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
 223         if (iface->dhcpv6)
 224                 adv.h.nd_ra_flags_reserved = ND_RA_FLAG_OTHER;
 225
 226         if (iface->managed >= RELAYD_MANAGED_MFLAG)
 227                 adv.h.nd_ra_flags_reserved |= ND_RA_FLAG_MANAGED;
 228
 229         if (iface->route_preference < 0)
 230                 adv.h.nd_ra_flags_reserved |= ND_RA_PREF_LOW;
 231         else if (iface->route_preference > 0)
 232                 adv.h.nd_ra_flags_reserved |= ND_RA_PREF_HIGH;
 233         odhcpd_get_mac(iface, adv.lladdr.data);
 234
 235         // If not currently shutting down
 236         struct odhcpd_ipaddr addrs[RELAYD_MAX_PREFIXES];
 237         ssize_t ipcnt = 0;
 238
 239         // If not shutdown
 240         if (event->cb) {
 241                 ipcnt = odhcpd_get_interface_addresses(iface->ifindex,
 242                                 addrs, ARRAY_SIZE(addrs));
 243
 244                 // Check default route
 245                 if (parse_routes(addrs, ipcnt) || iface->default_router > 1)
 246                         adv.h.nd_ra_router_lifetime =
 247                                         htons(3 * MaxRtrAdvInterval);
 248         }
 249
 250         // Construct Prefix Information options
 251         bool have_public = false;
 252         size_t cnt = 0;
 253
 254         struct in6_addr *dns_addr = NULL;
 255         uint32_t dns_time = 0;
 256         size_t dns_cnt = 1;
 257
 258         for (ssize_t i = 0; i < ipcnt; ++i) {
 259                 struct odhcpd_ipaddr *addr = &addrs[i];
 260                 if (addr->prefix > 64 || addr->has_class)
 261                         continue; // Address not suitable
 262
 263                 if (addr->preferred > MaxPreferredTime)
 264                         addr->preferred = MaxPreferredTime;
 265
 266                 if (addr->valid > MaxValidTime)
 267                         addr->valid = MaxValidTime;
 268
 269                 struct nd_opt_prefix_info *p = NULL;
 270                 for (size_t i = 0; i < cnt; ++i) {
 271                         if (!memcmp(&adv.prefix[i].nd_opt_pi_prefix,
 272                                         &addr->addr, 8))
 273                                 p = &adv.prefix[i];
 274                 }
 275
 276                 if (!p) {
 277                         if (cnt >= ARRAY_SIZE(adv.prefix))
 278                                 break;
 279
 280                         p = &adv.prefix[cnt++];
 281                 }
 282
 283                 if ((addr->addr.s6_addr[0] & 0xfe) != 0xfc && addr->preferred > 0)
 284                         have_public = true;
 285
 286                 memcpy(&p->nd_opt_pi_prefix, &addr->addr, 8);
 287                 p->nd_opt_pi_type = ND_OPT_PREFIX_INFORMATION;
 288                 p->nd_opt_pi_len = 4;
 289                 p->nd_opt_pi_prefix_len = 64;
 290                 p->nd_opt_pi_flags_reserved = 0;
 291                 if (!iface->ra_not_onlink)
 292                         p->nd_opt_pi_flags_reserved |= ND_OPT_PI_FLAG_ONLINK;
 293                 if (iface->managed < RELAYD_MANAGED_NO_AFLAG)
 294                         p->nd_opt_pi_flags_reserved |= ND_OPT_PI_FLAG_AUTO;
 295                 p->nd_opt_pi_valid_time = htonl(addr->valid);
 296                 p->nd_opt_pi_preferred_time = htonl(addr->preferred);
 297
 298                 if (addr->preferred > dns_time) {
 299                         dns_time = addr->preferred;
 300                         dns_addr = &addr->addr;
 301                 }
 302         }
 303
 304         if (!have_public && !iface->default_router && adv.h.nd_ra_router_lifetime) {
 305                 syslog(LOG_WARNING, "A default route is present but there is no public prefix "
 306                                 "on %s thus we don't announce a default route!", iface->ifname);
 307                 adv.h.nd_ra_router_lifetime = 0;
 308         }
 309
 310         if (have_public && iface->deprecate_ula_if_public_avail)
 311                 for (size_t i = 0; i < cnt; ++i)
 312                         if ((adv.prefix[i].nd_opt_pi_prefix.s6_addr[0] & 0xfe) == 0xfc)
 313                                 adv.prefix[i].nd_opt_pi_preferred_time = 0;
 314
