bird/proto/bgp/bgp.c

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/*
* 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.
*/
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/**
* 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.
*
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* Each instance of BGP (corresponding to a single BGP peer) is described by a &bgp_proto
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* 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
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* tracking code wanting to send a Open, Keepalive or Notification message), we call
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* 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.
*/
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#undef LOCAL_DEBUG
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#include "nest/bird.h"
#include "nest/iface.h"
#include "nest/protocol.h"
#include "nest/route.h"
#include "nest/locks.h"
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#include "conf/conf.h"
#include "lib/socket.h"
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#include "lib/resource.h"
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#include "lib/string.h"
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#include "bgp.h"
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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 */
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static char *bgp_state_names[] = { "Idle", "Connect", "Active", "OpenSent", "OpenConfirm", "Established" };
static void bgp_connect(struct bgp_proto *p);
static void bgp_initiate(struct bgp_proto *p);
static void bgp_setup_listen_sk(void);
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void
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bgp_close(struct bgp_proto *p UNUSED)
{
ASSERT(bgp_counter);
bgp_counter--;
if (!bgp_counter)
{
rfree(bgp_listen_sk);
bgp_listen_sk = NULL;
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rfree(bgp_linpool);
bgp_linpool = NULL;
}
}
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/**
* 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)
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{
/* The randomization procedure is specified in RFC 1771: 9.2.3.3 */
t->randomize = value / 4;
tm_start(t, value - t->randomize);
}
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else
tm_stop(t);
}
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/**
* 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.
*
* If the connection is being closed due to a protocol error, adjust
* the connection restart timer as well according to the error recovery
* policy set in the configuration.
*
* If the connection was marked as primary, it shuts down the protocol as well.
*/
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void
bgp_close_conn(struct bgp_conn *conn)
{
struct bgp_proto *p = conn->bgp;
struct bgp_config *cf = p->cf;
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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);
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conn->sk = NULL;
conn->state = BS_IDLE;
if (conn->error_flag > 1)
{
if (cf->disable_after_error)
p->p.disabled = 1;
if (p->last_connect && (bird_clock_t)(p->last_connect + cf->error_amnesia_time) < now)
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;
}
}
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if (conn->primary)
{
bgp_close(p);
p->conn = NULL;
proto_notify_state(&p->p, PS_DOWN);
}
else if (conn->error_flag > 1)
bgp_initiate(p);
}
static int
bgp_graceful_close_conn(struct bgp_conn *c)
{
switch (c->state)
{
case BS_IDLE:
return 0;
case BS_CONNECT:
case BS_ACTIVE:
bgp_close_conn(c);
return 1;
case BS_OPENSENT:
case BS_OPENCONFIRM:
case BS_ESTABLISHED:
bgp_error(c, 6, 0, NULL, 0);
return 1;
default:
bug("bgp_graceful_close_conn: Unknown state %d", c->state);
}
}
static void
bgp_send_open(struct bgp_conn *conn)
{
DBG("BGP: Sending open\n");
conn->sk->rx_hook = bgp_rx;
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conn->sk->tx_hook = bgp_tx;
tm_stop(conn->connect_retry_timer);
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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;
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struct bgp_proto *p = conn->bgp;
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BGP_TRACE(D_EVENTS, "Connected");
bgp_send_open(conn);
}
static void
bgp_connect_timeout(timer *t)
{
struct bgp_conn *conn = t->data;
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struct bgp_proto *p = conn->bgp;
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DBG("BGP: connect_timeout\n");
bgp_close_conn(conn);
