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

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Message-Id: <9a7cd34e2d8688364297d700bfd8aea60c3a6c7f.1584653622.git.dcaratti@redhat.com>
Date:   Thu, 19 Mar 2020 22:45:37 +0100
From:   Davide Caratti <dcaratti@...hat.com>
To:     Mat Martineau <mathew.j.martineau@...ux.intel.com>,
        Matthieu Baerts <matthieu.baerts@...sares.net>,
        "David S. Miller" <davem@...emloft.net>,
        Paolo Abeni <pabeni@...hat.com>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     netdev@...r.kernel.org, mptcp@...ts.01.org
Subject: [PATCH net-next] net: mptcp: don't hang in mptcp_sendmsg() after TCP fallback

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);
-- 
2.24.1