 315         // DNS Recursive DNS
 316         if (iface->dns_cnt > 0) {
 317                 dns_addr = iface->dns;
 318                 dns_cnt = iface->dns_cnt;
 319                 dns_time = 2 * MaxRtrAdvInterval;
 320         }
 321
 322         if (!dns_addr)
 323                 dns_cnt = 0;
 324
 325         struct {
 326                 uint8_t type;
 327                 uint8_t len;
 328                 uint8_t pad;
 329                 uint8_t pad2;
 330                 uint32_t lifetime;
 331         } dns = {ND_OPT_RECURSIVE_DNS, (1 + (2 * dns_cnt)), 0, 0, htonl(dns_time)};
 332
 333
 334
 335         // DNS Search options
 336         uint8_t search_buf[256], *search_domain = iface->search;
 337         size_t search_len = iface->search_len, search_padded = 0;
 338
 339         if (!search_domain && !res_init() && _res.dnsrch[0] && _res.dnsrch[0][0]) {
 340                 int len = dn_comp(_res.dnsrch[0], search_buf,
 341                                 sizeof(search_buf), NULL, NULL);
 342                 if (len > 0) {
 343                         search_domain = search_buf;
 344                         search_len = len;
 345                 }
 346         }
 347
 348         if (search_len > 0)
 349                 search_padded = ((search_len + 7) & (~7)) + 8;
 350
 351         struct {
 352                 uint8_t type;
 353                 uint8_t len;
 354                 uint8_t pad;
 355                 uint8_t pad2;
 356                 uint32_t lifetime;
 357                 uint8_t name[];
 358         } *search = alloca(sizeof(*search) + search_padded);
 359
 360         if (!search) {
 361                 syslog(LOG_ERR, "Alloca failed for dns search on interface %s", iface->ifname);
 362                 return;
 363         }
 364         search->type = ND_OPT_DNS_SEARCH;
 365         search->len = search_len ? ((sizeof(*search) + search_padded) / 8) : 0;
 366         search->pad = 0;
 367         search->pad2 = 0;
 368         search->lifetime = htonl(2 * MaxRtrAdvInterval);;
 369         memcpy(search->name, search_domain, search_len);
 370         memset(&search->name[search_len], 0, search_padded - search_len);
 371
 372
 373         size_t routes_cnt = 0;
 374         struct {
 375                 uint8_t type;
 376                 uint8_t len;
 377                 uint8_t prefix;
 378                 uint8_t flags;
 379                 uint32_t lifetime;
 380                 uint32_t addr[4];
 381         } routes[RELAYD_MAX_PREFIXES];
 382
 383         for (ssize_t i = 0; i < ipcnt; ++i) {
 384                 struct odhcpd_ipaddr *addr = &addrs[i];
 385                 if (addr->prefix > 64 || addr->prefix == 0) {
 386                         continue; // Address not suitable
 387                 } else if (addr->prefix > 32) {
 388                         addr->addr.s6_addr32[1] &= htonl(~((1U << (64 - addr->prefix)) - 1));
 389                 } else if (addr->prefix <= 32) {
 390                         addr->addr.s6_addr32[0] &= htonl(~((1U << (32 - addr->prefix)) - 1));
 391                         addr->addr.s6_addr32[1] = 0;
 392                 }
 393
 394                 routes[routes_cnt].type = ND_OPT_ROUTE_INFO;
 395                 routes[routes_cnt].len = sizeof(*routes) / 8;
 396                 routes[routes_cnt].prefix = addr->prefix;
 397                 routes[routes_cnt].flags = 0;
 398                 if (iface->route_preference < 0)
 399                         routes[routes_cnt].flags |= ND_RA_PREF_LOW;
 400                 else if (iface->route_preference > 0)
 401                         routes[routes_cnt].flags |= ND_RA_PREF_HIGH;
 402                 routes[routes_cnt].lifetime = htonl(addr->valid);
 403                 routes[routes_cnt].addr[0] = addr->addr.s6_addr32[0];
 404                 routes[routes_cnt].addr[1] = addr->addr.s6_addr32[1];
 405                 routes[routes_cnt].addr[2] = addr->addr.s6_addr32[2];
 406                 routes[routes_cnt].addr[3] = addr->addr.s6_addr32[3];
 407
 408                 ++routes_cnt;
 409         }
 410
 411
 412         struct iovec iov[] = {{&adv, (uint8_t*)&adv.prefix[cnt] - (uint8_t*)&adv},
 413                         {&routes, routes_cnt * sizeof(*routes)},
