Date: Tue, 20 Mar 2007 01:47:27 +0000 From: "Bruce M. Simpson" <bms@FreeBSD.org> To: Kevin Lahey <kml@patheticgeek.net> Cc: freebsd-net@freebsd.org Subject: Re: PMTU Discovery support Message-ID: <45FF3D2F.3040000@FreeBSD.org> In-Reply-To: <20070319172156.68cba0a9@yakko.patheticgeek.net> References: <994cd1cf0703050842r5e54daa6y5fe6af3083e15cd@mail.gmail.com> <45EC6E88.3080101@tomjudge.com> <20070305115615.W38684@orthanc.ca> <994cd1cf0703052105y375679a4t482f4e35988f9daf@mail.gmail.com> <20070319145422.39bfddcd@yakko.patheticgeek.net> <20070319172156.68cba0a9@yakko.patheticgeek.net>
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Kevin Lahey wrote: > > The boxes were running FreeBSD-6.1, but I can't really vouch for the > particular kernel configuration. It could well be that the problem is > with the loose nut behind the wheel, rather than with FreeBSD. :-) > I believe PMTU measurements may only be relied upon for active TCP connections, but it's been a while since I read this code. It would be useful if non-TCP drivers such as gre(4) could be extended to perform PMTU discovery and auto-tune their MTU based on this, as manually setting the MTU is a bit random and can result in horrible fragmentation when going across the big-I Internet. I imagine doing this would require changes to the icmp input path and a bit of abstraction. Regards, BMS
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