bgpd: Add support for Autonomous-System-Wide Unique BGP Identifier

Implement https://tools.ietf.org/html/rfc6286

Signed-off-by: Donatas Abraitis <donatas.abraitis@gmail.com>

diff --git a/bgpd/bgp_packet.c b/bgpd/bgp_packet.c
index 10e96497fb390bc1d1ad7b67988d612813018f3d..ae4f521b9c081565ef9dcc4db5e1bcdabba8953d 100644 (file)
--- a/bgpd/bgp_packet.c
+++ b/bgpd/bgp_packet.c
@@ -974,14 +974,21 @@ static int bgp_collision_detect(struct peer *new, struct in_addr remote_id)
                        return -1;
                } else if ((peer->status == OpenConfirm)
                           || (peer->status == OpenSent)) {
-                       /* 1. The BGP Identifier of the local system is compared
-                          to
-                          the BGP Identifier of the remote system (as specified
-                          in
-                          the OPEN message). */
-
+                       /* 1. The BGP Identifier of the local system is
+                        * compared to the BGP Identifier of the remote
+                        * system (as specified in the OPEN message).
+                        *
+                        * If the BGP Identifiers of the peers
+                        * involved in the connection collision
+                        * are identical, then the connection
+                        * initiated by the BGP speaker with the
+                        * larger AS number is preserved.
+                        */
                        if (ntohl(peer->local_id.s_addr)
-                           < ntohl(remote_id.s_addr))
+                                   < ntohl(remote_id.s_addr)
+                           || (ntohl(peer->local_id.s_addr)
+                                              == ntohl(remote_id.s_addr)
+                                      && peer->local_as < peer->as))
                                if (!CHECK_FLAG(peer->sflags,
                                                PEER_STATUS_ACCEPT_PEER)) {
                                        /* 2. If the value of the local BGP
@@ -1005,10 +1012,13 @@ static int bgp_collision_detect(struct peer *new, struct in_addr remote_id)
                                        return -1;
                                }
                        else {
-                               if (ntohl(peer->local_id.s_addr) ==
-                                   ntohl(remote_id.s_addr))
-                                       flog_err(EC_BGP_ROUTER_ID_SAME, "Peer's router-id %s is the same as ours",
-                                                inet_ntoa(remote_id));
+                               if (ntohl(peer->local_id.s_addr)
+                                           == ntohl(remote_id.s_addr)
+                                   && peer->local_as == peer->as)
+                                       flog_err(
+                                               EC_BGP_ROUTER_ID_SAME,
+                                               "Peer's router-id %s is the same as ours",
+                                               inet_ntoa(remote_id));
 
                                /* 3. Otherwise, the local system closes newly
                                   created
@@ -1197,10 +1207,17 @@ static int bgp_open_receive(struct peer *peer, bgp_size_t size)
                }
        }
 
-       /* remote router-id check. */
+       /* rfc6286:
+        * If the BGP Identifier field of the OPEN message
+        * is zero, or if it is the same as the BGP Identifier
+        * of the local BGP speaker and the message is from an
+        * internal peer, then the Error Subcode is set to
+        * "Bad BGP Identifier".
+        */
        if (remote_id.s_addr == INADDR_ANY
            || IPV4_CLASS_DE(ntohl(remote_id.s_addr))
-           || ntohl(peer->local_id.s_addr) == ntohl(remote_id.s_addr)) {
+           || (peer->sort == BGP_PEER_IBGP
+               && ntohl(peer->local_id.s_addr) == ntohl(remote_id.s_addr))) {
                if (bgp_debug_neighbor_events(peer))
                        zlog_debug("%s bad OPEN, wrong router identifier %s",
                                   peer->host, inet_ntoa(remote_id));