Re: [PATCH mptcp-net] mptcp: fix extra_subflows leak on failed passive join

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

Hi Matthieu,

Regarding the sync join failure, I have already submitted a PR.
https://github.com/multipath-tcp/packetdrill/pull/200

Thanks

在 2026/6/30 18:47, Matthieu Baerts 写道:
> Hi Chenguang,
>
> Thank you for the fix.
>
>> mptcp_pm_allow_new_subflow() increments extra_subflows
>> before __mptcp_finish_join() on the passive MP_JOIN path.
> I see that this code path is currently not exercised by our test suite:
>
>   https://ci-results.mptcp.dev/lcov/export/mptcp/protocol.c.gcov.html#L4031
>
> How did you spot the issue? Do you have a reproducer? Or was it by
> reading the code? Assisted by a tool (in this case, please add the
> Assisted-by tag)?
>
> I see we have a test for sync connect failure, but not sync join. Do you
> mind adding a new Packetdrill test please? Similar to simult_connect.pkt
> I suppose:
>
>   https://github.com/multipath-tcp/packetdrill/blob/mptcp-net-next/gtests/net/mptcp/syscalls/simult_connect.pkt
>
>> On synchronous join failure the subflow is dropped without
>> calling mptcp_close_ssk(), so the counter is not rolled back.
>>
>> Call mptcp_pm_close_subflow() when the join completion fails.
> A fix patch should always have a Fixes tag. Here, I guess it should be:
>
> Fixes: 10f6d46c943d ("mptcp: fix race between MP_JOIN and close")
>
> Apart from that, the modification looks good to me:
>
> Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
>