 414                         {&dns, (dns_cnt) ? sizeof(dns) : 0},
 415                         {dns_addr, dns_cnt * sizeof(*dns_addr)},
 416                         {search, search->len * 8}};
 417         struct sockaddr_in6 all_nodes = {AF_INET6, 0, 0, ALL_IPV6_NODES, 0};
 418         odhcpd_send(router_event.uloop.fd,
 419                         &all_nodes, iov, ARRAY_SIZE(iov), iface);
 420
 421         // Rearm timer
 422         int msecs;
 423         odhcpd_urandom(&msecs, sizeof(msecs));
 424         msecs = (labs(msecs) % (1000 * (MaxRtrAdvInterval
 425                         - MinRtrAdvInterval))) + (MinRtrAdvInterval * 1000);
 426         uloop_timeout_set(&iface->timer_rs, msecs);
 427 }
 428
 429
 430 // Forward router solicitation
 431 static void forward_router_solicitation(const struct interface *iface)
 432 {
 433         if (!iface)
 434                 return;
 435
 436         struct icmp6_hdr rs = {ND_ROUTER_SOLICIT, 0, 0, {{0}}};
 437         struct iovec iov = {&rs, sizeof(rs)};
 438         struct sockaddr_in6 all_routers =
 439                 {AF_INET6, 0, 0, ALL_IPV6_ROUTERS, iface->ifindex};
 440
 441         syslog(LOG_NOTICE, "Sending RS to %s", iface->ifname);
 442         odhcpd_send(router_event.uloop.fd, &all_routers, &iov, 1, iface);
 443 }
 444
 445
 446 // Handler for incoming router solicitations on slave interfaces
 447 static void forward_router_advertisement(uint8_t *data, size_t len)
 448 {
 449         struct nd_router_advert *adv = (struct nd_router_advert *)data;
 450
 451         // Rewrite options
 452         uint8_t *end = data + len;
 453         uint8_t *mac_ptr = NULL;
 454         struct in6_addr *dns_ptr = NULL;
 455         size_t dns_count = 0;
 456
 457         struct icmpv6_opt *opt;
 458         icmpv6_for_each_option(opt, &adv[1], end) {
 459                 if (opt->type == ND_OPT_SOURCE_LINKADDR) {
 460                         // Store address of source MAC-address
 461                         mac_ptr = opt->data;
 462                 } else if (opt->type == ND_OPT_RECURSIVE_DNS && opt->len > 1) {
 463                         // Check if we have to rewrite DNS
 464                         dns_ptr = (struct in6_addr*)&opt->data[6];
 465                         dns_count = (opt->len - 1) / 2;
 466                 }
 467         }
 468
 469         syslog(LOG_NOTICE, "Got a RA");
 470
 471         // Indicate a proxy, however we don't follow the rest of RFC 4389 yet
 472         adv->nd_ra_flags_reserved |= ND_RA_FLAG_PROXY;
 473
 474         // Forward advertisement to all slave interfaces
 475         struct sockaddr_in6 all_nodes = {AF_INET6, 0, 0, ALL_IPV6_NODES, 0};
 476         struct iovec iov = {data, len};
 477
 478         struct odhcpd_ipaddr addr;
 479         struct interface *iface;
 480         list_for_each_entry(iface, &interfaces, head) {
 481                 if (iface->ra != RELAYD_RELAY || iface->master)
 482                         continue;
 483
 484                 // Fixup source hardware address option
 485                 if (mac_ptr)
 486                         odhcpd_get_mac(iface, mac_ptr);
 487
 488                 // If we have to rewrite DNS entries
 489                 if (iface->always_rewrite_dns && dns_ptr && dns_count > 0) {
 490                         const struct in6_addr *rewrite = iface->dns;
 491                         size_t rewrite_cnt = iface->dns_cnt;
 492
 493                         if (rewrite_cnt == 0) {
 494                                 if (odhcpd_get_interface_addresses(iface->ifindex, &addr, 1) < 1)
 495                                         continue; // Unable to comply
 496
 497                                 rewrite = &addr.addr;
 498                                 rewrite_cnt = 1;
 499                         }
 500
 501                         // Copy over any other addresses
 502                         for (size_t i = 0; i < dns_count; ++i) {
 503                                 size_t j = (i < rewrite_cnt) ? i : rewrite_cnt - 1;
 504                                 dns_ptr[i] = rewrite[j];
 505                         }
 506                 }
 507
 508                 odhcpd_send(router_event.uloop.fd, &all_nodes, &iov, 1, iface);
 509         }
 510 }