Commit 2eadd36f authored by Ondřej Zajíček's avatar Ondřej Zajíček

BGP: AS-wide unique router ID (RFC 6286) support

RFC 6286 relaxed rules for router IDs, allowing EBGP sessions between
routers with the same ID (but different ASN).
parent 9aed29e6
......@@ -943,7 +943,8 @@ bgp_rx_open(struct bgp_conn *conn, byte *pkt, int len)
if (hold > 0 && hold < 3)
{ bgp_error(conn, 2, 6, pkt+22, 2); return; }
if (!id || id == 0xffffffff || id == p->local_id)
/* RFC 6286 2.2 - router ID is nonzero and AS-wide unique */
if (!id || (p->is_internal && id == p->local_id))
{ bgp_error(conn, 2, 3, pkt+24, -4); return; }
if ((conn->advertised_as != base_as) && (base_as != AS_TRANS))
......@@ -978,8 +979,23 @@ bgp_rx_open(struct bgp_conn *conn, byte *pkt, int len)
break;
case BS_OPENCONFIRM:
if ((p->local_id < id) == (conn == &p->incoming_conn))
{
/*
* Description of collision detection rules in RFC 4271 is confusing and
* contradictory, but it is essentially:
*
* 1. Router with higher ID is dominant
* 2. If both have the same ID, router with higher ASN is dominant [RFC6286]
* 3. When both connections are in OpenConfirm state, one initiated by
* the dominant router is kept.
*
* The first line in the expression below evaluates whether the neighbor
* is dominant, the second line whether the new connection was initiated
* by the neighbor. If both are true (or both are false), we keep the new
* connection, otherwise we keep the old one.
*/
if (((p->local_id < id) || ((p->local_id == id) && (p->local_as < p->remote_as)))
== (conn == &p->incoming_conn))
{
/* Should close the other connection */
BGP_TRACE(D_EVENTS, "Connection collision, giving up the other connection");
bgp_error(other, 6, 7, NULL, 0);
......
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