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
 134 // Event handler for incoming ICMPv6 packets
 135 static void handle_icmpv6(_unused void *addr, void *data, size_t len,
 136                 struct interface *iface)
 137 {
 138         struct icmp6_hdr *hdr = data;
 139         if ((iface->ra == RELAYD_SERVER && !iface->master)) { // Server mode
 140                 if (hdr->icmp6_type == ND_ROUTER_SOLICIT)
 141                         send_router_advert(&iface->timer_rs);
 142         } else if (iface->ra == RELAYD_RELAY) { // Relay mode
 143                 if (hdr->icmp6_type == ND_ROUTER_ADVERT && iface->master)
 144                         forward_router_advertisement(data, len);
 145                 else if (hdr->icmp6_type == ND_ROUTER_SOLICIT && !iface->master)
 146                         forward_router_solicitation(odhcpd_get_master_interface());
 147         }
 148 }
 149
 150
 151 static bool match_route(const struct odhcpd_ipaddr *n, const struct in6_addr *addr)
 152 {
 153         if (n->prefix <= 32)
 154                 return ntohl(n->addr.s6_addr32[0]) >> (32 - n->prefix) ==
 155                                 ntohl(addr->s6_addr32[0]) >> (32 - n->prefix);
 156
 157         if (n->addr.s6_addr32[0] != addr->s6_addr32[0])
 158                 return false;
 159
 160         return ntohl(n->addr.s6_addr32[1]) >> (64 - n->prefix) ==
 161                         ntohl(addr->s6_addr32[1]) >> (64 - n->prefix);
 162 }
 163
 164
 165 // Detect whether a default route exists, also find the source prefixes
 166 static bool parse_routes(struct odhcpd_ipaddr *n, ssize_t len)
 167 {
 168         rewind(fp_route);
 169
 170         char line[512], ifname[16];
 171         bool found_default = false;
 172         struct odhcpd_ipaddr p = {IN6ADDR_ANY_INIT, 0, false, 0, 0, 0};
 173         while (fgets(line, sizeof(line), fp_route)) {
 174                 uint32_t rflags;
 175                 if (sscanf(line, "00000000000000000000000000000000 00 "
 176                                 "%*s %*s %*s %*s %*s %*s %*s %15s", ifname) &&
 177                                 strcmp(ifname, "lo")) {
 178                         found_default = true;
 179                 } else if (sscanf(line, "%8" SCNx32 "%8" SCNx32 "%*8" SCNx32 "%*8" SCNx32 " %hhx %*s "
 180                                 "%*s 00000000000000000000000000000000 %*s %*s %*s %" SCNx32 " lo",
 181                                 &p.addr.s6_addr32[0], &p.addr.s6_addr32[1], &p.prefix, &rflags) &&
 182                                 p.prefix > 0 && (rflags & RTF_NONEXTHOP) && (rflags & RTF_REJECT)) {
 183                         // Find source prefixes by scanning through unreachable-routes
 184                         p.addr.s6_addr32[0] = htonl(p.addr.s6_addr32[0]);
 185                         p.addr.s6_addr32[1] = htonl(p.addr.s6_addr32[1]);
 186
 187                         for (ssize_t i = 0; i < len; ++i) {
 188                                 if (n[i].prefix <= 64 && n[i].prefix >= p.prefix &&
 189                                                 match_route(&p, &n[i].addr)) {
 190                                         n[i].prefix = p.prefix;
 191                                         break;
 192                                 }
 193                         }
 194
 195                 }
 196         }
 197
 198         return found_default;
 199 }
 200
 201
 202 // Router Advert server mode
 203 static void send_router_advert(struct uloop_timeout *event)
 204 {
 205         struct interface *iface =
 206                         container_of(event, struct interface, timer_rs);
 207
 208         int mtu = odhcpd_get_interface_mtu(iface->ifname);
 209         if (mtu < 0)
 210                 mtu = 1500;
 211
 212         struct {
 213                 struct nd_router_advert h;
 214                 struct icmpv6_opt lladdr;
 215                 struct nd_opt_mtu mtu;
 216                 struct nd_opt_prefix_info prefix[RELAYD_MAX_PREFIXES];
 217         } adv = {
 218                 .h = {{.icmp6_type = ND_ROUTER_ADVERT, .icmp6_code = 0}, 0, 0},
 219                 .lladdr = {ND_OPT_SOURCE_LINKADDR, 1, {0}},
 220                 .mtu = {ND_OPT_MTU, 1, 0, htonl(mtu)},