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bgp_connect(p);
}
static void
bgp_sock_err(sock *sk, int err)
{
struct bgp_conn *conn = sk->data;
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struct bgp_proto *p = conn->bgp;
if (err)
BGP_TRACE(D_EVENTS, "Connection lost (%M)", err);
else
BGP_TRACE(D_EVENTS, "Connection closed");
switch (conn->state)
{
case BS_CONNECT:
case BS_OPENSENT:
rfree(conn->sk);
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conn->sk = NULL;
conn->state = BS_ACTIVE;
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bgp_start_timer(conn->connect_retry_timer, p->cf->connect_retry_time);
break;
case BS_OPENCONFIRM:
case BS_ESTABLISHED:
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bgp_close_conn(conn);
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break;
default:
bug("bgp_sock_err called in invalid state %d", conn->state);
}
}
static void
bgp_hold_timeout(timer *t)
{
struct bgp_conn *conn = t->data;
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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;
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conn->packets_to_send = 0;
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conn->error_flag = 0;
conn->primary = 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;
}
static void
bgp_setup_sk(struct bgp_proto *p, struct bgp_conn *conn, sock *s)
{
s->data = conn;
s->ttl = p->cf->multihop ? : 1;
s->rbsize = BGP_RX_BUFFER_SIZE;
s->tbsize = BGP_TX_BUFFER_SIZE;
s->err_hook = bgp_sock_err;
s->tos = IP_PREC_INTERNET_CONTROL;
conn->sk = s;
}
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/**
* 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;
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struct bgp_conn *conn = &p->outgoing_conn;
DBG("BGP: Connecting\n");
p->last_connect = now;
s = sk_new(p->p.pool);
s->type = SK_TCP_ACTIVE;
if (ipa_nonzero(p->cf->source_addr))
s->saddr = p->cf->source_addr;
else
s->saddr = p->local_addr;
s->daddr = p->cf->remote_ip;
s->dport = BGP_PORT;
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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);
s->tx_hook = bgp_connected;
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);
}
static void
bgp_initiate(struct bgp_proto *p)
{
unsigned delay;
delay = p->cf->start_delay_time;
if (p->startup_delay > delay)
delay = p->startup_delay;
if (delay)
{
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BGP_TRACE(D_EVENTS, "Connect delayed by %d seconds", delay);
bgp_setup_conn(p, &p->outgoing_conn);
bgp_start_timer(p->outgoing_conn.connect_retry_timer, delay);
}
else
bgp_connect(p);
}
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/**
* 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
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bgp_incoming_connection(sock *sk, int dummy UNUSED)
{
struct proto_config *pc;
int match = 0;
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))
{
match = 1;
if ((p->p.proto_state == PS_START || p->p.proto_state == PS_UP) && p->neigh && p->neigh->iface)
{
BGP_TRACE(D_EVENTS, "Incoming connection from %I port %d", sk->daddr, sk->dport);
if (p->incoming_conn.sk)
{
DBG("BGP: But one incoming connection already exists, how is that possible?\n");
break;
}
bgp_setup_conn(p, &p->incoming_conn);
bgp_setup_sk(p, &p->incoming_conn, sk);
bgp_send_open(&p->incoming_conn);
return 0;
}
}
}
if (!match)
log(L_AUTH "BGP: Unauthorized connect from %I port %d", sk->daddr, sk->dport);
rfree(sk);
return 0;
}
static void
bgp_setup_listen_sk(void)
{
if (!bgp_listen_sk)
{
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->ttl = 1;
s->rbsize = BGP_RX_BUFFER_SIZE;
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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);
}
else
bgp_listen_sk = s;
}
}
static void
bgp_start_neighbor(struct bgp_proto *p)
{
p->local_addr = p->neigh->iface->addr->ip;
DBG("BGP: local=%I remote=%I\n", p->local_addr, p->next_hop);
#ifdef IPV6
{
struct ifa *a;
p->local_link = ipa_or(ipa_build(0xfe80,0,0,0), ipa_and(p->local_addr, ipa_build(0,0,~0,~0)));
WALK_LIST(a, p->neigh->iface->addrs)
if (a->scope == SCOPE_LINK)
{
p->local_link = a->ip;
break;
}
DBG("BGP: Selected link-level address %I\n", p->local_link);
}
#endif
bgp_initiate(p);
}
static void
bgp_neigh_notify(neighbor *n)
{
struct bgp_proto *p = (struct bgp_proto *) n->proto;
if (n->iface)
{
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BGP_TRACE(D_EVENTS, "Neighbor found");
bgp_start_neighbor(p);
}
else
{
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BGP_TRACE(D_EVENTS, "Neighbor lost");
/* Send cease packets, but don't wait for them to be delivered */
bgp_graceful_close_conn(&p->outgoing_conn);
bgp_graceful_close_conn(&p->incoming_conn);
proto_notify_state(&p->p, PS_DOWN);
}
}
static void
