netdev_findbyaddr() will not use a routing table if one is available. It will also make a better decision in the case there there is no routing table but only a single network interface.

ChangeLog

@@ -5702,4 +5702,10 @@
 	  touschscreen drive is basically functional) (2013-10-3)
 	* arch/arm/src/sama5/chip/sam_lcdc.h:  Add SAMA5 LCD register
 	  definition header file (2013-10-4).
+	* net/netdev_findbyaddr.c:  Now (1) uses the routing table
+	  if available to look up the router to get to a remote network,
+	  and (2) if there is only a single network device and no
+	  route, then it will simply return that single device.  The
+	  ARP logic will use the default router address associated with
+	  the interface in this case (2013-10-5).
  

net/net_close.c

@@ -176,7 +176,7 @@ static inline void netclose_disconnect(FAR struct socket *psock)
 
               /* Notify the device driver of the availaibilty of TX data */
 
-               netdev_txnotify(&conn->ripaddr);
+               netdev_txnotify(conn->ripaddr);
 
                /* Wait for the disconnect event */
 

net/net_internal.h

@@ -202,21 +202,21 @@ FAR struct uip_driver_s *netdev_findbyname(FAR const char *ifname);
 /* net_findbyaddr.c **********************************************************/
 
 #if CONFIG_NSOCKET_DESCRIPTORS > 0
-FAR struct uip_driver_s *netdev_findbyaddr(FAR const uip_ipaddr_t *raddr);
+FAR struct uip_driver_s *netdev_findbyaddr(const uip_ipaddr_t addr);
 #endif
 
 /* net_txnotify.c ************************************************************/
 
 #if CONFIG_NSOCKET_DESCRIPTORS > 0
-void netdev_txnotify(const uip_ipaddr_t *raddr);
+void netdev_txnotify(const uip_ipaddr_t addr);
 #endif
 
 /* net_rxnotify.c ************************************************************/
 
 #if CONFIG_NSOCKET_DESCRIPTORS > 0 && defined(CONFIG_NET_RXAVAIL)
-void netdev_rxnotify(const uip_ipaddr_t *raddr);
+void netdev_rxnotify(const uip_ipaddr_t addr);
 #else
-#  define netdev_rxnotify(raddr)
+#  define netdev_rxnotify(addr)
 #endif
 
 /* net_count.c ***************************************************************/

net/net_route.h

@@ -187,6 +187,12 @@ int net_delroute(uip_ipaddr_t target, uip_ipaddr_t netmask);
  *   router on a local network that can forward to the external network.
  *
  * Parameters:
+ *   target - An IP address on a remote network to use in the lookup.
+ *   router - The address of router on a local network that can forward our
+ *     packets to the target.
+ *
+ *   NOTE:  For IPv6, router will be an array, for IPv4 it will be a scalar
+ *   value.  Hence, the change in the function signature.
  *
  * Returned Value:
  *   OK on success; Negated errno on failure.
@@ -194,9 +200,9 @@ int net_delroute(uip_ipaddr_t target, uip_ipaddr_t netmask);
  ****************************************************************************/
 
 #ifdef CONFIG_NET_IPv6
-int net_router(uip_ipaddr_t target, uip_ipaddr_t *router);
-#else
 int net_router(uip_ipaddr_t target, uip_ipaddr_t router);
+#else
+int net_router(uip_ipaddr_t target, uip_ipaddr_t *router);
 #endif
 
 /****************************************************************************

net/net_router.c

@@ -109,6 +109,12 @@ static int net_match(FAR struct net_route_s *route, FAR void *arg)
  *   router on a local network that can forward to the external network.
  *
  * Parameters:
+ *   target - An IP address on a remote network to use in the lookup.
+ *   router - The address of router on a local network that can forward our
+ *     packets to the target.
+ *
+ *   NOTE:  For IPv6, router will be an array, for IPv4 it will be a scalar
+ *   value.  Hence, the change in the function signature.
  *
  * Returned Value:
  *   OK on success; Negated errno on failure.
@@ -116,9 +122,9 @@ static int net_match(FAR struct net_route_s *route, FAR void *arg)
  ****************************************************************************/
 
