netdev_findby_ipv[4|6]addr return netdev_default() as last resort but don't return loopback device if another network device is in the UP state.

net/netdev/netdev_default.c

@@ -1,7 +1,7 @@
 /****************************************************************************
  * net/netdev/netdev_default.c
  *
- *   Copyright (C) 2014-2015 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2014-2015, 2018 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <gnutt@nuttx.org>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -72,6 +72,7 @@
 
 FAR struct net_driver_s *netdev_default(void)
 {
+  FAR struct net_driver_s *ret = NULL;
   FAR struct net_driver_s *dev;
 
   /* Examine each registered network device */
@@ -83,17 +84,21 @@ FAR struct net_driver_s *netdev_default(void)
 
       if ((dev->d_flags & IFF_UP) != 0)
         {
-          /* Return a reference to the first device we find that is in the UP
+          /* Return a reference to the first device that we find in the UP
-           * state.
+           * state (but not the loopback device unless it is the only
+           * device).
            */
 
-          net_unlock();
+          ret = dev;
-          return dev;
+          if (dev->d_lltype != NET_LL_LOOPBACK)
+            {
+              break;
+            }
         }
     }
 
   net_unlock();
-  return NULL;
+  return ret;
 }
 
 #endif /* CONFIG_NET  */

net/netdev/netdev_findbyaddr.c

@@ -203,13 +203,9 @@ FAR struct net_driver_s *netdev_findby_ipv4addr(in_addr_t lipaddr,
            * broadcast packet out ALL locally available networks.  I am not
            * sure of that and, in any event, there is nothing we can do
            * about that here.
-           *
-           * REVISIT:  For now, arbitrarily return the first network
-           * interface in the list of network devices.  The broadcast
-           * will be sent on that device only.
            */
 
-          return g_netdevices;
+          return netdev_default();
         }
       else
         {
@@ -250,15 +246,11 @@ FAR struct net_driver_s *netdev_findby_ipv4addr(in_addr_t lipaddr,
 #endif /* CONFIG_NET_ROUTE */
 
   /* The above lookup will fail if the packet is being sent out of our
-   * out subnet to a router and there is no routing information.
+   * out subnet to a router and there is no routing information. Let's
+   * try the default network device.
    */
 
-  /* If we will did not find the network device, then we might as well fail
+  return netdev_default();
-   * because we are not configured properly to determine the route to the
-   * destination.
-   */
-
-  return dev;
 }
 #endif /* CONFIG_NET_IPv4 */
 
@@ -302,13 +294,9 @@ FAR struct net_driver_s *netdev_findby_ipv6addr(const net_ipv6addr_t lipaddr,
            * broadcast packet out ALL locally available networks.  I am not
            * sure of that and, in any event, there is nothing we can do
            * about that here.
-           *
-           * REVISIT:  For now, arbitrarily return the first network
-           * interface in the list of network devices.  The broadcast
-           * will be sent on that device only.
            */
 
-          return g_netdevices;
+          return netdev_default();
         }
       else
         {
@@ -349,15 +337,11 @@ FAR struct net_driver_s *netdev_findby_ipv6addr(const net_ipv6addr_t lipaddr,
 #endif /* CONFIG_NET_ROUTE */
 
   /* The above lookup will fail if the packet is being sent out of our
-   * out subnet to a router and there is no routing information.
+   * out subnet to a router and there is no routing information. Let's
+   * try the default network device.
    */
 
-  /* If we will did not find the network device, then we might as well fail
+  return netdev_default();
-   * because we are not configured properly to determine the route to the
-   * destination.
-   */
-
-  return dev;
 }
 #endif /* CONFIG_NET_IPv6 */