ra.c

   1 /**
   2  * Copyright (C) 2012-2013 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 <netinet/in.h>
  28 #include <netinet/icmp6.h>
  29
  30 #include <linux/rtnetlink.h>
  31
  32 #ifndef SOL_NETLINK
  33 #define SOL_NETLINK 270
  34 #endif
  35
  36 #ifndef NETLINK_ADD_MEMBERSHIP
  37 #define NETLINK_ADD_MEMBERSHIP 1
  38 #endif
  39
  40 #ifndef IFF_LOWER_UP
  41 #define IFF_LOWER_UP 0x10000
  42 #endif
  43
  44 #include "odhcp6c.h"
  45 #include "ra.h"
  46
  47
  48 static bool nocarrier = false;
  49
  50 static int sock = -1, rtnl = -1;
  51 static int if_index = 0;
  52 static char if_name[IF_NAMESIZE] = {0};
  53 static volatile int rs_attempt = 0;
  54 static struct in6_addr lladdr = IN6ADDR_ANY_INIT;
  55
  56 static void ra_send_rs(int signal __attribute__((unused)));
  57
  58 int ra_init(const char *ifname, const struct in6_addr *ifid)
  59 {
  60         const pid_t ourpid = getpid();
  61         sock = socket(AF_INET6, SOCK_RAW | SOCK_CLOEXEC, IPPROTO_ICMPV6);
  62         if (sock < 0)
  63                 return -1;
  64
  65         if_index = if_nametoindex(ifname);
  66         if (!if_index)
  67                 return -1;
  68
  69         strncpy(if_name, ifname, sizeof(if_name) - 1);
  70         lladdr = *ifid;
  71
  72         rtnl = socket(AF_NETLINK, SOCK_DGRAM | SOCK_CLOEXEC, NETLINK_ROUTE);
  73         if (rtnl < 0)
  74                 return -1;
  75
  76         struct sockaddr_nl rtnl_kernel = { .nl_family = AF_NETLINK };
  77         if (connect(rtnl, (const struct sockaddr*)&rtnl_kernel, sizeof(rtnl_kernel)) < 0)
  78                 return -1;
  79
  80         int val = RTNLGRP_LINK;
  81         setsockopt(rtnl, SOL_NETLINK, NETLINK_ADD_MEMBERSHIP, &val, sizeof(val));
  82         fcntl(rtnl, F_SETOWN, ourpid);
  83         fcntl(rtnl, F_SETFL, fcntl(sock, F_GETFL) | O_ASYNC);
  84
  85         struct {
  86                 struct nlmsghdr hdr;
  87                 struct ifinfomsg ifi;
  88         } req = {
  89                 .hdr = {sizeof(req), RTM_GETLINK, NLM_F_REQUEST, 1, 0},
  90                 .ifi = {.ifi_index = if_index}
  91         };
  92         send(rtnl, &req, sizeof(req), 0);
  93
  94         // Filter ICMPv6 package types
  95         struct icmp6_filter filt;
  96         ICMP6_FILTER_SETBLOCKALL(&filt);
  97         ICMP6_FILTER_SETPASS(ND_ROUTER_ADVERT, &filt);
  98         setsockopt(sock, IPPROTO_ICMPV6, ICMP6_FILTER, &filt, sizeof(filt));
  99
 100         // Bind to all-nodes
 101         struct ipv6_mreq an = {ALL_IPV6_NODES, if_index};
 102         setsockopt(sock, IPPROTO_IPV6, IPV6_ADD_MEMBERSHIP, &an, sizeof(an));
 103
 104         // Let the kernel compute our checksums
 105         val = 2;
 106         setsockopt(sock, IPPROTO_RAW, IPV6_CHECKSUM, &val, sizeof(val));
 107
 108         // This is required by RFC 4861
 109         val = 255;
 110         setsockopt(sock, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &val, sizeof(val));
 111
 112         // Receive multicast hops
 113         val = 1;
 114         setsockopt(sock, IPPROTO_IPV6, IPV6_RECVHOPLIMIT, &val, sizeof(val));
 115
 116         // Bind to one device
 117         setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE, ifname, strlen(ifname));
 118
 119         // Add async-mode
 120         fcntl(sock, F_SETOWN, ourpid);
 121         fcntl(sock, F_SETFL, fcntl(sock, F_GETFL) | O_ASYNC);
 122
 123         // Send RS
 124         signal(SIGALRM, ra_send_rs);
 125         ra_send_rs(SIGALRM);
 126
 127         return 0;
 128 }
 129
 130
 131 static void ra_send_rs(int signal __attribute__((unused)))
 132 {
 133         const struct icmp6_hdr rs = {ND_ROUTER_SOLICIT, 0, 0, {{0}}};
 134         const struct sockaddr_in6 dest = {AF_INET6, 0, 0, ALL_IPV6_ROUTERS, if_index};
