mptcp: using TOKEN_MAX_RETRIES instead of magic number

We have macro TOKEN_MAX_RETRIES for the number of token generate retries,
so using TOKEN_MAX_RETRIES in subflow_check_req().

And rename TOKEN_MAX_RETRIES to MPTCP_TOKEN_MAX_RETRIES as it is now
exposed.

Fixes: 535fb8152f ("mptcp: token: move retry to caller")
Reviewed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Jianguo Wu <wujianguo@chinatelecom.cn>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/mptcp/protocol.h

@@ -627,6 +627,8 @@ static inline void mptcp_write_space(struct sock *sk)
 
 void mptcp_destroy_common(struct mptcp_sock *msk);
 
+#define MPTCP_TOKEN_MAX_RETRIES	4
+
 void __init mptcp_token_init(void);
 static inline void mptcp_token_init_request(struct request_sock *req)
 {

net/mptcp/subflow.c

@@ -162,7 +162,7 @@ static int subflow_check_req(struct request_sock *req,
 	}
 
 	if (mp_opt.mp_capable && listener->request_mptcp) {
-		int err, retries = 4;
+		int err, retries = MPTCP_TOKEN_MAX_RETRIES;
 
 		subflow_req->ssn_offset = TCP_SKB_CB(skb)->seq;
 again:

net/mptcp/token.c

@@ -33,7 +33,6 @@
 #include <net/mptcp.h>
 #include "protocol.h"
 
-#define TOKEN_MAX_RETRIES	4
 #define TOKEN_MAX_CHAIN_LEN	4
 
 struct token_bucket {
@@ -153,7 +152,7 @@ int mptcp_token_new_connect(struct sock *sk)
 {
 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
-	int retries = TOKEN_MAX_RETRIES;
+	int retries = MPTCP_TOKEN_MAX_RETRIES;
 	struct token_bucket *bucket;
 
 again: