bgp.c

   1 /*
   2  * BGPv4
   3  * Used to advertise routes for upstream (l2tp port, rather than gratiutious
   4  * arp) and downstream--allowing routers to load-balance both.
   5  *
   6  * Implementation limitations:
   7  * - We never listen for incoming connections (session always initiated by us).
   8  * - Any routes advertised by the peer are accepted, but ignored.
   9  * - No password support; neither RFC1771 (which no-one seems to do anyway)
  10  *   nor RFC2385 (which requires a kernel patch on 2.4 kernels).
  11  */
  12
  13 char const *cvs_id_bgp = "$Id: bgp.c,v 1.9 2004/12/16 08:49:52 bodea Exp $";
  14
  15 #include <stdlib.h>
  16 #include <unistd.h>
  17 #include <string.h>
  18 #include <time.h>
  19 #include <errno.h>
  20 #include <sys/socket.h>
  21 #include <netinet/in.h>
  22 #include <arpa/inet.h>
  23 #include <netdb.h>
  24 #include <fcntl.h>
  25
  26 #include "l2tpns.h"
  27 #include "bgp.h"
  28 #include "util.h"
  29
  30 static void bgp_clear(struct bgp_peer *peer);
  31 static void bgp_set_retry(struct bgp_peer *peer);
  32 static void bgp_cidr(in_addr_t ip, in_addr_t mask, struct bgp_ip_prefix *pfx);
  33 static struct bgp_route_list *bgp_insert_route(struct bgp_route_list *head,
  34     struct bgp_route_list *new);
  35
  36 static void bgp_free_routes(struct bgp_route_list *routes);
  37 static char const *bgp_msg_type_str(uint8_t type);
  38 static int bgp_connect(struct bgp_peer *peer);
  39 static int bgp_handle_connect(struct bgp_peer *peer);
  40 static int bgp_write(struct bgp_peer *peer);
  41 static int bgp_read(struct bgp_peer *peer);
  42 static int bgp_handle_input(struct bgp_peer *peer);
  43 static int bgp_send_open(struct bgp_peer *peer);
  44 static int bgp_send_keepalive(struct bgp_peer *peer);
  45 static int bgp_send_update(struct bgp_peer *peer);
  46 static int bgp_send_notification(struct bgp_peer *peer, uint8_t code,
  47     uint8_t subcode);
  48
  49 static uint16_t our_as;
  50 static struct bgp_route_list *bgp_routes = 0;
  51
  52 int bgp_configured = 0;
  53 struct bgp_peer *bgp_peers = 0;
  54
  55 /* prepare peer structure, globals */
  56 int bgp_setup(int as)
  57 {
  58     int i;
  59     struct bgp_peer *peer;
  60
  61     for (i = 0; i < BGP_NUM_PEERS; i++)
  62     {
  63         peer = &bgp_peers[i];
  64         memset(peer, 0, sizeof(*peer));
  65
  66         peer->addr = INADDR_NONE;
  67         peer->sock = -1;
  68         peer->state = peer->next_state = Disabled;
  69
  70         if (!((peer->outbuf = malloc(sizeof(*peer->outbuf)))
  71             && (peer->inbuf = malloc(sizeof(*peer->inbuf)))))
  72         {
  73             LOG(0, 0, 0, "Can't allocate buffers for bgp peer (%s)\n",
  74                 strerror(errno));
  75
  76             return 0;
  77         }
  78     }
  79
  80     if (as < 1)
  81         as = 0;
  82
  83     if ((our_as = as))
  84         return 0;
  85
  86     bgp_routes = 0;
  87     bgp_configured = 0; /* set by bgp_start */
  88
  89     return 1;
  90 }
  91
  92 /* start connection with a peer */
  93 int bgp_start(struct bgp_peer *peer, char *name, int as, int keepalive,
  94     int hold, int enable)
  95 {
  96     struct hostent *h;
  97     int ibgp;
  98     int i;
  99     struct bgp_path_attr a;
 100     char path_attrs[64];
 101     char *p = path_attrs;
 102     in_addr_t ip;
 103     uint32_t metric = htonl(BGP_METRIC);
 104     uint32_t no_export = htonl(BGP_COMMUNITY_NO_EXPORT);
 105
 106     if (!our_as)
 107         return 0;
 108
 109     if (peer->state != Disabled)
 110         bgp_halt(peer);
 111
 112     snprintf(peer->name, sizeof(peer->name), "%s", name);
 113
 114     if (!(h = gethostbyname(name)) || h->h_addrtype != AF_INET)
 115     {
 116         LOG(0, 0, 0, "Can't get address for BGP peer %s (%s)\n",
