Date: Tue, 26 Apr 2005 10:43:37 +0100 From: David Malone <dwmalone@maths.tcd.ie> To: Andre Oppermann <andre@freebsd.org> Cc: freebsd-current@freebsd.org Subject: Re: DF (Don't frag) issues Message-ID: <20050426094337.GA44893@walton.maths.tcd.ie> In-Reply-To: <426D306B.7010000@freebsd.org> References: <20050424150211.GA87520@walton.maths.tcd.ie> <426BC78A.3E56D99B@freebsd.org> <426C1600.106@uq.edu.au> <426D2307.97D15253@freebsd.org> <426D306B.7010000@freebsd.org>
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On Mon, Apr 25, 2005 at 08:01:15PM +0200, Andre Oppermann wrote: > - Handling of received ICMP Needfrag messages. The logic was broken > for the cases where the ICMP didn't contain a suggested value. This > brokeness is in there since 5.2R and comes from my cleanup of the > routing table and introduction of TCP hostcache. However there is > no way to fix it at all. It was broken even before I broke it more. > The idea behind the old code was to step down the MTU when we got > a ICMP Needfrag by one step and try again. Unfortunatly it is very > likely that the tcp window was open by a few segments already when > we hit this. This gets us a number of those ICMP's in rapid succession > each stepping us one down. I wonder if we could look into the quoted IP header and extract the length of the IP packet that caused the needs-frag ICMP. That would stop us getting in knots when there are a few packets in flight and would give us a good idea about where we need to step down from. David.
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