 135         sendto(sock, &rs, sizeof(rs), MSG_DONTWAIT, (struct sockaddr*)&dest, sizeof(dest));
 136
 137         if (++rs_attempt <= 3)
 138                 alarm(4);
 139 }
 140
 141
 142 static int16_t pref_to_priority(uint8_t flags)
 143 {
 144         flags = (flags >> 3) & 0x03;
 145         return (flags == 0x0) ? 1024 : (flags == 0x1) ? 512 :
 146                         (flags == 0x3) ? 2048 : -1;
 147 }
 148
 149
 150 static void update_proc(const char *sect, const char *opt, uint32_t value)
 151 {
 152         char buf[64];
 153         snprintf(buf, sizeof(buf), "/proc/sys/net/ipv6/%s/%s/%s", sect, if_name, opt);
 154
 155         int fd = open(buf, O_WRONLY);
 156         write(fd, buf, snprintf(buf, sizeof(buf), "%u", value));
 157         close(fd);
 158 }
 159
 160
 161 bool ra_link_up(void)
 162 {
 163         static bool firstcall = true;
 164         struct {
 165                 struct nlmsghdr hdr;
 166                 struct ifinfomsg msg;
 167                 uint8_t pad[4000];
 168         } resp;
 169
 170         bool ret = false;
 171         ssize_t read;
 172
 173         do {
 174                 read = recv(rtnl, &resp, sizeof(resp), MSG_DONTWAIT);
 175                 if (read < 0 || !NLMSG_OK(&resp.hdr, (size_t)read) ||
 176                                 resp.hdr.nlmsg_type != RTM_NEWLINK ||
 177                                 resp.msg.ifi_index != if_index)
 178                         continue;
 179
 180                 bool hascarrier = resp.msg.ifi_flags & IFF_LOWER_UP;
 181                 if (!firstcall && nocarrier != !hascarrier)
 182                         ret = true;
 183
 184                 nocarrier = !hascarrier;
 185                 firstcall = false;
 186         } while (read > 0);
 187
 188         if (ret) {
 189                 syslog(LOG_NOTICE, "carrier => %i event on %s", (int)!nocarrier, if_name);
 190
 191                 rs_attempt = 0;
 192                 ra_send_rs(SIGALRM);
 193         }
 194
 195         return ret;
 196 }
 197
 198 static bool ra_icmpv6_valid(struct sockaddr_in6 *source, int hlim, uint8_t *data, size_t len)
 199 {
 200         struct icmp6_hdr *hdr = (struct icmp6_hdr*)data;
 201         struct icmpv6_opt *opt, *end = (struct icmpv6_opt*)&data[len];
 202
 203         if (hlim != 255 || len < sizeof(*hdr) || hdr->icmp6_code)
 204                 return false;
 205
 206         switch (hdr->icmp6_type) {
 207         case ND_ROUTER_ADVERT:
 208                 if (!IN6_IS_ADDR_LINKLOCAL(&source->sin6_addr))
 209                         return false;
 210
 211                 opt = (struct icmpv6_opt*)((struct nd_router_advert*)data + 1);
 212                 break;
 213
 214         default:
 215                 return false;
 216         }
 217
 218         icmpv6_for_each_option(opt, opt, end)
 219                 ;
 220
 221         return opt == end;
 222 }
 223
 224 bool ra_process(void)
 225 {
 226         bool found = false;
 227         bool changed = false;
 228         uint8_t buf[1500], cmsg_buf[128];
 229         struct nd_router_advert *adv = (struct nd_router_advert*)buf;
 230         struct odhcp6c_entry entry = {IN6ADDR_ANY_INIT, 0, 0, IN6ADDR_ANY_INIT, 0, 0, 0, 0, 0};
 231         const struct in6_addr any = IN6ADDR_ANY_INIT;
 232
 233         if (IN6_IS_ADDR_UNSPECIFIED(&lladdr)) {
 234                 // Autodetect interface-id if not specified
 235                 FILE *fp = fopen("/proc/net/if_inet6", "r");
 236                 if (fp) {
 237                         char addrbuf[33], ifbuf[16];
 238                         while (fscanf(fp, "%32s %*x %*x %*x %*x %15s", addrbuf, ifbuf) == 2) {
 239                                 if (!strcmp(ifbuf, if_name)) {
 240                                         script_unhexlify((uint8_t*)&lladdr, sizeof(lladdr), addrbuf);
 241                                         break;
