[pxe] Implement PXENV_UNDI_{GET,SET}_MCAST_ADDRESS

Symantec Ghost requires working multicast support.  gPXE configures
all (sufficiently supported) network adapters into "receive all
multicasts" mode, which means that PXENV_UNDI_SET_MCAST_ADDRESS is
actually a no-op, but the current implementation returns
PXENV_STATUS_UNSUPPORTED instead.

Fix by making PXENV_UNDI_SET_MCAST_ADDRESS return success.  For good
measure, also implement PXENV_UNDI_GET_MCAST_ADDRESS, since the
relevant functionality is now exposed by the net device core.

Note that this will silently fail if the gPXE driver for the NIC being
used fails to configure the NIC in "receive all multicasts" mode.

src/arch/i386/interface/pxe/pxe_undi.c

 	undi_tx_count = 0;
 }
 
+/**
+ * Dump multicast address list
+ *
+ * @v mcast		PXE multicast address list
+ */
+static void pxe_dump_mcast_list ( struct s_PXENV_UNDI_MCAST_ADDRESS *mcast ) {
+	struct ll_protocol *ll_protocol = pxe_netdev->ll_protocol;
+	unsigned int i;
+
+	for ( i = 0 ; i < mcast->MCastAddrCount ; i++ ) {
+		DBG ( " %s", ll_protocol->ntoa ( mcast->McastAddr[i] ) );
+	}
+}
+
 /* PXENV_UNDI_STARTUP
  *
  * Status: working
 					*undi_reset_adapter ) {
 	int rc;
 
-	DBG ( "PXENV_UNDI_RESET_ADAPTER %04x\n",
-	      undi_reset_adapter->R_Mcast_Buf.MCastAddrCount );
+	DBG ( "PXENV_UNDI_RESET_ADAPTER" );
+	pxe_dump_mcast_list ( &undi_reset_adapter->R_Mcast_Buf );
+	DBG ( "\n" );
 
 	pxe_netdev_close();
 	if ( ( rc = pxe_netdev_open() ) != 0 ) {
 PXENV_EXIT_t pxenv_undi_open ( struct s_PXENV_UNDI_OPEN *undi_open ) {
 	int rc;
 
-	DBG ( "PXENV_UNDI_OPEN flag %04x filter %04x mcast %04x\n",
-	      undi_open->OpenFlag, undi_open->PktFilter,
-	      undi_open->R_Mcast_Buf.MCastAddrCount );
+	DBG ( "PXENV_UNDI_OPEN flag %04x filter %04x",
+	      undi_open->OpenFlag, undi_open->PktFilter );
+	pxe_dump_mcast_list ( &undi_open->R_Mcast_Buf );
+	DBG ( "\n" );
 
 	if ( ( rc = pxe_netdev_open() ) != 0 ) {
 		DBG ( "PXENV_UNDI_OPEN could not open %s: %s\n",
 
 /* PXENV_UNDI_SET_MCAST_ADDRESS
  *
- * Status: stub (no PXE multicast support)
+ * Status: working (for NICs that support receive-all-multicast)
  */
 PXENV_EXIT_t
 pxenv_undi_set_mcast_address ( struct s_PXENV_UNDI_SET_MCAST_ADDRESS
 			       *undi_set_mcast_address ) {
-	DBG ( "PXENV_UNDI_SET_MCAST_ADDRESS %04x failed: unsupported\n",
-	      undi_set_mcast_address->R_Mcast_Buf.MCastAddrCount );
+	DBG ( "PXENV_UNDI_SET_MCAST_ADDRESS" );
+	pxe_dump_mcast_list ( &undi_set_mcast_address->R_Mcast_Buf );
+	DBG ( "\n" );
 
-	undi_set_mcast_address->Status = PXENV_STATUS_UNSUPPORTED;
-	return PXENV_EXIT_FAILURE;
+	undi_set_mcast_address->Status = PXENV_STATUS_SUCCESS;
+	return PXENV_EXIT_SUCCESS;
 }
 
 /* PXENV_UNDI_SET_STATION_ADDRESS
 
 /* PXENV_UNDI_GET_MCAST_ADDRESS
  *
- * Status: stub (no PXE multicast support)
+ * Status: working
  */
 PXENV_EXIT_t
 pxenv_undi_get_mcast_address ( struct s_PXENV_UNDI_GET_MCAST_ADDRESS
 			       *undi_get_mcast_address ) {
+	struct ll_protocol *ll_protocol = pxe_netdev->ll_protocol;
 	struct in_addr ip = { .s_addr = undi_get_mcast_address->InetAddr };
+	int rc;
 
-	DBG ( "PXENV_UNDI_GET_MCAST_ADDRESS %s failed: unsupported\n",
-	      inet_ntoa ( ip ) );
+	DBG ( "PXENV_UNDI_GET_MCAST_ADDRESS %s", inet_ntoa ( ip ) );
 
-	undi_get_mcast_address->Status = PXENV_STATUS_UNSUPPORTED;
-	return PXENV_EXIT_FAILURE;
+	if ( ( rc = ll_protocol->mc_hash ( AF_INET, &ip,
+				      undi_get_mcast_address->MediaAddr ))!=0){
+		DBG ( " failed: %s\n", strerror ( rc ) );
+		undi_get_mcast_address->Status = PXENV_STATUS ( rc );
+		return PXENV_EXIT_FAILURE;
+	}
+	DBG ( "=>%s\n",
+	      ll_protocol->ntoa ( undi_get_mcast_address->MediaAddr ) );
+
+	undi_get_mcast_address->Status = PXENV_STATUS_SUCCESS;
+	return PXENV_EXIT_SUCCESS;
 }
 
 /* PXENV_UNDI_GET_NIC_TYPE