From: Geliang Tang <tanggeliang@kylinos.cn>

This patch introduces a sk_is_msk() helper modeled after sk_is_tcp() to
determine whether the socket is an MPTCP one. Unlike sk_is_mptcp(), which
accepts a subflow socket as its parameter, this new helper specifically
accepts an MPTCP socket parameter.

Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
---
 include/net/mptcp.h | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/include/net/mptcp.h b/include/net/mptcp.h
index 4cf59e83c1c5..82660374859a 100644
--- a/include/net/mptcp.h
+++ b/include/net/mptcp.h
@@ -150,6 +150,13 @@ static inline bool rsk_drop_req(const struct request_sock *req)
 	return tcp_rsk(req)->is_mptcp && tcp_rsk(req)->drop_req;
 }
 
+static inline bool sk_is_msk(const struct sock *sk)
+{
+	return sk_is_inet(sk) &&
+	       sk->sk_type == SOCK_STREAM &&
+	       sk->sk_protocol == IPPROTO_MPTCP;
+}
+
 void mptcp_space(const struct sock *ssk, int *space, int *full_space);
 bool mptcp_syn_options(struct sock *sk, const struct sk_buff *skb,
 		       unsigned int *size, struct mptcp_out_options *opts);
@@ -258,6 +265,11 @@ static inline bool rsk_drop_req(const struct request_sock *req)
 	return false;
 }
 
+static inline bool sk_is_msk(const struct sock *sk)
+{
+	return false;
+}
+
 static inline bool mptcp_syn_options(struct sock *sk, const struct sk_buff *skb,
 				     unsigned int *size,
 				     struct mptcp_out_options *opts)
-- 
2.53.0