Re: [MPTCP][PATCH mptcp-next] mptcp: don't fallback when data_fin enabled

[Matthieu Baerts <matthieu.baerts@tessares.net>]

Hi Geliang,

On 07/05/2021 11:08, Geliang Tang wrote:
> Hi Matt,
> 
> Thanks for your review.
> 
> Matthieu Baerts <matthieu.baerts@tessares.net> 于2021年5月7日周五 下午4:51写道：
>>
>> Hi Geliang,
>>
>> On 07/05/2021 09:58, Geliang Tang wrote:
>>> This patch fixed this fallback error:
>>
>> Thank you for the patch!
>>
>>> diff --git a/net/mptcp/options.c b/net/mptcp/options.c
>>> index f3e379a0f08d..940b32511443 100644
>>> --- a/net/mptcp/options.c
>>> +++ b/net/mptcp/options.c
>>> @@ -901,7 +901,7 @@ static bool check_fully_established(struct mptcp_sock *msk, struct sock *ssk,
>>>        * MP_JOIN subflows.
>>>        */
>>>       if (!mp_opt->mp_capable) {
>>> -             if (subflow->mp_join)
>>> +             if (subflow->mp_join || mptcp_data_fin_enabled(msk))>                   goto reset;
>>
>> I don't think we should send a reset here. For me this behaviour is normal.
> 
> Yes, we don't need to send a reset here. What about just return here?
> Something like this:
> 
> diff --git a/net/mptcp/options.c b/net/mptcp/options.c
> index 3428c163299b..bd62dadfefdb 100644
> --- a/net/mptcp/options.c
> +++ b/net/mptcp/options.c
> @@ -905,6 +905,8 @@ static bool check_fully_established(struct
> mptcp_sock *msk, struct sock *ssk,
>         if (!mp_opt->mp_capable) {
>                 if (subflow->mp_join)
>                         goto reset;
> +               if (mptcp_data_fin_enabled(msk))
> +                       return false;
>                 subflow->mp_capable = 0;
>                 pr_fallback(msk);
>                 __mptcp_do_fallback(msk);

I think we still need to do a fallback here not to expect a DATA_ACK.
For example in __mptcp_check_send_data_fin(), we change the state
because we will not get a DATA_ACK.

So I think everything is OK there.

Just one thing: should we send a DATA_FIN if we were not "fully
established" when closing the socket?

Cheers,
Matt
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