FS#38159 - [dnsmasq] using 100% cpu.

Attached to Project: Arch Linux
Opened by F. Bogo the III. (fogobogo) - Monday, 16 December 2013, 12:14 GMT
Last edited by Dave Reisner (falconindy) - Monday, 16 December 2013, 18:48 GMT
Task Type Bug Report
Category Packages
Status Closed
Assigned To Dave Reisner (falconindy)
Architecture i686
Severity High
Priority Normal
Reported Version
Due in Version Undecided
Due Date Undecided
Percent Complete 100%
Votes 0
Private No

Details

Description:
dnsmasq started throwing tantrums, using 100% CPU and clogging the box, presumed suspect being the latest glibc update since rebuilding it seems to fix it.


Additional info:
* package version(s)
Name : dnsmasq
Version : 2.68-1

* config and/or log files etc.


Steps to reproduce:

run dnsmasq as service. works fine for a while, then 100% cpu

proposed fix:

rebuild dnsmasq with latest glibc
This task depends upon

Closed by  Dave Reisner (falconindy)
Monday, 16 December 2013, 18:48 GMT
Reason for closing:  Upstream
Comment by Dave Reisner (falconindy) - Monday, 16 December 2013, 14:19 GMT
Works for me.

No config, no backtrace or strace... not much I can work with here. I strongly doubt that rebuilding dnsmasq against a pkgrel bump of glibc would be anything more than placebo.
Comment by F. Bogo the III. (fogobogo) - Monday, 16 December 2013, 17:44 GMT
Ok, ok. I'll see what i can do.
Comment by F. Bogo the III. (fogobogo) - Monday, 16 December 2013, 18:39 GMT
Alright, there *is* a bug, however most likely upstream.
Here I have dns caching enabled as well as bogus-priv to get rid of the ISP DNS lookup error redirects.
seems iptables accidentally blocked port 53 which meant dnsmasq couldn't do dns caching which in turn triggers the evil loop by browsing to a nonexistant domain (e.g. fail.xzy).

This is all invisible to users because dnsmasq.service doesn't enable logging (whose switch is... -q (!?!) btw.) and theres probably something i missed about systemd but why does it run in the foreground?

Either way, bug closed. dnsmasq has some nasty loop when a bunch of circumstances come together
Comment by Dave Reisner (falconindy) - Monday, 16 December 2013, 18:48 GMT
The -q flag is bound to be absurdly noisy. I wouldn't suggest that be a default.

You should take this upstream[1]. The community is very receptive to detailed problem reports and generally has some useful advice to offer, if not an outright fix.

[1] http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss

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