Job scheduling for agentx in case of trap burst leads to bgpd freeze

[Dumontet]

Description

agentx protocol for trap notification is based on notification message/response.

           NOTIFICATION

snmpd <----------------------- agentX/bgpd
socket A

             RESPONSE

snmpd -----------------------> agentX/bgpd
socket B

Response is immediatly sent at "Notification" reception by snmpd.
agentX/bgpd reading is made by a dedicated thread function "agentx_read"

When a burst of neighbors creation/deletion occurs "agentx_read" function is not called due to multiple thead with higher
priority.

In that case a burst of trap notifications is send to snmpd through socket A.
snmpd immediatly forward this burst into response to agentx/bgpd through socket B.

Since "agentx_read" is not called, socket B writing buffer is overloaded and snmpd writing is blocked ( snmpd is using a blocking write call).
agentx is
Thus now snmpd stop to read Socket A notifications. and consecutivly socket A writing buffer is overloaded and agentX is blocked
(lib snmp is using a blocking write call).

Finally bgpd is fully blocked and freeze

Version

Hello, this is FRRouting (version 10.0 (frr-10.0-878-gde5898c37e)).
All frr
Aff net-snmp

How to reproduce

allow trap for bgpd
having a great number of neighbours.
making creation/ delation of theses neighbors.

Expected behavior

bgpd coutinue to work

Actual behavior

bgpd freeze, no crash. system is blocked

Additional context

Occurs on site

Checklist

• I have searched the open issues for this bug.
• I have not included sensitive information in this report.