Re: TCP bad checksum to localhost

Paul Rusty Russell (Paul.Russell@rustcorp.com.au)
Thu, 14 Oct 1999 09:57:54 +0930

In message <m3iu4b1l8i.fsf@fred.muc.de> you write:
> > This error appears when I make a TCP connection to `localhost' as
> > 127.0.0.1:
> >
> > TCPv4 bad checksum from 192.168.7.1:803c to 127.0.0.1:0017, len=20/40
> >
> > Kernel 2.3.21, gcc-2.95.1, binutils snapshot from 991012. Other TCP
> > connections to and from outside hosts work fine.
>
> Looks like someone (netfilter?) is changing skb->ip_summed from
> CHECKSUM_UNECESSARY to something else.

Worse; you should never be connecting from 192.168.7.1 to 127.0.0.1.
This is a NAT bug: what exactly are you doing?

Rusty.

--
Hacking time.


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