Add "Protocol" property -- AirPlay or AirPlay 2.

dbus-service.c

@@ -1,6 +1,6 @@
 /*
  * This file is part of Shairport Sync.
- * Copyright (c) Mike Brady 2018 -- 2019
+ * Copyright (c) Mike Brady 2018 -- 2022
  * All rights reserved.
  *
  * Permission is hereby granted, free of charge, to any person
@@ -1009,6 +1009,12 @@ static void on_dbus_name_acquired(GDBusConnection *connection, const gchar *name
 //    NULL);
 #endif
 
+#ifdef CONFIG_AIRPLAY_2
+  shairport_sync_set_protocol(SHAIRPORT_SYNC(shairportSyncSkeleton), "AirPlay 2");
+#else
+  shairport_sync_set_protocol(SHAIRPORT_SYNC(shairportSyncSkeleton), "AirPlay");
+#endif
+
   shairport_sync_set_version(SHAIRPORT_SYNC(shairportSyncSkeleton), PACKAGE_VERSION);
   char *vs = get_version_string();
   shairport_sync_set_version_string(SHAIRPORT_SYNC(shairportSyncSkeleton), vs);

org.gnome.ShairportSync.xml

@@ -22,6 +22,7 @@
     <property name="ALACDecoder" type="s" access="readwrite" />
     <property name="Version" type="s" access="read" />
     <property name="VersionString" type="s" access="read" />
+    <property name="Protocol" type="s" access="read" />
   </interface>
   <interface name="org.gnome.ShairportSync.Diagnostics">
     <property name="Verbosity" type="i" access="readwrite" />