SNMP timeouts and leaks under ASAN on Ubuntu 22.04

[iluuu1994]

Description

See be4db6b and https://github.com/php/php-src/actions/runs/4527719935/jobs/7973855747.

PHP Version

master

Operating System

Ubuntu 22.04

[nielsdos]

Looks like the leak only happens for PHPDBG.
I checked and the ext/snmp MINIT function is called multiple times for the phpdbg tests which leak. This means that snmp_init() is called multiple times. I see that the MSHUTDOWN does get called though. Looks like if the sequence of MINIT-MSHUTDOWN occurs once then there is no leak, but if it happens multiple times then it leaks.

This PR that was merged in the netsnmp library looks related: net-snmp/net-snmp#450. Looks like the PR isn't included yet in a released version unfortunately.

[iluuu1994]

I checked and the ext/snmp MINIT function is called multiple times for the phpdbg tests which leak.

Hmm... @bwoebi Is this something that should be happening?

The other mystery are the timeouts for which I have no explanation.

[bwoebi]

Generally repeated minit and mshutdown sequences ought something to be supported by extensions. I believe there's other circumstances where this may happen (with apache?! not sure right now).

[nielsdos]

The other mystery are the timeouts for which I have no explanation.

Isn't that just ASAN causing massive performance drops? I experience similar issues with another project in CI.

[iluuu1994]

Isn't that just ASAN causing massive performance drops? I experience similar issues with another project in CI.

We have tests failing (meaning they exceed 120s) that usually pass in 1-2s. So I'm not sure. (Usually ASAN/UBSAN causes 2-3x performance degradation). I also couldn't reproduce the timeouts locally with the same libsmnp and smnpd versions.