src/router.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 <errno.h>
  16 #include <fcntl.h>
  17 #include <signal.h>
  18 #include <resolv.h>
  19 #include <stdio.h>
  20 #include <stdlib.h>
  21 #include <unistd.h>
  22 #include <stdbool.h>
  23 #include <net/route.h>
  24
  25 #include "router.h"
  26 #include "odhcpd.h"
  27
  28
  29 static void forward_router_solicitation(const struct interface *iface);
  30 static void forward_router_advertisement(uint8_t *data, size_t len);
  31
  32 static void handle_icmpv6(void *addr, void *data, size_t len,
  33                 struct interface *iface);
  34 static void send_router_advert(struct uloop_timeout *event);
  35 static void sigusr1_refresh(int signal);
  36
  37 static struct odhcpd_event router_event = {{.fd = -1}, handle_icmpv6};
  38
  39 static FILE *fp_route = NULL;
  40
  41
  42 int init_router(void)
  43 {
  44         // Open ICMPv6 socket
  45         int sock = socket(AF_INET6, SOCK_RAW | SOCK_CLOEXEC, IPPROTO_ICMPV6);
  46         if (sock < 0 && errno != EAFNOSUPPORT) {
  47                 syslog(LOG_ERR, "Failed to open RAW-socket: %s", strerror(errno));
  48                 return -1;
  49         }
  50
  51         // Let the kernel compute our checksums
  52         int val = 2;
  53         setsockopt(sock, IPPROTO_RAW, IPV6_CHECKSUM, &val, sizeof(val));
  54
  55         // This is required by RFC 4861
  56         val = 255;
  57         setsockopt(sock, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &val, sizeof(val));
  58         setsockopt(sock, IPPROTO_IPV6, IPV6_UNICAST_HOPS, &val, sizeof(val));
  59
  60         // We need to know the source interface
  61         val = 1;
  62         setsockopt(sock, IPPROTO_IPV6, IPV6_RECVPKTINFO, &val, sizeof(val));
  63         setsockopt(sock, IPPROTO_IPV6, IPV6_RECVHOPLIMIT, &val, sizeof(val));
  64
  65         // Don't loop back
  66         val = 0;
  67         setsockopt(sock, IPPROTO_IPV6, IPV6_MULTICAST_LOOP, &val, sizeof(val));
  68
  69         // Filter ICMPv6 package types
  70         struct icmp6_filter filt;
  71         ICMP6_FILTER_SETBLOCKALL(&filt);
  72         ICMP6_FILTER_SETPASS(ND_ROUTER_ADVERT, &filt);
  73         ICMP6_FILTER_SETPASS(ND_ROUTER_SOLICIT, &filt);
  74         setsockopt(sock, IPPROTO_ICMPV6, ICMP6_FILTER, &filt, sizeof(filt));
  75
  76         // Register socket
  77         router_event.uloop.fd = sock;
  78         odhcpd_register(&router_event);
  79
  80         if (!(fp_route = fopen("/proc/net/ipv6_route", "r")))
  81                 syslog(LOG_ERR, "Failed to open routing table: %s",
  82                                 strerror(errno));
  83
  84         signal(SIGUSR1, sigusr1_refresh);
  85         return 0;
  86 }
  87
  88
  89 int setup_router_interface(struct interface *iface, bool enable)
  90 {
  91         struct ipv6_mreq all_nodes = {ALL_IPV6_NODES, iface->ifindex};
  92         struct ipv6_mreq all_routers = {ALL_IPV6_ROUTERS, iface->ifindex};
  93
  94         uloop_timeout_cancel(&iface->timer_rs);
  95         iface->timer_rs.cb = NULL;
  96
  97         setsockopt(router_event.uloop.fd, IPPROTO_IPV6, IPV6_DROP_MEMBERSHIP,
  98                         &all_nodes, sizeof(all_nodes));
  99         setsockopt(router_event.uloop.fd, IPPROTO_IPV6, IPV6_DROP_MEMBERSHIP,
 100                         &all_routers, sizeof(all_routers));
 101
 102         if (!enable) {
 103                 if (iface->ra)
 104                         send_router_advert(&iface->timer_rs);
 105         } else {
 106                 void *mreq = &all_routers;
 107
 108                 if (iface->ra == RELAYD_RELAY && iface->master) {
 109                         mreq = &all_nodes;
 110                         forward_router_solicitation(iface);
