From owner-freebsd-current@FreeBSD.ORG Tue Apr 26 09:55:33 2005 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id B587D16A4CE; Tue, 26 Apr 2005 09:55:33 +0000 (GMT) Received: from salmon.maths.tcd.ie (salmon.maths.tcd.ie [134.226.81.11]) by mx1.FreeBSD.org (Postfix) with SMTP id 6603E43D39; Tue, 26 Apr 2005 09:55:32 +0000 (GMT) (envelope-from dwmalone@maths.tcd.ie) Received: from walton.maths.tcd.ie ([134.226.81.10] helo=maths.tcd.ie) by salmon.maths.tcd.ie with SMTP id ; 26 Apr 2005 10:55:31 +0100 (BST) To: Andre Oppermann In-reply-to: Your message of "Tue, 26 Apr 2005 11:52:28 +0200." <426E0F5C.3F157398@freebsd.org> X-Request-Do: Date: Tue, 26 Apr 2005 10:55:31 +0100 From: David Malone Message-ID: <200504261055.aa95182@salmon.maths.tcd.ie> cc: silby@freebsd.org cc: qingli@freebsd.org cc: Matthew Sullivan cc: freebsd-current@freebsd.org Subject: Re: DF (Don't frag) issues X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.1 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: Tue, 26 Apr 2005 09:55:33 -0000 > > 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. > This is a really clever idea indeed. But it only works if part of > the original packet is attached. Broken implementations are likely > to omit that. But I'll implement your suggestion as well and post > a new patch later this evening. In the case of TCP PMTU we should be OK because we to get as far as the TCP code I think we'll always have enough quoted packet? Of course, in the more general case we can't always do this, but it should help in a lot of cases. David.