[Pkg-utopia-maintainers] Bug#754185: avahi-daemon: Packet too short or invalid while reading known answer record. (Maybe a UTF-8 problem?)

[Thorsten Glaser]

On Mon, 21 Jul 2014, Dominik George wrote:

> I think *cough* I triggered this message on Thorsten's machine at work

No, you weren’t it (alone).

Today while waiting for debbugs to accept a newly submitted report
so I could reference it in the d/changelog where I workarounded it,
I decided to run a little “sudo tcpdump -X port 5353 or port 35388”.

Turns out that it was this:

15:10:06.645999 IP pjakob-mb.lan.tarent.de.mdns > 224.0.0.251.mdns: 0 [2a] PTR (QM)? _googlecast._tcp.local. (56)
        0x0000:  4500 0054 0000 4000 0111 e868 ac1a 041b  E..T.. at ....h....
        0x0010:  e000 00fb 14e9 14e9 0040 2f70 0000 0000  .........@/p....
        0x0020:  0001 0002 0000 0000 0b5f 676f 6f67 6c65  ........._google
        0x0030:  6361 7374 045f 7463 7005 6c6f 6361 6c00  cast._tcp.local.
        0x0040:  000c 0001 0c31 3732 0368 656c 095f 7366  .....172.hel._sf
        0x0050:  7470 2d73                                tp-s

This perfectly matches the followig syslog entry:

Jul 24 15:10:06 tglase-nb avahi-daemon[1553]: server.c: Packet too short or invalid while reading known answer record. (Maybe a UTF-8 problem?)

The timestamp is ok, the two packets received prior to and after it
were distant enough (15:09:59.474377 and 15:10:12.173064, respectively).

Paweł, what the hell is “googlecast”, and why are you running it in
our network?
Please report the bug there that they multicast invalid packets.

@avahi maintainers: I think this may not be a bug in your package.
You may wish to leave this report open so that others know what to
look for when they encounter these messages (krfb and googlecast)
until those issues are fixed.

You may wish to add a filter ignoring packets from “googlecast”,
to reduce the overall noise. Up to you.

Thanks,
//mirabilos
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