 111                 } else if (iface->ra == RELAYD_SERVER && !iface->master) {
 112                         iface->timer_rs.cb = send_router_advert;
 113                         send_router_advert(&iface->timer_rs);
 114                 }
 115
 116                 if (iface->ra == RELAYD_RELAY || (iface->ra == RELAYD_SERVER && !iface->master))
 117                         setsockopt(router_event.uloop.fd, IPPROTO_IPV6,
 118                                         IPV6_ADD_MEMBERSHIP, mreq, sizeof(all_nodes));
 119         }
 120         return 0;
 121 }
 122
 123
 124 // Signal handler to resend all RDs
 125 static void sigusr1_refresh(_unused int signal)
 126 {
 127         struct interface *iface;
 128         list_for_each_entry(iface, &interfaces, head)
 129                 if (iface->ra == RELAYD_SERVER && !iface->master)
 130                         uloop_timeout_set(&iface->timer_rs, 1000);
 131 }
 132
 133 static bool router_icmpv6_valid(struct sockaddr_in6 *source, uint8_t *data, size_t len)
 134 {
 135         struct icmp6_hdr *hdr = (struct icmp6_hdr *)data;
 136         struct icmpv6_opt *opt, *end = (struct icmpv6_opt*)&data[len];
 137
 138         /* Hoplimit is already checked in odhcpd_receive_packets */
 139         if (len < sizeof(*hdr) || hdr->icmp6_code)
 140                 return false;
 141
 142         switch (hdr->icmp6_type) {
 143         case ND_ROUTER_ADVERT:
 144                 if (!IN6_IS_ADDR_LINKLOCAL(&source->sin6_addr))
 145                         return false;
 146
 147                 opt = (struct icmpv6_opt *)((struct nd_router_advert *)data + 1);
 148                 break;
 149
 150         case ND_ROUTER_SOLICIT:
 151                 opt = (struct icmpv6_opt *)((struct nd_router_solicit *)data + 1);
 152                 break;
 153
 154         default:
 155                 return false;
 156         }
 157
 158         icmpv6_for_each_option(opt, opt, end)
 159                 if (opt->type == ND_OPT_SOURCE_LINKADDR &&
 160                                 IN6_IS_ADDR_UNSPECIFIED(&source->sin6_addr) &&
 161                                 hdr->icmp6_type == ND_ROUTER_SOLICIT)
 162                         return false;
 163
 164         // Check all options parsed successfully
 165         return opt == end;
 166 }
 167
 168 // Event handler for incoming ICMPv6 packets
 169 static void handle_icmpv6(void *addr, void *data, size_t len,
 170                 struct interface *iface)
 171 {
 172         struct icmp6_hdr *hdr = data;
 173
 174         if (!router_icmpv6_valid(addr, data, len))
 175                 return;
 176
 177         if ((iface->ra == RELAYD_SERVER && !iface->master)) { // Server mode
 178                 if (hdr->icmp6_type == ND_ROUTER_SOLICIT)
 179                         send_router_advert(&iface->timer_rs);
 180         } else if (iface->ra == RELAYD_RELAY) { // Relay mode
 181                 if (hdr->icmp6_type == ND_ROUTER_ADVERT && iface->master)
 182                         forward_router_advertisement(data, len);
 183                 else if (hdr->icmp6_type == ND_ROUTER_SOLICIT && !iface->master)
 184                         forward_router_solicitation(odhcpd_get_master_interface());
 185         }
 186 }
 187
 188
 189 static bool match_route(const struct odhcpd_ipaddr *n, const struct in6_addr *addr)
 190 {
 191         if (n->prefix <= 32)
 192                 return ntohl(n->addr.s6_addr32[0]) >> (32 - n->prefix) ==
 193                                 ntohl(addr->s6_addr32[0]) >> (32 - n->prefix);
 194
 195         if (n->addr.s6_addr32[0] != addr->s6_addr32[0])
 196                 return false;
 197
 198         return ntohl(n->addr.s6_addr32[1]) >> (64 - n->prefix) ==
 199                         ntohl(addr->s6_addr32[1]) >> (64 - n->prefix);
 200 }
 201
