[syslog-ng] syslog-ng 3.3.7 DNS resolving Problem

Daniel Neubacher daniel.neubacher at xing.com
Wed Jan 9 10:10:48 CET 2013

I've got no errors yet. Sometimes syslog fooled me and waited to do it for a few days but I hope that's not the case this time. Thanks for your help.

-----Ursprüngliche Nachricht-----
Von: syslog-ng-bounces at lists.balabit.hu [mailto:syslog-ng-bounces at lists.balabit.hu] Im Auftrag von Gergely Nagy
Gesendet: Dienstag, 8. Januar 2013 09:59
An: Syslog-ng users' and developers' mailing list
Betreff: Re: [syslog-ng] syslog-ng 3.3.7 DNS resolving Problem

Daniel Neubacher <daniel.neubacher at xing.com> writes:

> I've got none of these errors with syslog-ng 3.4 beta1 - does this 
> make sense?

Interesting... all DNS-related code should be the same between 3.4beta1 and the latest 3.3 git master (compared to 3.3.7, both have a fix that uses thread-safe lookups).

Compared to 3.3.7, 3.4 beta1 has only one patch that is relevant:

commit 11b20b28f7586b2bf10c281328f28d93f39e279c
Author: Balazs Scheidler <bazsi at balabit.hu>
Date:   Fri Dec 14 17:54:39 2012 +0100

    resolve_sockaddr: fixed unsafe use of non-reentrant APIs to resolve IP addresses to names

    As it seems the use of the DNS cache hid the fact that we're not thread
    safe when resolving IPs to DNS names. This patch attempts to use
    getnameinfo() API if available that is thread safe and protects
    all other paths with a mutex.

    Reported-By: Brian Kroth <bpkroth at gmail.com>
    Tested-By: Gergely Nagy <algernon at balabit.hu>
    Signed-off-by: Balazs Scheidler <bazsi at balabit.hu>


Come to think of it, the lack of this patch might very well be the cause of your issue. Can you check if the latest 3.3 git master works for you?

There's an easily buildable tarball available at:

If this does fix the problem, then my apologies, I should've thought of it way sooner. :|


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