From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH net-next] ipv4: introduce new IP_MTU_DISCOVER mode IP_PMTUDISC_INTERFACE Date: Thu, 31 Oct 2013 00:29:11 -0400 (EDT) Message-ID: <20131031.002911.1316728367651608156.davem@davemloft.net> References: <20131030200725.GB9093@order.stressinduktion.org> <20131030.173608.2156276556221568210.davem@davemloft.net> <20131030225851.GB13902@order.stressinduktion.org> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, fweimer@redhat.com To: hannes@stressinduktion.org Return-path: Received: from shards.monkeyblade.net ([149.20.54.216]:36699 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750779Ab3JaE3M (ORCPT ); Thu, 31 Oct 2013 00:29:12 -0400 In-Reply-To: <20131030225851.GB13902@order.stressinduktion.org> Sender: netdev-owner@vger.kernel.org List-ID: From: Hannes Frederic Sowa Date: Wed, 30 Oct 2013 23:58:51 +0100 > DNS resolver can fallback to TCP for querying where we can honour the > path MTU because it won't do any harm and ensures connectivity. > > Also for TCP the socket is matched on the whole 4-tuple and we may > fallback to a 2-tuple lookup on unconnected UDP sockets. The new socket > option would let an application programmer choose to do path mtu discovery > because it knows it will only use a connected socket. On unconnected > sockets one can specify IP_PMTUDISC_INTERFACE to suppress the path MTU > updates and always use the interface MTU without the DF-bit set. This still sounds like a route scope policy with two binary states, one for connected sockets and one for unconnected ones.