Update EMAC connect logic with MAC address change

Do not fail EMAC interface during connect if MAC address change is
not supported in the selected interface.

Author: Arto Kinnunen

features/netsocket/EMACInterface.cpp

@@ -15,9 +15,12 @@
  */
 
 #include "EMACInterface.h"
+#include "mbed_trace.h"
 
 using namespace mbed;
 
+#define TRACE_GROUP "EMACi"
+
 /* Interface implementation */
 EMACInterface::EMACInterface(EMAC &emac, OnboardNetworkStack &stack) :
     _emac(emac),
@@ -69,10 +72,17 @@ nsapi_error_t EMACInterface::set_dhcp(bool dhcp)
 nsapi_error_t EMACInterface::connect()
 {
     if (!_interface) {
-        nsapi_error_t err;
+        nsapi_error_t err = NSAPI_ERROR_UNSUPPORTED;
+
         if (_hw_mac_addr_set) {
             err = _stack.add_ethernet_interface(_emac, true, &_interface, _hw_mac_addr);
-        } else {
+            if (err == NSAPI_ERROR_UNSUPPORTED) {
+                tr_error("Failed to set user MAC address");
+            }
+        }
+
+        if (err == NSAPI_ERROR_UNSUPPORTED)
+        {
             err = _stack.add_ethernet_interface(_emac, true, &_interface);
         }
 

features/netsocket/NetworkInterface.h

@@ -106,8 +106,9 @@ class NetworkInterface: public DNS {
      *  be unique globally. The address must be set before calling the interface
      *  connect() method.
      *
-     *  Not all interfaces are supporting MAC address set. A call to connect()
-     *  method will fail if MAC address is provided but not possible to use.
+     *  Not all interfaces are supporting MAC address set and an error is not returned
+     *  for this method call. Verify the changed MAC address by analysing packet
+     *  captures from the used network interface.
      *
      *  6-byte EUI-48 MAC addresses are used for Ethernet while Mesh interface is
      *  using 8-byte EUI-64 address.