Merge branch 'mptcp-path-manager-mode-selection'

Mat Martineau says:

====================
mptcp: Path manager mode selection

MPTCP already has an in-kernel path manager (PM) to add and remove TCP
subflows associated with a given MPTCP connection. This in-kernel PM has
been designed to handle typical server-side use cases, but is not very
flexible or configurable for client devices that may have more
complicated policies to implement.

This patch series from the MPTCP tree is the first step toward adding a
generic-netlink-based API for MPTCP path management, which a privileged
userspace daemon will be able to use to control subflow
establishment. These patches add a per-namespace sysctl to select the
default PM type (in-kernel or userspace) for new MPTCP sockets. New
self-tests confirm expected behavior when userspace PM is selected but
there is no daemon available to handle existing MPTCP PM events.

Subsequent patch series (already staged in the MPTCP tree) will add the
generic netlink path management API.
====================

Link: https://lore.kernel.org/r/20220427225002.231996-1-mathew.j.martineau@linux.intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>