Merge branch 'mptcp-miscellaneous-mptcp-fixes'

Mat Martineau says:

====================
mptcp: Miscellaneous MPTCP fixes

This is a collection of small fixup and minor enhancement patches that
have accumulated in the MPTCP tree while net-next was closed. These are
prerequisites for larger changes we have queued up.

Patch 1 refines receive buffer autotuning.

Patches 2 and 4 are some minor locking and refactoring changes.

Patch 3 improves GRO and RX coalescing with MPTCP skbs.

Patches 5-7 add a sysctl for tuning ADD_ADDR retransmission timeout,
corresponding test code, and documentation.

v2: Add sysctl documentation and fix signoff tags.
====================

Link: https://lore.kernel.org/r/20201103190509.27416-1-mathew.j.martineau@linux.intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>