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
  24 #include <net/if.h>
  25 #include <arpa/inet.h>
  26 #include <sys/socket.h>
  27 #include <sys/types.h>
  28 #include <netinet/in.h>
  29 #include <netinet/icmp6.h>
  30
  31 #include <linux/rtnetlink.h>
  32
  33 #ifndef SOL_NETLINK
  34 #define SOL_NETLINK 270
  35 #endif
  36
  37 #ifndef NETLINK_ADD_MEMBERSHIP
  38 #define NETLINK_ADD_MEMBERSHIP 1
  39 #endif
  40
  41 #ifndef IFF_LOWER_UP
  42 #define IFF_LOWER_UP 0x10000
  43 #endif
  44
  45 #include "odhcp6c.h"
  46 #include "ra.h"
  47
  48
  49 static bool nocarrier = false;
  50
  51 static int sock = -1, rtnl = -1;
  52 static int if_index = 0;
  53 static char if_name[IF_NAMESIZE] = {0};
  54 static volatile int rs_attempt = 0;
  55 static struct in6_addr lladdr = IN6ADDR_ANY_INIT;
  56
  57 struct {
  58         struct icmp6_hdr hdr;
  59         struct icmpv6_opt lladdr;
  60 } rs = {
  61         .hdr = {ND_ROUTER_SOLICIT, 0, 0, {{0}}},
  62         .lladdr = {ND_OPT_SOURCE_LINKADDR, 1, {0}},
  63 };
  64
  65
  66 static void ra_send_rs(int signal __attribute__((unused)));
  67
  68 int ra_init(const char *ifname, const struct in6_addr *ifid)
  69 {
  70         const pid_t ourpid = getpid();
  71         sock = socket(AF_INET6, SOCK_RAW | SOCK_CLOEXEC, IPPROTO_ICMPV6);
  72         if (sock < 0)
  73                 return -1;
  74
  75         if_index = if_nametoindex(ifname);
  76         if (!if_index)
  77                 return -1;
  78
  79         strncpy(if_name, ifname, sizeof(if_name) - 1);
  80         lladdr = *ifid;
  81
  82         rtnl = socket(AF_NETLINK, SOCK_DGRAM | SOCK_CLOEXEC, NETLINK_ROUTE);
  83         if (rtnl < 0)
  84                 return -1;
  85
  86         struct sockaddr_nl rtnl_kernel = { .nl_family = AF_NETLINK };
  87         if (connect(rtnl, (const struct sockaddr*)&rtnl_kernel, sizeof(rtnl_kernel)) < 0)
  88                 return -1;
  89
  90         int val = RTNLGRP_LINK;
  91         setsockopt(rtnl, SOL_NETLINK, NETLINK_ADD_MEMBERSHIP, &val, sizeof(val));
  92         fcntl(rtnl, F_SETOWN, ourpid);
  93         fcntl(rtnl, F_SETFL, fcntl(sock, F_GETFL) | O_ASYNC);
  94
  95         struct {
  96                 struct nlmsghdr hdr;
  97                 struct ifinfomsg ifi;
  98         } req = {
  99                 .hdr = {sizeof(req), RTM_GETLINK, NLM_F_REQUEST, 1, 0},
 100                 .ifi = {.ifi_index = if_index}
 101         };
 102         send(rtnl, &req, sizeof(req), 0);
 103         ra_link_up();
 104
 105         // Filter ICMPv6 package types
 106         struct icmp6_filter filt;
 107         ICMP6_FILTER_SETBLOCKALL(&filt);
 108         ICMP6_FILTER_SETPASS(ND_ROUTER_ADVERT, &filt);
 109         setsockopt(sock, IPPROTO_ICMPV6, ICMP6_FILTER, &filt, sizeof(filt));
 110
 111         // Bind to all-nodes
 112         struct ipv6_mreq an = {ALL_IPV6_NODES, if_index};
 113         setsockopt(sock, IPPROTO_IPV6, IPV6_ADD_MEMBERSHIP, &an, sizeof(an));
 114
 115         // Let the kernel compute our checksums
 116         val = 2;
 117         setsockopt(sock, IPPROTO_RAW, IPV6_CHECKSUM, &val, sizeof(val));
 118
 119         // This is required by RFC 4861
 120         val = 255;
 121         setsockopt(sock, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &val, sizeof(val));
 122
 123         // Receive multicast hops
 124         val = 1;
 125         setsockopt(sock, IPPROTO_IPV6, IPV6_RECVHOPLIMIT, &val, sizeof(val));
 126
 127         // Bind to one device
 128         setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE, ifname, strlen(ifname));
 129
 130         // Add async-mode
 131         fcntl(sock, F_SETOWN, ourpid);
 132         fcntl(sock, F_SETFL, fcntl(sock, F_GETFL) | O_ASYNC);
 133
 134         // Send RS
 135         signal(SIGALRM, ra_send_rs);
 136         ra_send_rs(SIGALRM);
 137
 138         return 0;
 139 }
 140
 141
 142 static void ra_send_rs(int signal __attribute__((unused)))
 143 {