 242                                 }
 243                         }
 244                         fclose(fp);
 245                 }
 246         }
 247
 248         while (true) {
 249                 struct sockaddr_in6 from;
 250                 struct iovec iov = {buf, sizeof(buf)};
 251                 struct msghdr msg = {&from, sizeof(from), &iov, 1,
 252                                 cmsg_buf, sizeof(cmsg_buf), 0};
 253
 254                 ssize_t len = recvmsg(sock, &msg, MSG_DONTWAIT);
 255                 if (len <= 0)
 256                         break;
 257
 258                 int hlim = 0;
 259                 for (struct cmsghdr *ch = CMSG_FIRSTHDR(&msg); ch != NULL;
 260                                 ch = CMSG_NXTHDR(&msg, ch))
 261                         if (ch->cmsg_level == IPPROTO_IPV6 &&
 262                                         ch->cmsg_type == IPV6_HOPLIMIT)
 263                                 memcpy(&hlim, CMSG_DATA(ch), sizeof(hlim));
 264
 265                 if (!ra_icmpv6_valid(&from, hlim, buf, len))
 266                         continue;
 267
 268                 // Stop sending solicits
 269                 if (rs_attempt > 0) {
 270                         alarm(0);
 271                         rs_attempt = 0;
 272                 }
 273
 274                 if (!found) {
 275                         odhcp6c_expire();
 276                         found = true;
 277                 }
 278                 uint32_t router_valid = ntohs(adv->nd_ra_router_lifetime);
 279
 280                 // Parse default route
 281                 entry.target = any;
 282                 entry.length = 0;
 283                 entry.router = from.sin6_addr;
 284                 entry.priority = pref_to_priority(adv->nd_ra_flags_reserved);
 285                 if (entry.priority < 0)
 286                         entry.priority = pref_to_priority(0);
 287                 entry.valid = router_valid;
 288                 entry.preferred = entry.valid;
 289                 changed |= odhcp6c_update_entry(STATE_RA_ROUTE, &entry);
 290
 291                 // Parse hoplimit
 292                 if (adv->nd_ra_curhoplimit)
 293                         update_proc("conf", "hop_limit", adv->nd_ra_curhoplimit);
 294
 295                 // Parse ND parameters
 296                 if (ntohl(adv->nd_ra_reachable) <= 3600000)
 297                         update_proc("neigh", "base_reachable_time_ms", ntohl(adv->nd_ra_reachable));
 298
 299                 if (ntohl(adv->nd_ra_retransmit) <= 60000)
 300                         update_proc("neigh", "retrans_time_ms", ntohl(adv->nd_ra_retransmit));
 301
 302
 303                 // Evaluate options
 304                 struct icmpv6_opt *opt;
 305                 icmpv6_for_each_option(opt, &adv[1], &buf[len]) {
 306                         if (opt->type == ND_OPT_MTU) {
 307                                 uint32_t *mtu = (uint32_t*)&opt->data[2];
 308                                 if (ntohl(*mtu) >= 1280 && ntohl(*mtu) <= 65535)
 309                                         update_proc("conf", "mtu", ntohl(*mtu));
 310                         } else if (opt->type == ND_OPT_ROUTE_INFORMATION && opt->len <= 3) {
 311                                 entry.router = from.sin6_addr;
 312                                 entry.target = any;
 313                                 entry.priority = pref_to_priority(opt->data[1]);
 314                                 entry.length = opt->data[0];
 315                                 uint32_t *valid = (uint32_t*)&opt->data[2];
 316                                 entry.valid = ntohl(*valid);
 317                                 memcpy(&entry.target, &opt->data[6], (opt->len - 1) * 8);
 318
 319                                 if (entry.length > 128 || IN6_IS_ADDR_LINKLOCAL(&entry.target)