 #ifdef CONFIG_NET_IPv6
-int net_router(uip_ipaddr_t target, uip_ipaddr_t *router)
-#else
 int net_router(uip_ipaddr_t target, uip_ipaddr_t router)
+#else
+int net_router(uip_ipaddr_t target, uip_ipaddr_t *router)
 #endif
 {
   struct route_match_s match;
@@ -133,9 +139,9 @@ int net_router(uip_ipaddr_t target, uip_ipaddr_t router)
 
   ret = net_foreachroute(net_match, &match) ? OK : -ENOENT;
 #ifdef CONFIG_NET_IPv6
-  uip_ipaddr_copy(*router, match.target);
-#else
   uip_ipaddr_copy(router, match.target);
+#else
+  uip_ipaddr_copy(*router, match.target);
 #endif
 
   return ret;

net/netdev_findbyaddr.c

@@ -47,6 +47,7 @@
 
 #include <nuttx/net/uip/uip-arch.h>
 
+#include "net_route.h"
 #include "net_internal.h"
 
 /****************************************************************************
@@ -73,16 +74,40 @@
  * Function: netdev_maskcmp
  ****************************************************************************/
 
-static inline bool netdev_maskcmp(const uip_ipaddr_t *ipaddr,
-                                  const uip_ipaddr_t *raddr,
-                                  const uip_ipaddr_t *netmask)
+/****************************************************************************
+ * Function: netdev_finddevice
+ *
+ * Description:
+ *   Find a previously registered network device by matching a local address
+ *   with the subnet served by the device
+ *
+ * Parameters:
+ *   addr - Pointer to the remote address of a connection
+ *
+ * Returned Value:
+ *  Pointer to driver on success; null on failure
+ *
+ * Assumptions:
+ *  Called from normal user mode
+ *
+ ****************************************************************************/
+
+static FAR struct uip_driver_s *netdev_finddevice(const uip_ipaddr_t addr)
 {
-#ifndef CONFIG_NET_IPv6
-  return (*ipaddr & *netmask) == (*raddr & *netmask);
-#else
-# warning "Not implemented for IPv6"
-  return false;
-#endif
+  struct uip_driver_s *dev;
+
+  netdev_semtake();
+  for (dev = g_netdevices; dev; dev = dev->flink)
+    {
+      if (uip_ipaddr_maskcmp(dev->d_ipaddr, addr, dev->d_netmask))
+        {
+          netdev_semgive();
+          return dev;
+        }
+    }
+
+  netdev_semgive();
+  return NULL;
 }
 
 /****************************************************************************
@@ -93,11 +118,11 @@ static inline bool netdev_maskcmp(const uip_ipaddr_t *ipaddr,
  * Function: netdev_findbyaddr
  *
  * Description:
- *   Find a previously registered network device by matching a remote address
- *   with the subnet served by the device
+ *   Find a previously registered network device by matching an arbitrary
+ *   IP address.
  *
  * Parameters:
- *   raddr - Pointer to the remote address of a connection
+ *   addr - Pointer to the remote address of a connection
  *
  * Returned Value:
  *  Pointer to driver on success; null on failure
@@ -107,24 +132,69 @@ static inline bool netdev_maskcmp(const uip_ipaddr_t *ipaddr,
  *
  ****************************************************************************/
 
-FAR struct uip_driver_s *netdev_findbyaddr(const uip_ipaddr_t *raddr)
+FAR struct uip_driver_s *netdev_findbyaddr(const uip_ipaddr_t addr)
 {
   struct uip_driver_s *dev;
+#ifdef CONFIG_NET_ROUTE
+  uip_ipaddr_t router;
+  int ret;
+#endif
 
