path: root/proto/bgp/bgp.c

/*
 *	BIRD -- The Border Gateway Protocol
 *
 *	(c) 2000 Martin Mares <mj@ucw.cz>
 *
 *	Can be freely distributed and used under the terms of the GNU GPL.
 */

/**
 * DOC: Border Gateway Protocol
 *
 * The BGP protocol is implemented in three parts: |bgp.c| which takes care of the
 * connection and most of the interface with BIRD core, |packets.c| handling
 * both incoming and outgoing BGP packets and |attrs.c| containing functions for
 * manipulation with BGP attribute lists.
 *
 * As opposed to the other existing routing daemons, BIRD has a sophisticated core
 * architecture which is able to keep all the information needed by BGP in the
 * primary routing table, therefore no complex data structures like a central
 * BGP table are needed. This increases memory footprint of a BGP router with
 * many connections, but not too much and, which is more important, it makes
 * BGP much easier to implement.
 *
 * Each instance of BGP (corresponding to a single BGP peer) is described by a &bgp_proto
 * structure to which are attached individual connections represented by &bgp_connection
 * (usually, there exists only one connection, but during BGP session setup, there
 * can be more of them). The connections are handled according to the BGP state machine
 * defined in the RFC with all the timers and all the parameters configurable.
 *
 * In incoming direction, we listen on the connection's socket and each time we receive
 * some input, we pass it to bgp_rx(). It decodes packet headers and the markers and
 * passes complete packets to bgp_rx_packet() which distributes the packet according
 * to its type.
 *
 * In outgoing direction, we gather all the routing updates and sort them to buckets
 * (&bgp_bucket) according to their attributes (we keep a hash table for fast comparison
 * of &rta's and a &fib which helps us to find if we already have another route for
 * the same destination queued for sending, so that we can replace it with the new one
 * immediately instead of sending both updates). There also exists a special bucket holding
 * all the route withdrawals which cannot be queued anywhere else as they don't have any
 * attributes. If we have any packet to send (due to either new routes or the connection
 * tracking code wanting to send a Open, Keepalive or Notification message), we call
 * bgp_schedule_packet() which sets the corresponding bit in a @packet_to_send
 * bit field in &bgp_conn and as soon as the transmit socket buffer becomes empty,
 * we call bgp_fire_tx(). It inspects state of all the packet type bits and calls
 * the corresponding bgp_create_xx() functions, eventually rescheduling the same packet
 * type if we have more data of the same type to send.
 *
 * The processing of attributes consists of two functions: bgp_decode_attrs() for checking
 * of the attribute blocks and translating them to the language of BIRD's extended attributes
 * and bgp_encode_attrs() which does the converse. Both functions are built around a
 * @bgp_attr_table array describing all important characteristics of all known attributes.
 * Unknown transitive attributes are attached to the route as %EAF_TYPE_OPAQUE byte streams.
 */

#undef LOCAL_DEBUG

#include "nest/bird.h"
#include "nest/iface.h"
#include "nest/protocol.h"
#include "nest/route.h"
#include "nest/locks.h"
#include "conf/conf.h"
#include "lib/socket.h"
#include "lib/resource.h"
#include "lib/string.h"

#include "bgp.h"

struct linpool *bgp_linpool;		/* Global temporary pool */
static sock *bgp_listen_sk;		/* Global listening socket */
static int bgp_counter;			/* Number of protocol instances using the listening socket */

static void bgp_close(struct bgp_proto *p, int apply_md5);
static void bgp_connect(struct bgp_proto *p);
static void bgp_active(struct bgp_proto *p);
static void bgp_stop(struct bgp_proto *p);
static sock *bgp_setup_listen_sk(void);