 117             name, h ? "no address" : hstrerror(h_errno));
 118
 119         return 0;
 120     }
 121
 122     memcpy(&peer->addr, h->h_addr, sizeof(peer->addr));
 123     peer->as = as > 0 ? as : our_as;
 124     ibgp = peer->as == our_as;
 125
 126     /* set initial timer values */
 127     peer->init_keepalive = keepalive == -1 ? BGP_KEEPALIVE_TIME : keepalive;
 128     peer->init_hold = hold == -1 ? BGP_HOLD_TIME : hold;
 129
 130     if (peer->init_hold < 3)
 131         peer->init_hold = 3;
 132
 133     if (peer->init_keepalive * 3 > peer->init_hold)
 134         peer->init_keepalive = peer->init_hold / 3;
 135
 136     /* clear buffers, go to Idle state */
 137     peer->next_state = Idle;
 138     bgp_clear(peer);
 139
 140     /* set initial routing state */
 141     peer->routing = enable;
 142
 143     /* all our routes use the same attributes, so prepare it in advance */
 144     if (peer->path_attrs)
 145         free(peer->path_attrs);
 146
 147     peer->path_attr_len = 0;
 148
 149     /* ORIGIN */
 150     a.flags = BGP_PATH_ATTR_FLAG_TRANS;
 151     a.code = BGP_PATH_ATTR_CODE_ORIGIN;
 152     a.data.s.len = 1;
 153     a.data.s.value[0] = BGP_PATH_ATTR_CODE_ORIGIN_IGP;
 154
 155 #define ADD_ATTRIBUTE()         do { \
 156     i = BGP_PATH_ATTR_SIZE(a);  \
 157     memcpy(p, &a, i);           \
 158     p += i;                     \
 159     peer->path_attr_len += i;   } while (0)
 160
 161     ADD_ATTRIBUTE();
 162
 163     /* AS_PATH */
 164     a.flags = BGP_PATH_ATTR_FLAG_TRANS;
 165     a.code = BGP_PATH_ATTR_CODE_AS_PATH;
 166     if (ibgp)
 167     {
 168         /* empty path */
 169         a.data.s.len = 0;
 170     }
 171     else
 172     {
 173         /* just our AS */
 174         struct {
 175             uint8_t type;
 176             uint8_t len;
 177             uint16_t value;
 178         } as_path = {
 179             BGP_PATH_ATTR_CODE_AS_PATH_AS_SEQUENCE,
 180             1,
 181             htons(our_as),
 182         };
 183
 184         a.data.s.len = sizeof(as_path);
 185         memcpy(&a.data.s.value, &as_path, sizeof(as_path));
 186     }
 187
 188     ADD_ATTRIBUTE();
 189
 190     /* NEXT_HOP */
 191     a.flags = BGP_PATH_ATTR_FLAG_TRANS;
 192     a.code = BGP_PATH_ATTR_CODE_NEXT_HOP;
 193     ip = my_address; /* we're it */
 194     a.data.s.len = sizeof(ip);
 195     memcpy(a.data.s.value, &ip, sizeof(ip));
 196
 197     ADD_ATTRIBUTE();
 198
 199     /* MULTI_EXIT_DISC */
 200     a.flags = BGP_PATH_ATTR_FLAG_OPTIONAL;
 201     a.code = BGP_PATH_ATTR_CODE_MULTI_EXIT_DISC;
 202     a.data.s.len = sizeof(metric);
 203     memcpy(a.data.s.value, &metric, sizeof(metric));
 204
 205     ADD_ATTRIBUTE();
 206
 207     if (ibgp)
 208     {
 209         uint32_t local_pref = htonl(BGP_LOCAL_PREF);
 210
 211         /* LOCAL_PREF */
 212         a.flags = BGP_PATH_ATTR_FLAG_TRANS;
 213         a.code = BGP_PATH_ATTR_CODE_LOCAL_PREF;
 214         a.data.s.len = sizeof(local_pref);
 215         memcpy(a.data.s.value, &local_pref, sizeof(local_pref));
 216
 217         ADD_ATTRIBUTE();
 218     }
 219
 220     /* COMMUNITIES */
 221     a.flags = BGP_PATH_ATTR_FLAG_OPTIONAL | BGP_PATH_ATTR_FLAG_TRANS;
 222     a.code = BGP_PATH_ATTR_CODE_COMMUNITIES;
 223     a.data.s.len = sizeof(no_export);
 224     memcpy(a.data.s.value, &no_export, sizeof(no_export));
 225
 226     ADD_ATTRIBUTE();
 227
 228     if (!(peer->path_attrs = malloc(peer->path_attr_len)))
 229     {
 230         LOG(0, 0, 0, "Can't allocate path_attrs for %s (%s)\n",
 231             name, strerror(errno));
 232
 233         return 0;
 234     }
 235
 236     memcpy(peer->path_attrs, path_attrs, peer->path_attr_len);
 237
 238     LOG(4, 0, 0, "Initiating BGP connection to %s (routing %s)\n",
 239         name, enable ? "enabled" : "suspended");
 240
