XDC Discovery

src/Nethermind/Nethermind.Network.Discovery/DiscoveryApp.cs

@@ -24,20 +24,20 @@ namespace Nethermind.Network.Discovery;
 public class DiscoveryApp : IDiscoveryApp
 {
     private readonly IDiscoveryConfig _discoveryConfig;
-    private readonly ITimestamper _timestamper;
+    protected readonly ITimestamper _timestamper;
     private readonly INodesLocator _nodesLocator;
-    private readonly IDiscoveryManager _discoveryManager;
+    protected readonly IDiscoveryManager _discoveryManager;
     private readonly INodeTable _nodeTable;
-    private readonly ILogManager _logManager;
+    protected readonly ILogManager _logManager;
     private readonly ILogger _logger;
-    private readonly IMessageSerializationService _messageSerializationService;
+    protected readonly IMessageSerializationService _messageSerializationService;
     private readonly ICryptoRandom _cryptoRandom;
     private readonly INetworkStorage _discoveryStorage;
     private readonly DiscoveryPersistenceManager _persistenceManager;
     private readonly IProcessExitSource _processExitSource;
     private readonly INetworkConfig _networkConfig;
     private readonly CancellationTokenSource _stopCts;
-    private readonly NodeFilter? _inboundMessageFilter;
+    protected readonly NodeFilter? _inboundMessageFilter;
 
     private NettyDiscoveryHandler? _discoveryHandler;
     private Task? _runningTask;
@@ -178,10 +178,12 @@ private void ResetUnreachableStatus(object? sender, NetworkAvailabilityEventArgs
         }
     }
 
+    protected virtual NettyDiscoveryHandler CreateDiscoveryHandler(IChannel channel) =>
+        new(_discoveryManager, channel, _messageSerializationService, _timestamper, _logManager, _inboundMessageFilter);
+
     public void InitializeChannel(IChannel channel)
     {
-        _discoveryHandler = new NettyDiscoveryHandler(_discoveryManager, channel, _messageSerializationService,
-            _timestamper, _logManager, _inboundMessageFilter);
+        _discoveryHandler = CreateDiscoveryHandler(channel);
         _discoveryManager.MsgSender = _discoveryHandler;
         _discoveryHandler.OnChannelActivated += OnChannelActivated;
 

src/Nethermind/Nethermind.Network.Discovery/Lifecycle/NodeLifecycleManager.cs

@@ -83,7 +83,7 @@ public void ProcessPingMsg(PingMsg pingMsg)
         RefreshNodeContactTime();
     }
 
-    private void SendEnrRequest()
+    protected virtual void SendEnrRequest()
     {
         EnrRequestMsg msg = new(ManagedNode.Address, CalculateExpirationTime());
         _discoveryManager.SendMessage(msg);

src/Nethermind/Nethermind.Network.Discovery/NettyDiscoveryHandler.cs

@@ -121,14 +121,11 @@ private bool TryParseMessage(DatagramPacket packet, out DiscoveryMsg? msg, out b
             return false;
         }
 
-        byte typeRaw = msgBytes[97];
-        if (!FastEnum.IsDefined((MsgType)typeRaw))
+        if (FromMsgTypeByte(msgBytes[97]) is not { } type)
         {
-            if (_logger.IsDebug) _logger.Debug($"Unsupported message type: {typeRaw}, sender: {address}, message {msgBytes.AsSpan(0, size).ToHexString()}");
+            if (_logger.IsDebug) _logger.Debug($"Unsupported message type: {msgBytes[97]}, sender: {address}, message {msgBytes.AsSpan(0, size).ToHexString()}");
             return false;
         }
-
-        MsgType type = (MsgType)typeRaw;
         if (_logger.IsTrace) _logger.Trace($"Received message: {type}");
 
         if (address is IPEndPoint remoteEndpoint && !TryAcceptInbound(remoteEndpoint))
@@ -194,6 +191,9 @@ protected override void ChannelRead0(IChannelHandlerContext ctx, DatagramPacket
         }
     }
 