/**
 * bgp_open - open a BGP instance
 * @p: BGP instance
 *
 * This function allocates and configures shared BGP resources.
 * Should be called as the last step during initialization
 * (when lock is acquired and neighbor is ready).
 * When error, state changed to PS_DOWN, -1 is returned and caller
 * should return immediately.
 */
static int
bgp_open(struct bgp_proto *p)
{
  bgp_counter++;

  if (!bgp_listen_sk)
    bgp_listen_sk = bgp_setup_listen_sk();

  if (!bgp_linpool)
    bgp_linpool = lp_new(&root_pool, 4080);

  if (p->cf->password)
    {
      int rv = sk_set_md5_auth(bgp_listen_sk, p->cf->remote_ip, p->cf->password);
      if (rv < 0)
	{
	  bgp_close(p, 0);
	  p->p.disabled = 1;
	  bgp_store_error(p, NULL, BE_MISC, BEM_INVALID_MD5);
	  proto_notify_state(&p->p, PS_DOWN);
	  return -1;
	}
    }

  return 0;
}

static void
bgp_startup(struct bgp_proto *p)
{
  BGP_TRACE(D_EVENTS, "Started");
  p->start_state = p->cf->capabilities ? BSS_CONNECT : BSS_CONNECT_NOCAP;
  bgp_active(p);
}

static void
bgp_startup_timeout(timer *t)
{
  bgp_startup(t->data);
}


static void
bgp_initiate(struct bgp_proto *p)
{
  if (p->startup_delay)
    {
      BGP_TRACE(D_EVENTS, "Startup delayed by %d seconds", p->startup_delay);
      bgp_start_timer(p->startup_timer, p->startup_delay);
    }
  else
    bgp_startup(p);
}

/**
 * bgp_close - close a BGP instance
 * @p: BGP instance
 * @apply_md5: 0 to disable unsetting MD5 auth
 *
 * This function frees and deconfigures shared BGP resources.
 * @apply_md5 is set to 0 when bgp_close is called as a cleanup
 * from failed bgp_open().
 */
static void
bgp_close(struct bgp_proto *p, int apply_md5)
{
  ASSERT(bgp_counter);
  bgp_counter--;

  if (p->cf->password && apply_md5)
    sk_set_md5_auth(bgp_listen_sk, p->cf->remote_ip, NULL);

  if (!bgp_counter)
    {
      rfree(bgp_listen_sk);
      bgp_listen_sk = NULL;
      rfree(bgp_linpool);
      bgp_linpool = NULL;
    }
}

/**
 * bgp_start_timer - start a BGP timer
 * @t: timer
 * @value: time to fire (0 to disable the timer)
 *
 * This functions calls tm_start() on @t with time @value and the
 * amount of randomization suggested by the BGP standard. Please use
 * it for all BGP timers.
 */
void
bgp_start_timer(timer *t, int value)
{
  if (value)
    {
      /* The randomization procedure is specified in RFC 1771: 9.2.3.3 */
      t->randomize = value / 4;
      tm_start(t, value - t->randomize);
    }
  else
    tm_stop(t);
}

/**
 * bgp_close_conn - close a BGP connection
 * @conn: connection to close
 *
 * This function takes a connection described by the &bgp_conn structure,
 * closes its socket and frees all resources associated with it.
 */
void
bgp_close_conn(struct bgp_conn *conn)
{
  struct bgp_proto *p = conn->bgp;

  DBG("BGP: Closing connection\n");
  conn->packets_to_send = 0;
  rfree(conn->connect_retry_timer);
  conn->connect_retry_timer = NULL;
  rfree(conn->keepalive_timer);
  conn->keepalive_timer = NULL;
  rfree(conn->hold_timer);
  conn->hold_timer = NULL;
  rfree(conn->sk);
  conn->sk = NULL;
  rfree(conn->tx_ev);
  conn->tx_ev = NULL;
}