 241     /* we have at least one peer configured */
 242     bgp_configured = 1;
 243
 244     /* connect */
 245     return bgp_connect(peer);
 246 }
 247
 248 /* clear counters, timers, routes and buffers; close socket; move to
 249    next_state, which may be Disabled or Idle */
 250 static void bgp_clear(struct bgp_peer *peer)
 251 {
 252     if (peer->sock != -1)
 253     {
 254         close(peer->sock);
 255         peer->sock = -1;
 256     }
 257
 258     peer->keepalive_time = 0;
 259     peer->expire_time = 0;
 260
 261     peer->keepalive = peer->init_keepalive;
 262     peer->hold = peer->init_hold;
 263
 264     bgp_free_routes(peer->routes);
 265     peer->routes = 0;
 266
 267     peer->outbuf->packet.header.len = 0;
 268     peer->outbuf->done = 0;
 269     peer->inbuf->packet.header.len = 0;
 270     peer->inbuf->done = 0;
 271
 272     peer->cli_flag = 0;
 273
 274     if (peer->state != peer->next_state)
 275     {
 276         peer->state = peer->next_state;
 277         peer->state_time = time_now;
 278
 279         LOG(4, 0, 0, "BGP peer %s: state %s\n", peer->name,
 280             bgp_state_str(peer->next_state));
 281     }
 282 }
 283
 284 /* initiate a clean shutdown */
 285 void bgp_stop(struct bgp_peer *peer)
 286 {
 287     LOG(4, 0, 0, "Terminating BGP connection to %s\n", peer->name);
 288     bgp_send_notification(peer, BGP_ERR_CEASE, 0);
 289 }
 290
 291 /* drop connection (if any) and set state to Disabled */
 292 void bgp_halt(struct bgp_peer *peer)
 293 {
 294     LOG(4, 0, 0, "Aborting BGP connection to %s\n", peer->name);
 295     peer->next_state = Disabled;
 296     bgp_clear(peer);
 297 }
 298
 299 /* drop connection (if any) and set to Idle for connection retry */
 300 int bgp_restart(struct bgp_peer *peer)
 301 {
 302     peer->next_state = Idle;
 303     bgp_clear(peer);
 304
 305     /* restart now */
 306     peer->retry_time = time_now;
 307     peer->retry_count = 0;
 308
 309     /* connect */
 310     return bgp_connect(peer);
 311 }
 312
 313 static void bgp_set_retry(struct bgp_peer *peer)
 314 {
 315     if (peer->retry_count++ < BGP_MAX_RETRY)
 316     {
 317         peer->retry_time = time_now + (BGP_RETRY_BACKOFF * peer->retry_count);
 318         peer->next_state = Idle;
 319         bgp_clear(peer);
 320     }
 321     else
 322         bgp_halt(peer); /* give up */
 323 }
 324
 325 /* convert ip/mask to CIDR notation */
 326 static void bgp_cidr(in_addr_t ip, in_addr_t mask, struct bgp_ip_prefix *pfx)
 327 {
 328     int i;
 329     uint32_t b;
 330
 331     /* convert to prefix notation */
 332     pfx->len = 32;
 333     pfx->prefix = ip;
 334
 335     if (!mask) /* bogus */
 336         mask = 0xffffffff;
 337
 338     for (i = 0; i < 32 && ((b = ntohl(1 << i)), !(mask & b)); i++)
 339     {
 340         pfx->len--;
 341         pfx->prefix &= ~b;
 342     }
 343 }
 344
 345 /* insert route into list; sorted */
 346 static struct bgp_route_list *bgp_insert_route(struct bgp_route_list *head,
 347     struct bgp_route_list *new)
 348 {
 349     struct bgp_route_list *p = head;
 350     struct bgp_route_list *e = 0;
 351
 352     while (p && memcmp(&p->dest, &new->dest, sizeof(p->dest)) < 0)
 353     {
 354         e = p;
 355         p = p->next;
 356     }
 357
 358     if (e)
 359     {
 360         new->next = e->next;
 361         e->next = new;
 362     }
 363     else
 364     {
 365         new->next = head;
 366         head = new;
 367     }
 368
 369     return head;
 370 }
 371
 372 /* add route to list for peers */
 373 /*
 374  * Note:  this doesn't do route aggregation, nor drop routes if a less
 375  * specific match already exists (partly because I'm lazy, but also so
 376  * that if that route is later deleted we don't have to be concerned
 377  * about adding back the more specific one).