+    protected virtual MsgType? FromMsgTypeByte(byte b) =>
+        FastEnum.IsDefined((MsgType)b) ? (MsgType)b : null;
+
     private DiscoveryMsg Deserialize(MsgType type, ArraySegment<byte> msg) => type switch
     {
         MsgType.Ping => _msgSerializationService.Deserialize<PingMsg>(msg),

src/Nethermind/Nethermind.Network.Discovery/Serializers/PingMsgSerializer.cs

@@ -13,12 +13,14 @@ namespace Nethermind.Network.Discovery.Serializers;
 
 public class PingMsgSerializer(IEcdsa ecdsa, [KeyFilter(IProtectedPrivateKey.NodeKey)] IPrivateKeyGenerator nodeKey, INodeIdResolver nodeIdResolver) : DiscoveryMsgSerializerBase(ecdsa, nodeKey, nodeIdResolver), IZeroInnerMessageSerializer<PingMsg>
 {
+    protected virtual byte MsgTypeByte => (byte)MsgType.Ping;
+
     public void Serialize(IByteBuffer byteBuffer, PingMsg msg)
     {
         (int totalLength, int contentLength, int sourceAddressLength, int destinationAddressLength) = GetLength(msg);
 
         byteBuffer.MarkIndex();
-        PrepareBufferForSerialization(byteBuffer, totalLength, (byte)msg.MsgType);
+        PrepareBufferForSerialization(byteBuffer, totalLength, MsgTypeByte);
         NettyRlpStream stream = new(byteBuffer);
         stream.StartSequence(contentLength);
         stream.Encode(msg.Version);

src/Nethermind/Nethermind.Network/MessageSerializationService.cs

@@ -30,7 +30,7 @@ public MessageSerializationService(params IReadOnlyList<SerializerInfo> serializ
                 ThrowInvalidSerializer(Serializer, expectedInterface);
             }
 
-            _zeroSerializers.TryAdd(MessageType.TypeHandle, Serializer);
+            _zeroSerializers[MessageType.TypeHandle] = Serializer;
         }
 
         [DoesNotReturn, StackTraceHidden]

src/Nethermind/Nethermind.Runner/configs/xdc-testnet.json

@@ -5,6 +5,13 @@
     "BaseDbPath": "nethermind_db/xdc-testnet",
     "LogFileName": "xdc-testnet.log"
   },
+  "Network": {
+    "FilterDiscoveryNodesByRecentIp": false,
+    "EnableEnrDiscovery": false
+  },
+  "Discovery": {
+    "DiscoveryVersion": "V4"
+  },
   "TxPool": {
     "BlobsSupport": "Disabled"
   },

src/Nethermind/Nethermind.Runner/configs/xdc.json

@@ -5,6 +5,13 @@
     "BaseDbPath": "nethermind_db/xdc",
     "LogFileName": "xdc.log"
   },
+  "Network": {
+    "FilterDiscoveryNodesByRecentIp": false,
+    "EnableEnrDiscovery": false
+  },
+  "Discovery": {
+    "DiscoveryVersion": "V4"
+  },
   "TxPool": {
     "BlobsSupport": "Disabled"
   },

src/Nethermind/Nethermind.Runner/packages.lock.json

@@ -1252,7 +1252,8 @@
           "Nethermind.Api": "[1.38.0-unstable, )",
           "Nethermind.Consensus": "[1.38.0-unstable, )",
           "Nethermind.Core": "[1.38.0-unstable, )",
-          "Nethermind.Init": "[1.38.0-unstable, )"
+          "Nethermind.Init": "[1.38.0-unstable, )",
+          "Nethermind.Network.Discovery": "[1.38.0-unstable, )"
         }
       },
       "AspNetCore.HealthChecks.UI": {