/**
 * bgp_update_startup_delay - update a startup delay
 * @p: BGP instance
 * @conn: related BGP connection
 * @code: BGP error code
 * @subcode: BGP error subcode
 *
 * This function updates a startup delay that is used to postpone next BGP connect.
 * It also handles disable_after_error and might stop BGP instance when error
 * happened and disable_after_error is on.
 *
 * It should be called when BGP protocol error happened.
 */
void
bgp_update_startup_delay(struct bgp_proto *p, struct bgp_conn *conn, unsigned code, unsigned subcode)
{
  struct bgp_config *cf = p->cf;

  /* Don't handle cease messages as errors */
  if (code == 6 && !subcode && p->last_error_class != BE_AUTO_DOWN)
    {
      p->startup_delay = 0;
      return;
    }

  /* During start, we only consider errors on outgoing connection, because
     otherwise delay timer for outgoing connection is already running and
     we could increase delay time two times (or more) per one attempt to
     connect.
  */
  if ((p->p.proto_state == PS_START) && (conn != &p->outgoing_conn))
    return;

  DBG("BGP: Updating startup delay %d %d\n", code, subcode);

  p->last_proto_error = now;

  if (cf->disable_after_error)
    {
      p->startup_delay = 0;
      p->p.disabled = 1;
      if (p->p.proto_state == PS_START)
	bgp_stop(p);

      return;
    }

  if (p->last_proto_error && ((now - p->last_proto_error) >= cf->error_amnesia_time))
    p->startup_delay = 0;

  if (!p->startup_delay)
    p->startup_delay = cf->error_delay_time_min;
  else
    {
      p->startup_delay *= 2;
      if (p->startup_delay > cf->error_delay_time_max)
	p->startup_delay = cf->error_delay_time_max;
    }
}

static void
bgp_graceful_close_conn(struct bgp_conn *conn)
{
  switch (conn->state)
    {
    case BS_IDLE:
    case BS_CLOSE:
      return;
    case BS_CONNECT:
    case BS_ACTIVE:
      bgp_conn_enter_idle_state(conn);
      return;
    case BS_OPENSENT:
    case BS_OPENCONFIRM:
    case BS_ESTABLISHED:
      bgp_error(conn, 6, 0, NULL, 0);
      return;
    default:
      bug("bgp_graceful_close_conn: Unknown state %d", conn->state);
    }
}

static void
bgp_down(struct bgp_proto *p)
{
  if (p->start_state > BSS_PREPARE)
    bgp_close(p, 1);

  DBG("BGP: DOWN\n");
  proto_notify_state(&p->p, PS_DOWN);
}

static void
bgp_decision(void *vp)
{
  struct bgp_proto *p = vp;

  DBG("BGP: Decision start\n");
  if ((p->p.proto_state == PS_START)
      && (p->outgoing_conn.state == BS_IDLE))
    bgp_active(p);

  if ((p->p.proto_state == PS_STOP)
      && (p->outgoing_conn.state == BS_IDLE)
      && (p->incoming_conn.state == BS_IDLE))
    bgp_down(p);
}

static void
bgp_stop(struct bgp_proto *p)
{
  proto_notify_state(&p->p, PS_STOP);
  bgp_graceful_close_conn(&p->outgoing_conn);
  bgp_graceful_close_conn(&p->incoming_conn);
  ev_schedule(p->event);
}

void
bgp_conn_enter_established_state(struct bgp_conn *conn)
{
  struct bgp_proto *p = conn->bgp;
 
  BGP_TRACE(D_EVENTS, "BGP session established");
  DBG("BGP: UP!!!\n");

  p->conn = conn;
  p->last_error_class = 0;
  p->last_error_code = 0;
  bgp_attr_init(conn->bgp);
  conn->state = BS_ESTABLISHED;
  proto_notify_state(&p->p, PS_UP);
}

static void
bgp_conn_leave_established_state(struct bgp_proto *p)
{
  BGP_TRACE(D_EVENTS, "BGP session closed");
  p->conn = NULL;

  if (p->p.proto_state == PS_UP)
    bgp_stop(p);
}

void
bgp_conn_enter_close_state(struct bgp_conn *conn)
{
  struct bgp_proto *p = conn->bgp;
  int os = conn->state;

