Merge branch 'ipmr-always-call-ip-6-_mr_forward-from-rcu-read-side-critical-section'

Ido Schimmel says:

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ipmr: Always call ip{,6}_mr_forward() from RCU read-side critical section

Patch #1 fixes a bug in ipmr code.

Patch #2 adds corresponding test cases.
====================

Link: https://lore.kernel.org/r/20220914075339.4074096-1-idosch@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>