Re: [PATCH mptcp-net 2/2] Squash-to: "mptcp: do not reschedule the RTX timer for fallback sockets"

[Matthieu Baerts <matttbe@kernel.org>]

On 26/08/2026 16:38, Paolo Abeni wrote:
> On 8/26/26 2:38 PM, Matthieu Baerts wrote:
>> On 26/08/2026 12:13, Paolo Abeni wrote:
>>> Sashiko noted that the 'RTX disabled' status is carried over
>>> across connect() failures, potentially to subsequent successful connect()
>>> or listen().
>>>
>>> Explicitly control the RTX enabling status across the whole msk life-cycle.
>>> To make the code more straight forward switch the newly introduced flag
>>> semantic.
>>
>> Thank you for looking at this!
>>
>>> Signed-off-by: Paolo Abeni <pabeni@redhat.com>
>>> ---
>>>  net/mptcp/protocol.c | 8 +++++---
>>>  net/mptcp/protocol.h | 2 +-
>>>  2 files changed, 6 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
>>> index 1e7e59d497c5..db745d9dde59 100644
>>> --- a/net/mptcp/protocol.c
>>> +++ b/net/mptcp/protocol.c
>>
>> (...)
>>
>>> @@ -3363,7 +3363,7 @@ void mptcp_set_state(struct sock *sk, int state)
>>>  		 */
>>>  		break;
>>>  	case TCP_CLOSE:
>>> -		set_bit(MPTCP_RTX_DISABLED, &mptcp_sk(sk)->flags);
>>> +		clear_bit(MPTCP_RTX_ENABLED, &mptcp_sk(sk)->flags);
>>
>> Could this be moved to mptcp_disconnect()? Or we prefer not, to stop
>> ASAP for some cases? (but I guess most of these cases switch to close
>> before transitioning to ESTABLISHED, no?)
> Why do you want to move the above to mptcp_disconnect()? It's better to
> prevent the rtx timer from taking action after the msk moved to close
> for any reason. IIRC we had a few syzkaller splat in the past without
> such check.

I was wondering if it could go with the other variables that are reset
there, but I also understand we want this bit set ASAP/in all cases when
switching to CLOSE. So this flag is particular, and it makes sense to
keep it there. Nothing to modify for this.

Cheers,
Matt
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