inet: add rsk_refcnt/ireq_refcnt to request socks

When request socks will be in ehash, they'll need to be refcounted.

This patch adds rsk_refcnt/ireq_refcnt macros, and adds
reqsk_put() function, but nothing yet use them.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/request_sock.h b/include/net/request_sock.h
index 7f830ff..e255ecf 100644
--- a/include/net/request_sock.h
+++ b/include/net/request_sock.h
@@ -49,6 +49,8 @@
  */
 struct request_sock {
 	struct sock_common		__req_common;
+#define rsk_refcnt			__req_common.skc_refcnt
+
 	struct request_sock		*dl_next;
 	u16				mss;
 	u8				num_retrans; /* number of retransmits */
@@ -86,6 +88,12 @@
 	__reqsk_free(req);
 }
 
+static inline void reqsk_put(struct request_sock *req)
+{
+	if (atomic_dec_and_test(&req->rsk_refcnt))
+		reqsk_free(req);
+}
+
 extern int sysctl_max_syn_backlog;
 
 /** struct listen_sock - listen state