bgp_start_locked(struct object_lock *lock)
{
struct bgp_proto *p = lock->data;
struct bgp_config *cf = p->cf;
DBG("BGP: Got lock\n");
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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 (!p->neigh)
{
log(L_ERR "%s: Invalid next hop %I", p->p.name, p->next_hop);
p->p.disabled = 1;
proto_notify_state(&p->p, PS_DOWN);
}
else if (p->neigh->iface)
bgp_start_neighbor(p);
else
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BGP_TRACE(D_EVENTS, "Waiting for %I to become my neighbor", p->next_hop);
}
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static int
bgp_start(struct proto *P)
{
struct bgp_proto *p = (struct bgp_proto *) P;
struct object_lock *lock;
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DBG("BGP: Startup.\n");
p->outgoing_conn.state = BS_IDLE;
p->incoming_conn.state = BS_IDLE;
p->startup_delay = 0;
p->neigh = NULL;
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bgp_counter++;
bgp_setup_listen_sk();
if (!bgp_linpool)
bgp_linpool = lp_new(&root_pool, 4080);
/*
* 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;
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}
static int
bgp_shutdown(struct proto *P)
{
struct bgp_proto *p = (struct bgp_proto *) P;
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BGP_TRACE(D_EVENTS, "Shutdown requested");
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/*
* We want to send the Cease notification message to all connections
* we have open, but we don't want to wait for all of them to complete.
* We are willing to handle the primary connection carefully, but for
* the others we just try to send the packet and if there is no buffer
* space free, we'll gracefully finish.
*/
proto_notify_state(&p->p, PS_STOP);
if (!p->conn)
{
if (p->outgoing_conn.state != BS_IDLE)
p->outgoing_conn.primary = 1; /* Shuts protocol down after connection close */
else if (p->incoming_conn.state != BS_IDLE)
p->incoming_conn.primary = 1;
}
if (bgp_graceful_close_conn(&p->outgoing_conn) || bgp_graceful_close_conn(&p->incoming_conn))
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return p->p.proto_state;
else
{
/* No connections open, shutdown automatically */
bgp_close(p);
return PS_DOWN;
}
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}
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->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;
}
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/**
* bgp_error - report a protocol error
* @c: connection
* @code: error code (according to the RFC)
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* @subcode: error sub-code
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* @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
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* error has occurred (including the data considered erroneous if possible) and
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* closes the connection.
*/
void
bgp_error(struct bgp_conn *c, unsigned code, unsigned subcode, byte *data, int len)
{
if (c->error_flag)
return;
bgp_log_error(c->bgp, "Error", code, subcode, data, (len > 0) ? len : -len);
c->error_flag = 1 + (code != 6);
c->notify_code = code;
c->notify_subcode = subcode;
c->notify_data = data;
c->notify_size = (len > 0) ? len : 0;
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if (c->primary)
proto_notify_state(&c->bgp->p, PS_STOP);
bgp_schedule_packet(c, PKT_NOTIFICATION);
}
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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");
}
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static void
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bgp_get_status(struct proto *P, byte *buf)
{
struct bgp_proto *p = (struct bgp_proto *) P;
if (P->proto_state == PS_DOWN)
buf[0] = 0;
else
strcpy(buf, bgp_state_names[MAX(p->incoming_conn.state, p->outgoing_conn.state)]);
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}
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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;
return !memcmp(((byte *) old) + sizeof(struct proto_config),
((byte *) new) + sizeof(struct proto_config),
sizeof(struct bgp_config) - sizeof(struct proto_config));
}
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struct protocol proto_bgp = {
name: "BGP",
template: "bgp%d",
attr_class: EAP_BGP,
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init: bgp_init,
start: bgp_start,
shutdown: bgp_shutdown,
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get_status: bgp_get_status,
get_attr: bgp_get_attr,
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reconfigure: bgp_reconfigure,
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get_route_info: bgp_get_route_info,
};