 202
 203 // Detect whether a default route exists, also find the source prefixes
 204 static bool parse_routes(struct odhcpd_ipaddr *n, ssize_t len)
 205 {
 206         rewind(fp_route);
 207
 208         char line[512], ifname[16];
 209         bool found_default = false;
 210         struct odhcpd_ipaddr p = {IN6ADDR_ANY_INIT, 0, false, 0, 0, 0};
 211         while (fgets(line, sizeof(line), fp_route)) {
 212                 uint32_t rflags;
 213                 if (sscanf(line, "00000000000000000000000000000000 00 "
 214                                 "%*s %*s %*s %*s %*s %*s %*s %15s", ifname) &&
 215                                 strcmp(ifname, "lo")) {
 216                         found_default = true;
 217                 } else if (sscanf(line, "%8" SCNx32 "%8" SCNx32 "%*8" SCNx32 "%*8" SCNx32 " %hhx %*s "
 218                                 "%*s 00000000000000000000000000000000 %*s %*s %*s %" SCNx32 " lo",
 219                                 &p.addr.s6_addr32[0], &p.addr.s6_addr32[1], &p.prefix, &rflags) &&
 220                                 p.prefix > 0 && (rflags & RTF_NONEXTHOP) && (rflags & RTF_REJECT)) {
 221                         // Find source prefixes by scanning through unreachable-routes
 222                         p.addr.s6_addr32[0] = htonl(p.addr.s6_addr32[0]);
 223                         p.addr.s6_addr32[1] = htonl(p.addr.s6_addr32[1]);
 224
 225                         for (ssize_t i = 0; i < len; ++i) {
 226                                 if (n[i].prefix <= 64 && n[i].prefix >= p.prefix &&
 227                                                 match_route(&p, &n[i].addr)) {
 228                                         n[i].prefix = p.prefix;
 229                                         break;
 230                                 }
 231                         }
 232
 233                 }
 234         }
 235
 236         return found_default;
 237 }
 238
 239
 240 // Router Advert server mode
 241 static void send_router_advert(struct uloop_timeout *event)
 242 {
 243         struct interface *iface =
 244                         container_of(event, struct interface, timer_rs);
 245
 246         int mtu = odhcpd_get_interface_mtu(iface->ifname);
 247         if (mtu < 0)
 248                 mtu = 1500;
 249
 250         struct {
 251                 struct nd_router_advert h;
 252                 struct icmpv6_opt lladdr;
 253                 struct nd_opt_mtu mtu;
 254                 struct nd_opt_prefix_info prefix[RELAYD_MAX_PREFIXES];
 255         } adv = {
 256                 .h = {{.icmp6_type = ND_ROUTER_ADVERT, .icmp6_code = 0}, 0, 0},
 257                 .lladdr = {ND_OPT_SOURCE_LINKADDR, 1, {0}},
 258                 .mtu = {ND_OPT_MTU, 1, 0, htonl(mtu)},
 259         };
 260
 261         if (iface->dhcpv6)
 262                 adv.h.nd_ra_flags_reserved = ND_RA_FLAG_OTHER;
 263
 264         if (iface->managed >= RELAYD_MANAGED_MFLAG)
 265                 adv.h.nd_ra_flags_reserved |= ND_RA_FLAG_MANAGED;
 266
 267         if (iface->route_preference < 0)
 268                 adv.h.nd_ra_flags_reserved |= ND_RA_PREF_LOW;
 269         else if (iface->route_preference > 0)
 270                 adv.h.nd_ra_flags_reserved |= ND_RA_PREF_HIGH;
 271         odhcpd_get_mac(iface, adv.lladdr.data);
 272
 273         // If not currently shutting down
 274         struct odhcpd_ipaddr addrs[RELAYD_MAX_PREFIXES];
 275         ssize_t ipcnt = 0;
 276
 277         // If not shutdown
 278         if (event->cb) {
 279                 ipcnt = odhcpd_get_interface_addresses(iface->ifindex,
 280                                 addrs, ARRAY_SIZE(addrs));
 281
 282                 // Check default route
 283                 if (parse_routes(addrs, ipcnt) || iface->default_router > 1)
