[efi] Veto the Dhcp6Dxe driver on all platforms

The reference implementation of Dhcp6Dxe in EDK2 has a fatal flaw: the
code in EfiDhcp6Stop() will poll the network in a tight loop until
either a response is received or a timer tick (at TPL_CALLBACK)
occurs.  When EfiDhcp6Stop() is called at TPL_CALLBACK or higher, this
will result in an endless loop and an apparently frozen system.

Since this is the reference implementation of Dhcp6Dxe, it is likely
that almost all platforms have the same problem.

Fix by vetoing the broken driver.  If the upstream driver is ever
fixed and a new version number issued, then we could plausibly test
against the version number exposed via the driver binding protocol.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/interface/efi/efi_veto.c

@@ -494,6 +494,32 @@ efi_veto_vmware_uefipxebc ( EFI_DRIVER_BINDING_PROTOCOL *binding __unused,
 	return 1;
 }
 
+/**
+ * Veto Dhcp6Dxe driver
+ *
+ * @v binding		Driver binding protocol
+ * @v loaded		Loaded image protocol
+ * @v wtf		Component name protocol, if present
+ * @v manufacturer	Manufacturer name, if present
+ * @v name		Driver name, if present
+ * @ret vetoed		Driver is to be vetoed
+ */
+static int efi_veto_dhcp6 ( EFI_DRIVER_BINDING_PROTOCOL *binding __unused,
+			    EFI_LOADED_IMAGE_PROTOCOL *loaded __unused,
+			    EFI_COMPONENT_NAME_PROTOCOL *wtf __unused,
+			    const char *manufacturer __unused,
+			    const CHAR16 *name ) {
+	static const CHAR16 dhcp6[] = L"DHCP6 Protocol Driver";
+
+	/* Check driver name */
+	if ( ! name )
+		return 0;
+	if ( memcmp ( name, dhcp6, sizeof ( dhcp6 ) ) != 0 )
+		return 0;
+
+	return 1;
+}
+
 /** Driver vetoes */
 static struct efi_veto_candidate efi_vetoes[] = {
 	{
@@ -508,6 +534,10 @@ static struct efi_veto_candidate efi_vetoes[] = {
 		.name = "VMware UefiPxeBc",
 		.veto = efi_veto_vmware_uefipxebc,
 	},
+	{
+		.name = "Dhcp6",
+		.veto = efi_veto_dhcp6,
+	},
 };
 
 /**