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

[Rob Leslie]

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.


-- System Information:
Debian Release: 5.0
  APT prefers stable
  APT policy: (500, 'stable')
Architecture: i386 (i686)

Kernel: Linux 2.6.26-1-686 (SMP w/2 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/bash

Versions of packages avahi-daemon depends on:
ii  adduser                3.110             add and remove users and groups
ii  bind9-host [host]      1:9.5.1.dfsg.P1-1 Version of 'host' bundled with BIN
ii  dbus                   1.2.1-5           simple interprocess messaging syst
ii  libavahi-common3       0.6.23-3lenny1    Avahi common library
ii  libavahi-core5         0.6.23-3lenny1    Avahi's embeddable mDNS/DNS-SD lib
ii  libc6                  2.7-18            GNU C Library: Shared libraries
ii  libcap2                2.11-2            support for getting/setting POSIX.
ii  libdaemon0             0.12-2lenny1      lightweight C library for daemons 
ii  libdbus-1-3            1.2.1-5           simple interprocess messaging syst
ii  libexpat1              2.0.1-4           XML parsing C library - runtime li
ii  lsb-base               3.2-20            Linux Standard Base 3.2 init scrip

Versions of packages avahi-daemon recommends:
ii  libnss-mdns                   0.10-3     NSS module for Multicast DNS name 

Versions of packages avahi-daemon suggests:
pn  avahi-autoipd                 <none>     (no description available)

-- no debconf information
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