src/Nethermind/Nethermind.Xdc.Test/Discovery/XdcDiscoveryTests.cs

@@ -0,0 +1,63 @@
+// SPDX-FileCopyrightText: 2026 Demerzel Solutions Limited
+// SPDX-License-Identifier: LGPL-3.0-only
+
+using System.Net;
+using DotNetty.Buffers;
+using Nethermind.Core;
+using Nethermind.Core.Test.Builders;
+using Nethermind.Crypto;
+using Nethermind.Network;
+using Nethermind.Network.Discovery;
+using Nethermind.Network.Discovery.Messages;
+using Nethermind.Network.Test;
+using Nethermind.Xdc.Discovery;
+using NSubstitute;
+using NUnit.Framework;
+
+namespace Nethermind.Xdc.Test.Discovery;
+
+[TestFixture, Parallelizable(ParallelScope.All)]
+public class XdcDiscoveryTests
+{
+    [Test]
+    public void XdcPingMsgSerializer_WritesXdcTypeByte()
+    {
+        // Packet layout: 32-byte MDC + 64-byte sig + 1-byte recovery id + 1-byte type = type at index 97
+        Ecdsa ecdsa = new();
+        XdcPingMsgSerializer serializer = new(ecdsa, new SameKeyGenerator(TestItem.PrivateKeyA), new NodeIdResolver(ecdsa));
+        PingMsg msg = new(
+            TestItem.PublicKeyA,
+            Timestamper.Default.UnixTime.SecondsLong + 1200,
+            new(IPAddress.Loopback, 30303),
+            new(IPAddress.Loopback, 30304),
+            new byte[32]
+            );
+
+        using DisposableByteBuffer buffer = Unpooled.Buffer().AsDisposable();
+        serializer.Serialize(buffer, msg);
+        Assert.That(buffer.GetByte(97), Is.EqualTo((byte)5));
+    }
+
+    private sealed class ExposedXdcNettyDiscoveryHandler : XdcNettyDiscoveryHandler
+    {
+        public ExposedXdcNettyDiscoveryHandler()
+            : base(
+                Substitute.For<IDiscoveryMsgListener>(),
+                Substitute.For<DotNetty.Transport.Channels.IChannel>(),
+                Substitute.For<IMessageSerializationService>(),
+                Timestamper.Default,
+                Nethermind.Logging.LimboLogs.Instance)
+        {
+        }
+
+        public MsgType? ExposedFromMsgTypeByte(byte b) => FromMsgTypeByte(b);
+    }
+
+    [TestCase((byte)5, MsgType.Ping)]
+    [TestCase((byte)1, null)]
+    public void XdcNettyDiscoveryHandler_FromMsgTypeByte(byte input, MsgType? expected)
+    {
+        ExposedXdcNettyDiscoveryHandler handler = new();
+        Assert.That(handler.ExposedFromMsgTypeByte(input), Is.EqualTo(expected));
+    }
+}

src/Nethermind/Nethermind.Xdc/Discovery/XdcDiscoveryApp.cs

@@ -0,0 +1,40 @@
+// SPDX-FileCopyrightText: 2026 Demerzel Solutions Limited
+// SPDX-License-Identifier: LGPL-3.0-only
+
+using Autofac.Features.AttributeFilters;
+using DotNetty.Transport.Channels;
+using Nethermind.Config;
+using Nethermind.Core;
+using Nethermind.Crypto;
+using Nethermind.Db;
+using Nethermind.Logging;
+using Nethermind.Network;
+using Nethermind.Network.Config;
+using Nethermind.Network.Discovery;
+using Nethermind.Network.Discovery.RoutingTable;
+
+namespace Nethermind.Xdc.Discovery;
+
+// Parameters mirror DiscoveryApp so Autofac resolves [KeyFilter] attributes via WithAttributeFiltering().
+public class XdcDiscoveryApp(
+    [KeyFilter(IProtectedPrivateKey.NodeKey)] IProtectedPrivateKey nodeKey,
+    INodesLocator nodesLocator,
+    IDiscoveryManager? discoveryManager,
+    INodeTable? nodeTable,
+    IMessageSerializationService? msgSerializationService,
+    ICryptoRandom? cryptoRandom,
+    [KeyFilter(DbNames.DiscoveryNodes)] INetworkStorage? discoveryStorage,
+    DiscoveryPersistenceManager discoveryPersistenceManager,
+    IProcessExitSource processExitSource,
+    INetworkConfig? networkConfig,
+    IDiscoveryConfig? discoveryConfig,
+    ITimestamper? timestamper,
+    ILogManager? logManager,
+    NodeFilter? inboundMessageFilter = null)
+    : DiscoveryApp(nodeKey, nodesLocator, discoveryManager, nodeTable, msgSerializationService, cryptoRandom,
+        discoveryStorage, discoveryPersistenceManager, processExitSource, networkConfig, discoveryConfig,
+        timestamper, logManager, inboundMessageFilter)
+{
+    protected override NettyDiscoveryHandler CreateDiscoveryHandler(IChannel channel) =>
+        new XdcNettyDiscoveryHandler(_discoveryManager, channel, _messageSerializationService, _timestamper, _logManager, _inboundMessageFilter);
+}

