sock: Introduce named constants for sk_reuse

Name them in a "backward compatible" manner, i.e. reuse or not
are still 1 and 0 respectively. The reuse value of 2 means that
the socket with it will forcibly reuse everyone else's port.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/sock.h

@@ -376,6 +376,17 @@ struct sock {
 	void                    (*sk_destruct)(struct sock *sk);
 };
 
+/*
+ * SK_CAN_REUSE and SK_NO_REUSE on a socket mean that the socket is OK
+ * or not whether his port will be reused by someone else. SK_FORCE_REUSE
+ * on a socket means that the socket will reuse everybody else's port
+ * without looking at the other's sk_reuse value.
+ */
+
+#define SK_NO_REUSE	0
+#define SK_CAN_REUSE	1
+#define SK_FORCE_REUSE	2
+
 static inline int sk_peek_offset(struct sock *sk, int flags)
 {
 	if ((flags & MSG_PEEK) && (sk->sk_peek_off >= 0))