Thanks Mikael for reporting this issue. And thanks David for the bisection. Let me spend some time to reproduce it and see what is going on.
From: David Ahern <dsah...@gmail.com> Date: Mon, May 13, 2019 at 8:35 PM To: Mikael Magnusson, <netdev@vger.kernel.org>, Martin KaFai Lau, Wei Wang > On 5/13/19 1:22 PM, Mikael Magnusson wrote: > > Hello list, > > > > I think I have found a regression in 4.15+ kernels. IPv6 PMTU discovery > > doesn't seem to work with source-specific routing (AKA source-address > > dependent routing, SADR). > > > > I made a test script (see attachment). It sets up a test environment > > with three network namespaces (a, b and c) using SADR. The link between > > b and c is configured with MTU 1280. It then runs a ping test with large > > packets. > > > > I have tested a couple of kernels on Ubuntu 19.04 with the following > > results. > > > > mainline 4.14.117-0414117-generic SUCCESS > > ubuntu 4.15.0-1036-oem FAIL > > mainline 5.1.0-050100-generic FAIL > > > > git bisect shows > > good: 38fbeeeeccdb38d0635398e8e344d245f6d8dc52 > bad: 2b760fcf5cfb34e8610df56d83745b2b74ae1379 > > Those are back to back commits so > 2b760fcf5cfb ipv6: hook up exception table to store dst cache > > has to be the bad commit. > > Your patch may work, but does not seem logical relative to code at the > time of 4.15 and the commit that caused the failure. cc'ing authors of > the changes referenced above.
