From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: [RFC] ECN and IP defragmentation Date: Wed, 05 Jan 2011 01:13:51 +0100 Message-ID: <1294186431.3420.19.camel@edumazet-laptop> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: netdev To: David Miller Return-path: Received: from mail-ww0-f44.google.com ([74.125.82.44]:51646 "EHLO mail-ww0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750940Ab1AEANz (ORCPT ); Tue, 4 Jan 2011 19:13:55 -0500 Received: by wwa36 with SMTP id 36so15759053wwa.1 for ; Tue, 04 Jan 2011 16:13:54 -0800 (PST) Sender: netdev-owner@vger.kernel.org List-ID: Hi David It seems ip_fragment.c doesnt comply with RFC3168, section 5.3 5.3. Fragmentation ECN-capable packets MAY have the DF (Don't Fragment) bit set. Reassembly of a fragmented packet MUST NOT lose indications of congestion. In other words, if any fragment of an IP packet to be reassembled has the CE codepoint set, then one of two actions MUST be taken: * Set the CE codepoint on the reassembled packet. However, this MUST NOT occur if any of the other fragments contributing to this reassembly carries the Not-ECT codepoint. * The packet is dropped, instead of being reassembled, for any other reason. Should we fix this ? (I tried to use ECN on UDP messages and noticed this problem) Thanks