  conn->state = BS_CLOSE;
  tm_stop(conn->hold_timer);
  tm_stop(conn->keepalive_timer);
  conn->sk->rx_hook = NULL;

  if (os == BS_ESTABLISHED)
    bgp_conn_leave_established_state(p);
}

void
bgp_conn_enter_idle_state(struct bgp_conn *conn)
{
  struct bgp_proto *p = conn->bgp;
  int os = conn->state;

  bgp_close_conn(conn);
  conn->state = BS_IDLE;
  ev_schedule(p->event);

  if (os == BS_ESTABLISHED)
    bgp_conn_leave_established_state(p);
}

static void
bgp_send_open(struct bgp_conn *conn)
{
  conn->start_state = conn->bgp->start_state;
  conn->want_as4_support = conn->bgp->cf->enable_as4 && (conn->start_state != BSS_CONNECT_NOCAP);
  conn->peer_as4_support = 0;	// Default value, possibly changed by receiving capability.

  DBG("BGP: Sending open\n");
  conn->sk->rx_hook = bgp_rx;
  conn->sk->tx_hook = bgp_tx;
  tm_stop(conn->connect_retry_timer);
  bgp_schedule_packet(conn, PKT_OPEN);
  conn->state = BS_OPENSENT;
  bgp_start_timer(conn->hold_timer, conn->bgp->cf->initial_hold_time);
}

static void
bgp_connected(sock *sk)
{
  struct bgp_conn *conn = sk->data;
  struct bgp_proto *p = conn->bgp;

  BGP_TRACE(D_EVENTS, "Connected");
  bgp_send_open(conn);
}

static void
bgp_connect_timeout(timer *t)
{
  struct bgp_conn *conn = t->data;
  struct bgp_proto *p = conn->bgp;

  DBG("BGP: connect_timeout\n");
  if (p->p.proto_state == PS_START)
    {
      bgp_close_conn(conn);
      bgp_connect(p);
    }
  else
    bgp_conn_enter_idle_state(conn);
}

static void
bgp_sock_err(sock *sk, int err)
{
  struct bgp_conn *conn = sk->data;
  struct bgp_proto *p = conn->bgp;

  bgp_store_error(p, conn, BE_SOCKET, err);

  if (err)
    BGP_TRACE(D_EVENTS, "Connection lost (%M)", err);
  else
    BGP_TRACE(D_EVENTS, "Connection closed");

  bgp_conn_enter_idle_state(conn);
}

static void
bgp_hold_timeout(timer *t)
{
  struct bgp_conn *conn = t->data;

  DBG("BGP: Hold timeout, closing connection\n");
  bgp_error(conn, 4, 0, NULL, 0);
}

static void
bgp_keepalive_timeout(timer *t)
{
  struct bgp_conn *conn = t->data;

  DBG("BGP: Keepalive timer\n");
  bgp_schedule_packet(conn, PKT_KEEPALIVE);
}

static void
bgp_setup_conn(struct bgp_proto *p, struct bgp_conn *conn)
{
  timer *t;

  conn->sk = NULL;
  conn->bgp = p;
  conn->packets_to_send = 0;

  t = conn->connect_retry_timer = tm_new(p->p.pool);
  t->hook = bgp_connect_timeout;
  t->data = conn;
  t = conn->hold_timer = tm_new(p->p.pool);
  t->hook = bgp_hold_timeout;
  t->data = conn;
  t = conn->keepalive_timer = tm_new(p->p.pool);
  t->hook = bgp_keepalive_timeout;
  t->data = conn;
  conn->tx_ev = ev_new(p->p.pool);
  conn->tx_ev->hook = bgp_kick_tx;
  conn->tx_ev->data = conn;
}

static void
bgp_setup_sk(struct bgp_proto *p, struct bgp_conn *conn, sock *s)
{
  s->data = conn;
  s->err_hook = bgp_sock_err;
  conn->sk = s;
}

static void
bgp_active(struct bgp_proto *p)
{
  int delay = MIN(1, p->cf->start_delay_time);
  struct bgp_conn *conn = &p->outgoing_conn;

