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 struct {
  59         struct icmp6_hdr hdr;
  60         struct icmpv6_opt lladdr;
  61 } rs = {
  62         .hdr = {ND_ROUTER_SOLICIT, 0, 0, {{0}}},
  63         .lladdr = {ND_OPT_SOURCE_LINKADDR, 1, {0}},
  64 };
  65
  66
  67 static void ra_send_rs(int signal __attribute__((unused)));
  68
  69 int ra_init(const char *ifname, const struct in6_addr *ifid)
  70 {
  71         const pid_t ourpid = getpid();
  72         sock = socket(AF_INET6, SOCK_RAW | SOCK_CLOEXEC, IPPROTO_ICMPV6);
  73         if (sock < 0)
  74                 return -1;
  75
  76         if_index = if_nametoindex(ifname);
  77         if (!if_index)
  78                 return -1;
  79
  80         strncpy(if_name, ifname, sizeof(if_name) - 1);
  81         lladdr = *ifid;
  82
  83         rtnl = socket(AF_NETLINK, SOCK_DGRAM | SOCK_CLOEXEC, NETLINK_ROUTE);
  84         if (rtnl < 0)
  85                 return -1;
  86
  87         struct sockaddr_nl rtnl_kernel = { .nl_family = AF_NETLINK };
  88         if (connect(rtnl, (const struct sockaddr*)&rtnl_kernel, sizeof(rtnl_kernel)) < 0)
  89                 return -1;
  90
  91         int val = RTNLGRP_LINK;
  92         setsockopt(rtnl, SOL_NETLINK, NETLINK_ADD_MEMBERSHIP, &val, sizeof(val));
  93         fcntl(rtnl, F_SETOWN, ourpid);
  94         fcntl(rtnl, F_SETFL, fcntl(sock, F_GETFL) | O_ASYNC);
  95
  96         struct {
  97                 struct nlmsghdr hdr;
  98                 struct ifinfomsg ifi;
  99         } req = {
 100                 .hdr = {sizeof(req), RTM_GETLINK, NLM_F_REQUEST, 1, 0},
 101                 .ifi = {.ifi_index = if_index}
 102         };
 103         send(rtnl, &req, sizeof(req), 0);
 104         ra_link_up();
 105
 106         // Filter ICMPv6 package types
 107         struct icmp6_filter filt;
 108         ICMP6_FILTER_SETBLOCKALL(&filt);
 109         ICMP6_FILTER_SETPASS(ND_ROUTER_ADVERT, &filt);
 110         setsockopt(sock, IPPROTO_ICMPV6, ICMP6_FILTER, &filt, sizeof(filt));
 111
 112         // Bind to all-nodes
 113         struct ipv6_mreq an = {ALL_IPV6_NODES, if_index};
 114         setsockopt(sock, IPPROTO_IPV6, IPV6_ADD_MEMBERSHIP, &an, sizeof(an));
 115
 116         // Let the kernel compute our checksums
 117         val = 2;
 118         setsockopt(sock, IPPROTO_RAW, IPV6_CHECKSUM, &val, sizeof(val));
 119
 120         // This is required by RFC 4861
 121         val = 255;
 122         setsockopt(sock, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &val, sizeof(val));
 123
 124         // Receive multicast hops
 125         val = 1;
 126         setsockopt(sock, IPPROTO_IPV6, IPV6_RECVHOPLIMIT, &val, sizeof(val));
 127
 128         // Bind to one device
 129         setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE, ifname, strlen(ifname));
 130
 131         // Add async-mode
 132         fcntl(sock, F_SETOWN, ourpid);
 133         fcntl(sock, F_SETFL, fcntl(sock, F_GETFL) | O_ASYNC);
 134
 135         // Send RS
 136         signal(SIGALRM, ra_send_rs);
 137         ra_send_rs(SIGALRM);
 138
 139         return 0;
 140 }
 141
 142
 143 static void ra_send_rs(int signal __attribute__((unused)))
 144 {
 145         const struct sockaddr_in6 dest = {AF_INET6, 0, 0, ALL_IPV6_ROUTERS, if_index};
 146         const struct icmpv6_opt llnull = {ND_OPT_SOURCE_LINKADDR, 1, {0}};
 147         size_t len;
 148
 149         if ((rs_attempt % 2 == 0) && memcmp(&rs.lladdr, &llnull, sizeof(llnull)))
 150                 len = sizeof(rs);
 151         else
 152                 len = sizeof(struct icmp6_hdr);
 153
 154         sendto(sock, &rs, len, MSG_DONTWAIT, (struct sockaddr*)&dest, sizeof(dest));
 155
 156         if (++rs_attempt <= 3)
 157                 alarm(4);
 158 }
 159
 160
 161 static int16_t pref_to_priority(uint8_t flags)
 162 {
 163         flags = (flags >> 3) & 0x03;
 164         return (flags == 0x0) ? 1024 : (flags == 0x1) ? 512 :
 165                         (flags == 0x3) ? 2048 : -1;
 166 }
 167
 168
 169 static void update_proc(const char *sect, const char *opt, uint32_t value)
