ui/vnc: Require audiodev= to enable audio

If there is no audiodev do not send the audio ack in response to
VNC_ENCODING_AUDIO, so that clients aren't told audio exists, and
immediately drop the client if they try to send any audio control messages
when audio is not advertised.

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

docs/about/deprecated.rst

@@ -45,13 +45,11 @@ backend settings instead of environment variables.  To ease migration to
 the new format, the ``-audiodev-help`` option can be used to convert
 the current values of the environment variables to ``-audiodev`` options.
 
-Creating sound card devices and vnc without ``audiodev=`` property (since 4.2)
-''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
+Creating sound card devices without ``audiodev=`` property (since 4.2)
+''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
 
 When not using the deprecated legacy audio config, each sound card
-should specify an ``audiodev=`` property.  Additionally, when using
-vnc, you should specify an ``audiodev=`` property if you plan to
-transmit audio through the VNC protocol.
+should specify an ``audiodev=`` property.
 
 Short-form boolean options (since 6.0)
 ''''''''''''''''''''''''''''''''''''''

docs/about/removed-features.rst

@@ -436,6 +436,12 @@ the process listing. This was replaced by the new ``password-secret``
 option which lets the password be securely provided on the command
 line using a ``secret`` object instance.
 
+Creating vnc without ``audiodev=`` property (removed in 8.2)
+''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
+
+When using vnc, you should specify an ``audiodev=`` property if
+you plan to transmit audio through the VNC protocol.
+
 QEMU Machine Protocol (QMP) commands
 ------------------------------------
 

ui/vnc.c

@@ -2195,7 +2195,10 @@ static void set_encodings(VncState *vs, int32_t *encodings, size_t n_encodings)
             send_ext_key_event_ack(vs);
             break;
         case VNC_ENCODING_AUDIO:
-            send_ext_audio_ack(vs);
+            if (vs->vd->audio_state) {
+                vs->features |= VNC_FEATURE_AUDIO_MASK;
+                send_ext_audio_ack(vs);
+            }
             break;
         case VNC_ENCODING_WMVi:
             vs->features |= VNC_FEATURE_WMVI_MASK;
@@ -2502,6 +2505,12 @@ static int protocol_client_msg(VncState *vs, uint8_t *data, size_t len)
                           read_u32(data, 4), read_u32(data, 8));
             break;
         case VNC_MSG_CLIENT_QEMU_AUDIO:
+            if (!vnc_has_feature(vs, VNC_FEATURE_AUDIO)) {
+                error_report("Audio message %d with audio disabled", read_u8(data, 2));
+                vnc_client_error(vs);
+                break;
+            }
+
             if (len == 2)
                 return 4;
 

ui/vnc.h

@@ -464,6 +464,7 @@ enum VncFeatures {
     VNC_FEATURE_LED_STATE,
     VNC_FEATURE_XVP,
     VNC_FEATURE_CLIPBOARD_EXT,
+    VNC_FEATURE_AUDIO,
 };
 
 #define VNC_FEATURE_RESIZE_MASK              (1 << VNC_FEATURE_RESIZE)
@@ -481,6 +482,7 @@ enum VncFeatures {
 #define VNC_FEATURE_LED_STATE_MASK           (1 << VNC_FEATURE_LED_STATE)
 #define VNC_FEATURE_XVP_MASK                 (1 << VNC_FEATURE_XVP)
 #define VNC_FEATURE_CLIPBOARD_EXT_MASK       (1 <<  VNC_FEATURE_CLIPBOARD_EXT)
+#define VNC_FEATURE_AUDIO_MASK               (1 <<  VNC_FEATURE_AUDIO)
 
 
 /* Client -> Server message IDs */