Merge branch 'mptcp-endpoint-readd-fixes' into main

Matthieu Baerts says:

====================
mptcp: fix signal endpoint readd

Issue #501 [1] showed that the Netlink PM currently doesn't correctly
support removal and re-add of signal endpoints.

Patches 1 and 2 address the issue: the first one in the userspace path-
manager, introduced in v5.19 ; and the second one in the in-kernel path-
manager, introduced in v5.7.

Patch 3 introduces a related selftest. There is no 'Fixes' tag, because
it might be hard to backport it automatically, as missing helpers in
Bash will not be caught when compiling the kernel or the selftests.

The last two patches address two small issues in the MPTCP selftests,
one introduced in v6.6., and the other one in v5.17.

Link: https://github.com/multipath-tcp/mptcp_net-next/issues/501 [1]
====================

Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>