Merge branch 'mlxsw-add-support-for-blackhole-nexthops'

Ido Schimmel says:

====================
mlxsw: Add support for blackhole nexthops

This patch set adds support for blackhole nexthops in mlxsw. These
nexthops are exactly the same as other nexthops, but instead of
forwarding packets to an egress router interface (RIF), they are
programmed to silently drop them.

Patches #1-#4 are preparations.

Patch #5 adds support for blackhole nexthops and removes the check that
prevented them from being programmed.

Patch #6 adds a selftests over mlxsw which tests that blackhole nexthops
can be programmed and are marked as offloaded.

Patch #7 extends the existing nexthop forwarding test to also test
blackhole functionality.

Patches #8-#10 add support for a new packet trap ('blackhole_nexthop')
which should be triggered whenever packets are dropped by a blackhole
nexthop. Obviously, by default, the trap action is set to 'drop' so that
dropped packets will not be reported.
====================

Link: https://lore.kernel.org/r/20201123071230.676469-1-idosch@idosch.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>