Re: [PATCH 6.1.y 3/3] mptcp: reset fallback status gracefully at disconnect() time

[Sasha Levin <sashal@kernel.org>]

[ Sasha's backport helper bot ]

Hi,

✅ All tests passed successfully. No issues detected.
No action required from the submitter.

The upstream commit SHA1 provided is correct: da9b2fc7b73d147d88abe1922de5ab72d72d7756

WARNING: Author mismatch between patch and upstream commit:
Backport author: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Commit author: Paolo Abeni <pabeni@redhat.com>

Status in newer kernel trees:
6.15.y | Not found
6.12.y | Not found
6.6.y | Not found

Note: The patch differs from the upstream commit:
---
1:  da9b2fc7b73d ! 1:  96832530025f mptcp: reset fallback status gracefully at disconnect() time
    @@ Metadata
      ## Commit message ##
         mptcp: reset fallback status gracefully at disconnect() time
     
    +    commit da9b2fc7b73d147d88abe1922de5ab72d72d7756 upstream.
    +
         mptcp_disconnect() clears the fallback bit unconditionally, without
         touching the associated flags.
     
    @@ Commit message
         Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
         Link: https://patch.msgid.link/20250714-net-mptcp-fallback-races-v1-3-391aff963322@kernel.org
         Signed-off-by: Jakub Kicinski <kuba@kernel.org>
    +    [ Conflicts in protocol.c, because commit ebc1e08f01eb ("mptcp: drop
    +      last_snd and MPTCP_RESET_SCHEDULER") is not in this version and
    +      changed the context. The same modification can still be applied at the
    +      same place. ]
    +    Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
     
      ## net/mptcp/protocol.c ##
     @@ net/mptcp/protocol.c: static int mptcp_disconnect(struct sock *sk, int flags)
    - 	 * subflow
      	 */
      	mptcp_destroy_common(msk, MPTCP_CF_FASTCLOSE);
    + 	msk->last_snd = NULL;
     +
     +	/* The first subflow is already in TCP_CLOSE status, the following
     +	 * can't overlap with a fallback anymore
    @@ net/mptcp/protocol.c: static int mptcp_disconnect(struct sock *sk, int flags)
     +
      	msk->cb_flags = 0;
      	msk->recovery = false;
    - 	WRITE_ONCE(msk->can_ack, false);
    + 	msk->can_ack = false;

---

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| 6.1                       | Success     | Success    |