[Pkg-utopia-maintainers] Bug#517683: Bug#517683: avahi-daemon: reflector creates packet storm on legacy unicast traffic

[Michael Biebl]

Rob Leslie wrote:
> Package: avahi-daemon
> Version: 0.6.23-3lenny1
> Severity: important
> Tags: patch
> 
> The avahi-daemon reflector contains a bug that causes packet storms when
> reflecting legacy unicast mDNS traffic. What happens is the reflector
> forwards the initial multicast query onto the other interfaces, and then
> receives it back from the same interfaces (IP_MULTICAST_LOOP) but doesn't
> recognize it as the legacy unicast packet it just forwarded. It therefore
> acts as though it were a separate query and forwards it back onto all the
> other interfaces (including the original) and the process repeats ad
> infinitum -- until the box locks up (I've had some automatically reboot via
> watchdog) or if lucky the legacy unicast reflection slots that avahi-daemon
> maintains will fill up and the storm will abate. A symptom of the latter
> case is the syslog message "No slot available for legacy unicast reflection,
> dropping query packet." (See also Avahi ticket #216 which seems to be
> indicative of this problem.)
> 
> The problem is that the originates_from_local_legacy_unicast_socket()
> routine in avahi-core/server.c fails to take the network byte order of
> .sin_port into account when examining incoming multicast packets. The
> attached patch corrects this problem.
> 

Hi Rob,

thanks for the bug report and the patch.

Looks like this is filed as CVE-2009-0758 [1]

Nico, do you consider that important enough for a s-s-u upload?

Cheers,
Michael

[1] http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2009-0758

-- 
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