Maintained by: NLnet Labs

[Unbound-users] segfault when using dnstap at high load

Robert Edmonds
Tue Apr 7 03:44:40 CEST 2015

Rogerio Bastos wrote:
> I'm trying to test unbound witk dnstap. It works fine with low load, but
> exists with segfault at high load. The segfault only happens when dnstap is
> enabled in configuration.
> I am using the debian package (version 1.5.3) avaible in [1] and recompiled
> with dnstap enabled.
> I'm following instruction descripted in [2] and using fstrm version 0.2.0.
> To test the server, I'm using dnsblast [3] with the follow command:
> ./dnsblast <server address> 50000 500

Hi, Rogerio:

Sorry to hear that.  I would be happy to help debug dnstap (I wrote the
dnstap patchset for Unbound).  Can I get some information about your

Can you show the "dnstap:" block of settings from your config, and the
"num-threads" server setting?

Does fstrm's "make check" test suite succeed?

What version of protobuf-c are you using?  (Did you compile from source,
or did you use a packaged version?)

What OS version are you using?  (Based on your mention of the Debian
package from experimental, I would guess Debian or Ubuntu.)

Are you using a uniprocessor or SMP machine?  Also, since there are some
architecture-specific parts in fstrm, what architecture are you using?


Robert Edmonds
edmonds at