-  if (raddr)
+  /* First, see if the address maps to the a local network */
+
+  dev = netdev_finddevice(addr);
+  if (dev)
     {
-      netdev_semtake();
-      for (dev = g_netdevices; dev; dev = dev->flink)
-        {
-          if (netdev_maskcmp(&dev->d_ipaddr, raddr, &dev->d_netmask))
-            {
-              netdev_semgive();
-              return dev;
-            }
-        }
-      netdev_semgive();
+      return dev;
     }
-  return NULL;
+
+  /* No.. The address lies on an external network */
+
+#ifdef CONFIG_NET_ROUTE
+  /* If we have a routing table, then perhaps we can find the the local
+   * address of a router that can forward packets to the external network.
+   */
+
+#ifdef CONFIG_NET_IPv6
+  ret = net_router(addr, router);
+#else
+  ret = net_router(addr, &router);
+#endif
+  if (ret >= 0)
+    {
+      /* Success... try to find the network device associated with the local
+       * router address
+       */
+
+      dev = netdev_finddevice(router);
+      if (dev)
+        {
+          return dev;
+        }
+    }
+#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.
+   *
+   * However, if there is only a single, registered network interface, then
+   * the decision is pretty easy.  Use that device and its default router
+   * address.
+   */
+
+  netdev_semtake();
+  if (g_netdevices && !g_netdevices->flink)
+    {
+      dev = g_netdevices;
+    }
+  netdev_semgive();
+
+  /* If we will did not find the network device, then we might as well fail
+   * because we are not configured properly to determine the route to the
+   * target.
+   */
+
+  return dev;
 }
 
 #endif /* CONFIG_NET && CONFIG_NSOCKET_DESCRIPTORS */

net/netdev_txnotify.c

@@ -90,25 +90,12 @@
  *
  ****************************************************************************/
 
-void netdev_txnotify(const uip_ipaddr_t *raddr)
+void netdev_txnotify(const uip_ipaddr_t raddr)
 {
   /* Find the device driver that serves the subnet of the remote address */
 
   struct uip_driver_s *dev = netdev_findbyaddr(raddr);
 
-  /* The above lookup will fail if the packet is being sent out of our
-   * out subnet to a router.  REVISIT:  For now, we fall back and try "eth0".
-   */ 
-
-  if (dev == NULL)
-    {
-      /* If the destination address is not in our subnet, assume eth0 as the
-       * default device.
-       */
-
-      dev = netdev_findbyname("eth0");
-    }
-
   if (dev && dev->d_txavail)
     {
       /* Notify the device driver that new TX data is available. */

net/send.c

@@ -576,7 +576,7 @@ ssize_t psock_send(FAR struct socket *psock, FAR const void *buf, size_t len,
 
           /* Notify the device driver of the availaibilty of TX data */
 
-          netdev_txnotify(&conn->ripaddr);
+          netdev_txnotify(conn->ripaddr);
 
           /* Wait for the send to complete or an error to occur:  NOTES: (1)
            * uip_lockedwait will also terminate if a signal is received, (2) interrupts

net/sendto.c

@@ -402,7 +402,7 @@ ssize_t psock_sendto(FAR struct socket *psock, FAR const void *buf,
 
       /* Notify the device driver of the availabilty of TX data */
 
-      netdev_txnotify(&conn->ripaddr);
+      netdev_txnotify(conn->ripaddr);
 
       /* Wait for either the receive to complete or for an error/timeout to occur.
        * NOTES:  (1) uip_lockedwait will also terminate if a signal is received, (2)

net/uip/uip_icmpping.c

@@ -352,7 +352,7 @@ int uip_ping(uip_ipaddr_t addr, uint16_t id, uint16_t seqno,
 
       /* Notify the device driver of the availaibilty of TX data */
 
-      netdev_txnotify(&state.png_addr);
+      netdev_txnotify(state.png_addr);
 
       /* Wait for either the full round trip transfer to complete or
        * for timeout to occur. (1) uip_lockedwait will also terminate if a