  BGP_TRACE(D_EVENTS, "Connect delayed by %d seconds", delay);
  bgp_setup_conn(p, conn);
  conn->state = BS_ACTIVE;
  bgp_start_timer(conn->connect_retry_timer, delay);
}

int
bgp_apply_limits(struct bgp_proto *p)
{
  if (p->cf->route_limit && (p->p.stats.imp_routes > p->cf->route_limit))
    {
      log(L_WARN "%s: Route limit exceeded, shutting down", p->p.name);
      bgp_store_error(p, NULL, BE_AUTO_DOWN, BEA_ROUTE_LIMIT_EXCEEDED);
      bgp_stop(p);
      return -1;
    }

  return 0;
}


/**
 * bgp_connect - initiate an outgoing connection
 * @p: BGP instance
 *
 * The bgp_connect() function creates a new &bgp_conn and initiates
 * a TCP connection to the peer. The rest of connection setup is governed
 * by the BGP state machine as described in the standard.
 */
static void
bgp_connect(struct bgp_proto *p)	/* Enter Connect state and start establishing connection */
{
  sock *s;
  struct bgp_conn *conn = &p->outgoing_conn;

  DBG("BGP: Connecting\n");
  s = sk_new(p->p.pool);
  s->type = SK_TCP_ACTIVE;
  s->saddr = p->source_addr;
  s->daddr = p->cf->remote_ip;
  s->dport = BGP_PORT;
  s->ttl = p->cf->multihop ? : 1;
  s->rbsize = BGP_RX_BUFFER_SIZE;
  s->tbsize = BGP_TX_BUFFER_SIZE;
  s->tos = IP_PREC_INTERNET_CONTROL;
  s->password = p->cf->password;
  s->tx_hook = bgp_connected;
  BGP_TRACE(D_EVENTS, "Connecting to %I from local address %I", s->daddr, s->saddr);
  bgp_setup_conn(p, conn);
  bgp_setup_sk(p, conn, s);
  conn->state = BS_CONNECT;
  if (sk_open(s))
    {
      bgp_sock_err(s, 0);
      return;
    }
  DBG("BGP: Waiting for connect success\n");
  bgp_start_timer(conn->connect_retry_timer, p->cf->connect_retry_time);
}

/**
 * bgp_incoming_connection - handle an incoming connection
 * @sk: TCP socket
 * @dummy: unused
 *
 * This function serves as a socket hook for accepting of new BGP
 * connections. It searches a BGP instance corresponding to the peer
 * which has connected and if such an instance exists, it creates a
 * &bgp_conn structure, attaches it to the instance and either sends
 * an Open message or (if there already is an active connection) it
 * closes the new connection by sending a Notification message.
 */
static int
bgp_incoming_connection(sock *sk, int dummy UNUSED)
{
  struct proto_config *pc;

  DBG("BGP: Incoming connection from %I port %d\n", sk->daddr, sk->dport);
  WALK_LIST(pc, config->protos)
    if (pc->protocol == &proto_bgp && pc->proto)
      {
	struct bgp_proto *p = (struct bgp_proto *) pc->proto;
	if (ipa_equal(p->cf->remote_ip, sk->daddr))
	  {
	    /* We are in proper state and there is no other incoming connection */
	    int acc = (p->p.proto_state == PS_START || p->p.proto_state == PS_UP) &&
	      (p->start_state >= BSS_CONNECT) && (!p->incoming_conn.sk);

