rtnl fd check

Prevent accidental damage from rtnl library if fd is uninitialized.
Signed-off-by: Stephen Hemminger <shemminger@osdl.org>

ip/ip.c

@@ -36,7 +36,7 @@ int timestamp = 0;
 char * _SL_ = NULL;
 char *batch_file = NULL;
 int force = 0;
-struct rtnl_handle rth;
+struct rtnl_handle rth = { .fd = -1 };
 
 static void usage(void) __attribute__((noreturn));
 

lib/libnetlink.c

@@ -27,7 +27,10 @@
 
 void rtnl_close(struct rtnl_handle *rth)
 {
+	if (rth->fd >= 0) {
 		close(rth->fd);
+		rth->fd = -1;
+	}
 }
 
 int rtnl_open_byproto(struct rtnl_handle *rth, unsigned subscriptions,