From e0ae285eb8beeef7b43bdadc073d8ae346eaeb6c Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Lo=C3=AFc=20Sang?= Date: Wed, 19 Jun 2024 16:19:22 +0200 Subject: [PATCH] bgpd: avoid clearing routes for peers that were never established MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Under heavy system load with many peers in passive mode and a large number of routes, bgpd can enter an infinite loop. This occurs while processing timeout BGP_OPEN messages, which prevents it from accepting new connections. The following log entries illustrate the issue: >bgpd[6151]: [VX6SM-8YE5W][EC 33554460] 3.3.2.224: nexthop_set failed, resetting connection - intf 0x0 >bgpd[6151]: [P790V-THJKS][EC 100663299] bgp_open_receive: bgp_getsockname() failed for peer: 3.3.2.224 >bgpd[6151]: [HTQD2-0R1WR][EC 33554451] bgp_process_packet: BGP OPEN receipt failed for peer: 3.3.2.224 ... repeating The issue occurs when bgpd handles a massive number of routes in the RIB while receiving numerous BGP_OPEN packets. If bgpd is overloaded, it fails to process these packets promptly, leading the remote peer to close the connection and resend BGP_OPEN packets. When bgpd eventually starts processing these timeout BGP_OPEN packets, it finds the TCP connection closed by the remote peer, resulting in "bgp_stop()" being called. For each timeout peer, bgpd must iterate through the routing table, which is time-consuming and causes new incoming BGP_OPEN packets to timeout, perpetuating the infinite loop. To address this issue, the code is modified to check if the peer has been established at least once before calling "bgp_clear_route_all()". This ensures that routes are only cleared for peers that had a successful session, preventing unnecessary iterations over the routing table for peers that never established a connection. With this change, BGP_OPEN timeout messages may still occur, but in the worst case, bgpd will stabilize. Before this patch, bgpd could enter a loop where it was unable to accpet any new connections. Signed-off-by: Loïc Sang --- bgpd/bgp_fsm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/bgpd/bgp_fsm.c b/bgpd/bgp_fsm.c index 15cc5dbe2ea0..d41ef8abbac9 100644 --- a/bgpd/bgp_fsm.c +++ b/bgpd/bgp_fsm.c @@ -1241,7 +1241,7 @@ void bgp_fsm_change_status(struct peer_connection *connection, /* Transition into Clearing or Deleted must /always/ clear all routes.. * (and must do so before actually changing into Deleted.. */ - if (status >= Clearing) { + if (status >= Clearing && (peer->established || peer == bgp->peer_self)) { bgp_clear_route_all(peer); /* If no route was queued for the clear-node processing,