 144         const struct sockaddr_in6 dest = {AF_INET6, 0, 0, ALL_IPV6_ROUTERS, if_index};
 145         const struct icmpv6_opt llnull = {ND_OPT_SOURCE_LINKADDR, 1, {0}};
 146         size_t len;
 147
 148         if ((rs_attempt % 2 == 0) && memcmp(&rs.lladdr, &llnull, sizeof(llnull)))
 149                 len = sizeof(rs);
 150         else
 151                 len = sizeof(struct icmp6_hdr);
 152
 153         sendto(sock, &rs, len, MSG_DONTWAIT, (struct sockaddr*)&dest, sizeof(dest));
 154
 155         if (++rs_attempt <= 3)
 156                 alarm(4);
 157 }
 158
 159
 160 static int16_t pref_to_priority(uint8_t flags)
 161 {
 162         flags = (flags >> 3) & 0x03;
 163         return (flags == 0x0) ? 512 : (flags == 0x1) ? 384 :
 164                         (flags == 0x3) ? 640 : -1;
 165 }
 166
 167
 168 static int update_proc(const char *sect, const char *opt, uint32_t value)
 169 {
 170         char buf[64];
 171         snprintf(buf, sizeof(buf), "/proc/sys/net/ipv6/%s/%s/%s", sect, if_name, opt);
 172
 173         int fd = open(buf, O_WRONLY);
 174         int ret = write(fd, buf, snprintf(buf, sizeof(buf), "%u", value));
 175         close(fd);
 176
 177         return ret;
 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                 ssize_t alen = NLMSG_PAYLOAD(&resp.hdr, sizeof(resp.msg));
 201                 for (struct rtattr *rta = (struct rtattr*)(resp.pad);
 202                                 RTA_OK(rta, alen); rta = RTA_NEXT(rta, alen)) {
 203                         if (rta->rta_type == IFLA_ADDRESS &&
 204                                         RTA_PAYLOAD(rta) >= sizeof(rs.lladdr.data))
 205                                 memcpy(rs.lladdr.data, RTA_DATA(rta), sizeof(rs.lladdr.data));
 206                 }
 207
 208                 bool hascarrier = resp.msg.ifi_flags & IFF_LOWER_UP;
 209                 if (!firstcall && nocarrier != !hascarrier)
 210                         ret = true;
 211
 212                 nocarrier = !hascarrier;
 213                 firstcall = false;
 214         } while (read > 0);
 215
 216         if (ret) {
 217                 syslog(LOG_NOTICE, "carrier => %i event on %s", (int)!nocarrier, if_name);
 218
 219                 rs_attempt = 0;
 220                 ra_send_rs(SIGALRM);
 221         }
 222
 223         return ret;
 224 }
 225
 226 static bool ra_icmpv6_valid(struct sockaddr_in6 *source, int hlim, uint8_t *data, size_t len)
 227 {
 228         struct icmp6_hdr *hdr = (struct icmp6_hdr*)data;
 229         struct icmpv6_opt *opt, *end = (struct icmpv6_opt*)&data[len];
 230
 231         if (hlim != 255 || len < sizeof(*hdr) || hdr->icmp6_code)
 232                 return false;
 233
 234         switch (hdr->icmp6_type) {
 235         case ND_ROUTER_ADVERT:
 236                 if (!IN6_IS_ADDR_LINKLOCAL(&source->sin6_addr))
 237                         return false;
 238
 239                 opt = (struct icmpv6_opt*)((struct nd_router_advert*)data + 1);
 240                 break;
 241
 242         default:
 243                 return false;
 244         }
 245
 246         icmpv6_for_each_option(opt, opt, end)
 247                 ;
 248
 249         return opt == end;
 250 }
 251
 252 bool ra_process(void)
 253 {
 254         bool found = false;
 255         bool changed = false;
 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 (IN6_IS_ADDR_UNSPECIFIED(&lladdr)) {
 262                 struct sockaddr_in6 addr = {AF_INET6, 0, 0, ALL_IPV6_ROUTERS, if_index};
 263                 socklen_t alen = sizeof(addr);
 264                 int sock = socket(AF_INET6, SOCK_RAW, IPPROTO_ICMPV6);
 265
 266                 if (!connect(sock, (struct sockaddr*)&addr, sizeof(addr)) &&
 267                                 !getsockname(sock, (struct sockaddr*)&addr, &alen))
 268                         lladdr = addr.sin6_addr;
 269
 270                 close(sock);
 271         }
 272
 273         while (true) {
 274                 struct sockaddr_in6 from;
