[MPTCP] Re: [MPTCP][RFC PATCH mptcp-next 3/6] mptcp: add prio_changed flag

[MPTCP] Re: [MPTCP][RFC PATCH mptcp-next 3/6] mptcp: add prio_changed flag

[Mat Martineau]

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On Thu, 5 Nov 2020, Geliang Tang wrote:

> This patch add a new flag named prio_changed in msk. When we received
> the MP_PRIO suboption, we set this flag to true.
>
> In mptcp_subflow_get_send, we check whether prio_changed is set. If it
> is, we pick a new subflow to send data.
>
> Signed-off-by: Geliang Tang <geliangtang(a)gmail.com>

Hi Geliang -

This patch should be dropped. mptcp_subflow_get_send() already uses 
subflow->backup when choosing a subflow to transmit on.


Thanks,

Mat


> ---
> net/mptcp/pm.c       | 1 +
> net/mptcp/protocol.c | 4 +++-
> net/mptcp/protocol.h | 1 +
> 3 files changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/net/mptcp/pm.c b/net/mptcp/pm.c
> index a4dc4aa39ad8..b6f4f54e6546 100644
> --- a/net/mptcp/pm.c
> +++ b/net/mptcp/pm.c
> @@ -195,6 +195,7 @@ void mptcp_pm_mp_prio_received(struct sock *sk, u8 prio_bkup)
>
> 	spin_lock_bh(&msk->pm.lock);
> 	subflow->backup = prio_bkup;
> +	WRITE_ONCE(msk->prio_changed, true);
> 	spin_unlock_bh(&msk->pm.lock);
> }
>
> diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
> index a6bd06c724d5..7a7561ba9edf 100644
> --- a/net/mptcp/protocol.c
> +++ b/net/mptcp/protocol.c
> @@ -1133,7 +1133,8 @@ static struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk,
> 	/* re-use last subflow, if the burst allow that */
> 	if (msk->last_snd && msk->snd_burst > 0 &&
> 	    sk_stream_memory_free(msk->last_snd) &&
> -	    mptcp_subflow_active(mptcp_subflow_ctx(msk->last_snd))) {
> +	    mptcp_subflow_active(mptcp_subflow_ctx(msk->last_snd)) &&
> +	    !READ_ONCE(msk->prio_changed)) {
> 		mptcp_for_each_subflow(msk, subflow) {
> 			ssk =  mptcp_subflow_tcp_sock(subflow);
> 			*sndbuf = max(tcp_sk(ssk)->snd_wnd, *sndbuf);
> @@ -1180,6 +1181,7 @@ static struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk,
> 		msk->last_snd = send_info[0].ssk;
> 		msk->snd_burst = min_t(int, MPTCP_SEND_BURST_SIZE,
> 				       sk_stream_wspace(msk->last_snd));
> +		WRITE_ONCE(msk->prio_changed, false);
> 		return msk->last_snd;
> 	}
> 	return NULL;
> diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
> index 871b73046de0..c3386a6a7a16 100644
> --- a/net/mptcp/protocol.h
> +++ b/net/mptcp/protocol.h
> @@ -240,6 +240,7 @@ struct mptcp_sock {
> 	bool		rcv_data_fin;
> 	bool		snd_data_fin_enable;
> 	bool		use_64bit_ack; /* Set when we received a 64-bit DSN */
> +	bool		prio_changed;
> 	spinlock_t	join_list_lock;
> 	struct work_struct work;
> 	struct sk_buff  *ooo_last_skb;
> -- 
> 2.26.2
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>

--
Mat Martineau
Intel