	    BGP_TRACE(D_EVENTS, "Incoming connection from %I (port %d) %s",
		      sk->daddr, sk->dport, acc ? "accepted" : "rejected");

	    if (!acc)
	      goto err;

	    bgp_setup_conn(p, &p->incoming_conn);
	    bgp_setup_sk(p, &p->incoming_conn, sk);
	    sk_set_ttl(sk, p->cf->multihop ? : 1);
	    bgp_send_open(&p->incoming_conn);
	    return 0;
	  }
      }

  log(L_WARN "BGP: Unexpected connect from unknown address %I (port %d)", sk->daddr, sk->dport);
 err:
  rfree(sk);
  return 0;
}

static sock *
bgp_setup_listen_sk(void)
{
  sock *s = sk_new(&root_pool);
  DBG("BGP: Creating incoming socket\n");
  s->type = SK_TCP_PASSIVE;
  s->sport = BGP_PORT;
  s->tos = IP_PREC_INTERNET_CONTROL;
  s->rbsize = BGP_RX_BUFFER_SIZE;
  s->tbsize = BGP_TX_BUFFER_SIZE;
  s->rx_hook = bgp_incoming_connection;
  if (sk_open(s))
    {
      log(L_ERR "Unable to open incoming BGP socket");
      rfree(s);
      return NULL;
    }
  else
    return s;
}

static void
bgp_start_neighbor(struct bgp_proto *p)
{
  p->local_addr = p->neigh->iface->addr->ip;
  p->source_addr = ipa_nonzero(p->cf->source_addr) ? p->cf->source_addr : p->local_addr;

  DBG("BGP: local=%I remote=%I\n", p->source_addr, p->next_hop);
#ifdef IPV6
  {
    struct ifa *a;
    p->local_link = IPA_NONE;
    WALK_LIST(a, p->neigh->iface->addrs)
      if (a->scope == SCOPE_LINK)
        {
	  p->local_link = a->ip;
	  break;
	}

    if (! ipa_nonzero(p->local_link))
      log(L_WARN "%s: Missing link local address on interface %s", p->p.name,  p->neigh->iface->name);

    DBG("BGP: Selected link-level address %I\n", p->local_link);
  }
#endif

  int rv = bgp_open(p);
  if (rv < 0)
    return;

  bgp_initiate(p);
}

static void
bgp_neigh_notify(neighbor *n)
{
  struct bgp_proto *p = (struct bgp_proto *) n->proto;

  if (n->iface)
    {
      if ((p->p.proto_state == PS_START) && (p->start_state == BSS_PREPARE))
	{
	  BGP_TRACE(D_EVENTS, "Neighbor found");
	  bgp_start_neighbor(p);
	}
    }
  else
    {
      if ((p->p.proto_state == PS_START) || (p->p.proto_state == PS_UP))
	{
	  BGP_TRACE(D_EVENTS, "Neighbor lost");
	  bgp_store_error(p, NULL, BE_MISC, BEM_NEIGHBOR_LOST);
	  bgp_stop(p);
	}
    }
}

static void
bgp_start_locked(struct object_lock *lock)
{
  struct bgp_proto *p = lock->data;
  struct bgp_config *cf = p->cf;

  if (p->p.proto_state != PS_START)
    {
      DBG("BGP: Got lock in different state %d\n", p->p.proto_state);
    return;
    }

  DBG("BGP: Got lock\n");
  p->local_id = cf->c.global->router_id;
  p->next_hop = cf->multihop ? cf->multihop_via : cf->remote_ip;
  p->neigh = neigh_find(&p->p, &p->next_hop, NEF_STICKY);

  if (cf->rr_client)
    {
      p->rr_cluster_id = cf->rr_cluster_id ? cf->rr_cluster_id : p->local_id;
      p->rr_client = cf->rr_client;
    }

  p->rs_client = cf->rs_client;

  if (!p->neigh)
    {
      log(L_ERR "%s: Invalid next hop %I", p->p.name, p->next_hop);
      /* As we do not start yet, we can just disable protocol */
      p->p.disabled = 1;
      bgp_store_error(p, NULL, BE_MISC, BEM_INVALID_NEXT_HOP);
      proto_notify_state(&p->p, PS_DOWN);
      return;
    }
  
  if (p->neigh->iface)
    bgp_start_neighbor(p);
  else
    BGP_TRACE(D_EVENTS, "Waiting for %I to become my neighbor", p->next_hop);
}

static int
bgp_start(struct proto *P)
{
  struct bgp_proto *p = (struct bgp_proto *) P;
  struct object_lock *lock;

