netdev - Re: Piggyback the final ACK of the three way TCP connection establishment with the data

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Date:	Wed, 21 Mar 2012 17:00:52 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Vincent Li <vincent.mc.li@...il.com>
Cc:	netdev@...r.kernel.org
Subject: Re: Piggyback the final ACK of the three way TCP connection
 establishment with the data

On Wed, 2012-03-21 at 16:38 -0700, Vincent Li wrote:
> Hi,
> 
> I happen to see this link
> http://h20000.www2.hp.com/bc/docs/support/SupportManual/c02020743/c02020743.pdf
> and
> 
> tcp_delay_final_twh_ack:
>             Piggyback the final ACK of the three way TCP connection
>             establishment with the data by delaying the final ack by
>            10ms.
> 
>            0: Send the final ACK as soon as the SYN+ACK packet
>                arrives from the remote host.
> 
>            1: Delay the sending of the final ACK by 10ms. If
>                there is data available to be sent with in the
>                next 10ms, piggyback the ACK for the SYN.
> [0-1] Default: 1
> 
> It appears this feature is not available in kernel tcp implementation,
> is it trivial to make a custom patch to make this feature available?
> can someone give a hint on how to make a patch for this?
> 
> We had a situation that we want to make linux kernel tcp stack behave
> this way so we can reproduce another issue at hand.
> 

No kernel patch is needed, you already can do this on linux.

Check file net/ipv4/tcp_input.c lines around 5722


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