 170 {
 171         char buf[64];
 172         snprintf(buf, sizeof(buf), "/proc/sys/net/ipv6/%s/%s/%s", sect, if_name, opt);
 173
 174         int fd = open(buf, O_WRONLY);
 175         write(fd, buf, snprintf(buf, sizeof(buf), "%u", value));
 176         close(fd);
 177 }
 178
 179
 180 bool ra_link_up(void)
 181 {
 182         static bool firstcall = true;
 183         struct {
 184                 struct nlmsghdr hdr;
 185                 struct ifinfomsg msg;
 186                 uint8_t pad[4000];
 187         } resp;
 188
 189         bool ret = false;
 190         ssize_t read;
 191
 192         do {
 193                 read = recv(rtnl, &resp, sizeof(resp), MSG_DONTWAIT);
 194                 if (read < 0 || !NLMSG_OK(&resp.hdr, (size_t)read) ||
 195                                 resp.hdr.nlmsg_type != RTM_NEWLINK ||
 196                                 resp.msg.ifi_index != if_index)
 197                         continue;
 198
 199                 ssize_t alen = NLMSG_PAYLOAD(&resp.hdr, sizeof(resp.msg));
 200                 for (struct rtattr *rta = (struct rtattr*)(resp.pad);
 201                                 RTA_OK(rta, alen); rta = RTA_NEXT(rta, alen)) {
 202                         if (rta->rta_type == IFLA_ADDRESS &&
 203                                         RTA_PAYLOAD(rta) >= sizeof(rs.lladdr.data))
 204                                 memcpy(rs.lladdr.data, RTA_DATA(rta), sizeof(rs.lladdr.data));
 205                 }
 206
 207                 bool hascarrier = resp.msg.ifi_flags & IFF_LOWER_UP;
 208                 if (!firstcall && nocarrier != !hascarrier)
 209                         ret = true;
 210
 211                 nocarrier = !hascarrier;
 212                 firstcall = false;
 213         } while (read > 0);
 214
 215         if (ret) {
 216                 syslog(LOG_NOTICE, "carrier => %i event on %s", (int)!nocarrier, if_name);
 217
 218                 rs_attempt = 0;
 219                 ra_send_rs(SIGALRM);
 220         }
 221
 222         return ret;
 223 }
 224
 225 static bool ra_icmpv6_valid(struct sockaddr_in6 *source, int hlim, uint8_t *data, size_t len)
 226 {
 227         struct icmp6_hdr *hdr = (struct icmp6_hdr*)data;
 228         struct icmpv6_opt *opt, *end = (struct icmpv6_opt*)&data[len];
 229
 230         if (hlim != 255 || len < sizeof(*hdr) || hdr->icmp6_code)
 231                 return false;
 232
 233         switch (hdr->icmp6_type) {
 234         case ND_ROUTER_ADVERT:
 235                 if (!IN6_IS_ADDR_LINKLOCAL(&source->sin6_addr))
 236                         return false;
 237
 238                 opt = (struct icmpv6_opt*)((struct nd_router_advert*)data + 1);
 239                 break;
 240
 241         default:
 242                 return false;
 243         }
 244
 245         icmpv6_for_each_option(opt, opt, end)
 246                 ;
 247
 248         return opt == end;
 249 }
 250
 251 bool ra_process(void)
 252 {
 253         bool found = false;
 254         bool changed = false;
 255         bool has_lladdr = !IN6_IS_ADDR_UNSPECIFIED(&lladdr);
 256         uint8_t buf[1500], cmsg_buf[128];
 257         struct nd_router_advert *adv = (struct nd_router_advert*)buf;
 258         struct odhcp6c_entry entry = {IN6ADDR_ANY_INIT, 0, 0, IN6ADDR_ANY_INIT, 0, 0, 0, 0, 0, 0};
 259         const struct in6_addr any = IN6ADDR_ANY_INIT;
 260
 261         if (!has_lladdr) {
 262                 // Autodetect interface-id if not specified
 263                 struct ifaddrs *ifaddr, *ifa;
 264
 265                 if (getifaddrs(&ifaddr) == 0) {
 266                         for (ifa = ifaddr; ifa != NULL; ifa = ifa->ifa_next) {
 267                                 struct sockaddr_in6 *addr;
 268
 269                                 if (ifa->ifa_addr == NULL || ifa->ifa_addr->sa_family != AF_INET6)
 270                                         continue;
 271
 272                                 addr = (struct sockaddr_in6*)ifa->ifa_addr;
 273
 274                                 if (!IN6_IS_ADDR_LINKLOCAL(&addr->sin6_addr))