  DBG("BGP: Startup.\n");
  p->start_state = BSS_PREPARE;
  p->outgoing_conn.state = BS_IDLE;
  p->incoming_conn.state = BS_IDLE;
  p->neigh = NULL;

  p->event = ev_new(p->p.pool);
  p->event->hook = bgp_decision;
  p->event->data = p;

  p->startup_timer = tm_new(p->p.pool);
  p->startup_timer->hook = bgp_startup_timeout;
  p->startup_timer->data = p;

  /*
   *  Before attempting to create the connection, we need to lock the
   *  port, so that are sure we're the only instance attempting to talk
   *  with that neighbor.
   */

  lock = p->lock = olock_new(P->pool);
  lock->addr = p->cf->remote_ip;
  lock->type = OBJLOCK_TCP;
  lock->port = BGP_PORT;
  lock->iface = NULL;
  lock->hook = bgp_start_locked;
  lock->data = p;
  olock_acquire(lock);

  return PS_START;
}

static int
bgp_shutdown(struct proto *P)
{
  struct bgp_proto *p = (struct bgp_proto *) P;

  BGP_TRACE(D_EVENTS, "Shutdown requested");
  bgp_store_error(p, NULL, BE_MAN_DOWN, 0);
  p->startup_delay = 0;
  bgp_stop(p);

  return p->p.proto_state;
}

static struct proto *
bgp_init(struct proto_config *C)
{
  struct bgp_config *c = (struct bgp_config *) C;
  struct proto *P = proto_new(C, sizeof(struct bgp_proto));
  struct bgp_proto *p = (struct bgp_proto *) P;

  P->accept_ra_types = RA_OPTIMAL;
  P->rt_notify = bgp_rt_notify;
  P->rte_better = bgp_rte_better;
  P->import_control = bgp_import_control;
  P->neigh_notify = bgp_neigh_notify;
  p->cf = c;
  p->local_as = c->local_as;
  p->remote_as = c->remote_as;
  p->is_internal = (c->local_as == c->remote_as);
  return P;
}

/**
 * bgp_error - report a protocol error
 * @c: connection
 * @code: error code (according to the RFC)
 * @subcode: error sub-code
 * @data: data to be passed in the Notification message
 * @len: length of the data
 *
 * bgp_error() sends a notification packet to tell the other side that a protocol
 * error has occurred (including the data considered erroneous if possible) and
 * closes the connection.
 */
void
bgp_error(struct bgp_conn *c, unsigned code, unsigned subcode, byte *data, int len)
{
  if (c->state == BS_CLOSE)
    return;

  bgp_log_error(c->bgp, "Error", code, subcode, data, (len > 0) ? len : -len);
  bgp_store_error(c->bgp, c, BE_BGP_TX, (code << 16) | subcode);
  bgp_update_startup_delay(c->bgp, c, code, subcode);
  bgp_conn_enter_close_state(c);

  c->notify_code = code;
  c->notify_subcode = subcode;
  c->notify_data = data;
  c->notify_size = (len > 0) ? len : 0;
  bgp_schedule_packet(c, PKT_NOTIFICATION);
}

/**
 * bgp_store_error - store last error for status report
 * @p: BGP instance
 * @c: connection
 * @class: error class (BE_xxx constants)
 * @code: error code (class specific)
 *
 * bgp_store_error() decides whether given error is interesting enough
 * and store that error to last_error variables of @p
 */
void
bgp_store_error(struct bgp_proto *p, struct bgp_conn *c, u8 class, u32 code)
{
  /* During PS_UP, we ignore errors on secondary connection */
  if ((p->p.proto_state == PS_UP) && c && (c != p->conn))
    return;