 275                 struct iovec iov = {buf, sizeof(buf)};
 276                 struct msghdr msg = {
 277                         .msg_name = (void *) &from,
 278                         .msg_namelen = sizeof(from),
 279                         .msg_iov = &iov,
 280                         .msg_iovlen = 1,
 281                         .msg_control = cmsg_buf,
 282                         .msg_controllen = sizeof(cmsg_buf),
 283                         .msg_flags = 0
 284                 };
 285
 286                 ssize_t len = recvmsg(sock, &msg, MSG_DONTWAIT);
 287                 if (len <= 0)
 288                         break;
 289
 290                 if (IN6_IS_ADDR_UNSPECIFIED(&lladdr))
 291                         continue;
 292
 293                 int hlim = 0;
 294                 for (struct cmsghdr *ch = CMSG_FIRSTHDR(&msg); ch != NULL;
 295                                 ch = CMSG_NXTHDR(&msg, ch))
 296                         if (ch->cmsg_level == IPPROTO_IPV6 &&
 297                                         ch->cmsg_type == IPV6_HOPLIMIT)
 298                                 memcpy(&hlim, CMSG_DATA(ch), sizeof(hlim));
 299
 300                 if (!ra_icmpv6_valid(&from, hlim, buf, len))
 301                         continue;
 302
 303                 // Stop sending solicits
 304                 if (rs_attempt > 0) {
 305                         alarm(0);
 306                         rs_attempt = 0;
 307                 }
 308
 309                 if (!found) {
 310                         odhcp6c_expire();
 311                         found = true;
 312                 }
 313                 uint32_t router_valid = ntohs(adv->nd_ra_router_lifetime);
 314
 315                 // Parse default route
 316                 entry.target = any;
 317                 entry.length = 0;
 318                 entry.router = from.sin6_addr;
 319                 entry.priority = pref_to_priority(adv->nd_ra_flags_reserved);
 320                 if (entry.priority < 0)
 321                         entry.priority = pref_to_priority(0);
 322                 entry.valid = router_valid;
 323                 entry.preferred = entry.valid;
 324                 changed |= odhcp6c_update_entry(STATE_RA_ROUTE, &entry, 0, true);
 325
 326                 // Parse hoplimit
 327                 if (adv->nd_ra_curhoplimit)
 328                         update_proc("conf", "hop_limit", adv->nd_ra_curhoplimit);
 329
 330                 // Parse ND parameters
 331                 uint32_t reachable = ntohl(adv->nd_ra_reachable);
 332                 if (reachable > 0 && reachable <= 3600000)
 333                         update_proc("neigh", "base_reachable_time_ms", reachable);
 334
 335                 uint32_t retransmit = ntohl(adv->nd_ra_retransmit);
 336                 if (retransmit > 0 && retransmit <= 60000)
 337                         update_proc("neigh", "retrans_time_ms", retransmit);
 338
 339
 340                 // Evaluate options
 341                 struct icmpv6_opt *opt;
 342                 icmpv6_for_each_option(opt, &adv[1], &buf[len]) {
 343                         if (opt->type == ND_OPT_MTU) {
 344                                 uint32_t *mtu = (uint32_t*)&opt->data[2];
 345                                 if (ntohl(*mtu) >= 1280 && ntohl(*mtu) <= 65535)
 346                                         update_proc("conf", "mtu", ntohl(*mtu));
 347                         } else if (opt->type == ND_OPT_ROUTE_INFORMATION && opt->len <= 3) {
 348                                 entry.router = from.sin6_addr;
 349                                 entry.target = any;
 350                                 entry.priority = pref_to_priority(opt->data[1]);
 351                                 entry.length = opt->data[0];
 352                                 uint32_t *valid = (uint32_t*)&opt->data[2];
 353                                 entry.valid = ntohl(*valid);
