When mptcp_connect() fails before the socket reaches SS_CONNECTING,
->disconnect() is not called. Early fallback may already have set
MPTCP_FALLBACK_DONE and cleared request_mptcp, so a later connect()
on the same fd stays TCP-only.

Patch 1 undoes that state on the connect error path.
Patch 2 adds a mptcp_join.sh coverage for the same-fd retry.

Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/633
---
Quanye Yang (2):
      mptcp: reset msk state on early connect failure
      selftests: mptcp: join: retry connect after early fallback

 net/mptcp/protocol.c                               |  22 ++-
 tools/testing/selftests/net/mptcp/.gitignore       |   1 +
 tools/testing/selftests/net/mptcp/Makefile         |   1 +
 .../selftests/net/mptcp/mptcp_connect_retry.c      | 216 +++++++++++++++++++++
 tools/testing/selftests/net/mptcp/mptcp_join.sh    | 108 +++++++++++
 5 files changed, 345 insertions(+), 3 deletions(-)
---
base-commit: 38b6be101006d3e7af972999f45d4f1e8250587a
change-id: 20260910-mptcp-connect-undo-net-b80e14ae1fa2

Best regards,
--  
Quanye Yang <quanyeyang@proton.me>

Hi Quanye,

Thank you for your modifications, that's great!

Our CI did some validations and here is its report:

- KVM Validation: normal (except selftest_mptcp_join): Success! ✅
- KVM Validation: normal (only selftest_mptcp_join): Unstable: 1 failed test(s): selftest_mptcp_join ⚠️ 
- KVM Validation: debug (except selftest_mptcp_join): Success! ✅
- KVM Validation: debug (only selftest_mptcp_join): Unstable: 1 failed test(s): selftest_mptcp_join ⚠️ 
- KVM Validation: btf-normal (only bpftest_all): Success! ✅
- KVM Validation: btf-debug (only bpftest_all): Success! ✅
- Perf: Unstable ⚠️
- Task: https://github.com/multipath-tcp/mptcp_net-next/actions/runs/34478188118

Initiator: Patchew Applier
Commits: https://github.com/multipath-tcp/mptcp_net-next/commits/103aae4aeeaf
Patchwork: https://patchwork.kernel.org/project/mptcp/list/?series=1162041


If there are some issues, you can reproduce them using the same environment as
the one used by the CI thanks to a docker image, e.g.:

    $ cd [kernel source code]
    $ docker run -v "${PWD}:${PWD}:rw" -w "${PWD}" --privileged --rm -it \
        --pull always mptcp/mptcp-upstream-virtme-docker:latest \
        auto-normal

For more details:

    https://github.com/multipath-tcp/mptcp-upstream-virtme-docker


Please note that despite all the efforts that have been already done to have a
stable tests suite when executed on a public CI like here, it is possible some
reported issues are not due to your modifications. Still, do not hesitate to
help us improve that ;-)

Cheers,
MPTCP GH Action bot
Bot operated by Matthieu Baerts (NGI0 Core)