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/ > - > : 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 - : 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
