excessive TCP duplicate acks?

[Peter Jeremy]

On 2007-Mar-03 16:12:32 +0100, Andre Oppermann <andre at freebsd.org> wrote:
>Peter Jeremy wrote:
>>On 2007-Jan-26 11:59:06 -0500, Andrew Gallatin <gallatin at cs.duke.edu> 
>>wrote:
>>
>>>When running some benchmarks, I noticed tons of duplicate acks showing
>>>up in systat -tcp (thousands, or tens of thousands per second).
>>
>>Whilst investigating other problems, I've just seen the same on 6.2.
...
>This thing is really strange and difficult to debug.

At least for me, it's not readily reproducable.  I've written a perl
script to try and locate the problem in tcpdumps I've taken for other
reasons and haven't seen any recurrences of it.

>I haven't experienced this bug myself which makes it even harder to debug.

It's not something you'd probably notice unless you were specifically
looking.  In my case, I only noticed because I am trying to track an
ipfilter bug and that connection setup had been flagged so I was
studying the tcpdump output.

Any ideas on where to add some checks to try and detect this without
needing to pour over tcpdump traces?

-- 
Peter Jeremy
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