 378  */
 379 int bgp_add_route(in_addr_t ip, in_addr_t mask)
 380 {
 381     struct bgp_route_list *r = bgp_routes;
 382     struct bgp_route_list add;
 383     int i;
 384
 385     bgp_cidr(ip, mask, &add.dest);
 386     add.next = 0;
 387
 388     /* check for duplicate */
 389     while (r)
 390     {
 391         i = memcmp(&r->dest, &add.dest, sizeof(r->dest));
 392         if (!i)
 393             return 1; /* already covered */
 394
 395         if (i > 0)
 396             break;
 397
 398         r = r->next;
 399     }
 400
 401     /* insert into route list; sorted */
 402     if (!(r = malloc(sizeof(*r))))
 403     {
 404         LOG(0, 0, 0, "Can't allocate route for %s/%d (%s)\n",
 405             fmtaddr(add.dest.prefix, 0), add.dest.len, strerror(errno));
 406
 407         return 0;
 408     }
 409
 410     memcpy(r, &add, sizeof(*r));
 411     bgp_routes = bgp_insert_route(bgp_routes, r);
 412
 413     /* flag established peers for update */
 414     for (i = 0; i < BGP_NUM_PEERS; i++)
 415         if (bgp_peers[i].state == Established)
 416             bgp_peers[i].update_routes = 1;
 417
 418     LOG(4, 0, 0, "Registered BGP route %s/%d\n",
 419         fmtaddr(add.dest.prefix, 0), add.dest.len);
 420
 421     return 1;
 422 }
 423
 424 /* remove route from list for peers */
 425 int bgp_del_route(in_addr_t ip, in_addr_t mask)
 426 {
 427     struct bgp_route_list *r = bgp_routes;
 428     struct bgp_route_list *e = 0;
 429     struct bgp_route_list del;
 430     int i;
 431
 432     bgp_cidr(ip, mask, &del.dest);
 433     del.next = 0;
 434
 435     /* find entry in routes list and remove */
 436     while (r)
 437     {
 438         i = memcmp(&r->dest, &del.dest, sizeof(r->dest));
 439         if (!i)
 440         {
 441             if (e)
 442                 e->next = r->next;
 443             else
 444                 bgp_routes = r->next;
 445
 446             free(r);
 447             break;
 448         }
 449
 450         e = r;
 451
 452         if (i > 0)
 453             r = 0; /* stop */
 454         else
 455             r = r->next;
 456     }
 457
 458     /* not found */
 459     if (!r)
 460         return 1;
 461
 462     /* flag established peers for update */
 463     for (i = 0; i < BGP_NUM_PEERS; i++)
 464         if (bgp_peers[i].state == Established)
 465             bgp_peers[i].update_routes = 1;
 466
 467     LOG(4, 0, 0, "Removed BGP route %s/%d\n",
 468         fmtaddr(del.dest.prefix, 0), del.dest.len);
 469
 470     return 1;
 471 }
 472
 473 /* enable or disable routing */
 474 void bgp_enable_routing(int enable)
 475 {
 476     int i;
 477
 478     for (i = 0; i < BGP_NUM_PEERS; i++)
 479     {
 480         bgp_peers[i].routing = enable;
 481
 482         /* flag established peers for update */
 483         if (bgp_peers[i].state == Established)
 484             bgp_peers[i].update_routes = 1;
 485     }
 486
 487     LOG(4, 0, 0, "%s BGP routing\n", enable ? "Enabled" : "Suspended");
 488 }
 489
 490 /* return a bitmask indicating if the socket should be added to the
 491    read set (1) and or write set (2) for select */
 492 int bgp_select_state(struct bgp_peer *peer)
 493 {
 494     int flags = 0;
 495
 496     if (!bgp_configured)
 497         return 0;
 498
 499     if (peer->state == Disabled || peer->state == Idle)
 500         return 0;
 501
 502     if (peer->inbuf->done < BGP_MAX_PACKET_SIZE)
 503         flags |= 1;
 504
 505     if (peer->state == Connect ||               /* connection in progress */
 506         peer->update_routes ||                  /* routing updates */
 507         peer->outbuf->packet.header.len)        /* pending output */
 508         flags |= 2;
 509
 510     return flags;
 511 }
 512
 513 /* process bgp peer */
 514 int bgp_process(struct bgp_peer *peer, int readable, int writable)
 515 {
 516     if (!bgp_configured)
 517         return 0;
 518
 519     if (*peer->name && peer->cli_flag == BGP_CLI_RESTART)
 520         return bgp_restart(peer);
 521
 522     if (peer->state == Disabled)
 523         return 1;
 524
 525     if (peer->cli_flag)
 526     {
 527         switch (peer->cli_flag)
 528         {
 529         case BGP_CLI_SUSPEND:
 530             if (peer->routing)
 531             {
 532                 peer->routing = 0;
 533                 if (peer->state == Established)
 534                     peer->update_routes = 1;
 535             }
 536
 537             break;
 538
 539         case BGP_CLI_ENABLE:
 540             if (!peer->routing)
 541             {
 542                 peer->routing = 1;
 543                 if (peer->state == Established)
 544                     peer->update_routes = 1;
 545             }
 546
 547             break;
 548         }
 549
 550         peer->cli_flag = 0;
 551     }
 552
 553     /* handle empty/fill of buffers */
 554     if (writable)
 555     {
 556         int r = 1;
 557         if (peer->state == Connect)
 558             r = bgp_handle_connect(peer);
 559         else if (peer->outbuf->packet.header.len)
