bad checksum problem

[Jeremias]

I got a high network traffic as an answer of:
mount //server/media /mnt/media -t smbfs -o username=user,password=pw
without doing something!

I captured some packages with ethereal/tcpdump and got a lot of bad checksum errors on udp and tcp protocols, only on packages sent out of my pc. But ifconfig and netstat shows no error.

[user@pc ~]$ ifconfig eth1
eth1 Link encap:Ethernet HWaddr 00:50:04:2C:D5:01
inet addr:192.168.6.244 Bcast:192.168.6.255 Mask:255.255.255.0
inet6 addr: fe80::250:4ff:fe2c:d501/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:8296 errors:0 dropped:0 overruns:0 frame:0
TX packets:11212 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:2422982 (2.3 MiB) TX bytes:1716296 (1.6 MiB)
Interrupt:9 Base address:0xa800
[user@pc ~]$ netstat -in eth1
Kernel Interface table
Iface MTU Met RX-OK RX-ERR RX-DRP RX-OVR TX-OK TX-ERR TX-DRP TX-OVR Flg
eth1 1500 0 8332 0 0 0 11248 0 0 0 BMRU
[user@pc ~]$ tcpdump eth1 | grep cksum
09:44:27.978790 IP (tos 0x0, ttl 64, id 47122, offset 0, flags [DF], proto 17, length: 70) 192.168.6.244.32780 > router.hometown.domain: [bad udp cksum 53dc!] 63908+ PTR? 1.6.168.192.in-addr.arpa. (42)
09:44:28.019048 IP (tos 0x0, ttl 64, id 59335, offset 0, flags [DF], proto 6, length: 52) 192.168.6.244.35520 > server.hometown.microsoft-ds: . [tcp sum ok] 279:279(0) ack 545 win 1460 <nop,nop,timestamp 2537531 61868669>
0
...
09:17:31.282177 IP (tos 0x0, ttl 64, id 53098, offset 0, flags [DF], proto 6, length: 57) 192.168.6.244.54166 > baym-cs237.msgr.hotmail.com.1863: P [bad tcp cksum 9d13 (->af9e)!] 10:15(5) ack 17 win 2264 <nop,nop,timestamp 920548 2261424>
09:18:19.539379 IP (tos 0x0, ttl 64, id 51308, offset 0, flags [DF], proto 17, length: 60) 192.168.6.244.32780 > router.hometown.domain: [bad udp cksum d8be!] 19895+ AAAA? foxtown.ath.cx. (32)
09:18:19.703905 IP (tos 0x0, ttl 64, id 51473, offset 0, flags [DF], proto 17, length: 69) 192.168.6.244.32780 > router.hometown.domain: [bad udp cksum 31a1!] 36005+ AAAA? foxtown.ath.cx.hometown. (41)
...
205.188.8.200.5190: P [bad tcp cksum 9e41 (->9613)!] 18:24(6) ack 1 win 20400
09:18:31.282043 IP (tos 0x0, ttl 64, id 53102, offset 0, flags [DF], proto 6, length: 57) 192.168.6.244.54166 > baym-cs237.msgr.hotmail.com.1863: P [bad tcp cksum 9d13 (->c2d0)!] 15:20(5) ack 25 win 2264 <nop,nop,timestamp 980557 2262023>
09:19:27.544287 IP (tos 0x0, ttl 64, id 47298, offset 0, flags [DF], proto 6, length: 46) 192.168.6.244.49319 > 205.188.8.200.5190: P [bad tcp cksum 9e41 (->960c)!] 24:30(6) ack 1 win 20400
09:19:31.281721 IP (tos 0x0, ttl 64, id 53106, offset 0, flags [DF], proto 6, length: 57) 192.168.6.244.54166 > baym-cs237.msgr.hotmail.com.1863: P [bad tcp cksum 9d13 (->d600)!] 20:25(5) ack 33 win 2264 <nop,nop,timestamp 1040566 2262624>
0
...

I'm running FC4, with Kernel 2.6.12-1.1447_FC4 on a 800MHz Intel Pentium III
NIC1: 3Com, XL PCI, Fast Etherlink, 3C905B-TX
NIC2: 3Com, XL PCI, Fast Etherlink, 3C905B-TX
else: Hauppauge WinTV, ATI Rage

Thanks for help!

[vkaci]

I have the same problem. Can you got some answere for this problem?

[Jeremias]

Unfortunately not. I've this problem (bad checksum) on another machine with FC3 too, but there isn't a high network traffic without a reason.

I really haven't a clue! Perhaps someone else?
Sorry.

[swint144]

Same problem on my machine - but still looking for answers.