Merge branch 'mptcp-another-set-of-miscellaneous-mptcp-fixes'

Mat Martineau says:

====================
mptcp: Another set of miscellaneous MPTCP fixes

This is another collection of MPTCP fixes and enhancements that we have
tested in the MPTCP tree:

Patch 1 cleans up cgroup attachment for in-kernel subflow sockets.

Patches 2 and 3 make sure that deletion of advertised addresses by an
MPTCP path manager when flushing all addresses behaves similarly to the
remove-single-address operation, and adds related tests.

Patches 4 and 8 do some minor cleanup.

Patches 5-7 add MPTCP_FASTCLOSE functionality. Note that patch 6 adds MPTCP
option parsing to tcp_reset().

Patch 9 optimizes skb size for outgoing MPTCP packets.
====================

Link: https://lore.kernel.org/r/20201210222506.222251-1-mathew.j.martineau@linux.intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>