Fix audio issues with multiple users in the channel (#3251)

src/Discord.Net.WebSocket/Audio/DaveSessionManager.cs

@@ -1,4 +1,4 @@
-using Discord.API.Voice;
+using Discord.API.Voice;
 using Discord.LibDave;
 using Discord.LibDave.Binding;
 using Discord.Logging;
@@ -175,11 +175,27 @@ await _logger.DebugAsync(
 
         await _logger.DebugAsync($"Processed dave MLS proposals, has data?: {result.HasData}");
 
-        if (result.HasData) await SendMLSCommitWelcomeAsync(result.ToMemory());
+        if (result.HasData)
+            await SendMLSCommitWelcomeAsync(result.ToMemory());
     }
 
     private async ValueTask OnDaveMLSAnnounceCommitTransactionAsync(ushort transitionId, ReadOnlyMemory<byte> payload)
     {
+        if (payload.IsEmpty)
+        {
+            await _logger.DebugAsync(
+                $"Payload for commit was empty; transaction id: {transitionId}, getting new key package..."
+            );
+
+            await SendMLSInvalidCommitWelcomeAsync(transitionId);
+            using var keyPackage = _session.GetMarshalledKeyPackage();
+            await SendMLSKeyPackageAsync(keyPackage.ToMemory());
+
+            await HandleDaveProtocolInitAsync(transitionId);
+
+            return;
+        }
+
         using var commit = _session.ProcessCommit(payload);
 
         if (commit.IsIgnored)
@@ -188,6 +204,7 @@ private async ValueTask OnDaveMLSAnnounceCommitTransactionAsync(ushort transitio
             await _logger.DebugAsync(
                 $"Commit result ignored, transaction id: {transitionId}, was prepared and removed? {wasRemoved}"
             );
+            UpdateEncryptorRatchet(_session.ProtocolVersion);
             return;
         }
 
@@ -220,20 +237,16 @@ await _logger.DebugAsync(
 
         foreach (var (id, decryptor) in _decryptors)
         {
-            if (id == SelfUserId) continue;
+            if (id == SelfUserId)
+                continue;
 
             decryptor.PrepareTransition(_session, id, protocolVersion);
         }
 
+        UpdateEncryptorRatchet(protocolVersion);
+
         if (transitionId is Dave.InitTransitionId)
         {
-            var ratchet = _session.GetKeyRatchet(SelfUserId);
-
-            Encryptor.IsInPassthroughMode = protocolVersion is Dave.DisabledProtocolVersion || ratchet.IsNull;
-
-            if (protocolVersion is not Dave.DisabledProtocolVersion && !ratchet.IsNull)
-                Encryptor.Ratchet = ratchet;
-
             // Streams created before DAVE was initialized lack the DaveDecryptStream layer.
             // Rebuild them now that keys are ready.
             await _client.RebuildInputStreamsForDaveAsync();
@@ -262,7 +275,8 @@ public async Task HandleDaveProtocolInitAsync(ushort protocolVersion)
 
     public async Task HandlePrepareEpochAsync(ulong epoch, ushort protocolVersion)
     {
-        if (epoch is not Dave.MLSNewGroupExpectedEpoch) return;
+        if (epoch is not Dave.MLSNewGroupExpectedEpoch)
+            return;
 
         await _logger.DebugAsync($"Initializing dave session: epoch {epoch}, protocol version {protocolVersion}");
 
@@ -321,6 +335,18 @@ private Task SendDaveProtocolReadyForTransitionAsync(ushort transitionId)
             new DaveMLSTransitionParams() { TransitionId = transitionId }
         );
 
+    private void UpdateEncryptorRatchet(ushort protocolVersion)
+    {
+        var ratchet = _session.GetKeyRatchet(SelfUserId);
+
+        var isDisabled = protocolVersion is Dave.DisabledProtocolVersion || ratchet.IsNull;
+
+        Encryptor.IsInPassthroughMode = isDisabled;
+
+        if (!isDisabled)
+            Encryptor.Ratchet = ratchet;
+    }
+
     public void Dispose()
     {
         foreach (var (_, decryptor) in _decryptors)