[PATCH v3 net-next 0/2] net: centralize net_device MTU bounds checking

[Jarod Wilson]

Jarod Wilson (2):
  net: centralize net_device min/max MTU checking
  net: deprecate eth_change_mtu, remove usage

While looking into an MTU issue with sfc, I started noticing that almost
every NIC driver with an ndo_change_mtu function implemented almost
exactly the same range checks, and in many cases, that was the only
practical thing their ndo_change_mtu function was doing. Quite a few
drivers have either 68, 64, 60 or 46 as their minimum MTU value checked,
and then various sizes from 1500 to 65535 for their maximum MTU value. We
can remove a whole lot of redundant code here if we simple store min_mtu
and max_mtu in net_device, and check against those in net/core/dev.c's
dev_set_mtu().

This pair of patches looks to introduce centralized MTU range checking
infrastructure, while maintaining compatibility with all existing drivers,
and start to make use of it, converting all eth_change_mtu/ether_setup users
over to this new infra.

Assuming these pass review muster, I've got a ton of follow-on patches to
clean up MTU settings for everything in the kernel with an ndo_change_mtu.

This work is all staged in a (rebasing) git tree here:

https://github.com/jarodwilson/linux-muck

The master branch is based on net-next from Oct 7, and carries these two
patches, plus a ton of follow-on patches to eliminate MTU range checks
and change_mtu functions where possible. All patches were successfully
built across 160 various arch and config combos by the 0-day folks.
(Thanks to Andrew Lunn for the suggestion to get that going).

Jarod Wilson (2):
  net: centralize net_device min/max MTU checking
  net: deprecate eth_change_mtu, remove usage

CC: netdev@xxxxxxxxxxxxxxx
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