From owner-freebsd-current@FreeBSD.ORG Mon Mar 8 01:56:57 2010 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 061541065670 for ; Mon, 8 Mar 2010 01:56:57 +0000 (UTC) (envelope-from dave@dogwood.com) Received: from mail-vw0-f54.google.com (mail-vw0-f54.google.com [209.85.212.54]) by mx1.freebsd.org (Postfix) with ESMTP id 9D8E68FC08 for ; Mon, 8 Mar 2010 01:56:56 +0000 (UTC) Received: by vws14 with SMTP id 14so2829167vws.13 for ; Sun, 07 Mar 2010 17:56:55 -0800 (PST) MIME-Version: 1.0 Received: by 10.220.127.4 with SMTP id e4mr2534952vcs.79.1268013415516; Sun, 07 Mar 2010 17:56:55 -0800 (PST) In-Reply-To: <07C6C4E7-3512-4003-BDDE-DEDB549F6EA8@mac.com> References: <4B9425C4.5060309@freebsd.org> <07C6C4E7-3512-4003-BDDE-DEDB549F6EA8@mac.com> Date: Sun, 7 Mar 2010 15:56:55 -1000 Message-ID: <4ab61a81003071756p1d5b273coa59cb6c075cb56fb@mail.gmail.com> From: David Cornejo To: Chuck Swiger Content-Type: text/plain; charset=ISO-8859-1 X-Content-Filtered-By: Mailman/MimeDel 2.1.5 Cc: Tim Kientzle , "freebsd-current@freebsd.org" Subject: Re: Wireless TCP aborts X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 08 Mar 2010 01:56:57 -0000 On Sun, Mar 7, 2010 at 1:08 PM, Chuck Swiger wrote: > Hi, Tim-- > > On Mar 7, 2010, at 2:16 PM, Tim Kientzle wrote: > [ ... ] > > Corrupted MAC on input. > > Disconnecting: Packet corrupt > > rsync: connection unexpectedly closed ... [receiver] > > > > and then the rsync session is dead. > > > > It seems odd that a single corrupt packet would terminate the TCP > connection. > > It's not TCP itself which is closing the connection; if a garbage packet as > far as TCP or IP layer checksums was seen, it would be dropped and normal > resend mechanisms would compensate. However, SSH adds it's own layer of > data integrity checking called HMAC, which uses block-based hashes like MD5 > or SHA, and is much stronger than the 32-bit CRCs used at TCP/IP layers. > > See: > > /usr/src/crypto/openssh/packet.c > http://en.wikipedia.org/wiki/HMAC > > The implication is that the data is being corrupted before it gets munged > into network packets; failing memory is a likely cause, but bugs in the > network stack, the NIC driver, or OpenSSL are also lower-order > possibilities. > > Regards, > -- > -Chuck > > I have seen this same symptom many times with PCEngines ALIX boards but on the vr interfaces. It seems to come and go as I update kernels and worse yet, it seems to vary by board - have four boards all purchased at the same time a couple of years ago and some seem more prone to it than others. All have worked and failed at one time or another. I had, at one point, thought it to be related to power problems, because a high-power mini-PCI WiFi card seemed to exacerbate the problem, but removing the card made no difference, and the problem cleared up with an update and recompile of my source tree. It's a very disconcerting problem because FTP'ed files were being silently corrupted, so it's not just an SSH problem either. dave c