bgpd: fix addressing information of non established outgoing sessions

When trying to connect to a BGP peer that does not respons, the 'show
bgp neighbors' command does not give any indication on the local and
remote addresses used:

> # show bgp neighbors
>  BGP neighbor is 192.0.2.150, remote AS 65500, local AS 65500, internal link
>   Local Role: undefined
>   Remote Role: undefined
>   BGP version 4, remote router ID 0.0.0.0, local router ID 192.0.2.1
>   BGP state = Connect
> [..]
>   Connections established 0; dropped 0
>   Last reset 00:00:04,   Waiting for peer OPEN (n/a)
>   Internal BGP neighbor may be up to 255 hops away.
> BGP Connect Retry Timer in Seconds: 120
> Next connect timer due in 117 seconds
> Read thread: off  Write thread: off  FD used: 27

The addressing information (address and port) are only available
when TCP session is established, whereas this information is present
at the system level:

> root@ubuntu2204:~# netstat -pan | grep 192.0.2.1
> tcp        0      0 192.0.2.1:179           192.0.2.150:38060       SYN_RECV    -
> tcp        0      1 192.0.2.1:46526         192.0.2.150:179         SYN_SENT    488310/bgpd

Add the display for outgoing BGP session, as the information in
the getsockname() API provides information for connected streams.
When getpeername() API does not give any information, use the peer
configuration (destination port is encoded in peer->port).

> # show bgp neighbors
> BGP neighbor is 192.0.2.150, remote AS 65500, local AS 65500, internal link
>   Local Role: undefined
>   Remote Role: undefined
>   BGP version 4, remote router ID 0.0.0.0, local router ID 192.0.2.1
>   BGP state = Connect
> [..]
>   Connections established 0; dropped 0
>   Last reset 00:00:16,   Waiting for peer OPEN (n/a)
> Local host: 192.0.2.1, Local port: 46084
> Foreign host: 192.0.2.150, Foreign port: 179

Signed-off-by: Philippe Guibert <[email protected]>
(cherry picked from commit 78ce639)

bgpd/bgp_fsm.c

@@ -1800,6 +1800,22 @@ bgp_connect_fail(struct peer_connection *connection)
 	return bgp_stop(connection);
 }
 
+/* after connect is called(), getpeername is able to return
+ * port and address on non established streams
+ */
+static void bgp_connect_in_progress_update_connection(struct peer *peer)
+{
+	bgp_getsockname(peer);
+	if (!peer->su_remote && !BGP_CONNECTION_SU_UNSPEC(peer->connection)) {
+		/* if connect initiated, then dest port and dest addresses are well known */
+		peer->su_remote = sockunion_dup(&peer->connection->su);
+		if (sockunion_family(peer->su_remote) == AF_INET)
+			peer->su_remote->sin.sin_port = htons(peer->port);
+		else if (sockunion_family(peer->su_remote) == AF_INET6)
+			peer->su_remote->sin6.sin6_port = htons(peer->port);
+	}
+}
+
 /* This function is the first starting point of all BGP connection. It
  * try to connect to remote peer with non-blocking IO.
  */
@@ -1896,6 +1912,8 @@ static enum bgp_fsm_state_progress bgp_start(struct peer_connection *connection)
 				 __func__, peer->connection->fd);
 			return BGP_FSM_FAILURE;
 		}
+		bgp_connect_in_progress_update_connection(peer);
+
 		/*
 		 * - when the socket becomes ready, poll() will signify POLLOUT
 		 * - if it fails to connect, poll() will signify POLLHUP