[MPTCP] Re: [PATCH] mptcp: copy mptcp receive buffer setting to subflow

[MPTCP] Re: [PATCH] mptcp: copy mptcp receive buffer setting to subflow

[Mat Martineau]

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On Thu, 12 Mar 2020, Florian Westphal wrote:

> For incoming/outgoing connections, initial window is chosen based om
> the subflow receive buffer size.
>
> In case mptcp socket has a fixed buffer size, we should copy it to the
> subflow/tcp socket as well.

Does this need to be synced later in the connection when SO_RECVBUF is 
changed? If it does, this patch is not really blocked: copying the value 
at subflow creation time allows initial window tuning that isn't currently 
possible.

Mat


>
> Signed-off-by: Florian Westphal <fw(a)strlen.de>
> ---
> I'll pass this to netdev@ unless there are objections.
>
> net/mptcp/protocol.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
> index ddfd02ab6e31..a65cedcb905f 100644
> --- a/net/mptcp/protocol.c
> +++ b/net/mptcp/protocol.c
> @@ -89,6 +89,15 @@ static bool __mptcp_can_create_subflow(const struct mptcp_sock *msk)
> 	return !msk->first;
> }
>
> +static void sync_rcvbuf(const struct sock *msk, struct sock *ssk)
> +{
> +	if (unlikely((msk->sk_userlocks & SOCK_RCVBUF_LOCK) &&
> +	     ssk->sk_rcvbuf != msk->sk_rcvbuf)) {
> +		ssk->sk_userlocks |= SOCK_RCVBUF_LOCK;
> +		WRITE_ONCE(ssk->sk_rcvbuf, msk->sk_rcvbuf);
> +	}
> +}
> +
> static struct socket *__mptcp_socket_create(struct mptcp_sock *msk, int state)
> {
> 	struct mptcp_subflow_context *subflow;
> @@ -107,6 +116,7 @@ static struct socket *__mptcp_socket_create(struct mptcp_sock *msk, int state)
> 	if (err)
> 		return ERR_PTR(err);
>
> +	sync_rcvbuf(sk, ssock->sk);
> 	msk->first = ssock->sk;
> 	msk->subflow = ssock;
> 	subflow = mptcp_subflow_ctx(ssock->sk);
> -- 
> 2.24.1
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>

--
Mat Martineau
Intel