netdev: Set *flagsp to 0 if flags cannot be obtained.

This interface is more convenient for some clients.

diff --git a/lib/netdev.c b/lib/netdev.c
index de8ee62199412f2cc9302c831c50db5037d83d1a..113b8471f21a403c8981793626c07392f7e9ceb2 100644 (file)
--- a/lib/netdev.c
+++ b/lib/netdev.c
@@ -825,7 +825,8 @@ netdev_get_in6(const struct netdev *netdev, struct in6_addr *in6)
 }
 
 /* Obtains the current flags for 'netdev' and stores them into '*flagsp'.
- * Returns 0 if successful, otherwise a positive errno value. */
+ * Returns 0 if successful, otherwise a positive errno value.  On failure,
+ * stores 0 into '*flagsp'. */
 int
 netdev_get_flags(const struct netdev *netdev, enum netdev_flags *flagsp)
 {
@@ -1023,7 +1024,7 @@ netdev_enumerate(struct svec *svec)
 
 /* Obtains the current flags for the network device named 'netdev_name' and
  * stores them into '*flagsp'.  Returns 0 if successful, otherwise a positive
- * errno value.
+ * errno value.  On error, stores 0 into '*flagsp'.
  *
  * If only device flags are needed, this is more efficient than calling
  * netdev_open(), netdev_get_flags(), netdev_close(). */
@@ -1034,12 +1035,12 @@ netdev_nodev_get_flags(const char *netdev_name, enum netdev_flags *flagsp)
 
     init_netdev();
 
+    *flagsp = 0;
     error = get_flags(netdev_name, &flags);
     if (error) {
         return error;
     }
 
-    *flagsp = 0;
     if (flags & IFF_UP) {
         *flagsp |= NETDEV_UP;
     }