 354                                 memcpy(&entry.target, &opt->data[6], (opt->len - 1) * 8);
 355
 356                                 if (entry.length > 128 || IN6_IS_ADDR_LINKLOCAL(&entry.target)
 357                                                 || IN6_IS_ADDR_LOOPBACK(&entry.target)
 358                                                 || IN6_IS_ADDR_MULTICAST(&entry.target))
 359                                         continue;
 360
 361                                 if (entry.priority > 0)
 362                                         changed |= odhcp6c_update_entry(STATE_RA_ROUTE, &entry, 0, true);
 363                         } else if (opt->type == ND_OPT_PREFIX_INFORMATION && opt->len == 4) {
 364                                 struct nd_opt_prefix_info *pinfo = (struct nd_opt_prefix_info*)opt;
 365                                 entry.router = any;
 366                                 entry.target = pinfo->nd_opt_pi_prefix;
 367                                 entry.priority = 256;
 368                                 entry.length = pinfo->nd_opt_pi_prefix_len;
 369                                 entry.valid = ntohl(pinfo->nd_opt_pi_valid_time);
 370                                 entry.preferred = ntohl(pinfo->nd_opt_pi_preferred_time);
 371
 372                                 if (entry.length > 128 || IN6_IS_ADDR_LINKLOCAL(&entry.target)
 373                                                 || IN6_IS_ADDR_LOOPBACK(&entry.target)
 374                                                 || IN6_IS_ADDR_MULTICAST(&entry.target)
 375                                                 || entry.valid < entry.preferred)
 376                                         continue;
 377
 378                                 if (pinfo->nd_opt_pi_flags_reserved & ND_OPT_PI_FLAG_ONLINK)
 379                                         changed |= odhcp6c_update_entry(STATE_RA_ROUTE, &entry, 7200, true);
 380
 381                                 if (!(pinfo->nd_opt_pi_flags_reserved & ND_OPT_PI_FLAG_AUTO) ||
 382                                                 pinfo->nd_opt_pi_prefix_len != 64)
 383                                         continue;
 384
 385                                 entry.target.s6_addr32[2] = lladdr.s6_addr32[2];
 386                                 entry.target.s6_addr32[3] = lladdr.s6_addr32[3];
 387
 388                                 changed |= odhcp6c_update_entry(STATE_RA_PREFIX, &entry, 7200, true);
 389                         } else if (opt->type == ND_OPT_RECURSIVE_DNS && opt->len > 2) {
 390                                 entry.router = from.sin6_addr;
 391                                 entry.priority = 0;
 392                                 entry.length = 128;
 393                                 uint32_t *valid = (uint32_t*)&opt->data[2];
 394                                 entry.valid = ntohl(*valid);
 395                                 entry.preferred = 0;
 396
 397                                 for (ssize_t i = 0; i < (opt->len - 1) / 2; ++i) {
 398                                         memcpy(&entry.target, &opt->data[6 + i * sizeof(entry.target)],
 399                                                         sizeof(entry.target));
 400                                         changed |= odhcp6c_update_entry(STATE_RA_DNS, &entry, 0, true);
 401                                 }
 402                         }
 403                 }
 404
 405                 size_t ra_dns_len;
 406                 struct odhcp6c_entry *entry = odhcp6c_get_state(STATE_RA_DNS, &ra_dns_len);
 407                 for (size_t i = 0; i < ra_dns_len / sizeof(*entry); ++i)
 408                         if (IN6_ARE_ADDR_EQUAL(&entry[i].router, &from.sin6_addr) &&
 409                                         entry[i].valid > router_valid)
 410                                 entry[i].valid = router_valid;
 411         }
 412
 413         if (found)
 414                 odhcp6c_expire();
 415
 416         return found && changed;
 417 }