From: "R. Parameswaran" <parameswaran...@gmail.com> Date: Thu, 22 Sep 2016 13:52:43 -0700 (PDT)
> From ed585bdd6d3d2b3dec58d414f514cd764d89159d Mon Sep 17 00:00:00 2001 > From: "R. Parameswaran" <rpara...@brocade.com> > Date: Thu, 22 Sep 2016 13:19:25 -0700 > Subject: [PATCH] L2TP:Adjust intf MTU,factor underlay L3,overlay L2 > > Take into account all of the tunnel encapsulation headers when setting > up the MTU on the L2TP logical interface device. Otherwise, packets > created by the applications on top of the L2TP layer are larger > than they ought to be, relative to the underlay MTU, leading to > needless fragmentation once the outer IP encap is added. > > Specifically, take into account the (outer, underlay) IP header > imposed on the encapsulated L2TP packet, and the Layer 2 header > imposed on the inner IP packet prior to L2TP encapsulation. > > Do not assume an Ethernet (non-jumbo) underlay. Use 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). Fall back to Ethernet MTU > if this fails. > > Signed-off-by: R. Parameswaran <rpara...@brocade.com> > > Reviewed-by: "N. Prachanda" <nprac...@brocade.com>, > Reviewed-by: "R. Shearman" <rshea...@brocade.com>, > Reviewed-by: "D. Fawcus" <dfaw...@brocade.com> I have to ask, how do other tunnels over UDP such as VXLAN handle this problem?
