Comment 14 for bug 1928890

Doing some more research and testing, looking at the upstream commit that added the test (1a01727676a8), this is in the bottom of the message:

    [ The IPv6 MTU test still fails with the symmetric routing setup. It
      appears to be caused by source address selection picking ::1. Fixing
      this is beyond the scope of this series. ]

Running the test in the failing state, we are indeed getting a Packet too big message but we never seem to get it.

Now, within the create_vrf function, if we change the address added from ::1 to ::3
(ip -netns "${ns}" -6 addr add ::3 dev "${vrf}" nodad), it will start to work. I wonder if its getting confused since in the failing case, the src is ::1 and the dest is 2001:db8:16:1:1 so maybe the packet is going around in a loop or something.