Intel 82550 Pro/100 Ethernet and TSO troubles

[Andrea Venturoli]

On 12/14/11 20:59, YongHyeon PYUN wrote:

> AFAIK the firmware of controller has no known TSO issue so it
> indicates a bug in driver.
> What makes me wonder is ICMP ECHO packet should not be affected by
> TSO and I have no clue at this moment.

I wasn't talking about ICMP ECHO.

What happened was:
a) the client connected to my server, advertising a TCP MSS of X;
b) my server started sending with packets larger than X (possibly it 
misinterpreted MSS size???);
c) an ICMP packet arrived, asking my server to send packets no larger 
than Y (I guess it was ignored);
d) my server kept resending the same (too big) packets;
e) it eventually reduced packet size, but it was still larger than Y;
...

Wireshark showed some wrong checksums (I believe on the ICMP packet, but 
I might remember wrong).
Of course this made a bell ring and removing TSO solved everything.



> (Here, I assume you've
> captured packets on receiver side since bpf sees packets before
> hardware computes checksum.)

Yes, although I don't have them anymore.



> If you have a reliable way that reproduces the issue, let me know.

I can turn TSO on again, save the packets and send them to you.
I just hope nothing changes on the Internet in between the server and 
the client.
Let me know if you need/want this and I'll arrange in the next few days.



  bye & Thanks
	av.