fix(dvc): drop data for a channel that is not open instead of failing

crates/ironrdp-dvc/src/client.rs

@@ -470,11 +470,19 @@ impl DrdynvcClient {
 
     fn process_data(&mut self, data: DrdynvcDataPdu) -> PduResult<Vec<SvcMessage>> {
         let channel_id = data.channel_id();
-        let messages = self
-            .dynamic_channels
-            .get_by_channel_id_mut(channel_id)
-            .ok_or_else(|| pdu_other_err!("access to non existing DVC channel"))?
-            .process(data)?;
+        let Some(channel) = self.dynamic_channels.get_by_channel_id_mut(channel_id) else {
+            // A server can send data on a channel before it sees the client decline it in the
+            // Create Response (GNOME Remote Desktop does this for AUDIO_PLAYBACK_DVC). The data has
+            // nowhere to go; dropping it is enough, ending the session over it is not warranted.
+            // Logged at debug, as `DrdynvcServer` logs a declined channel: it is not a fault, and a
+            // server may keep sending such data for as long as the session lasts.
+            debug!(
+                channel_id,
+                "Dropping data for a dynamic virtual channel that is not open"
+            );
+            return Ok(Vec::new());
+        };
+        let messages = channel.process(data)?;
 
         encode_dvc_messages(channel_id, messages, ChannelFlags::empty()).map_err(|e| encode_err!(e))
     }

crates/ironrdp-testsuite-core/tests/dvc/client.rs

@@ -88,6 +88,41 @@ fn exchange_capabilities(client: &mut DrdynvcClient) {
     client.process(&caps).expect("Capabilities Request should be processed");
 }
 
+#[test]
+fn data_for_a_channel_that_is_not_open_is_dropped() {
+    // A server can send data on a channel before it sees the client decline it in the Create
+    // Response (GNOME Remote Desktop does this for AUDIO_PLAYBACK_DVC). The session must survive it.
+    let mut client = DrdynvcClient::new();
+    client
+        .attach_established_dynamic_channel(7, RecordedDvc::default())
+        .expect("recorded channel should attach");
+    let data = |channel_id: u32, payload: &[u8]| {
+        encode_vec(&DrdynvcServerPdu::Data(DrdynvcDataPdu::Data(DataPdu::new(
+            channel_id,
+            payload.to_vec(),
+        ))))
+        .expect("DVC data should encode")
+    };
+
+    assert!(
+        client
+            .process(&data(4, b"declined"))
+            .expect("data for a channel that is not open should be dropped, not fail")
+            .is_empty()
+    );
+    assert!(
+        client
+            .process(&data(7, b"open"))
+            .expect("open channels are unaffected")
+            .is_empty()
+    );
+
+    let channel = client
+        .get_dvc_by_channel_id::<RecordedDvc>(7)
+        .expect("recorded channel should remain attached");
+    assert_eq!(channel.processor().received, vec![b"open".to_vec()]);
+}
+
 #[test]
 fn established_dynamic_channel_routes_recorded_data_without_negotiation() {
     let mut client = DrdynvcClient::new();