svn commit: r242251 - head/sys/netinet

[Andre Oppermann]

On 28.10.2012 18:30, Andre Oppermann wrote:
> Author: andre
> Date: Sun Oct 28 17:30:28 2012
> New Revision: 242251
> URL: http://svn.freebsd.org/changeset/base/242251
>
> Log:
>    When SYN or SYN/ACK had to be retransmitted RFC5681 requires us to
>    reduce the initial CWND to one segment.  This reduction got lost
>    some time ago due to a change in initialization ordering.
>
>    Additionally in tcp_timer_rexmt() avoid entering fast recovery when
>    we're still in TCPS_SYN_SENT state.

Oops, this was the wrong commit message for this change.  Here is the
correct one:

   Defer sending an independent window update if a delayed ACK is pending
   saving a packet.  The window update then gets piggy-backed on the next
   already scheduled ACK.

I've forced commit r242311 with some grammar fixes to provide this information.

-- 
Andre

>    MFC after:	2 weeks
>
> Modified:
>    head/sys/netinet/tcp_output.c
>
> Modified: head/sys/netinet/tcp_output.c
> ==============================================================================
> --- head/sys/netinet/tcp_output.c	Sun Oct 28 17:25:08 2012	(r242250)
> +++ head/sys/netinet/tcp_output.c	Sun Oct 28 17:30:28 2012	(r242251)
> @@ -551,10 +551,14 @@ after_sack_rexmit:
>   	 * max size segments, or at least 50% of the maximum possible
>   	 * window, then want to send a window update to peer.
>   	 * Skip this if the connection is in T/TCP half-open state.
> -	 * Don't send pure window updates when the peer has closed
> -	 * the connection and won't ever send more data.
> +	 *
> +	 * Don't send an independent window update if a delayed
> +	 * ACK is pending (it will get piggy-backed on it) or the
> +	 * remote side already has done a half-close and won't send
> +	 * more data.
>   	 */
>   	if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) &&
> +	    !(tp->t_flags & TF_DELACK) &&
>   	    !TCPS_HAVERCVDFIN(tp->t_state)) {
>   		/*
>   		 * "adv" is the amount we can increase the window,
>
>