[Fwd: Re: Networking messed up, bad checksum, incorrect length]
kadlec at blackhole.kfki.hu
Mon Oct 30 09:29:24 CET 2006
On Mon, 30 Oct 2006, Jozsef Kadlecsik wrote:
> On Mon, 30 Oct 2006, Carlos Velasco wrote:
> > I'm forwarding a mail from Linux Kernel, as it seems a bug in Netfilter
> > in 2.6.18.
> The TCP session dies because a NAT device between the communicating
> parties does not adjust the sequence numbers in the SACK fields.
> Is there a NATing device, which is not identical with the machine running
> 2.6.28, between the client and the server?
No, it's not a NATing device. It's a 'smart' box which munges the TCP
sequence numbers and misses to do so in the SACK fields: the first packet
from both recordings:
23:29:27.912908 IP (tos 0x0, ttl 64, id 51776, offset 0, flags [DF],
length: 60) 192.168.128.182.45020 > 188.8.131.52.25: S [tcp sum ok]
426197099:426197099(0) win 5840
<mss 1460,sackOK,timestamp 46238251 0,nop,wscale 7>
23:29:28.017284 IP (tos 0x0, ttl 54, id 51776, offset 0, flags [DF],
length: 60) 184.108.40.206.45020 > 220.127.116.11.25: S [tcp sum ok]
888737236:888737236(0) win 5840
<mss 1380,sackOK,timestamp 46238251 0,nop,wscale 7>
It's definitely not a 2.6.18 bug.
E-mail : kadlec at blackhole.kfki.hu, kadlec at sunserv.kfki.hu
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