netdev - [PATCH net-next 01/14] mptcp: avoid unneeded mptcp_token

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Date: Fri, 11 Aug 2023 17:57:14 +0200
From: Matthieu Baerts <matthieu.baerts@...sares.net>
To: mptcp@...ts.linux.dev, Mat Martineau <martineau@...nel.org>, 
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
 David Ahern <dsahern@...nel.org>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Matthieu Baerts <matthieu.baerts@...sares.net>
Subject: [PATCH net-next 01/14] mptcp: avoid unneeded mptcp_token_destroy()
 calls

From: Paolo Abeni <pabeni@...hat.com>

The MPTCP protocol currently clears the msk token both at connect() and
listen() time. That is needed to deal with failing connect() calls that
can create a new token while leaving the sk in TCP_CLOSE,SS_UNCONNECTED
status and thus allowing later connect() and/or listen() calls.

Let's deal with such failures explicitly, cleaning the token in a timely
manner and avoid the confusing early mptcp_token_destroy().

Signed-off-by: Paolo Abeni <pabeni@...hat.com>
Reviewed-by: Mat Martineau <martineau@...nel.org>
Signed-off-by: Matthieu Baerts <matthieu.baerts@...sares.net>
---
 net/mptcp/protocol.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 48e649fe2360..abb310548c37 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -3594,7 +3594,6 @@ static int mptcp_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
 	if (IS_ERR(ssock))
 		return PTR_ERR(ssock);

-	mptcp_token_destroy(msk);
 	inet_sk_state_store(sk, TCP_SYN_SENT);
 	subflow = mptcp_subflow_ctx(ssock->sk);
 #ifdef CONFIG_TCP_MD5SIG
@@ -3624,6 +3623,8 @@ static int mptcp_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
 	 * subflow_finish_connect()
 	 */
 	if (unlikely(err && err != -EINPROGRESS)) {
+		/* avoid leaving a dangling token in an unconnected socket */
+		mptcp_token_destroy(msk);
 		inet_sk_state_store(sk, inet_sk_state_load(ssock->sk));
 		return err;
 	}
@@ -3713,7 +3714,6 @@ static int mptcp_listen(struct socket *sock, int backlog)
 		goto unlock;
 	}

-	mptcp_token_destroy(msk);
 	inet_sk_state_store(sk, TCP_LISTEN);
 	sock_set_flag(sk, SOCK_RCU_FREE);

-- 
2.40.1