xfrm: enable to set non-wildcard mark 0 on SAs and SPs

ip xfrm considers that the user-defined mark is "any" as soon as
(mark.v & mark.m == 0), which prevents from specifying non-wildcard
marks that include the value 0 (typically 0/0xffffffff).

Yet, matching exactly mark 0 is useful for instance to separate
vti policies from global policies.

Always configure the user mark if mark.m != 0.
Signed-off-by: Christophe Gouault <christophe.gouault@6wind.com>

ip/xfrm_policy.c

@@ -373,7 +373,7 @@ static int xfrm_policy_modify(int cmd, unsigned flags, int argc, char **argv)
 			  (void *)tmpls_buf, tmpls_len);
 	}
 
-	if (mark.m & mark.v) {
+	if (mark.m) {
 		int r = addattr_l(&req.n, sizeof(req.buf), XFRMA_MARK,
 				  (void *)&mark, sizeof(mark));
 		if (r < 0) {

ip/xfrm_state.c

@@ -528,7 +528,7 @@ static int xfrm_state_modify(int cmd, unsigned flags, int argc, char **argv)
 		exit(1);
 	}
 
-	if (mark.m & mark.v) {
+	if (mark.m) {
 		int r = addattr_l(&req.n, sizeof(req.buf), XFRMA_MARK,
 				  (void *)&mark, sizeof(mark));
 		if (r < 0) {