 221         };
 222         adv.h.nd_ra_flags_reserved = ND_RA_FLAG_OTHER;
 223         if (iface->managed >= RELAYD_MANAGED_MFLAG)
 224                 adv.h.nd_ra_flags_reserved |= ND_RA_FLAG_MANAGED;
 225
 226         if (iface->route_preference < 0)
 227                 adv.h.nd_ra_flags_reserved |= ND_RA_PREF_LOW;
 228         else if (iface->route_preference > 0)
 229                 adv.h.nd_ra_flags_reserved |= ND_RA_PREF_HIGH;
 230         odhcpd_get_mac(iface, adv.lladdr.data);
 231
 232         // If not currently shutting down
 233         struct odhcpd_ipaddr addrs[RELAYD_MAX_PREFIXES];
 234         ssize_t ipcnt = 0;
 235
 236         // If not shutdown
 237         if (event->cb) {
 238                 ipcnt = odhcpd_get_interface_addresses(iface->ifindex,
 239                                 addrs, ARRAY_SIZE(addrs));
 240
 241                 // Check default route
 242                 if (parse_routes(addrs, ipcnt) || iface->default_router > 1)
 243                         adv.h.nd_ra_router_lifetime =
 244                                         htons(3 * MaxRtrAdvInterval);
 245         }
 246
 247         // Construct Prefix Information options
 248         bool have_public = false;
 249         size_t cnt = 0;
 250
 251         struct in6_addr *dns_addr = NULL;
 252         uint32_t dns_time = 0;
 253         size_t dns_cnt = 1;
 254
 255         for (ssize_t i = 0; i < ipcnt; ++i) {
 256                 struct odhcpd_ipaddr *addr = &addrs[i];
 257                 if (addr->prefix > 64 || addr->has_class)
 258                         continue; // Address not suitable
 259
 260                 if (addr->preferred > MaxPreferredTime)
 261                         addr->preferred = MaxPreferredTime;
 262
 263                 if (addr->valid > MaxValidTime)
 264                         addr->valid = MaxValidTime;
 265
 266                 struct nd_opt_prefix_info *p = NULL;
 267                 for (size_t i = 0; i < cnt; ++i) {
 268                         if (!memcmp(&adv.prefix[i].nd_opt_pi_prefix,
 269                                         &addr->addr, 8))
 270                                 p = &adv.prefix[i];
 271                 }
 272
 273                 if (!p) {
 274                         if (cnt >= ARRAY_SIZE(adv.prefix))
 275                                 break;
 276
 277                         p = &adv.prefix[cnt++];
 278                 }
 279
 280                 if ((addr->addr.s6_addr[0] & 0xfe) != 0xfc && addr->preferred > 0)
 281                         have_public = true;
 282
 283                 memcpy(&p->nd_opt_pi_prefix, &addr->addr, 8);
 284                 p->nd_opt_pi_type = ND_OPT_PREFIX_INFORMATION;
 285                 p->nd_opt_pi_len = 4;
 286                 p->nd_opt_pi_prefix_len = 64;
 287                 p->nd_opt_pi_flags_reserved = 0;
 288                 if (!iface->ra_not_onlink)
 289                         p->nd_opt_pi_flags_reserved |= ND_OPT_PI_FLAG_ONLINK;
 290                 if (iface->managed < RELAYD_MANAGED_NO_AFLAG)
 291                         p->nd_opt_pi_flags_reserved |= ND_OPT_PI_FLAG_AUTO;
 292                 p->nd_opt_pi_valid_time = htonl(addr->valid);
 293                 p->nd_opt_pi_preferred_time = htonl(addr->preferred);
 294
 295                 if (addr->preferred > dns_time) {
 296                         dns_time = addr->preferred;
 297                         dns_addr = &addr->addr;
 298                 }
 299         }
 300
 301         if (!have_public && !iface->default_router && adv.h.nd_ra_router_lifetime) {
 302                 syslog(LOG_WARNING, "A default route is present but there is no public prefix "
 303                                 "on %s thus we don't announce a default route!", iface->ifname);
 304                 adv.h.nd_ra_router_lifetime = 0;
 305         }
 306
 307         if (have_public && iface->deprecate_ula_if_public_avail)
 308                 for (size_t i = 0; i < cnt; ++i)
 309                         if ((adv.prefix[i].nd_opt_pi_prefix.s6_addr[0] & 0xfe) == 0xfc)
 310                                 adv.prefix[i].nd_opt_pi_preferred_time = 0;
 311
 312         // DNS Recursive DNS
 313         if (iface->dns_cnt > 0) {
