bgpd not sending NOTIFICATION (cease/Peer De-configured) message when neighbor unconfigured

[arunsesh]

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Describe the bug
When a neighbor is unconfigured/removed, BGPD (speaker) is properly closing TCP connection by sending TCP FIN message. However, it is expected to send NOTIFICATION message with error code: Cease and error subcode : Peer De-configured (3).

Refer https://tools.ietf.org/html/rfc4486.
If a BGP speaker decides to de-configure a peer, then the speaker SHOULD send a NOTIFICATION message with the Error Code Cease and the Error Subcode "Peer De-configured".

This is working fine when BGPD is sent SIGTERM signal (closure of bgpd daemon).

(put "x" in "[ ]" if you already tried following)
[ ] Did you check if this is a duplicate issue?
[ ] Did you test it on the latest FRRouting/frr master branch?

To Reproduce
Steps to reproduce the behavior:

1. Do a BGP peering with another router.
2. Delete (unconfigure the peered neighbour) - no neighbor x.x.x.x

Note: Doing a "systemctl restart frr.service" or ""systemctl stop frr.service" or "kill -SIGTERM --- sends Notification cease/peer unconfigured to the peer.

Expected behavior
BGP Peering will be lost/terminated. (TCP closure)
However, it is expected to send NOTIFICATION message with error code: Cease and error subcode : Peer De-configured (3) before tearing down the connection.

Screenshots
None

Versions

• OS Kernel: CentOS 7
• FRR Version : 7.1
  Additional context
  Add any other context about the problem here.

[amodmish]

There are implementation which does not allow [no] neighbor and instead execute neighbor shutdown first and post that [no] neighbor commands would be allowed. Would it be good to follow that ?

[amodmish]

if you shutdown the neighbor prior how will it receive de-configure message?
I meant - As part of neighbor shutdown send de-confiugure message to peer. And on no neighbor remove the peer from config.

[arunsesh]

Not sure if the changes done is causing regression. On termination of bgpd (kill of bgpd process) --- 2 cease Notification messages sent to peer.

1st NOTIFICATION cease message sent with minor-code = Peer-DeConfigured.
2nd NOTIFICATION cease message sent with minor-code = Administratively Shutdown