 284                         adv.h.nd_ra_router_lifetime =
 285                                         htons(3 * MaxRtrAdvInterval);
 286         }
 287
 288         // Construct Prefix Information options
 289         bool have_public = false;
 290         size_t cnt = 0;
 291
 292         struct in6_addr *dns_addr = NULL;
 293         uint32_t dns_time = 0;
 294         size_t dns_cnt = 1;
 295
 296         for (ssize_t i = 0; i < ipcnt; ++i) {
 297                 struct odhcpd_ipaddr *addr = &addrs[i];
 298                 if (addr->prefix > 64 || addr->has_class)
 299                         continue; // Address not suitable
 300
 301                 if (addr->preferred > MaxPreferredTime)
 302                         addr->preferred = MaxPreferredTime;
 303
 304                 if (addr->valid > MaxValidTime)
 305                         addr->valid = MaxValidTime;
 306
 307                 struct nd_opt_prefix_info *p = NULL;
 308                 for (size_t i = 0; i < cnt; ++i) {
 309                         if (!memcmp(&adv.prefix[i].nd_opt_pi_prefix,
 310                                         &addr->addr, 8))
 311                                 p = &adv.prefix[i];
 312                 }
 313
 314                 if (!p) {
 315                         if (cnt >= ARRAY_SIZE(adv.prefix))
 316                                 break;
 317
 318                         p = &adv.prefix[cnt++];
 319                 }
 320
 321                 if ((addr->addr.s6_addr[0] & 0xfe) != 0xfc && addr->preferred > 0)
 322                         have_public = true;
 323
 324                 memcpy(&p->nd_opt_pi_prefix, &addr->addr, 8);
 325                 p->nd_opt_pi_type = ND_OPT_PREFIX_INFORMATION;
 326                 p->nd_opt_pi_len = 4;
 327                 p->nd_opt_pi_prefix_len = 64;
 328                 p->nd_opt_pi_flags_reserved = 0;
 329                 if (!iface->ra_not_onlink)
 330                         p->nd_opt_pi_flags_reserved |= ND_OPT_PI_FLAG_ONLINK;
 331                 if (iface->managed < RELAYD_MANAGED_NO_AFLAG)
 332                         p->nd_opt_pi_flags_reserved |= ND_OPT_PI_FLAG_AUTO;
 333                 p->nd_opt_pi_valid_time = htonl(addr->valid);
 334                 p->nd_opt_pi_preferred_time = htonl(addr->preferred);
 335
 336                 if (addr->preferred > dns_time) {
 337                         dns_time = addr->preferred;
 338                         dns_addr = &addr->addr;
 339                 }
 340         }
 341
 342         if (!have_public && !iface->default_router && adv.h.nd_ra_router_lifetime) {
 343                 syslog(LOG_WARNING, "A default route is present but there is no public prefix "
 344                                 "on %s thus we don't announce a default route!", iface->ifname);
 345                 adv.h.nd_ra_router_lifetime = 0;
 346         }
 347
 348         // DNS Recursive DNS
 349         if (iface->dns_cnt > 0) {
 350                 dns_addr = iface->dns;
 351                 dns_cnt = iface->dns_cnt;
 352                 dns_time = 2 * MaxRtrAdvInterval;
 353         }
 354
 355         if (!dns_addr)
 356                 dns_cnt = 0;
 357
 358         struct {
 359                 uint8_t type;
 360                 uint8_t len;
 361                 uint8_t pad;
 362                 uint8_t pad2;
 363                 uint32_t lifetime;
 364         } dns = {ND_OPT_RECURSIVE_DNS, (1 + (2 * dns_cnt)), 0, 0, htonl(dns_time)};
 365
 366
 367
 368         // DNS Search options
 369         uint8_t search_buf[256], *search_domain = iface->search;
 370         size_t search_len = iface->search_len, search_padded = 0;
 371
 372         if (!search_domain && !res_init() && _res.dnsrch[0] && _res.dnsrch[0][0]) {
 373                 int len = dn_comp(_res.dnsrch[0], search_buf,
