When a network device is specified to tcpip_tx() or it's children, treat

it as a fallback network device rather than an explicitly forced network
device.

Clear routing table entries before re-attempting DHCP.

src/net/ipv4.c

  * @v pkb		Packet buffer
  * @v tcpip		Transport-layer protocol
  * @v st_dest		Destination network-layer address
- * @v netdev		Network device (or NULL to route automatically)
+ * @v netdev		Network device to use if no route found, or NULL
  * @v trans_csum	Transport-layer checksum to complete, or NULL
  * @ret rc		Status
  *
 	if ( ( rc = ipv4_ll_addr ( next_hop, iphdr->src, netdev,
 				   ll_dest ) ) != 0 ) {
 		DBG ( "IPv4 has no link-layer address for %s: %s\n",
-		      inet_ntoa ( iphdr->dest ), strerror ( rc ) );
+		      inet_ntoa ( next_hop ), strerror ( rc ) );
 		goto err;
 	}
 

src/net/tcpip.c

  * @v pkb		Packet buffer
  * @v tcpip_protocol	Transport-layer protocol
  * @v st_dest		Destination address
- * @v netdev		Network device (or NULL to route automatically)
+ * @v netdev		Network device to use if no route found, or NULL
  * @v trans_csum	Transport-layer checksum to complete, or NULL
  * @ret rc		Return status code
  */

src/net/udp.c

  *
  * @v conn		UDP connection
  * @v peer		Destination address
- * @v netdev		Net device via which to send (or NULL)
+ * @v netdev		Network device to use if no route found, or NULL
  * @v data		Data to send
  * @v len		Length of data
  * @ret rc		Return status code

src/usr/dhcpmgmt.c

 		dhcp_options = NULL;
 	}
 
+	/* Clear any existing routing table entry */
+	del_ipv4_address ( netdev );
+
 	/* Issue DHCP request */
 	printf ( "DHCP (%s %s)...", netdev->name, netdev_hwaddr ( netdev ) );
 	memset ( &dhcp, 0, sizeof ( dhcp ) );