[IPSEC]: Make xfrm_lookup flags argument a bit-field

This patch introduces an enum for bits in the flags argument of xfrm_lookup.
This is so that we can cram more information into it later.

Since all current users use just the values 0 and 1, XFRM_LOOKUP_WAIT has
been added with the value 1 << 0 to represent the current meaning of flags.

The test in __xfrm_lookup has been changed accordingly.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/dst.h

@@ -265,6 +265,11 @@ static inline struct dst_entry *dst_check(struct dst_entry *dst, u32 cookie)
 
 extern void		dst_init(void);
 
+/* Flags for xfrm_lookup flags argument. */
+enum {
+	XFRM_LOOKUP_WAIT = 1 << 0,
+};
+
 struct flowi;
 #ifndef CONFIG_XFRM
 static inline int xfrm_lookup(struct dst_entry **dst_p, struct flowi *fl,

net/xfrm/xfrm_policy.c

@@ -1565,7 +1565,7 @@ int __xfrm_lookup(struct dst_entry **dst_p, struct flowi *fl,
 				xfrm_pol_put(policy);
 				return -EREMOTE;
 			}
-			if (err == -EAGAIN && flags) {
+			if (err == -EAGAIN && (flags & XFRM_LOOKUP_WAIT)) {
 				DECLARE_WAITQUEUE(wait, current);
 
 				add_wait_queue(&km_waitq, &wait);