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SubjectRe: Networking messed up, bad checksum, incorrect length
Carlos Velasco <> wrote:
> 03:12:22.484863 00:13:21:cc:54:a6 > 00:0d:bc:a0:e2:82, ethertype IPv4
> (0x0800), length 12546: > .
> 68786:81266(12480) ack 228 win 40 <nop,nop,timestamp 9644391 425655748>
> LENGTH: 12546 !!

> But still worse, I wrote the full sniffer traces to a file for further
> analysis with Ethereal, and there I see that not only these long packets
> are above MTU, all they have bad TCP checksums.

These packets look like normal TSO packets. Linux will send a
packet containing more data than fits in a packet to the NIC. The
NIC will then segment the packet for us.

In order to see what really goes out, you'll need to run a packet
dump beyond the NIC.

If that is not possible, you can try disabling TSO with ethtool -K.

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