From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: NAT stops forwarding ACKs after PMTU discovery Date: Mon, 19 Aug 2013 09:00:31 -0700 Message-ID: <1376928031.4226.66.camel@edumazet-glaptop> References: <1376839467.21329.36.camel@edumazet-glaptop> <1376870425.4226.25.camel@edumazet-glaptop> <1376870592.4226.27.camel@edumazet-glaptop> <5211DAA6.1070302@fatooh.org> <20130819123314.GC3583@cpaasch-mac> <1376918657.4226.59.camel@edumazet-glaptop> <20130819134919.GF3583@cpaasch-mac> <1376920685.4226.61.camel@edumazet-glaptop> <20130819143509.GA31320@linuxace.com> <20130819153328.GH3583@cpaasch-mac> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Phil Oester , Corey Hickey , Jozsef Kadlecsik , Linux Netdev List , netfilter-devel@vger.kernel.org To: Christoph Paasch Return-path: Received: from mail-pa0-f51.google.com ([209.85.220.51]:64540 "EHLO mail-pa0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751073Ab3HSQAk (ORCPT ); Mon, 19 Aug 2013 12:00:40 -0400 In-Reply-To: <20130819153328.GH3583@cpaasch-mac> Sender: netdev-owner@vger.kernel.org List-ID: On Mon, 2013-08-19 at 17:33 +0200, Christoph Paasch wrote: > > Unfortunately, they will hardly go away in the near futur. Rather the > opposite is the case. > > > If you have a public server running, I would be interested in the count of > invalid SACK-blocks received (netstat -s | grep TCPSACKDiscard). This is an > indication for such kind of middlebox between your server and the client, > implying that these connections cannot benefit from TCP-FastRetransmission > and each packet-loss will require an RTO to recover. > If the (random) sequence offset is small rather than completely out of window, it's going to be hard to detect all problems. Show us your patch ;)