From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: Piggyback the final ACK of the three way TCP connection establishment with the data Date: Wed, 21 Mar 2012 17:00:52 -0700 Message-ID: <1332374452.9433.15.camel@edumazet-glaptop> References: Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org To: Vincent Li Return-path: Received: from mail-pz0-f46.google.com ([209.85.210.46]:54346 "EHLO mail-pz0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932072Ab2CVAAz (ORCPT ); Wed, 21 Mar 2012 20:00:55 -0400 Received: by dajr28 with SMTP id r28so2269941daj.19 for ; Wed, 21 Mar 2012 17:00:55 -0700 (PDT) In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: 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