From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH net-next v5 0/2] L2TP:Adjust intf MTU, add underlay L3, L2 hdrs. Date: Thu, 06 Apr 2017 13:43:49 -0700 (PDT) Message-ID: <20170406.134349.901826134748051625.davem@davemloft.net> References: Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, jchapman@katalix.com, kleptog@svana.org, nprachan@brocade.com, rshearma@brocade.com, stephen@networkplumber.org, sdietric@brocade.com, ciwillia@brocade.com, lboccass@brocade.com, dfawcus@brocade.com, bhong@brocade.com, jblunck@brocade.com, linux-kernel@vger.kernel.org To: parameswaran.r7@gmail.com Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org From: "R. Parameswaran" Date: Wed, 5 Apr 2017 17:05:49 -0700 (PDT) > > Existing L2TP kernel code does not derive the optimal MTU for Ethernet > pseudowires and instead leaves this to a userspace L2TP daemon or > operator. If an MTU is not specified, the existing kernel code chooses > an MTU that does not take account of all tunnel header overheads, which > can lead to unwanted IP fragmentation. When L2TP is used without a > control plane (userspace daemon), we would prefer that the kernel does a > better job of choosing a default pseudowire MTU, taking account of all > tunnel header overheads, including IP header options, if any. This patch > addresses this. > > Change-set is organized as a two part patch series, with one patch > introducing a new kernel function to compute the IP overhead on a > socket, and the other patch using this new kernel function to compute > the default L2TP MTU for an Ethernet pseudowire. > > Existing code also seems to assume an Ethernet (non-jumbo) underlay. The > change proposed here uses the PMTU mechanism and the dst entry in the > L2TP tunnel socket to directly pull up the underlay MTU (as the baseline > number on top of which the encapsulation headers are factored in). > An default MTU value of 1500 bytes is assumed as a fallback only if > this fails. > > Fixed the kbuild test robot error in the previous posting. Series applied, thanks.