From: Geliang Tang <tanggeliang@kylinos.cn>

This patch introduces a dedicated MPTCP helper, sock_set_reuseaddr, which
sets the address reuse flag on the first subflow socket of an MPTCP
connection, and applies it to the target side in the 'NVMe over MPTCP'
implementation.

Co-developed-by: zhenwei pi <zhenwei.pi@linux.dev>
Signed-off-by: zhenwei pi <zhenwei.pi@linux.dev>
Co-developed-by: Hui Zhu <zhuhui@kylinos.cn>
Signed-off-by: Hui Zhu <zhuhui@kylinos.cn>
Co-developed-by: Gang Yan <yangang@kylinos.cn>
Signed-off-by: Gang Yan <yangang@kylinos.cn>
Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
---
 drivers/nvme/target/tcp.c |  2 ++
 include/net/mptcp.h       |  4 ++++
 net/mptcp/protocol.c      | 15 +++++++++++++++
 3 files changed, 21 insertions(+)

diff --git a/drivers/nvme/target/tcp.c b/drivers/nvme/target/tcp.c
index 8452d38614a6..5111c0e690ee 100644
--- a/drivers/nvme/target/tcp.c
+++ b/drivers/nvme/target/tcp.c
@@ -2086,6 +2086,8 @@ static int nvmet_tcp_add_port(struct nvmet_port *nport)
 	port->sock->sk->sk_user_data = port;
 	port->data_ready = port->sock->sk->sk_data_ready;
 	port->sock->sk->sk_data_ready = nvmet_tcp_listen_data_ready;
+	sk_is_msk(port->sock->sk) ?
+	mptcp_sock_set_reuseaddr(port->sock->sk) :
 	sock_set_reuseaddr(port->sock->sk);
 	sk_is_msk(port->sock->sk) ?
 	mptcp_sock_set_nodelay(port->sock->sk) :
diff --git a/include/net/mptcp.h b/include/net/mptcp.h
index 60cbf29448b0..63b64b7699e3 100644
--- a/include/net/mptcp.h
+++ b/include/net/mptcp.h
@@ -246,6 +246,8 @@ static inline __be32 mptcp_reset_option(const struct sk_buff *skb)
 void mptcp_active_detect_blackhole(struct sock *sk, bool expired);
 
 void mptcp_sock_set_nodelay(struct sock *sk);
+
+void mptcp_sock_set_reuseaddr(struct sock *sk);
 #else
 
 static inline void mptcp_init(void)
@@ -339,6 +341,8 @@ static inline __be32 mptcp_reset_option(const struct sk_buff *skb)  { return hto
 static inline void mptcp_active_detect_blackhole(struct sock *sk, bool expired) { }
 
 static inline void mptcp_sock_set_nodelay(struct sock *sk) { }
+
+static inline void mptcp_sock_set_reuseaddr(struct sock *sk) { }
 #endif /* CONFIG_MPTCP */
 
 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 451bc4df4fa4..61f4eba02b37 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -3823,6 +3823,21 @@ void mptcp_sock_set_nodelay(struct sock *sk)
 }
 EXPORT_SYMBOL(mptcp_sock_set_nodelay);
 
+void mptcp_sock_set_reuseaddr(struct sock *sk)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct sock *ssk;
+
+	lock_sock(sk);
+	ssk = __mptcp_nmpc_sk(msk);
+	if (IS_ERR(ssk))
+		goto unlock;
+	ssk->sk_reuse = SK_CAN_REUSE;
+unlock:
+	release_sock(sk);
+}
+EXPORT_SYMBOL(mptcp_sock_set_reuseaddr);
+
 bool mptcp_finish_join(struct sock *ssk)
 {
 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
-- 
2.53.0