From owner-freebsd-stable@FreeBSD.ORG Wed Feb 13 22:01:34 2013 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by hub.freebsd.org (Postfix) with ESMTP id D8471F2B for ; Wed, 13 Feb 2013 22:01:34 +0000 (UTC) (envelope-from jdc@koitsu.org) Received: from qmta01.emeryville.ca.mail.comcast.net (qmta01.emeryville.ca.mail.comcast.net [IPv6:2001:558:fe2d:43:76:96:30:16]) by mx1.freebsd.org (Postfix) with ESMTP id B44D0222 for ; Wed, 13 Feb 2013 22:01:34 +0000 (UTC) Received: from omta13.emeryville.ca.mail.comcast.net ([76.96.30.52]) by qmta01.emeryville.ca.mail.comcast.net with comcast id zsjL1k00P17UAYkA1y1ZKe; Wed, 13 Feb 2013 22:01:33 +0000 Received: from koitsu.strangled.net ([67.180.84.87]) by omta13.emeryville.ca.mail.comcast.net with comcast id zy1Y1k0091t3BNj8Zy1YG0; Wed, 13 Feb 2013 22:01:33 +0000 Received: by icarus.home.lan (Postfix, from userid 1000) id 2288F73A1C; Wed, 13 Feb 2013 14:01:32 -0800 (PST) Date: Wed, 13 Feb 2013 14:01:32 -0800 From: Jeremy Chadwick To: Doug Hardie Subject: Re: Unusual TCP/IP Packet Size Message-ID: <20130213220132.GA68113@icarus.home.lan> References: <96AE8BD1-79C2-4743-854F-B8386C54E4A1@lafn.org> <511B6B21.5030606@rdtc.ru> <796949D9-C945-478F-BF63-A5C0BC0CF6A9@lafn.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <796949D9-C945-478F-BF63-A5C0BC0CF6A9@lafn.org> User-Agent: Mutt/1.5.21 (2010-09-15) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=comcast.net; s=q20121106; t=1360792893; bh=F7+90MTFgxqEbTFtPWji/NGJloowvC5E1cVI86K8gFI=; h=Received:Received:Received:Date:From:To:Subject:Message-ID: MIME-Version:Content-Type; b=JEWb8/7PuL8c+nWWCRGHNNIkomvfs80LFeYtxiZ/P+aEzMi7IAyM9lLn/yYY7zSLl e3a65pKvx/3LaEnT0O8MHz5bfzpiQLWK86u43RJ9YYs4RSqY/JBAU+/+Nk5hZXZ2TH enlhgMXizamV0I8jr6pDxEZ/TBRsDhoGmmEg4z0GliQAApEpdSEr2jmd4qzFMt12Mt mWOG/gCtK/nlYr5rbpNn68jzDRI4hegXEgMjaBf6JLB2kMZz7M+Zmi2EJZ2LenIiqU Xgiag4M35qNZlFLhg/S5dwLLSDqrdaqrW4K+Bqu/cpypUCxLTg62skxwgPT44ioMCm TBNcTC54V4cTQ== Cc: freebsd-stable@freebsd.org, Eugene Grosbein , yongari@freebsd.org X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 13 Feb 2013 22:01:35 -0000 On Wed, Feb 13, 2013 at 01:57:38PM -0800, Doug Hardie wrote: > > On 13 February 2013, at 02:29, Eugene Grosbein wrote: > > > 13.02.2013 17:25, Doug Hardie ??????????: > >> Monitoring a tcpdump between two systems, a FreeBSD 9.1 system has the following interface: > >> > >> msk0: flags=8843 metric 0 mtu 1500 > >> options=c011b > >> ether 00:11:2f:2a:c7:03 > >> inet 10.0.1.199 netmask 0xffffff00 broadcast 10.0.1.255 > >> inet6 fe80::211:2fff:fe2a:c703%msk0 prefixlen 64 scopeid 0x1 > >> nd6 options=29 > >> media: Ethernet autoselect (100baseTX ) > >> status: active > >> > >> > >> It sent the following packet: (data content abbreviated) > >> > >> 02:14:42.081617 IP 10.0.1.199.443 > 10.0.1.2.61258: Flags [P.], seq 930:4876, ack 846, win 1040, options [nop,nop,TS val 401838072 ecr 920110183], length 3946 > >> 0x0000: 4500 0f9e ea89 4000 4006 2a08 0a00 01c7 E.....@.@.*..... > >> 0x0010: 0a00 0102 01bb ef4a ece1 680b ae37 1bbc .......J..h..7.. > >> 0x0020: 8018 0410 3407 0000 0101 080a 17f3 8ff8 ....4...??????. > >> > >> > >> The indicated packet length is 3946 and the load of data shown is that size. The MTU on both interfaces is 1500. The receiving system received 3 packets. There is a router and switch between them. One of them fragmented that packet. This is part of a SSL/TLS exchange and one side or the other is hanging on this and just dropping the connection. I suspect the packet size is the issue. ssldump complains about the packet too and stops monitoring. Could this possibly be related to the hardware checksums? > > > > You have TSO enabled on the interface, so large outgoing TCP packet is pretty normal. > > It will be split by the NIC. Disable TSO with ifconfig if it interferes with your ssldump. > > Thanks. Now all the packets are 1500 or under. They all are received with a SSL header. If disabling TSO on msk(4) fixed the issue of the remote end dropping/ignoring the packet, that sounds like a bug in msk(4). Yong-Hyeon, do you have any recent msk(4) patches relating to TSO? -- | Jeremy Chadwick jdc@koitsu.org | | UNIX Systems Administrator http://jdc.koitsu.org/ | | Mountain View, CA, US | | Making life hard for others since 1977. PGP 4BD6C0CB |