 560             r = bgp_write(peer);
 561
 562         if (!r)
 563             return 0;
 564     }
 565
 566     if (readable)
 567     {
 568         if (!bgp_read(peer))
 569             return 0;
 570     }
 571
 572     /* process input buffer contents */
 573     while (peer->inbuf->done >= sizeof(peer->inbuf->packet.header)
 574         && !peer->outbuf->packet.header.len) /* may need to queue a response */
 575     {
 576         if (bgp_handle_input(peer) < 0)
 577             return 0;
 578     }
 579
 580     /* process pending updates */
 581     if (peer->update_routes
 582         && !peer->outbuf->packet.header.len) /* ditto */
 583     {
 584         if (!bgp_send_update(peer))
 585             return 0;
 586     }
 587
 588     /* process timers */
 589     if (peer->state == Established)
 590     {
 591         if (time_now > peer->expire_time)
 592         {
 593             LOG(1, 0, 0, "No message from BGP peer %s in %ds\n",
 594                 peer->name, peer->hold);
 595
 596             bgp_send_notification(peer, BGP_ERR_HOLD_TIMER_EXP, 0);
 597             return 0;
 598         }
 599
 600         if (time_now > peer->keepalive_time && !peer->outbuf->packet.header.len)
 601             bgp_send_keepalive(peer);
 602     }
 603     else if (peer->state == Idle)
 604     {
 605         if (time_now > peer->retry_time)
 606             return bgp_connect(peer);
 607     }
 608     else if (time_now > peer->state_time + BGP_STATE_TIME)
 609     {
 610         LOG(1, 0, 0, "%s timer expired for BGP peer %s\n",
 611             bgp_state_str(peer->state), peer->name);
 612
 613         return bgp_restart(peer);
 614     }
 615
 616     return 1;
 617 }
 618
 619 static void bgp_free_routes(struct bgp_route_list *routes)
 620 {
 621     struct bgp_route_list *tmp;
 622
 623     while ((tmp = routes))
 624     {
 625         routes = tmp->next;
 626         free(tmp);
 627     }
 628 }
 629
 630 char const *bgp_state_str(enum bgp_state state)
 631 {
 632     switch (state)
 633     {
 634     case Disabled:      return "Disabled";
 635     case Idle:          return "Idle";
 636     case Connect:       return "Connect";
 637     case Active:        return "Active";
 638     case OpenSent:      return "OpenSent";
 639     case OpenConfirm:   return "OpenConfirm";
 640     case Established:   return "Established";
 641     }
 642
 643     return "?";
 644 }
 645
 646 static char const *bgp_msg_type_str(uint8_t type)
 647 {
 648     switch (type)
 649     {
 650     case BGP_MSG_OPEN:          return "OPEN";
 651     case BGP_MSG_UPDATE:        return "UPDATE";
 652     case BGP_MSG_NOTIFICATION:  return "NOTIFICATION";
 653     case BGP_MSG_KEEPALIVE:     return "KEEPALIVE";
 654     }
 655
 656     return "?";
 657 }
 658
 659 /* attempt to connect to peer */
 660 static int bgp_connect(struct bgp_peer *peer)
 661 {
 662     static int bgp_port = 0;
 663     struct sockaddr_in addr;
 664
 665     if (!bgp_port)
 666     {
 667         struct servent *serv;
 668         if (!(serv = getservbyname("bgp", "tcp")))
 669         {
 670             LOG(0, 0, 0, "Can't get bgp service (%s)\n", strerror(errno));
 671             return 0;
 672         }
 673
 674         bgp_port = serv->s_port;
 675     }
 676
 677     if ((peer->sock = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0)
 678     {
 679         LOG(0, 0, 0, "Can't create a socket for BGP peer %s (%s)\n",
 680             peer->name, strerror(errno));
 681
 682         peer->state = peer->next_state = Disabled;
 683         return 0;
 684     }
 685
 686     /* set to non-blocking */
 687     fcntl(peer->sock, F_SETFL, fcntl(peer->sock, F_GETFL, 0) | O_NONBLOCK);
 688
 689     /* try connect */
 690     memset(&addr, 0, sizeof(addr));
 691     addr.sin_family = AF_INET;
 692     addr.sin_port = bgp_port;
 693     addr.sin_addr.s_addr = peer->addr;
 694
 695     while (connect(peer->sock, (struct sockaddr *) &addr, sizeof(addr)) == -1)
 696     {
 697         if (errno == EINTR) /* SIGALARM handler */
 698             continue;
 699
 700         if (errno != EINPROGRESS)
 701         {
 702             LOG(1, 0, 0, "Can't connect to BGP peer %s (%s)\n",
 703                 inet_ntoa(addr.sin_addr), strerror(errno));
 704
 705             bgp_set_retry(peer);
 706             return 0;
 707         }
 708
 709         peer->state = Connect;
 710         peer->state_time = time_now;
 711
 712         LOG(4, 0, 0, "BGP peer %s: state Connect\n", peer->name);
 713         return 1;
 714     }
 715
 716     peer->state = Active;
 717     peer->state_time = time_now;
 718     peer->retry_time = peer->retry_count = 0;
 719
 720     LOG(4, 0, 0, "BGP peer %s: state Active\n", inet_ntoa(addr.sin_addr));
 721
 722     return bgp_send_open(peer);
 723 }
 724
 725 /* complete partial connection (state = Connect) */
 726 static int bgp_handle_connect(struct bgp_peer *peer)
 727 {
 728     int err = 0;
 729     int len = sizeof(int);
 730     getsockopt(peer->sock, SOL_SOCKET, SO_ERROR, &err, &len);
