 size_t ra_dns_len;
 389                 struct odhcp6c_entry *entry = odhcp6c_get_state(STATE_RA_DNS, &ra_dns_len);
 390                 for (size_t i = 0; i < ra_dns_len / sizeof(*entry); ++i)
 391                         if (IN6_ARE_ADDR_EQUAL(&entry[i].router, &from.sin6_addr) &&
 392                                         entry[i].valid > router_valid)
 393                                 entry[i].valid = router_valid;
 394         }
 395
 396         if (found)
 397                 odhcp6c_expire();
 398
 399         return found && changed;
 400 }