 275                                         continue;
 276
 277                                 if (!strcmp(ifa->ifa_name, if_name)) {
 278                                         lladdr = addr->sin6_addr;
 279                                         has_lladdr = true;
 280                                         break;
 281                                 }
 282                         }
 283
 284                         freeifaddrs(ifaddr);
 285                 }
 286         }
 287
 288         while (true) {
 289                 struct sockaddr_in6 from;
 290                 struct iovec iov = {buf, sizeof(buf)};
 291                 struct msghdr msg = {&from, sizeof(from), &iov, 1,
 292                                 cmsg_buf, sizeof(cmsg_buf), 0};
 293
 294                 ssize_t len = recvmsg(sock, &msg, MSG_DONTWAIT);
 295                 if (len <= 0)
 296                         break;
 297
 298                 if (!has_lladdr)
 299                         continue;
 300
 301                 int hlim = 0;
 302                 for (struct cmsghdr *ch = CMSG_FIRSTHDR(&msg); ch != NULL;
 303                                 ch = CMSG_NXTHDR(&msg, ch))
 304                         if (ch->cmsg_level == IPPROTO_IPV6 &&
 305                                         ch->cmsg_type == IPV6_HOPLIMIT)
 306                                 memcpy(&hlim, CMSG_DATA(ch), sizeof(hlim));
 307
 308                 if (!ra_icmpv6_valid(&from, hlim, buf, len))
 309                         continue;
 310
 311                 // Stop sending solicits
 312                 if (rs_attempt > 0) {
 313                         alarm(0);
 314                         rs_attempt = 0;
 315                 }
 316
 317                 if (!found) {
 318                         odhcp6c_expire();
 319                         found = true;
 320                 }
 321                 uint32_t router_valid = ntohs(adv->nd_ra_router_lifetime);
 322
 323                 // Parse default route
 324                 entry.target = any;
 325                 entry.length = 0;
 326                 entry.router = from.sin6_addr;
 327                 entry.priority = pref_to_priority(adv->nd_ra_flags_reserved);
 328                 if (entry.priority < 0)
 329                         entry.priority = pref_to_priority(0);
 330                 entry.valid = router_valid;
 331                 entry.preferred = entry.valid;
 332                 changed |= odhcp6c_update_entry(STATE_RA_ROUTE, &entry, 0, true);
 333
 334                 // Parse hoplimit
 335                 if (adv->nd_ra_curhoplimit)
 336                         update_proc("conf", "hop_limit", adv->nd_ra_curhoplimit);
 337
 338                 // Parse ND parameters
 339                 uint32_t reachable = ntohl(adv->nd_ra_reachable);
 340                 if (reachable > 0 && reachable <= 3600000)
 341                         update_proc("neigh", "base_reachable_time_ms", reachable);
 342
 343                 uint32_t retransmit = ntohl(adv->nd_ra_retransmit);
 344                 if (retransmit > 0 && retransmit <= 60000)
 345                         update_proc("neigh", "retrans_time_ms", retransmit);
 346
 347
 348                 // Evaluate options
 349                 struct icmpv6_opt *opt;
 350                 icmpv6_for_each_option(opt, &adv[1], &buf[len]) {
 351                         if (opt->type == ND_OPT_MTU) {
 352                                 uint32_t *mtu = (uint32_t*)&opt->data[2];
 353                                 if (ntohl(*mtu) >= 1280 && ntohl(*mtu) <= 65535)
 354                                         update_proc("conf", "mtu", ntohl(*mtu));
 355                         } else if (opt->type == ND_OPT_ROUTE_INFORMATION && opt->len <= 3) {
 356                                 entry.router = from.sin6_addr;
 357                                 entry.target = any;
 358                                 entry.priority = pref_to_priority(opt->data[1]);
 359                                 entry.length = opt->data[0];
 360                                 uint32_t *valid = (uint32_t*)&opt->data[2];
