Comment 4 for bug 1742505

Mirroring some of the thread on the ovs dev ML:

From Christina

"Thanks Eric, that matches my findings, glad that there seems to be an
accepted fix already.
But it is fairly recent and only in since 4.15-rc8 levels afaik.

But OTOH its description at [1] reads pretty much like my notes so far.

@James - do you think you could test a super-recent mainline kernel
build from [2] in regard to this issue?

[1]: https://github.com/torvalds/linux/commit/cfddd4c33c254954927942599d299b3865743146
[2]: http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.15-rc8/"

This kernel fix resolves a secondary issue I saw with the 4.13 kernel where the workaround we used for 4.4 did not work - the kernel was applying a 1500 max limit to all GRE devices.

This was fixed in [1] which I've confirmed on my test but the original OVS bug still exists - gre_sys is still configured with MTU 1472, implying the IFLA_MTU value provided via netlink is being ignored by the kernel.