From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ketan Kulkarni Subject: [Query] TCP TFO Query Date: Tue, 11 Dec 2012 22:59:02 +0530 Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 To: netdev@vger.kernel.org Return-path: Received: from mail-ie0-f182.google.com ([209.85.223.182]:57406 "EHLO mail-ie0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753240Ab2LKRg7 (ORCPT ); Tue, 11 Dec 2012 12:36:59 -0500 Received: by mail-ie0-f182.google.com with SMTP id s9so13253167iec.41 for ; Tue, 11 Dec 2012 09:36:58 -0800 (PST) Sender: netdev-owner@vger.kernel.org List-ID: Hi, I am testing tcp tfo behavior with httping client and polipo server on 3.7rc-8 One observation from my TFO testing -If for a connection server sends a cookie to client, client always does TFO for subsequent connections. This is ok. If for some reason, server stops supporting TFO (either because server got restarted without TFO support (in my case) or because path changed and the nw node is dropping packet with unknown syn option or stripping the option), client does not clear up its cookie cache. It always sends data in syn and server never acks the syn-data and client retransmits. As per kernel code -if syn-data is not acked it is retransmitted immediately - with the assumption first syn was dropped (but the assumption server stopped supporting TFO might not have been considered) Will it be better to flush the cookie for this server and re-attempt the cookie "negotiation" on subsequent connection than to retransmit the data every time? Your thoughts? Thanks, Ketan