From: "R. Parameswaran" <parameswaran...@gmail.com> 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.
