Merge branch 'mptcp-pm-in-kernel-increase-limits'

Matthieu Baerts says:

====================
mptcp: pm: in-kernel: increase limits

Allow switching from 8 to 64 for the maximum number of subflows and
accepted ADD_ADDR, and from 8 to 255 for the number of MPTCP endpoints.

The previous limit of 8 subflows makes sense in most cases. Using more
subflows will very likely *not* improve the situation, and could even
decrease the performances. But there are no technical limitations nor
performance impact to raise this limit, so let's do it: this will allow
people with very specific use-cases, and researchers to easily create
more subflows, and measure the performance impact by themselves.

- Patches 1-2: increase subflows and accepted ADD_ADDR limits.

- Patches 3-4: increase endpoints limit.

- Patches 5-7: validate the new limits: 64 subflows, 255 endpoints.

- Patch 8: selftests: use send()/recv() instead of sendto()/recvfrom().
====================

Link: https://patch.msgid.link/20260508-net-next-mptcp-pm-inc-limits-v1-0-c84e3fdf9b6a@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>