 374                                 sizeof(search_buf), NULL, NULL);
 375                 if (len > 0) {
 376                         search_domain = search_buf;
 377                         search_len = len;
 378                 }
 379         }
 380
 381         if (search_len > 0)
 382                 search_padded = ((search_len + 7) & (~7)) + 8;
 383
 384         struct {
 385                 uint8_t type;
 386                 uint8_t len;
 387                 uint8_t pad;
 388                 uint8_t pad2;
 389                 uint32_t lifetime;
 390                 uint8_t name[];
 391         } *search = alloca(sizeof(*search) + search_padded);
 392
 393         if (!search) {
 394                 syslog(LOG_ERR, "Alloca failed for dns search on interface %s", iface->ifname);
 395                 return;
 396         }
 397         search->type = ND_OPT_DNS_SEARCH;
 398         search->len = search_len ? ((sizeof(*search) + search_padded) / 8) : 0;
 399         search->pad = 0;
 400         search->pad2 = 0;
 401         search->lifetime = htonl(2 * MaxRtrAdvInterval);;
 402         memcpy(search->name, search_domain, search_len);
 403         memset(&search->name[search_len], 0, search_padded - search_len);
 404
 405
 406         size_t routes_cnt = 0;
 407         struct {
 408                 uint8_t type;
 409                 uint8_t len;
 410                 uint8_t prefix;
 411                 uint8_t flags;
 412                 uint32_t lifetime;
 413                 uint32_t addr[4];
 414         } routes[RELAYD_MAX_PREFIXES];
 415
 416         for (ssize_t i = 0; i < ipcnt; ++i) {
 417                 struct odhcpd_ipaddr *addr = &addrs[i];
 418                 if (addr->prefix > 64 || addr->prefix == 0) {
 419                         continue; // Address not suitable
 420                 } else if (addr->prefix > 32) {
 421                         addr->addr.s6_addr32[1] &= htonl(~((1U << (64 - addr->prefix)) - 1));
 422                 } else if (addr->prefix <= 32) {
 423                         addr->addr.s6_addr32[0] &= htonl(~((1U << (32 - addr->prefix)) - 1));
 424                         addr->addr.s6_addr32[1] = 0;
 425                 }
 426
 427                 routes[routes_cnt].type = ND_OPT_ROUTE_INFO;
 428                 routes[routes_cnt].len = sizeof(*routes) / 8;
 429                 routes[routes_cnt].prefix = addr->prefix;
 430                 routes[routes_cnt].flags = 0;
 431                 if (iface->route_preference < 0)
 432                         routes[routes_cnt].flags |= ND_RA_PREF_LOW;
 433                 else if (iface->route_preference > 0)
 434                         routes[routes_cnt].flags |= ND_RA_PREF_HIGH;
 435                 routes[routes_cnt].lifetime = htonl(addr->valid);
 436                 routes[routes_cnt].addr[0] = addr->addr.s6_addr32[0];
 437                 routes[routes_cnt].addr[1] = addr->addr.s6_addr32[1];
 438                 routes[routes_cnt].addr[2] = addr->addr.s6_addr32[2];
 439                 routes[routes_cnt].addr[3] = addr->addr.s6_addr32[3];
 440
 441                 ++routes_cnt;
 442         }
 443
 444
 445         struct iovec iov[] = {{&adv, (uint8_t*)&adv.prefix[cnt] - (uint8_t*)&adv},
 446                         {&routes, routes_cnt * sizeof(*routes)},
 447                         {&dns, (dns_cnt) ? sizeof(dns) : 0},
 448                         {dns_addr, dns_cnt * sizeof(*dns_addr)},
 449                         {search, search->len * 8}};
 450         struct sockaddr_in6 all_nodes = {AF_INET6, 0, 0, ALL_IPV6_NODES, 0};
 451         odhcpd_send(router_event.uloop.fd,
 452                         &all_nodes, iov, ARRAY_SIZE(iov), iface);
 453
 454         // Rearm timer
 455         int msecs;