 314                 dns_addr = iface->dns;
 315                 dns_cnt = iface->dns_cnt;
 316                 dns_time = 2 * MaxRtrAdvInterval;
 317         }
 318
 319         if (!dns_addr)
 320                 dns_cnt = 0;
 321
 322         struct {
 323                 uint8_t type;
 324                 uint8_t len;
 325                 uint8_t pad;
 326                 uint8_t pad2;
 327                 uint32_t lifetime;
 328         } dns = {ND_OPT_RECURSIVE_DNS, (1 + (2 * dns_cnt)), 0, 0, htonl(dns_time)};
 329
 330
 331
 332         // DNS Search options
 333         uint8_t search_buf[256], *search_domain = iface->search;
 334         size_t search_len = iface->search_len, search_padded = 0;
 335
 336         if (!search_domain && !res_init() && _res.dnsrch[0] && _res.dnsrch[0][0]) {
 337                 int len = dn_comp(_res.dnsrch[0], search_buf,
 338                                 sizeof(search_buf), NULL, NULL);
 339                 if (len > 0) {
 340                         search_domain = search_buf;
 341                         search_len = len;
 342                 }
 343         }
 344
 345         if (search_len > 0)
 346                 search_padded = ((search_len + 7) & (~7)) + 8;
 347
 348         struct {
 349                 uint8_t type;
 350                 uint8_t len;
 351                 uint8_t pad;
 352                 uint8_t pad2;
 353                 uint32_t lifetime;
 354                 uint8_t name[];
 355         } *search = alloca(sizeof(*search) + search_padded);
 356
 357         if (!search) {
 358                 syslog(LOG_ERR, "Alloca failed for dns search on interface %s", iface->ifname);
 359                 return;
 360         }
 361         search->type = ND_OPT_DNS_SEARCH;
 362         search->len = search_len ? ((sizeof(*search) + search_padded) / 8) : 0;
 363         search->pad = 0;
 364         search->pad2 = 0;
 365         search->lifetime = htonl(2 * MaxRtrAdvInterval);;
 366         memcpy(search->name, search_domain, search_len);
 367         memset(&search->name[search_len], 0, search_padded - search_len);
 368
 369
 370         size_t routes_cnt = 0;
 371         struct {
 372                 uint8_t type;
 373                 uint8_t len;
 374                 uint8_t prefix;
 375                 uint8_t flags;
 376                 uint32_t lifetime;
 377                 uint32_t addr[4];
 378         } routes[RELAYD_MAX_PREFIXES];
 379
 380         for (ssize_t i = 0; i < ipcnt; ++i) {
 381                 struct odhcpd_ipaddr *addr = &addrs[i];
 382                 if (addr->prefix > 64 || addr->prefix == 0) {
 383                         continue; // Address not suitable
 384                 } else if (addr->prefix > 32) {
 385                         addr->addr.s6_addr32[1] &= htonl(~((1U << (64 - addr->prefix)) - 1));
 386                 } else if (addr->prefix <= 32) {
 387                         addr->addr.s6_addr32[0] &= htonl(~((1U << (32 - addr->prefix)) - 1));
 388                         addr->addr.s6_addr32[1] = 0;
 389                 }
 390
 391                 routes[routes_cnt].type = ND_OPT_ROUTE_INFO;
 392                 routes[routes_cnt].len = sizeof(*routes) / 8;
 393                 routes[routes_cnt].prefix = addr->prefix;
 394                 routes[routes_cnt].flags = 0;
 395                 if (iface->route_preference < 0)
 396                         routes[routes_cnt].flags |= ND_RA_PREF_LOW;
 397                 else if (iface->route_preference > 0)
 398                         routes[routes_cnt].flags |= ND_RA_PREF_HIGH;
 399                 routes[routes_cnt].lifetime = htonl(addr->valid);
 400                 routes[routes_cnt].addr[0] = addr->addr.s6_addr32[0];
 401                 routes[routes_cnt].addr[1] = addr->addr.s6_addr32[1];
 402                 routes[routes_cnt].addr[2] = addr->addr.s6_addr32[2];
 403                 routes[routes_cnt].addr[3] = addr->addr.s6_addr32[3];
 404
 405                 ++routes_cnt;
 406         }
 407
 408
 409         struct iovec iov[] = {{&adv, (uint8_t*)&adv.prefix[cnt] - (uint8_t*)&adv},
 410                         {&routes, routes_cnt * sizeof(*routes)},
 411                         {&dns, (dns_cnt) ? sizeof(dns) : 0},