 731     if (err)
 732     {
 733         LOG(1, 0, 0, "Can't connect to BGP peer %s (%s)\n", peer->name,
 734             strerror(err));
 735
 736         bgp_set_retry(peer);
 737         return 0;
 738     }
 739
 740     peer->state = Active;
 741     peer->state_time = time_now;
 742
 743     LOG(4, 0, 0, "BGP peer %s: state Active\n", peer->name);
 744
 745     return bgp_send_open(peer);
 746 }
 747
 748 /* initiate a write */
 749 static int bgp_write(struct bgp_peer *peer)
 750 {
 751     int len = htons(peer->outbuf->packet.header.len);
 752     int r;
 753
 754     while ((r = write(peer->sock, &peer->outbuf->packet + peer->outbuf->done,
 755         len - peer->outbuf->done)) == -1)
 756     {
 757         if (errno == EINTR)
 758             continue;
 759
 760         if (errno == EAGAIN)
 761             return 1;
 762
 763         if (errno == EPIPE)
 764             LOG(1, 0, 0, "Connection to BGP peer %s closed\n", peer->name);
 765         else
 766             LOG(1, 0, 0, "Can't write to BGP peer %s (%s)\n", peer->name,
 767                 strerror(errno));
 768
 769         bgp_set_retry(peer);
 770         return 0;
 771     }
 772
 773     if (r < len)
 774     {
 775         peer->outbuf->done += r;
 776         return 1;
 777     }
 778
 779     LOG(4, 0, 0, "Sent %s to BGP peer %s\n",
 780         bgp_msg_type_str(peer->outbuf->packet.header.type), peer->name);
 781
 782     peer->outbuf->packet.header.len = 0;
 783     peer->outbuf->done = 0;
 784
 785     if (peer->state == Established)
 786         peer->keepalive_time = time_now + peer->keepalive;
 787
 788     if (peer->state != peer->next_state)
 789     {
 790         if (peer->next_state == Disabled || peer->next_state == Idle)
 791         {
 792             bgp_clear(peer);
 793             return 0;
 794         }
 795
 796         peer->state = peer->next_state;
 797         peer->state_time = time_now;
 798
 799         LOG(4, 0, 0, "BGP peer %s: state %s\n", peer->name,
 800             bgp_state_str(peer->state));
 801     }
 802
 803     return 1;
 804 }
 805
 806 /* initiate a read */
 807 static int bgp_read(struct bgp_peer *peer)
 808 {
 809     int r;
 810
 811     while ((r = read(peer->sock, &peer->inbuf->packet + peer->inbuf->done,
 812         BGP_MAX_PACKET_SIZE - peer->inbuf->done)) < 1)
 813     {
 814         if (!r)
 815         {
 816             LOG(1, 0, 0, "Connection to BGP peer %s closed\n", peer->name);
 817         }
 818         else
 819         {
 820             if (errno == EINTR)
 821                 continue;
 822
 823             if (errno == EAGAIN)
 824                 return 1;
 825
 826             LOG(1, 0, 0, "Can't read from BGP peer %s (%s)\n", peer->name,
 827                 strerror(errno));
 828         }
 829
 830         bgp_set_retry(peer);
 831         return 0;
 832     }
 833
 834     peer->inbuf->done += r;
 835     return 1;
 836 }
 837
 838 /* process buffered packets */
 839 static int bgp_handle_input(struct bgp_peer *peer)
 840 {
 841     struct bgp_packet *p = &peer->inbuf->packet;
 842     int len = ntohs(p->header.len);
 843
 844     if (len > BGP_MAX_PACKET_SIZE)
 845     {
 846         LOG(1, 0, 0, "Bad header length from BGP %s\n", peer->name);
 847         bgp_send_notification(peer, BGP_ERR_HEADER, BGP_ERR_HDR_BAD_LEN);
 848         return 0;
 849     }
 850
 851     if (peer->inbuf->done < len)
 852         return 0;
 853
 854     LOG(4, 0, 0, "Received %s from BGP peer %s\n",
 855         bgp_msg_type_str(p->header.type), peer->name);
 856
 857     switch (p->header.type)
 858     {
 859     case BGP_MSG_OPEN:
 860         {
 861             struct bgp_data_open data;
 862             int hold;
 863             int i;
 864
 865             for (i = 0; i < sizeof(p->header.marker); i++)
 866             {
 867                 if ((unsigned char) p->header.marker[i] != 0xff)
 868                 {
 869                     LOG(1, 0, 0, "Invalid marker from BGP peer %s\n",
 870                         peer->name);
 871
 872                     bgp_send_notification(peer, BGP_ERR_HEADER,
 873                         BGP_ERR_HDR_NOT_SYNC);
 874
 875                     return 0;
 876                 }
 877             }
 878
 879             if (peer->state != OpenSent)
 880             {
 881                 LOG(1, 0, 0, "OPEN from BGP peer %s in %s state\n",
 882                     peer->name, bgp_state_str(peer->state));
 883
 884                 bgp_send_notification(peer, BGP_ERR_FSM, 0);
 885                 return 0;
 886             }
 887
 888             memcpy(&data, p->data, len - sizeof(p->header));
 889
 890             if (data.version != BGP_VERSION)
 891             {
 892                 LOG(1, 0, 0, "Bad version (%d) sent by BGP peer %s\n",
 893                     (int) data.version, peer->name);
 894
 895                 bgp_send_notification(peer, BGP_ERR_OPEN, BGP_ERR_OPN_VERSION);
 896                 return 0;
 897             }
 898
 899             if (ntohs(data.as) != peer->as)
