Subject: Re: MTU and TCP transmit offload.

From: Rick Jones <[email-masked]>
Date: Wed, 21 Sep 2011 16:58:22 -0700

>>> Isn't that covered by setsockopt() support for TCP_MAX_SEG? With
>>> TSO what gets passed to the NIC isn't the MTU, but the
>>> connection's MSS derived (in part at least) from the MTU of the
>>> egress interface. If one had made a setsockopt(TCP_MAX_SEG) call
>>> prior to the connect() or listen() call, presumably that would
>>> have influenced the MSS exchange at connection establishment.
>>
>> Ohh, that looks promising!
>>
>> I'll give that a try.
>
> This works like a charm. I'm so glad I don't need to hack
> a new sockopt!

Glad it works for you.

happy benchmarking,

rick jones

One of these days I'll have to decide if I add that as an option to 
netperf, which presently only does the getsockopt(TCP_MAX_SEG).  Folks 
with a strong preference one way or t'other should feel free to contact 
me on the side or via netperf-talk at netperf.org.