netdev - Re: [PATCH net-next] net: mptcp: don't hang in mptcp

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Date:   Thu, 19 Mar 2020 23:48:21 +0100
From:   Paolo Abeni <pabeni@...hat.com>
To:     Davide Caratti <dcaratti@...hat.com>,
        Mat Martineau <mathew.j.martineau@...ux.intel.com>,
        Matthieu Baerts <matthieu.baerts@...sares.net>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     netdev@...r.kernel.org, mptcp@...ts.01.org
Subject: Re: [PATCH net-next] net: mptcp: don't hang in mptcp_sendmsg()
 after TCP fallback

On Thu, 2020-03-19 at 22:45 +0100, Davide Caratti wrote:
> it's still possible for packetdrill to hang in mptcp_sendmsg(), when the
> MPTCP socket falls back to regular TCP (e.g. after receiving unsupported
> flags/version during the three-way handshake). Adjust MPTCP socket state
> earlier, to ensure correct functionality of mptcp_sendmsg() even in case
> of TCP fallback.
> 
> Fixes: 767d3ded5fb8 ("net: mptcp: don't hang before sending 'MP capable with data'")
> Fixes: 1954b86016cf ("mptcp: Check connection state before attempting send")
> Signed-off-by: Davide Caratti <dcaratti@...hat.com>
> ---
>  net/mptcp/protocol.c | 4 ----
>  net/mptcp/subflow.c  | 6 ++++++
>  2 files changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
> index e959104832ef..92d5382e71f4 100644
> --- a/net/mptcp/protocol.c
> +++ b/net/mptcp/protocol.c
> @@ -1055,10 +1055,6 @@ void mptcp_finish_connect(struct sock *ssk)
>  	WRITE_ONCE(msk->write_seq, subflow->idsn + 1);
>  	WRITE_ONCE(msk->ack_seq, ack_seq);
>  	WRITE_ONCE(msk->can_ack, 1);
> -	if (inet_sk_state_load(sk) != TCP_ESTABLISHED) {
> -		inet_sk_state_store(sk, TCP_ESTABLISHED);
> -		sk->sk_state_change(sk);
> -	}
>  }
>  
>  static void mptcp_sock_graft(struct sock *sk, struct socket *parent)
> diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
> index 052d72a1d3a2..06b9075333c5 100644
> --- a/net/mptcp/subflow.c
> +++ b/net/mptcp/subflow.c
> @@ -109,9 +109,15 @@ static void subflow_v6_init_req(struct request_sock *req,
>  static void subflow_finish_connect(struct sock *sk, const struct sk_buff *skb)
>  {
>  	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
> +	struct sock *parent = subflow->conn;
>  
>  	subflow->icsk_af_ops->sk_rx_dst_set(sk, skb);
>  
> +	if (inet_sk_state_load(parent) != TCP_ESTABLISHED) {
> +		inet_sk_state_store(parent, TCP_ESTABLISHED);
> +		parent->sk_state_change(parent);
> +	}
> +
>  	if (!subflow->conn_finished) {
>  		pr_debug("subflow=%p, remote_key=%llu", mptcp_subflow_ctx(sk),
>  			 subflow->remote_key);

LGTM, thanks Davide!

Acked-by: Paolo Abeni <pabeni@...hat.com>