[avahi] Linsys E4200: Received response with invalid source port

Andrew knoppix at rngresearch.com
Mon Jul 18 23:31:01 PDT 2011

> On 18 July 2011 15:01, Eric Martel <shrodi+avahi at gmail.com> wrote:
>> But doesn't the draft also specify that "Multicast DNS implementations
>> MUST silently ignore any Multicast DNS Responses they receive where the
>> source UDP port is not 5353."? Shouldn't avahi therefore ignore thos
>> responses instead of reporting them? Is there a way for me to tell it
>> so?
> It is ignoring, in the way that is not considering it a valid answer,
> but it is reporting.
> Now "silent" I'd say it's just semantics, it's nice to have a warning
> or a message that "something weird is happening", it does not affect
> the system at all. When the draft says "silently" it implies "nothing
> should be done", logging the event is a nice thing IMHO, you would
> spend a lot more time to conclude this fact if it was not for the
> reporting.
> Use tcpdump and verify that avahi is correct (ie: source port is
> wrong), if it is, it's your router's fault.
> I don't know much of avahi, I only know mdns quite well.

Ideally, you should be able to tell avahi, via its conf file and/or
command line, what priorities (e.g., err, notice, debug) you want logged. 
Supposing this particular message has a priority of "notice" (normal, but
significant), you could tell avahi to log only up to "err" or "warning". 
However, I don't see any provision for this on the avahi man pages.

On the syslog side of things, you might try this:  Determine what
"facility" name avahi is using for logging.  Then determine what log level
avahi is using for this particular message that is "clogging" your logs. 
Assuming the level is just, say "info", or perhaps even "notice", adjust
/etc/syslog.conf to filter out this log level for this facility (or to
direct such messages to a separate log file).

The only problem with this suggestion is, of course, that all messages of
this log level for this particular facility will also be lost (or placed
in the alternate file).

I hope this helps.

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