lkml.org 
[lkml]   [2003]   [Aug]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: 2.6.0: Bad udp checksum in loopback interface (me too!)
Hi!

I have almost the same program.
cups sends on udp browse informations.
It sends 3 + 1 udps.
The last one has bad checksum.


> tcpdump -v shows bad udp checksum in the loopback interface. But I'm not sure
> if the packets is discarded or the error is ignored.
>
> ponti:~# tcpdump -i lo -n -v
>
> ponti:~# dig @192.168.0.3 gallimedina.net
>
> 13:02:12.360728 192.168.0.3.32827 > 192.168.0.3.53: [bad udp cksum 5e6d!]
> 35220+ A? gallimedina.net. (33) (DF) [ttl 0] (id 0, len 61)
> 13:02:12.364470 192.168.0.3.53 > 192.168.0.3.32827: 35220* 1/1/1
> gallimedina.net. A 192.168.0.10 (85) (DF) [ttl 0] (id 12492, len 113)
>
> ponti:~# dig @127.0.0.1 gallimedina.net
>
>
> 13:03:53.299883 127.0.0.1.32827 > 127.0.0.1.53: [bad udp cksum 167d!] 32901+
> A? gallimedina.net. (33) (DF) [ttl 0] (id 0, len 61)
> 13:03:53.303448 127.0.0.1.53 > 127.0.0.1.32827: 32901* 1/1/1 gallimedina.net.
> A 192.168.0.10 (85) (DF) [ttl 0] (id 7725, len 113)
>
>
>
> This machine has a bridge, but I also tried in another one with netcat (nc -l
> -u localhost -p 2000 and nc -u localhost 2000)
>
> antoli:~# tcpdump -i lo -n -v
> tcpdump: listening on lo
> 13:09:04.125385 127.0.0.1.32890 > 127.0.0.1.2000: [bad udp cksum 5a0!] udp 14
> (DF) [ttl 0] (id 32006, len 42)
> 13:09:12.472940 127.0.0.1.2000 > 127.0.0.1.32890: [bad udp cksum 837!] udp 7
> (DF) [ttl 0] (id 34086, len 35)
>
>
> I saw the short message does arrive to the listening netcat, but tcpdump still
> gives the bad udp error message.
>
> Regards,
>
> --
> ricardo galli GPG id C8114D34
> http://mnm.uib.es/~gallir/
> -
> To unsubscribe from this list: send the line "unsubscribe linux-net" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
>

---
Catalin(ux) BOIE
catab@deuroconsult.ro
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:47    [W:0.055 / U:1.956 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site