 412                         {dns_addr, dns_cnt * sizeof(*dns_addr)},
 413                         {search, search->len * 8}};
 414         struct sockaddr_in6 all_nodes = {AF_INET6, 0, 0, ALL_IPV6_NODES, 0};
 415         odhcpd_send(router_event.uloop.fd,
 416                         &all_nodes, iov, ARRAY_SIZE(iov), iface);
 417
 418         // Rearm timer
 419         int msecs;
 420         odhcpd_urandom(&msecs, sizeof(msecs));
 421         msecs = (labs(msecs) % (1000 * (MaxRtrAdvInterval
 422                         - MinRtrAdvInterval))) + (MinRtrAdvInterval * 1000);
 423         uloop_timeout_set(&iface->timer_rs, msecs);
 424 }
 425
 426
 427 // Forward router solicitation
 428 static void forward_router_solicitation(const struct interface *iface)
 429 {
 430         if (!iface)
 431                 return;
 432
 433         struct icmp6_hdr rs = {ND_ROUTER_SOLICIT, 0, 0, {{0}}};
 434         struct iovec iov = {&rs, sizeof(rs)};
 435         struct sockaddr_in6 all_routers =
 436                 {AF_INET6, 0, 0, ALL_IPV6_ROUTERS, iface->ifindex};
 437
 438         syslog(LOG_NOTICE, "Sending RS to %s", iface->ifname);
 439         odhcpd_send(router_event.uloop.fd, &all_routers, &iov, 1, iface);
 440 }
 441
 442
 443 // Handler for incoming router solicitations on slave interfaces
 444 static void forward_router_advertisement(uint8_t *data, size_t len)
 445 {
 446         struct nd_router_advert *adv = (struct nd_router_advert *)data;
 447
 448         // Rewrite options
 449         uint8_t *end = data + len;
 450         uint8_t *mac_ptr = NULL;
 451         struct in6_addr *dns_ptr = NULL;
 452         size_t dns_count = 0;
 453
 454         struct icmpv6_opt *opt;
 455         icmpv6_for_each_option(opt, &adv[1], end) {
 456                 if (opt->type == ND_OPT_SOURCE_LINKADDR) {
 457                         // Store address of source MAC-address
 458                         mac_ptr = opt->data;
 459                 } else if (opt->type == ND_OPT_RECURSIVE_DNS && opt->len > 1) {
 460                         // Check if we have to rewrite DNS
 461                         dns_ptr = (struct in6_addr*)&opt->data[6];
 462                         dns_count = (opt->len - 1) / 2;
 463                 }
 464         }
 465
 466         syslog(LOG_NOTICE, "Got a RA");
 467
 468         // Indicate a proxy, however we don't follow the rest of RFC 4389 yet
 469         adv->nd_ra_flags_reserved |= ND_RA_FLAG_PROXY;
 470
 471         // Forward advertisement to all slave interfaces
 472         struct sockaddr_in6 all_nodes = {AF_INET6, 0, 0, ALL_IPV6_NODES, 0};
 473         struct iovec iov = {data, len};
 474
 475         struct odhcpd_ipaddr addr;
 476         struct interface *iface;
 477         list_for_each_entry(iface, &interfaces, head) {
 478                 if (iface->ra != RELAYD_RELAY || iface->master)
 479                         continue;
 480
 481                 // Fixup source hardware address option
 482                 if (mac_ptr)
 483                         odhcpd_get_mac(iface, mac_ptr);
 484
 485                 // If we have to rewrite DNS entries
 486                 if (iface->always_rewrite_dns && dns_ptr && dns_count > 0) {
 487                         const struct in6_addr *rewrite = iface->dns;
 488                         size_t rewrite_cnt = iface->dns_cnt;
 489
 490                         if (rewrite_cnt == 0) {
 491                                 if (odhcpd_get_interface_addresses(iface->ifindex, &addr, 1) < 1)
 492                                         continue; // Unable to comply
 493
 494                                 rewrite = &addr.addr;
 495                                 rewrite_cnt = 1;
 496                         }
 497
 498                         // Copy over any other addresses
 499                         for (size_t i = 0; i < dns_count; ++i) {
 500                                 size_t j = (i < rewrite_cnt) ? i : rewrite_cnt - 1;
 501                                 dns_ptr[i] = rewrite[j];
 502                         }
 503                 }
 504
 505                 odhcpd_send(router_event.uloop.fd, &all_nodes, &iov, 1, iface);
 506         }
 507 }