 361                                 entry.valid = ntohl(*valid);
 362                                 memcpy(&entry.target, &opt->data[6], (opt->len - 1) * 8);
 363
 364                                 if (entry.length > 128 || IN6_IS_ADDR_LINKLOCAL(&entry.target)
 365                                                 || IN6_IS_ADDR_LOOPBACK(&entry.target)
 366                                                 || IN6_IS_ADDR_MULTICAST(&entry.target))
 367                                         continue;
 368
 369                                 if (entry.priority > 0)
 370                                         changed |= odhcp6c_update_entry(STATE_RA_ROUTE, &entry, 0, true);
 371                         } else if (opt->type == ND_OPT_PREFIX_INFORMATION && opt->len == 4) {
 372                                 struct nd_opt_prefix_info *pinfo = (struct nd_opt_prefix_info*)opt;
 373                                 entry.router = any;
 374                                 entry.target = pinfo->nd_opt_pi_prefix;
 375                                 entry.priority = 256;
 376                                 entry.length = pinfo->nd_opt_pi_prefix_len;
 377                                 entry.valid = ntohl(pinfo->nd_opt_pi_valid_time);
 378                                 entry.preferred = ntohl(pinfo->nd_opt_pi_preferred_time);
 379
 380                                 if (entry.length > 128 || IN6_IS_ADDR_LINKLOCAL(&entry.target)
 381                                                 || IN6_IS_ADDR_LOOPBACK(&entry.target)
 382                                                 || IN6_IS_ADDR_MULTICAST(&entry.target)
 383                                                 || entry.valid < entry.preferred)
 384                                         continue;
 385
 386                                 if (pinfo->nd_opt_pi_flags_reserved & ND_OPT_PI_FLAG_ONLINK)
 387                                         changed |= odhcp6c_update_entry(STATE_RA_ROUTE, &entry, 7200, true);
 388
 389                                 if (!(pinfo->nd_opt_pi_flags_reserved & ND_OPT_PI_FLAG_AUTO) ||
 390                                                 pinfo->nd_opt_pi_prefix_len != 64)
 391                                         continue;
 392
 393                                 entry.target.s6_addr32[2] = lladdr.s6_addr32[2];
 394                                 entry.target.s6_addr32[3] = lladdr.s6_addr32[3];
 395
 396                                 changed |= odhcp6c_update_entry(STATE_RA_PREFIX, &entry, 7200, true);
 397                         } else if (opt->type == ND_OPT_RECURSIVE_DNS && opt->len > 2) {
 398                                 entry.router = from.sin6_addr;
 399                                 entry.priority = 0;
 400                                 entry.length = 128;
 401                                 uint32_t *valid = (uint32_t*)&opt->data[2];
 402                                 entry.valid = ntohl(*valid);
 403                                 entry.preferred = 0;
 404
 405                                 for (ssize_t i = 0; i < (opt->len - 1) / 2; ++i) {
 406                                         memcpy(&entry.target, &opt->data[6 + i * sizeof(entry.target)],
 407                                                         sizeof(entry.target));
 408                                         changed |= odhcp6c_update_entry(STATE_RA_DNS, &entry, 0, true);
 409                                 }
 410                         }
 411                 }
 412
 413                 size_t ra_dns_len;
 414                 struct odhcp6c_entry *entry = odhcp6c_get_state(STATE_RA_DNS, &ra_dns_len);
 415                 for (size_t i = 0; i < ra_dns_len / sizeof(*entry); ++i)
 416                         if (IN6_ARE_ADDR_EQUAL(&entry[i].router, &from.sin6_addr) &&
 417                                         entry[i].valid > router_valid)
 418                                 entry[i].valid = router_valid;
 419         }
 420
 421         if (found)
 422                 odhcp6c_expire();
 423
 424         return found && changed;
 425 }