From mboxrd@z Thu Jan 1 00:00:00 1970 From: "James Nichols" Subject: Re: After many hours all outbound connections get stuck in SYN_SENT Date: Wed, 19 Dec 2007 11:53:06 -0500 Message-ID: <83a51e120712190853q33d9c7c1t4a46380665b7538b@mail.gmail.com> References: <83a51e120712141239u52d2dd68p1b6ee7ed08f2cecf@mail.gmail.com> <83a51e120712180845k6cadf67bn5dd66fb2d3ac72d4@mail.gmail.com> <83a51e120712181009pf954f43mcb63ea4dab638458@mail.gmail.com> <83a51e120712181021p4c4c2a13g8820271f1e00361b@mail.gmail.com> <4768123A.7040603@cosmosbay.com> <83a51e120712181144l65633b32r72cc369f9d012f47@mail.gmail.com> <47682F8C.20205@cosmosbay.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: "Jan Engelhardt" , linux-kernel@vger.kernel.org, "Linux Netdev List" To: "Eric Dumazet" Return-path: Received: from mu-out-0910.google.com ([209.85.134.186]:17201 "EHLO mu-out-0910.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751732AbXLSQxJ (ORCPT ); Wed, 19 Dec 2007 11:53:09 -0500 Received: by mu-out-0910.google.com with SMTP id i10so4245849mue.5 for ; Wed, 19 Dec 2007 08:53:07 -0800 (PST) In-Reply-To: <47682F8C.20205@cosmosbay.com> Content-Disposition: inline Sender: netdev-owner@vger.kernel.org List-ID: > So you see outgoing SYN packets, but no SYN replies coming from the remote > peer ? (you mention ACKS, but the first packet received from the remote > peer should be a SYN+ACK), Right, I meant to say SYN+ACK. I don't see them coming back. > When the problem comes, instead of restarting the application, please take a > tcpdump of say 10.000 packets. > Then turn off tcp_sack and take a 2nd tcpdump sample, and make both samples > available to us. I can take these captures and take a look at the results. Unfortunately, I don't think I'll be able to make the captures available to the general public. > If turning off tcp_sack makes the problem go away, why dont you turn it off > all the time ? Unfortunately, I think that will be the answer if I can't get any help fixing this problem in the kernel. It's a bummer, because many of the remote hosts my application communicates with are on wireless links, so there may be performance implications to turning SACK off.