From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH 1/1] tcp: Wrong timeout for SYN segments Date: Thu, 30 Aug 2012 12:45:43 -0400 (EDT) Message-ID: <20120830.124543.1590020152319166487.davem@davemloft.net> References: <1346230305.2522.15.camel@edumazet-glaptop> <1346332350.2586.10.camel@edumazet-glaptop> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: hkjerry.chu@gmail.com, alex@linlab.net, netdev@vger.kernel.org, linux-kernel@vger.kernel.org To: eric.dumazet@gmail.com Return-path: In-Reply-To: <1346332350.2586.10.camel@edumazet-glaptop> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org From: Eric Dumazet Date: Thu, 30 Aug 2012 06:12:30 -0700 > On Wed, 2012-08-29 at 10:25 -0700, H.K. Jerry Chu wrote: > >> But it probably matter slightly more for TCP Fast Open (the server >> side patch has >> been completed and will be posted soon, after I finish breaking it up >> into smaller >> pieces for ease of review purpose), when a full socket will be created with data >> passed to the app upon a valid SYN+data. Dropping a fully functioning socket >> won't be the same as dropping a request_sock unknown to the app and letting >> the other side retransmitting SYN (w/o data this time). >> >> > >> > Sure, RFC numbers are what they are, but in practice, I doubt someone >> > will really miss the extra SYNACK sent after ~32 seconds, since it would >> > matter only for the last SYN attempted. >> >> I'd slightly prefer 1 extra retry plus longer wait time just to make >> TCP Fast Open >> a little more robust (even though the app protocol is required to be >> idempotent). >> But this is not a showstopper. > > Thats very good points indeed, thanks. > > Maybe we can increase SYNACK max retrans only if the FastOpen SYN cookie > was validated. > > This way, we increase reliability without amplifying the effect of wild > SYN packets. Can we come to a final conclusion on this last point and arrive at a final patch? Thanks.