 900             {
 901                 LOG(1, 0, 0, "Bad AS sent by BGP peer %s (got %d, "
 902                     "expected %d)\n", peer->name, (int) htons(data.as),
 903                     (int) peer->as);
 904
 905                 bgp_send_notification(peer, BGP_ERR_OPEN, BGP_ERR_OPN_BAD_AS);
 906                 return 0;
 907             }
 908
 909             if ((hold = ntohs(data.hold_time)) < 3)
 910             {
 911                 LOG(1, 0, 0, "Bad hold time (%d) from BGP peer %s\n",
 912                     hold, peer->name);
 913
 914                 bgp_send_notification(peer, BGP_ERR_OPEN, BGP_ERR_OPN_HOLD_TIME);
 915                 return 0;
 916             }
 917
 918             /* pick lowest hold time */
 919             if (hold < peer->hold)
 920                 peer->hold = hold;
 921
 922             /* adjust our keepalive based on negotiated hold value */
 923             if (peer->keepalive * 3 > peer->hold)
 924                 peer->keepalive = peer->hold / 3;
 925
 926             /* next transition requires an exchange of keepalives */
 927             bgp_send_keepalive(peer);
 928
 929             /* FIXME: may need to check for optional params */
 930         }
 931
 932         break;
 933
 934     case BGP_MSG_KEEPALIVE:
 935         if (peer->state == OpenConfirm)
 936         {
 937             peer->state = peer->next_state = Established;
 938             peer->state_time = time_now;
 939             peer->keepalive_time = time_now + peer->keepalive;
 940             peer->update_routes = 1;
 941             peer->retry_count = 0;
 942             peer->retry_time = 0;
 943
 944             LOG(4, 0, 0, "BGP peer %s: state Established\n", peer->name);
 945         }
 946
 947         break;
 948
 949     case BGP_MSG_NOTIFICATION:
 950         if (len > sizeof(p->header))
 951         {
 952             struct bgp_data_notification *notification =
 953                 (struct bgp_data_notification *) p->data;
 954
 955             if (notification->error_code == BGP_ERR_CEASE)
 956             {
 957                 LOG(4, 0, 0, "BGP peer %s sent CEASE\n", peer->name);
 958                 bgp_halt(peer);
 959                 return 0;
 960             }
 961
 962             /* FIXME: should handle more notifications */
 963             LOG(4, 0, 0, "BGP peer %s sent unhandled NOTIFICATION %d\n",
 964                 peer->name, (int) notification->error_code);
 965         }
 966
 967         break;
 968     }
 969
 970     /* reset timer */
 971     peer->expire_time = time_now + peer->hold;
 972
 973     /* see if there's another message in the same packet/buffer */
 974     if (peer->inbuf->done > len)
 975     {
 976         peer->inbuf->done -= len;
 977         memmove(p, (char *) p + len, peer->inbuf->done);
 978     }
 979     else
 980     {
 981         peer->inbuf->packet.header.len = 0;
 982         peer->inbuf->done = 0;
 983     }
 984
 985     return peer->inbuf->done;
 986 }
 987
 988 /* send/buffer OPEN message */
 989 static int bgp_send_open(struct bgp_peer *peer)
 990 {
 991     struct bgp_data_open data;
 992     uint16_t len = sizeof(peer->outbuf->packet.header);
 993
 994     memset(peer->outbuf->packet.header.marker, 0xff,
 995         sizeof(peer->outbuf->packet.header.marker));
 996
 997     peer->outbuf->packet.header.type = BGP_MSG_OPEN;
 998
 999     data.version = BGP_VERSION;
1000     data.as = htons(our_as);
1001     data.hold_time = htons(peer->hold);
1002     data.identifier = my_address;
1003     data.opt_len = 0;
1004
1005     memcpy(peer->outbuf->packet.data, &data, BGP_DATA_OPEN_SIZE);
1006     len += BGP_DATA_OPEN_SIZE;
1007
1008     peer->outbuf->packet.header.len = htons(len);
1009     peer->outbuf->done = 0;
1010     peer->next_state = OpenSent;
1011
1012     return bgp_write(peer);
1013 }
1014
1015 /* send/buffer KEEPALIVE message */
1016 static int bgp_send_keepalive(struct bgp_peer *peer)
1017 {
1018     memset(peer->outbuf->packet.header.marker, 0xff,
1019         sizeof(peer->outbuf->packet.header.marker));
1020
1021     peer->outbuf->packet.header.type = BGP_MSG_KEEPALIVE;
1022     peer->outbuf->packet.header.len =
1023         htons(sizeof(peer->outbuf->packet.header));
1024
1025     peer->outbuf->done = 0;
1026     peer->next_state = (peer->state == OpenSent) ? OpenConfirm : peer->state;
1027
1028     return bgp_write(peer);
1029 }
1030
1031 /* send/buffer UPDATE message */
1032 static int bgp_send_update(struct bgp_peer *peer)
1033 {
1034     uint16_t unf_len = 0;
1035     uint16_t attr_len;
1036     uint16_t len = sizeof(peer->outbuf->packet.header);
1037     struct bgp_route_list *have = peer->routes;
1038     struct bgp_route_list *want = peer->routing ? bgp_routes : 0;
1039     struct bgp_route_list *e = 0;
1040     struct bgp_route_list *add = 0;
1041     int s;
1042
1043     char *data = (char *) &peer->outbuf->packet.data;
1044
1045     /* need leave room for attr_len, bgp_path_attrs and one prefix */
1046     char *max = (char *) &peer->outbuf->packet.data
