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mptcp: reset msk state on early connect failure

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mptcp_connect() can fall back before the subflow SYN is sent, for
example when the netns is in an MPTCP blackhole, token allocation fails,
or MD5SIG is in use. If the subsequent subflow connect() fails
immediately (EAFNOSUPPORT, ENETUNREACH, ...), __inet_stream_connect()
returns while the socket is still SS_UNCONNECTED and never calls
->disconnect(). This was reported by Clashiko [1].

The error path only dropped the token and moved the msk back to
TCP_CLOSE. MPTCP_FALLBACK_DONE, allow_subflows and
request_mptcp were left as after early fallback, so a later
connect() on the same fd stayed TCP-only.

Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/633 [1]
Fixes: 0235d075a5 ("mptcp: mark as fallback even early ones")
Cc: stable@vger.kernel.org
Signed-off-by: Quanye Yang <quanyeyang@proton.me>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20261013-net-mptcp-misc-fixes-7-3-rc8-v1-1-932c9b182fc7@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Quanye Yang 2026-10-13 16:29:19 +02:00 committed by Jakub Kicinski
parent 23e687079e
commit 29afe67082
1 changed files with 8 additions and 1 deletions
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9
net/mptcp/protocol.c
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@ -4212,9 +4212,16 @@ static int mptcp_connect(struct sock *sk, struct sockaddr_unsized *uaddr,
* subflow_finish_connect()
*/
if (unlikely(err)) {
/* avoid leaving a dangling token in an unconnected socket */
mptcp_token_destroy(msk);
mptcp_set_state(sk, TCP_CLOSE);
spin_lock_bh(&msk->fallback_lock);
msk->allow_subflows = true;
msk->allow_infinite_fallback = true;
clear_bit(MPTCP_FALLBACK_DONE, &msk->flags);
spin_unlock_bh(&msk->fallback_lock);
mptcp_subflow_ctx_reset(mptcp_subflow_ctx(ssk));
return err;
}