Fix voice IP discovery

Apparently this changed at some point without much notice. The old way was deprecated in 2019 and stopped working March 15th 2023.

Author: Francessco121

src/Discore/Voice/DiscordVoiceConnection.Sockets.cs

@@ -18,7 +18,7 @@ partial class DiscordVoiceConnection
         int? heartbeatInterval;
         IPAddress? udpIP;
         int? udpPort;
-        int? ssrc;
+        uint? ssrc;
         string[]? encryptionModes;
         Task? heartbeatLoopTask;
         VoiceUdpSocket? udpSocket;
@@ -705,6 +705,8 @@ async Task StartIPDiscovery(CancellationToken ct)
             if (udpSocket == null)
                 throw new InvalidOperationException("[StartIPDiscovery] udpSocket must not be null!");
 
+            log.LogVerbose("[StartIPDiscovery] Discovering our IP...");
+
             try
             {
                 await udpSocket.StartIPDiscoveryAsync().ConfigureAwait(false);
@@ -724,7 +726,7 @@ async Task ReceiveIPDiscovery(CancellationToken ct)
 
             IPDiscoveryEventArgs ipData = await udpSocket.IPDiscoveryQueue.TakeAsync(ct).ConfigureAwait(false);
 
-            log.LogVerbose($"[ReceiveIPDiscovery] Discovered end-point: {ipData.IP}:{ipData.Port}");
+            log.LogVerbose($"[ReceiveIPDiscovery] Discovered our endpoint: {ipData.IP}:{ipData.Port}");
 
             discoveredIP = ipData.IP;
             discoveredPort = ipData.Port;

src/Discore/Voice/Internal/VoiceReadyEventArgs.cs

@@ -7,10 +7,10 @@ class VoiceReadyEventArgs : EventArgs
     {
         public IPAddress IP { get; }
         public int Port { get; }
-        public int Ssrc { get; }
+        public uint Ssrc { get; }
         public string[] EncryptionModes { get; }
 
-        public VoiceReadyEventArgs(IPAddress ip, int port, int ssrc, string[] encryptionModes)
+        public VoiceReadyEventArgs(IPAddress ip, int port, uint ssrc, string[] encryptionModes)
         {
             IP = ip;
             Port = port;

src/Discore/Voice/Internal/VoiceUDPSocket.cs

@@ -1,5 +1,6 @@
 using Nito.AsyncEx;
 using System;
+using System.Buffers.Binary;
 using System.Net;
 using System.Net.Sockets;
 using System.Text;
@@ -27,7 +28,7 @@ class VoiceUdpSocket : IDisposable
         public AsyncCollection<IPDiscoveryEventArgs> IPDiscoveryQueue { get; } =
             new AsyncCollection<IPDiscoveryEventArgs>();
 
-        public int Ssrc { get; }
+        public uint Ssrc { get; }
 
         public bool IsPaused { get; set; }
 
@@ -46,7 +47,7 @@ class VoiceUdpSocket : IDisposable
         readonly CircularBuffer sendBuffer;
         readonly DiscoreLogger log;
 
-        public VoiceUdpSocket(string loggingName, int ssrc)
+        public VoiceUdpSocket(string loggingName, uint ssrc)
         {
             log = new DiscoreLogger(loggingName);
 
@@ -155,11 +156,13 @@ async Task HandleIPDiscoveryPacket(byte[] data)
         {
             discoveringIP = false;
 
+            // Discovery response packet is the same as the request but followed by the IP and port
+
             // Read IP as null-terminated string
-            string ip = Encoding.UTF8.GetString(data, 4, 70 - 6).TrimEnd('\0');
+            string ip = Encoding.UTF8.GetString(data, index: 8, count: 64).TrimEnd('\0');
 
             // Read port
-            int port = (ushort)(data[68] | data[69] << 8);
+            int port = (ushort)(data[72] | data[73] << 8);
 
             await IPDiscoveryQueue.AddAsync(new IPDiscoveryEventArgs(ip, port)).ConfigureAwait(false);
         }
@@ -175,7 +178,7 @@ async Task ReceiveLoop()
                     int read = await socket.ReceiveAsync(buffer, SocketFlags.None)
                         .ConfigureAwait(false);
 
-                    if (read == 70 && discoveringIP)
+                    if (read == 74 && discoveringIP) // IP discovery response packet is exactly 74 bytes long
                     {
                         await HandleIPDiscoveryPacket(buffer.Array!);
 
@@ -218,6 +221,8 @@ async Task ReceiveLoop()
                     break;
                 }
             }
+
+            log.LogVerbose("[ReceiveLoop] Exited receive loop.");
         }
         #endregion
 
@@ -235,11 +240,13 @@ void Send(byte[] buffer, int offset, int count)
         /// <exception cref="SocketException">Thrown if the socket encounters an error while sending data.</exception>
         public Task StartIPDiscoveryAsync()
         {
-            byte[] packet = new byte[70];
-            packet[0] = (byte)(Ssrc >> 24);
-            packet[1] = (byte)(Ssrc >> 16);
-            packet[2] = (byte)(Ssrc >> 8);
-            packet[3] = (byte)(Ssrc >> 0);
+            byte[] packet = new byte[74];
+            Span<byte> span = packet.AsSpan();
+
+            BinaryPrimitives.WriteInt16BigEndian(span[0..2], 1); // Mark as request (type)
+            BinaryPrimitives.WriteInt16BigEndian(span[2..4], 70); // Message length (excluding type and length fields)
+            BinaryPrimitives.WriteUInt32BigEndian(span[4..8], Ssrc); // SSRC
+            // Remainder of packet is empty for requests
 
             discoveringIP = true;
             return SendAsync(new ArraySegment<byte>(packet));

src/Discore/Voice/Internal/VoiceWebSocket.Payloads.cs

@@ -31,7 +31,7 @@ async Task HandleReadyPayload(JsonElement payload, JsonElement data)
         {
             var ip = IPAddress.Parse(data.GetProperty("ip").GetString()!);
             int port = data.GetProperty("port").GetInt32();
-            int ssrc = data.GetProperty("ssrc").GetInt32();
+            uint ssrc = data.GetProperty("ssrc").GetUInt32();
 
             JsonElement modesArray = data.GetProperty("modes");
             string[] modes = new string[modesArray.GetArrayLength()];
@@ -205,13 +205,13 @@ void BuildPayload(Utf8JsonWriter writer)
                 writer.WriteEndObject();
             }
 
-            log.LogVerbose($"[SelectProtocol] Sending to {ip}:{port}...");
+            log.LogVerbose($"[SelectProtocol] Using response endpoint {ip}:{port} and requesting encryption mode {encryptionMode}...");
             return SendPayload(VoiceOPCode.SelectProtocol, BuildPayload);
         }
 
         /// <exception cref="DiscordWebSocketException">Thrown if the payload fails to send because of a WebSocket error.</exception>
         /// <exception cref="InvalidOperationException">Thrown if the socket is not connected.</exception>
-        public Task SendSpeakingPayload(SpeakingFlag flags, int ssrc)
+        public Task SendSpeakingPayload(SpeakingFlag flags, uint ssrc)
         {
             void BuildPayload(Utf8JsonWriter writer)
             {