 456         odhcpd_urandom(&msecs, sizeof(msecs));
 457         msecs = (labs(msecs) % (1000 * (MaxRtrAdvInterval
 458                         - MinRtrAdvInterval))) + (MinRtrAdvInterval * 1000);
 459         uloop_timeout_set(&iface->timer_rs, msecs);
 460 }
 461
 462
 463 // Forward router solicitation
 464 static void forward_router_solicitation(const struct interface *iface)
 465 {
 466         if (!iface)
 467                 return;
 468
 469         struct icmp6_hdr rs = {ND_ROUTER_SOLICIT, 0, 0, {{0}}};
 470         struct iovec iov = {&rs, sizeof(rs)};
 471         struct sockaddr_in6 all_routers =
 472                 {AF_INET6, 0, 0, ALL_IPV6_ROUTERS, iface->ifindex};
 473
 474         syslog(LOG_NOTICE, "Sending RS to %s", iface->ifname);
 475         odhcpd_send(router_event.uloop.fd, &all_routers, &iov, 1, iface);
 476 }
 477
 478
 479 // Handler for incoming router solicitations on slave interfaces
 480 static void forward_router_advertisement(uint8_t *data, size_t len)
 481 {
 482         struct nd_router_advert *adv = (struct nd_router_advert *)data;
 483
 484         // Rewrite options
 485         uint8_t *end = data + len;
 486         uint8_t *mac_ptr = NULL;
 487         struct in6_addr *dns_ptr = NULL;
 488         size_t dns_count = 0;
 489
 490         struct icmpv6_opt *opt;
 491         icmpv6_for_each_option(opt, &adv[1], end) {
 492                 if (opt->type == ND_OPT_SOURCE_LINKADDR) {
 493                         // Store address of source MAC-address
 494                         mac_ptr = opt->data;
 495                 } else if (opt->type == ND_OPT_RECURSIVE_DNS && opt->len > 1) {
 496                         // Check if we have to rewrite DNS
 497                         dns_ptr = (struct in6_addr*)&opt->data[6];
 498                         dns_count = (opt->len - 1) / 2;
 499                 }
 500         }
 501
 502         syslog(LOG_NOTICE, "Got a RA");
 503
 504         // Indicate a proxy, however we don't follow the rest of RFC 4389 yet
 505         adv->nd_ra_flags_reserved |= ND_RA_FLAG_PROXY;
 506
 507         // Forward advertisement to all slave interfaces
 508         struct sockaddr_in6 all_nodes = {AF_INET6, 0, 0, ALL_IPV6_NODES, 0};
 509         struct iovec iov = {data, len};
 510
 511         struct odhcpd_ipaddr addr;
 512         struct interface *iface;
 513         list_for_each_entry(iface, &interfaces, head) {
 514                 if (iface->ra != RELAYD_RELAY || iface->master)
 515                         continue;
 516
 517                 // Fixup source hardware address option
 518                 if (mac_ptr)
 519                         odhcpd_get_mac(iface, mac_ptr);
 520
 521                 // If we have to rewrite DNS entries
 522                 if (iface->always_rewrite_dns && dns_ptr && dns_count > 0) {
 523                         const struct in6_addr *rewrite = iface->dns;
 524                         size_t rewrite_cnt = iface->dns_cnt;
 525
 526                         if (rewrite_cnt == 0) {
 527                                 if (odhcpd_get_interface_addresses(iface->ifindex, &addr, 1) < 1)
 528                                         continue; // Unable to comply
 529
 530                                 rewrite = &addr.addr;
 531                                 rewrite_cnt = 1;
 532                         }
 533
 534                         // Copy over any other addresses
 535                         for (size_t i = 0; i < dns_count; ++i) {
 536                                 size_t j = (i < rewrite_cnt) ? i : rewrite_cnt - 1;
 537                                 dns_ptr[i] = rewrite[j];
 538                         }
 539                 }
 540
 541                 odhcpd_send(router_event.uloop.fd, &all_nodes, &iov, 1, iface);
 542         }
 543 }