From: Geliang Tang <tanggeliang@kylinos.cn>

Allow MPTCP sockets to set the TCP_ULP socket option to enable TLS.
Add mptcp_setsockopt_tcp_ulp() which validates the socket state (must
not be CLOSE or LISTEN), only accepts "tls" as the ULP name, and then
calls tcp_set_ulp().

Include TCP_ULP in the list of supported options in supported_sockopt(),
and handle it in setsockopt_sol_tcp() instead of returning -EOPNOTSUPP.

Call tcp_cleanup_ulp() in mptcp_destroy_common() to release ULP module's
reference count.

Co-developed-by: Gang Yan <yangang@kylinos.cn>
Signed-off-by: Gang Yan <yangang@kylinos.cn>
Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
---
 net/mptcp/protocol.c |  1 +
 net/mptcp/sockopt.c  | 35 ++++++++++++++++++++++++++++++++++-
 2 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 9d20170614fa..d1987958ff2e 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -3635,6 +3635,7 @@ static void mptcp_destroy(struct sock *sk)
 	/* allow the following to close even the initial subflow */
 	msk->free_first = 1;
 	mptcp_destroy_common(msk);
+	tcp_cleanup_ulp(sk);
 	sk_sockets_allocated_dec(sk);
 }
 
diff --git a/net/mptcp/sockopt.c b/net/mptcp/sockopt.c
index 11e071b0994e..1059efbd4f8f 100644
--- a/net/mptcp/sockopt.c
+++ b/net/mptcp/sockopt.c
@@ -12,6 +12,7 @@
 #include <net/protocol.h>
 #include <net/tcp.h>
 #include <net/mptcp.h>
+#include <net/tls.h>
 #include "protocol.h"
 
 #define MIN_INFO_OPTLEN_SIZE		16
@@ -567,6 +568,7 @@ static bool mptcp_supported_sockopt(int level, int optname)
 		case TCP_FASTOPEN_CONNECT:
 		case TCP_FASTOPEN_KEY:
 		case TCP_FASTOPEN_NO_COOKIE:
+		case TCP_ULP:
 			return true;
 		}
 
@@ -815,6 +817,37 @@ static int mptcp_setsockopt_all_sf(struct mptcp_sock *msk, int level,
 	return ret;
 }
 
+static int mptcp_setsockopt_tcp_ulp(struct sock *sk, sockptr_t optval,
+				    unsigned int optlen)
+{
+	char name[TCP_ULP_NAME_MAX];
+	int err = 0;
+	size_t len;
+	int val;
+
+	if (optlen < 1)
+		return -EINVAL;
+
+	len = min_t(long, TCP_ULP_NAME_MAX - 1, optlen);
+	val = strncpy_from_sockptr(name, optval, len);
+	if (val < 0)
+		return -EFAULT;
+	name[val] = 0;
+
+	if (strcmp(name, "tls"))
+		return -EOPNOTSUPP;
+
+	sockopt_lock_sock(sk);
+	if ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) {
+		err = -ENOTCONN;
+		goto out;
+	}
+	err = tcp_set_ulp(sk, name);
+out:
+	sockopt_release_sock(sk);
+	return err;
+}
+
 static int mptcp_setsockopt_sol_tcp(struct mptcp_sock *msk, int optname,
 				    sockptr_t optval, unsigned int optlen)
 {
@@ -823,7 +856,7 @@ static int mptcp_setsockopt_sol_tcp(struct mptcp_sock *msk, int optname,
 
 	switch (optname) {
 	case TCP_ULP:
-		return -EOPNOTSUPP;
+		return mptcp_setsockopt_tcp_ulp(sk, optval, optlen);
 	case TCP_CONGESTION:
 		return mptcp_setsockopt_sol_tcp_congestion(msk, optval, optlen);
 	case TCP_DEFER_ACCEPT:
-- 
2.53.0