On Thu, Apr 05, 2018 at 05:36:36PM +0200, Stefano Brivio wrote:
On Wed, 04 Apr 2018 01:09:16 +0100 Ben Hutchings ben.hutchings@codethink.co.uk wrote:
On Fri, 2018-03-23 at 10:55 +0100, Greg Kroah-Hartman wrote:
4.4-stable review patch. If anyone has any objections, please let me know.
From: Alexey Kodanev alexey.kodanev@oracle.com
[ Upstream commit 53c81e95df1793933f87748d36070a721f6cb287 ]
[...]
There are a couple of follow-ups to this:
c6741fbed6dc vti6: Properly adjust vti6 MTU from MTU of lower device 7a67e69a339a vti6: Keep set MTU on link creation or change, validate it
The second of those will fail to build on branches older than 4.10 though. It might be better to revert this one instead.
Thanks Ben for spotting this.
Actually, 53c81e95df17 ("ip6_vti: adjust vti mtu according to mtu of lower device") alone improves things already, despite being "fixed" by c6741fbed6dc ("vti6: Properly adjust vti6 MTU from MTU of lower device")
With just 53c81e95df17 the MTU of a vti6 interface will be somewhat linked to the MTU of the lower layer, but will be underestimated.
With c6741fbed6dc the calculation of MTU from lower layer will be accurate instead.
However, without 7a67e69a339a ("vti6: Keep set MTU on link creation or change, validate it") but with 53c81e95df17 ("ip6_vti: adjust vti mtu according to mtu of lower device") assignment of MTU on link change is discarded, so this would actually introduce a bug.
Fixing 7a67e69a339a ("vti6: Keep set MTU on link creation or change, validate it") for 4.4 up to 4.9 is trivial, we simply need to adjust for the lack of b96f9afee4eb ("ipv4/6: use core net MTU range checking") and reflect the change introduced by f8a554b4aa96 ("vti6: Fix dev->max_mtu setting").
So, Greg, here comes the backport of 7a67e69a339a ("vti6: Keep set MTU on link creation or change, validate it") based on latest linux-4.4.y branch, in case you want to keep the existing change and add the follow-ups on top. Please let me know if I should submit it formally.
Ick, that's a mess. How about I just revert this patch from the stable trees, and then someone sends me either a list of git commits to apply, or patches, for the different trees if it's really needed?
thanks,
greg k-h