Merge branch 'mptcp-socket-options'

Mat Martineau says:

====================
mptcp: Improve socket option handling

MPTCP sockets have previously had limited socket option support. The
architecture of MPTCP sockets (one userspace-facing MPTCP socket that
manages one or more in-kernel TCP subflow sockets) adds complexity for
passing options through to lower levels. This patch set adds MPTCP
support for socket options commonly used with TCP.

Patch 1 reverts an interim socket option fix (a socket option blocklist)
that was merged in the net tree for v5.12.

Patch 2 moves the socket option code to a separate file, with no
functional changes.

Patch 3 adds an allowlist for socket options that are known to function
with MPTCP. Later patches in this set add more allowed options.

Patches 4 and 5 add infrastructure for syncing MPTCP-level options with
the TCP subflows.

Patches 6-12 add support for specific socket options.

Patch 13 adds a socket option self test.
====================

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