After updating xymon-server to 4.3.18, xymonnet started to crash when checking network services. I could trace this back to http://sourceforge.net/p/xymon/code/7484/tree//branches/4.3.18/xymonnet/dns2.c?diff=516c17fd34309d2eb14bcb64:7483 and indeed I'm using AAAA records. Appending a NULL to addtobuffer_many()'s arguments worked for me to prevent the crash, but no idea if that's really correct.
Auto-assigned to maintainer feld@FreeBSD.org
Hey that's fantastic! I recently hit this as well and I couldn't figure it out. It was only crashing for me on the DNS check and I suspected it may have been related to other issues people have had in the past with c-ares, but disabling c-ares for xymonnet didn't work! I disabled my DNS checks as a temporary workaround.
I dont know if the NULL is appropriate but if it works that's good news. I'll see what I can figure out.
Thanks for the report! I'll get a patch into ports as soon as possible.
A commit references this bug:
Date: Mon Jan 5 14:00:04 UTC 2015
New revision: 376300
Add patch to fix xymonnet crashing when a DNS check returns an AAAA
Submitted by: firstname.lastname@example.org
You were correct. addtobuffer_many() in case T_AAAA is a variadic function that needs to terminate in a NULL.
I've also emailed the xymon mailing list. Hopefully it will be incorporated into the next release.