  /* During PS_STOP, we ignore any errors, as we want to report
   * the error that caused transition to PS_STOP
   */
  if (p->p.proto_state == PS_STOP)
    return;

  p->last_error_class = class;
  p->last_error_code = code;
}

void
bgp_check(struct bgp_config *c)
{
  if (!c->local_as)
    cf_error("Local AS number must be set");

  if (!c->remote_as)
    cf_error("Neighbor must be configured");

  if (!bgp_as4_support && c->enable_as4)
    cf_error("AS4 support disabled globally");

  if (!bgp_as4_support && (c->local_as > 0xFFFF))
    cf_error("Local AS number out of range");

  if (!(c->capabilities && c->enable_as4) && (c->remote_as > 0xFFFF))
    cf_error("Neighbor AS number out of range (AS4 not available)");

  if ((c->local_as != c->remote_as) && (c->rr_client))
    cf_error("Only internal neighbor can be RR client");

  if ((c->local_as == c->remote_as) && (c->rs_client))
    cf_error("Only external neighbor can be RS client");
}

static char *bgp_state_names[] = { "Idle", "Connect", "Active", "OpenSent", "OpenConfirm", "Established", "Close" };
static char *bgp_err_classes[] = { "", "Error: ", "Socket: ", "Received: ", "BGP Error: ", "Automatic shutdown: ", ""};
static char *bgp_misc_errors[] = { "", "Neighbor lost", "Invalid next hop", "Kernel MD5 auth failed" };
static char *bgp_auto_errors[] = { "", "Route limit exceeded"};


static void
bgp_get_status(struct proto *P, byte *buf)
{
  struct bgp_proto *p = (struct bgp_proto *) P;

  const byte *err1 = bgp_err_classes[p->last_error_class];
  const byte *err2 = "";
  byte errbuf[32];

  switch (p->last_error_class)
    {
    case BE_MISC:
      err2 = bgp_misc_errors[p->last_error_code];
      break;
    case BE_SOCKET:
      err2 = (p->last_error_code == 0) ? "Connection closed" : strerror(p->last_error_code);
      break;
    case BE_BGP_RX:
    case BE_BGP_TX:
      err2 = bgp_error_dsc(errbuf, p->last_error_code >> 16, p->last_error_code & 0xFF);
      break;
    case BE_AUTO_DOWN:
      err2 = bgp_auto_errors[p->last_error_code];
      break;
    }

  if (P->proto_state == PS_DOWN)
    bsprintf(buf, "%s%s", err1, err2);
  else
    bsprintf(buf, "%-14s%s%s",
	     bgp_state_names[MAX(p->incoming_conn.state, p->outgoing_conn.state)],
	     err1, err2);
}

static int
bgp_reconfigure(struct proto *P, struct proto_config *C)
{
  struct bgp_config *new = (struct bgp_config *) C;
  struct bgp_proto *p = (struct bgp_proto *) P;
  struct bgp_config *old = p->cf;

  int same = !memcmp(((byte *) old) + sizeof(struct proto_config),
		     ((byte *) new) + sizeof(struct proto_config),
		     sizeof(struct bgp_config) - sizeof(struct proto_config));

  /* We should update our copy of configuration ptr as old configuration will be freed */
  if (same)
    p->cf = new;

  return same;
}

struct protocol proto_bgp = {
  name:			"BGP",
  template:		"bgp%d",
  attr_class:		EAP_BGP,
  init:			bgp_init,
  start:		bgp_start,
  shutdown:		bgp_shutdown,
  get_status:		bgp_get_status,
  get_attr:		bgp_get_attr,
  reconfigure:		bgp_reconfigure,
  get_route_info:	bgp_get_route_info,
};