[PATCH mptcp-next RFC v5 0/3] mptcp: fallback to TCP on MP_FAIL with a single subflow

[Chenguang Zhao <chenguang.zhao@linux.dev>]

From: Chenguang Zhao <zhaochenguang@kylinos.cn>

Patch1:
 Add MPFailFallback MIB counter

Patch2:
 Move the FALLBACK_DONE flag setting to right after MP_FAIL is received.

Patch3:
 Add a __mptcp_check_fallback() check inside mptcp_can_accept_new_subflow()
 to reject MP_JOIN requests earlier.

I have tested with the script from the linked URL, and the kernel is now
able to reject MP_JOIN requests early.
 https://github.com/chrisocean716-star/packetdrill/blob/fed57fab92c407eb433acdb8c8ce72bd8e3e2f37/gtests/net/mptcp/mp_join/mp_join_server_after_fallback.pkt

Chenguang Zhao (3):
  mptcp: add MPFailFallback MIB counter
  mptcp: fallback immediately on MP_FAIL reception
  mptcp: reject new subflows after fallback

 net/mptcp/mib.c      | 1 +
 net/mptcp/mib.h      | 1 +
 net/mptcp/pm.c       | 5 +++++
 net/mptcp/protocol.c | 8 +-------
 net/mptcp/subflow.c  | 1 +
 5 files changed, 9 insertions(+), 7 deletions(-)

v4:
 https://lore.kernel.org/all/20260818091417.2200986-1-chenguang.zhao@linux.dev/

v3:
 https://lore.kernel.org/all/20260812054653.43799-1-chenguang.zhao@linux.dev/

v2:
 https://lore.kernel.org/all/20260715061830.1057851-1-chenguang.zhao@linux.dev/

v1:
 https://lore.kernel.org/all/20260713064134.914507-1-chenguang.zhao@linux.dev/
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2.25.1