bgpd: Implement `neighbor X remote-as auto`

In some cases (large scale) it's desired to avoid changing configurations, but
let the BGP to automatically handle ASN changes.

`auto` means the peering can be iBGP or eBGP. It will be automatically detected
and adjusted from the OPEN message.

Signed-off-by: Donatas Abraitis <donatas@opensourcerouting.org>

1 files changed, 6 insertions, 1 deletions

diff --git a/bgpd/bgp_updgrp.c b/bgpd/bgp_updgrp.c
index 124e7a388..b717793a4 100644
--- a/bgpd/bgp_updgrp.c
+++ b/bgpd/bgp_updgrp.c
@@ -343,7 +343,12 @@ static unsigned int updgrp_hash_key_make(const void *p)
 
 	key = 0;
 
-	key = jhash_1word(peer->sort, key); /* EBGP or IBGP */
+	/* `remote-as auto` technically uses identical peer->sort.
+	 * After OPEN message is parsed, this is updated accordingly, but
+	 * we need to call the peer_sort() here also to properly create
+	 * separate subgroups.
+	 */
+	key = jhash_1word(peer_sort((struct peer *)peer), key);
 	key = jhash_1word(peer->sub_sort, key); /* OAD */
 	key = jhash_1word((peer->flags & PEER_UPDGRP_FLAGS), key);
 	key = jhash_1word((flags & PEER_UPDGRP_AF_FLAGS), key);