Merge branch 'Pass-extack-to-NETDEV_PRE_UP'

Petr Machata says:

====================
Pass extack to NETDEV_PRE_UP

Drivers may need to validate configuration of a device that's about to
be upped. An example is mlxsw, which needs to check the configuration of
a VXLAN device attached to an offloaded bridge. Should the validation
fail, there's currently no way to communicate details of the failure to
the user, beyond an error number.

Therefore this patch set extends the NETDEV_PRE_UP event to include
extack, if available.

There are three vectors through which NETDEV_PRE_UP invocation can be
reached. The two major ones are dev_open() and dev_change_flags(), the
last is then __dev_change_flags().

In patch #1, the first access vector, dev_open() is addressed. An extack
parameter is added and all users converted to use it.

Before addressing the second vector, two preparatory patches propagate
extack argument to the proximity of the dev_change_flags() call in VRF
and IPVLAN drivers. That happens in patches #2 and #3. Then in patch #4,
dev_change_flags() is treated similarly to dev_open().

Likewise in patch #5, __dev_change_flags() is extended.

Then in patches #6 and #7, the extack is finally propagated all the way
to the point where the notification is emitted.

This change allows particularly mlxsw (which already has code to
leverage extack if available) to communicate to the user error messages
regarding VXLAN configuration. In patch #8, add a test case that
exercises this code and checks that an error message is propagated.

For example:

	local 192.0.2.17 remote 192.0.2.18 \
	dstport 4789 nolearning noudpcsum tos inherit ttl 100
	local 192.0.2.17 remote 192.0.2.18 \
	dstport 4789 nolearning noudpcsum tos inherit ttl 100
Error: mlxsw_spectrum: Conflicting NVE tunnels configuration.

v2:
- Add David Ahern's tags.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>