 320                                                 || IN6_IS_ADDR_LOOPBACK(&entry.target)
 321                                                 || IN6_IS_ADDR_MULTICAST(&entry.target))
 322                                         continue;
 323
 324                                 if (entry.priority > 0)
 325                                         changed |= odhcp6c_update_entry(STATE_RA_ROUTE, &entry);
 326                         } else if (opt->type == ND_OPT_PREFIX_INFORMATION && opt->len == 4) {
 327                                 struct nd_opt_prefix_info *pinfo = (struct nd_opt_prefix_info*)opt;
 328                                 entry.router = any;
 329                                 entry.target = pinfo->nd_opt_pi_prefix;
 330                                 entry.priority = 256;
 331                                 entry.length = pinfo->nd_opt_pi_prefix_len;
 332                                 entry.valid = ntohl(pinfo->nd_opt_pi_valid_time);
 333                                 entry.preferred = ntohl(pinfo->nd_opt_pi_preferred_time);
 334
 335                                 if (entry.length > 128 || IN6_IS_ADDR_LINKLOCAL(&entry.target)
 336                                                 || IN6_IS_ADDR_LOOPBACK(&entry.target)
 337                                                 || IN6_IS_ADDR_MULTICAST(&entry.target)
 338                                                 || entry.valid < entry.preferred)
 339                                         continue;
 340
 341                                 if (pinfo->nd_opt_pi_flags_reserved & ND_OPT_PI_FLAG_ONLINK)
 342                                         changed |= odhcp6c_update_entry_safe(STATE_RA_ROUTE, &entry, 7200);
 343
 344                                 if (!(pinfo->nd_opt_pi_flags_reserved & ND_OPT_PI_FLAG_AUTO) ||
 345                                                 pinfo->nd_opt_pi_prefix_len != 64)
 346                                         continue;
 347
 348                                 entry.target.s6_addr32[2] = lladdr.s6_addr32[2];
 349                                 entry.target.s6_addr32[3] = lladdr.s6_addr32[3];
 350
 351                                 changed |= odhcp6c_update_entry_safe(STATE_RA_PREFIX, &entry, 7200);
 352                         } else if (opt->type == ND_OPT_RECURSIVE_DNS && opt->len > 2) {
 353                                 entry.router = from.sin6_addr;
 354                                 entry.priority = 0;
 355                                 entry.length = 128;
 356                                 uint32_t *valid = (uint32_t*)&opt->data[2];
 357                                 entry.valid = ntohl(*valid);
 358                                 entry.preferred = 0;
 359
 360                                 for (ssize_t i = 0; i < (opt->len - 1) / 2; ++i) {
 361                                         memcpy(&entry.target, &opt->data[6 + i * sizeof(entry.target)],
 362                                                         sizeof(entry.target));
 363                                         changed |= odhcp6c_update_entry(STATE_RA_DNS, &entry);
 364                                 }
 365                         }
 366                 }
 367
 368                 size_t ra_dns_len;
 369                 struct odhcp6c_entry *entry = odhcp6c_get_state(STATE_RA_DNS, &ra_dns_len);
 370                 for (size_t i = 0; i < ra_dns_len / sizeof(*entry); ++i)
 371                         if (IN6_ARE_ADDR_EQUAL(&entry[i].router, &from.sin6_addr) &&
 372                                         entry[i].valid > router_valid)
 373                                 entry[i].valid = router_valid;
 374         }
 375
 376         if (found)
 377                 odhcp6c_expire();
 378
 379         return found && changed;
 380 }