From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Ilya V. Matveychikov" Subject: Re: question: update_pmtu doesn't update dst mtu Date: Thu, 3 Apr 2014 16:07:21 +0400 Message-ID: <533D4EF9.60608@securitycode.ru> References: <533D47FD.9020904@securitycode.ru> <20140403115809.GA13354@order.stressinduktion.org> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: To: Hannes Frederic Sowa Return-path: Received: from itna.infosec.ru ([82.198.190.199]:29580 "EHLO itna.infosec.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751938AbaDCMGk (ORCPT ); Thu, 3 Apr 2014 08:06:40 -0400 In-Reply-To: <20140403115809.GA13354@order.stressinduktion.org> Sender: netdev-owner@vger.kernel.org List-ID: On 03.04.2014 15:58, Hannes Frederic Sowa wrote: > On Thu, Apr 03, 2014 at 03:37:33PM +0400, Ilya V. Matveychikov wrote: >> Looking through the code gives me that rt_pmtu is always 0 for the skb->dst >> entry and ipv4_mtu that called via the dst->ops->mtu() uses dev->mtu :( > > At this point you have to drop skb_dst and have to relookup the route. During > that a new dst will be created which gets the mtu value from the next hop > exception, which got created by update_pmtu. > > Normally routes are checked with dst_check if they are still valid > and a relookup should happen. In your example just do the relookup > unconditionally. > Does it mean that the next packet must have an updated route without any problems? I meant that if the first packet xmitting leads to updating the route PMTU via the exception creating (or updating) so the next packets must have an updated route? Am I right?