Comment 0 for bug 1788623

IPv6 PMTU discovery fails when using source-specific routing on Ubuntu 18.04.

I have attached a test case called pmtu-sads.sh which is based on tools/testing/selftests/net/pmtu.sh in the linux source.

I have verified that the test succeeds on:
Ubuntu 16.04 with 4.4.0.131.137

And it fails on:
Ubuntu 18.04 with 4.15.0-30.32
Ubuntu 18.04 with 4.17.0-041700.201806041953
Ubuntu 18.04 with 4.18.3-041803.201808180530

System information:
Ubuntu 4.15.0-30.32-generic 4.15.18

Description: Ubuntu 18.04.1 LTS
Release: 18.04

See below for a patch which is working for me. I'm currently using linux kernel 4.15.0-32.35 built from git://kernel.ubuntu.com/ubuntu/ubuntu-bionic.git with this patch.