1047         + sizeof(peer->outbuf->packet.data)
1048         - sizeof(attr_len) - peer->path_attr_len - sizeof(struct bgp_ip_prefix);
1049
1050     /* skip over unf_len */
1051     data += sizeof(unf_len);
1052     len += sizeof(unf_len);
1053
1054     memset(peer->outbuf->packet.header.marker, 0xff,
1055         sizeof(peer->outbuf->packet.header.marker));
1056
1057     peer->outbuf->packet.header.type = BGP_MSG_UPDATE;
1058
1059     peer->update_routes = 0; /* tentatively clear */
1060
1061     /* find differences */
1062     while ((have || want) && data < (max - sizeof(struct bgp_ip_prefix)))
1063     {
1064         if (have)
1065             s = want
1066                 ? memcmp(&have->dest, &want->dest, sizeof(have->dest))
1067                 : -1;
1068         else
1069             s = 1;
1070
1071         if (s < 0) /* found one to delete */
1072         {
1073             struct bgp_route_list *tmp = have;
1074             have = have->next;
1075
1076             s = BGP_IP_PREFIX_SIZE(tmp->dest);
1077             memcpy(data, &tmp->dest, s);
1078             data += s;
1079             unf_len += s;
1080             len += s;
1081
1082             LOG(5, 0, 0, "Withdrawing route %s/%d from BGP peer %s\n",
1083                 fmtaddr(tmp->dest.prefix, 0), tmp->dest.len, peer->name);
1084
1085             free(tmp);
1086
1087             if (e)
1088                 e->next = have;
1089             else
1090                 peer->routes = have;
1091         }
1092         else
1093         {
1094             if (!s) /* same */
1095             {
1096                 e = have; /* stash the last found to relink above */
1097                 have = have->next;
1098                 want = want->next;
1099             }
1100             else if (s > 0) /* addition reqd. */
1101             {
1102                 if (add)
1103                 {
1104                     peer->update_routes = 1; /* only one add per packet */
1105                     if (!have)
1106                         break;
1107                 }
1108                 else
1109                     add = want;
1110
1111                 if (want)
1112                     want = want->next;
1113             }
1114         }
1115     }
1116
1117     if (have || want)
1118         peer->update_routes = 1; /* more to do */
1119
1120     /* anything changed? */
1121     if (!(unf_len || add))
1122         return 1;
1123
1124     /* go back and insert unf_len */
1125     unf_len = htons(unf_len);
1126     memcpy(&peer->outbuf->packet.data, &unf_len, sizeof(unf_len));
1127
1128     if (add)
1129     {
1130         if (!(e = malloc(sizeof(*e))))
1131         {
1132             LOG(0, 0, 0, "Can't allocate route for %s/%d (%s)\n",
1133                 fmtaddr(add->dest.prefix, 0), add->dest.len, strerror(errno));
1134
1135             return 0;
1136         }
1137
1138         memcpy(e, add, sizeof(*e));
1139         e->next = 0;
1140         peer->routes = bgp_insert_route(peer->routes, e);
1141
1142         attr_len = htons(peer->path_attr_len);
1143         memcpy(data, &attr_len, sizeof(attr_len));
1144         data += sizeof(attr_len);
1145         len += sizeof(attr_len);
1146
1147         memcpy(data, peer->path_attrs, peer->path_attr_len);
1148         data += peer->path_attr_len;
1149         len += peer->path_attr_len;
1150
1151         s = BGP_IP_PREFIX_SIZE(add->dest);
1152         memcpy(data, &add->dest, s);
1153         data += s;
1154         len += s;
1155
1156         LOG(5, 0, 0, "Advertising route %s/%d to BGP peer %s\n",
1157             fmtaddr(add->dest.prefix, 0), add->dest.len, peer->name);
1158     }
1159     else
1160     {
1161         attr_len = 0;
1162         memcpy(data, &attr_len, sizeof(attr_len));
1163         data += sizeof(attr_len);
1164         len += sizeof(attr_len);
1165     }
1166
1167     peer->outbuf->packet.header.len = htons(len);
1168     peer->outbuf->done = 0;
1169
1170     return bgp_write(peer);
1171 }
1172
1173 /* send/buffer NOTIFICATION message */
1174 static int bgp_send_notification(struct bgp_peer *peer, uint8_t code,
1175     uint8_t subcode)
1176 {
1177     struct bgp_data_notification data;
1178     uint16_t len = 0;
1179
1180     data.error_code = code;
1181     len += sizeof(data.error_code);
1182
1183     data.error_subcode = subcode;
1184     len += sizeof(data.error_code);
1185
1186     memset(peer->outbuf->packet.header.marker, 0xff,
1187         sizeof(peer->outbuf->packet.header.marker));
1188
1189     peer->outbuf->packet.header.type = BGP_MSG_NOTIFICATION;
1190     peer->outbuf->packet.header.len =
1191         htons(sizeof(peer->outbuf->packet.header) + len);
1192
1193     memcpy(peer->outbuf->packet.data, &data, len);
1194
1195     peer->outbuf->done = 0;
1196     peer->next_state = code == BGP_ERR_CEASE ? Disabled : Idle;
1197
1198     /* we're dying; ignore any pending input */
1199     peer->inbuf->packet.header.len = 0;
1200     peer->inbuf->done = 0;
1201
1202     return bgp_write(peer);
1203 }