From: Geliang Tang <tanggeliang@kylinos.cn>

This patch extracts TCP_ULP getsockopt operation into a tcp_sock_get_ulp()
helper so that it can also be used in MPTCP.

TCP_ULP was obtained by calling mptcp_getsockopt_first_sf_only() to get
ULP of the first subflow. Now that the mechanism has changed, a new helper
mptcp_getsockopt_tcp_ulp() is added to get ULP of msk.

Co-developed-by: Gang Yan <yangang@kylinos.cn>
Signed-off-by: Gang Yan <yangang@kylinos.cn>
Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
---
 include/linux/tcp.h |  1 +
 net/ipv4/tcp.c      | 36 ++++++++++++++++++++++--------------
 net/mptcp/sockopt.c | 12 ++++++++++++
 3 files changed, 35 insertions(+), 14 deletions(-)

diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index 20b8c6e21fef..6f0becc26402 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -644,6 +644,7 @@ void tcp_sock_set_quickack(struct sock *sk, int val);
 int tcp_sock_set_syncnt(struct sock *sk, int val);
 int tcp_sock_set_user_timeout(struct sock *sk, int val);
 int tcp_sock_set_maxseg(struct sock *sk, int val);
+int tcp_sock_get_ulp(struct sock *sk, sockptr_t optval, sockptr_t optlen);
 
 static inline bool dst_tcp_usec_ts(const struct dst_entry *dst)
 {
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index ed6dc29d422d..5ea4d94d67db 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -4436,6 +4436,27 @@ struct sk_buff *tcp_get_timestamping_opt_stats(const struct sock *sk,
 	return stats;
 }
 
+int tcp_sock_get_ulp(struct sock *sk, sockptr_t optval, sockptr_t optlen)
+{
+	struct inet_connection_sock *icsk = inet_csk(sk);
+	int len;
+
+	if (copy_from_sockptr(&len, optlen, sizeof(int)))
+		return -EFAULT;
+	len = min_t(unsigned int, len, TCP_ULP_NAME_MAX);
+	if (!icsk->icsk_ulp_ops) {
+		len = 0;
+		if (copy_to_sockptr(optlen, &len, sizeof(int)))
+			return -EFAULT;
+		return 0;
+	}
+	if (copy_to_sockptr(optlen, &len, sizeof(int)))
+		return -EFAULT;
+	if (copy_to_sockptr(optval, icsk->icsk_ulp_ops->name, len))
+		return -EFAULT;
+	return 0;
+}
+
 int do_tcp_getsockopt(struct sock *sk, int level,
 		      int optname, sockptr_t optval, sockptr_t optlen)
 {
@@ -4545,20 +4566,7 @@ int do_tcp_getsockopt(struct sock *sk, int level,
 		return 0;
 
 	case TCP_ULP:
-		if (copy_from_sockptr(&len, optlen, sizeof(int)))
-			return -EFAULT;
-		len = min_t(unsigned int, len, TCP_ULP_NAME_MAX);
-		if (!icsk->icsk_ulp_ops) {
-			len = 0;
-			if (copy_to_sockptr(optlen, &len, sizeof(int)))
-				return -EFAULT;
-			return 0;
-		}
-		if (copy_to_sockptr(optlen, &len, sizeof(int)))
-			return -EFAULT;
-		if (copy_to_sockptr(optval, icsk->icsk_ulp_ops->name, len))
-			return -EFAULT;
-		return 0;
+		return tcp_sock_get_ulp(sk, optval, optlen);
 
 	case TCP_FASTOPEN_KEY: {
 		u64 key[TCP_FASTOPEN_KEY_BUF_LENGTH / sizeof(u64)];
diff --git a/net/mptcp/sockopt.c b/net/mptcp/sockopt.c
index de90a2897d2d..a6230f7910fd 100644
--- a/net/mptcp/sockopt.c
+++ b/net/mptcp/sockopt.c
@@ -1393,6 +1393,17 @@ static int mptcp_put_int_option(struct mptcp_sock *msk, char __user *optval,
 	return 0;
 }
 
+static int mptcp_getsockopt_tcp_ulp(struct sock *sk, char __user *optval,
+				    int __user *optlen)
+{
+	int ret;
+
+	lock_sock(sk);
+	ret = tcp_sock_get_ulp(sk, USER_SOCKPTR(optval), USER_SOCKPTR(optlen));
+	release_sock(sk);
+	return ret;
+}
+
 static int mptcp_getsockopt_sol_tcp(struct mptcp_sock *msk, int optname,
 				    char __user *optval, int __user *optlen)
 {
@@ -1400,6 +1411,7 @@ static int mptcp_getsockopt_sol_tcp(struct mptcp_sock *msk, int optname,
 
 	switch (optname) {
 	case TCP_ULP:
+		return mptcp_getsockopt_tcp_ulp(sk, optval, optlen);
 	case TCP_CONGESTION:
 	case TCP_INFO:
 	case TCP_CC_INFO:
-- 
2.51.0