From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Eugene B. Berdnikov" Subject: Path MTU discovery and tuntap Date: Tue, 22 Nov 2011 00:33:59 +0400 Message-ID: <20111121203359.GE2640@sie.protva.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii To: netdev@vger.kernel.org Return-path: Received: from tornado.rdtex.ru ([80.252.139.3]:55552 "EHLO tornado.rdtex.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751966Ab1KUVWO (ORCPT ); Mon, 21 Nov 2011 16:22:14 -0500 Received: from localhost ([127.0.0.1]:58836) by tornado.rdtex.ru with esmtp (Exim 4.69) (envelope-from ) id 1RSaZ0-0005wF-KF size 1565 for netdev@vger.kernel.org; Tue, 22 Nov 2011 00:34:02 +0400 Received: from tornado.rdtex.ru ([127.0.0.1]) by localhost (tornado.rdtex.ru [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id Z6+wkzBYuhfO for ; Tue, 22 Nov 2011 00:34:00 +0400 (MSK) Received: from [192.168.27.13] (port=45752 helo=sie.protva.ru) by tornado.rdtex.ru with esmtp (Exim 4.69) (envelope-from ) id 1RSaYy-0005w4-64 size 1063 for netdev@vger.kernel.org; Tue, 22 Nov 2011 00:34:00 +0400 Received: from berd by sie.protva.ru with local (Exim 4.77) (envelope-from ) id 1RSaYx-0001EK-3a for netdev@vger.kernel.org; Tue, 22 Nov 2011 00:33:59 +0400 Content-Disposition: inline Sender: netdev-owner@vger.kernel.org List-ID: Hi folks. I have two routers running a tun-based tunneling applications. Both forward packets from eth (mtu=1500) to tun (mtu=1300), emitting icmp[frag-need] if DF=1 and packet size > 1300. That's nice. But one router simply drops oversized packet after icmp emittion, and other one delivers oversized packet to application's tun. The difference is that 1st router runs 2.6.30 (it drops packet) and the 2nd runs 3.0.0 (delivers to app). Kernels are from Debian/testing. The question is: was it an intentional change or some bug? -- Eugene Berdnikov