src/Nethermind/Nethermind.Xdc/Discovery/XdcNettyDiscoveryHandler.cs

@@ -0,0 +1,32 @@
+// SPDX-FileCopyrightText: 2026 Demerzel Solutions Limited
+// SPDX-License-Identifier: LGPL-3.0-only
+
+using DotNetty.Transport.Channels;
+using Nethermind.Core;
+using Nethermind.Logging;
+using Nethermind.Network;
+using Nethermind.Network.Discovery;
+using Nethermind.Network.Discovery.Messages;
+
+namespace Nethermind.Xdc.Discovery;
+
+public class XdcNettyDiscoveryHandler(
+    IDiscoveryMsgListener? discoveryManager,
+    IChannel? channel,
+    IMessageSerializationService? msgSerializationService,
+    ITimestamper? timestamper,
+    ILogManager? logManager,
+    NodeFilter? inboundMessageFilter = null)
+    : NettyDiscoveryHandler(discoveryManager, channel, msgSerializationService, timestamper, logManager, inboundMessageFilter)
+{
+    // XDC remapped the standard disc-v4 type bytes: byte 1 (standard Ping) is unused;
+    // byte 5 is XDC's pingXDC. ENR (bytes 5/6 in standard geth) is not supported by XDC
+    protected override MsgType? FromMsgTypeByte(byte b) => b switch
+    {
+        2 => MsgType.Pong,
+        3 => MsgType.FindNode,
+        4 => MsgType.Neighbors,
+        5 => MsgType.Ping,
+        _ => null
+    };
+}

src/Nethermind/Nethermind.Xdc/Discovery/XdcNodeLifecycleManager.cs

@@ -0,0 +1,33 @@
+// SPDX-FileCopyrightText: 2026 Demerzel Solutions Limited
+// SPDX-License-Identifier: LGPL-3.0-only
+
+using Nethermind.Core;
+using Nethermind.Logging;
+using Nethermind.Network.Discovery;
+using Nethermind.Network.Discovery.Lifecycle;
+using Nethermind.Network.Discovery.RoutingTable;
+using Nethermind.Network.Enr;
+using Nethermind.Stats;
+using Nethermind.Stats.Model;
+
+namespace Nethermind.Xdc.Discovery;
+
+/// <summary>XDC-aware lifecycle manager that suppresses ENR requests.</summary>
+/// <remarks>
+/// XDC does not support ENR (disc-v4 bytes 5/6). XDC remaps byte 5 to its own pingXDC type,
+/// so a standard ENR request would be misread as a Ping by XDC peers.
+/// </remarks>
+public class XdcNodeLifecycleManager(
+    Node node,
+    IDiscoveryManager discoveryManager,
+    INodeTable nodeTable,
+    IEvictionManager evictionManager,
+    INodeStats nodeStats,
+    NodeRecord nodeRecord,
+    IDiscoveryConfig discoveryConfig,
+    ITimestamper timestamper,
+    ILogger logger)
+    : NodeLifecycleManager(node, discoveryManager, nodeTable, evictionManager, nodeStats, nodeRecord, discoveryConfig, timestamper, logger)
+{
+    protected override void SendEnrRequest() { }
+}

src/Nethermind/Nethermind.Xdc/Discovery/XdcNodeLifecycleManagerFactory.cs

@@ -0,0 +1,52 @@
+// SPDX-FileCopyrightText: 2026 Demerzel Solutions Limited
+// SPDX-License-Identifier: LGPL-3.0-only
+
+using System;
+using Nethermind.Core;
+using Nethermind.Logging;
+using Nethermind.Network.Discovery;
+using Nethermind.Network.Discovery.Lifecycle;
+using Nethermind.Network.Discovery.RoutingTable;
+using Nethermind.Network.Enr;
+using Nethermind.Stats;
+using Nethermind.Stats.Model;
+
+namespace Nethermind.Xdc.Discovery;
+
+public class XdcNodeLifecycleManagerFactory(
+    INodeTable nodeTable,
+    IEvictionManager evictionManager,
+    INodeStatsManager nodeStatsManager,
+    INodeRecordProvider nodeRecordProvider,
+    IDiscoveryConfig discoveryConfig,
+    ITimestamper timestamper,
+    ILogManager? logManager) : INodeLifecycleManagerFactory
+{
+    private readonly INodeTable _nodeTable = nodeTable ?? throw new ArgumentNullException(nameof(nodeTable));
+    private readonly ILogger _logger = logManager?.GetClassLogger<XdcNodeLifecycleManagerFactory>() ?? throw new ArgumentNullException(nameof(logManager));
+    private readonly IDiscoveryConfig _discoveryConfig = discoveryConfig ?? throw new ArgumentNullException(nameof(discoveryConfig));
+    private readonly ITimestamper _timestamper = timestamper ?? throw new ArgumentNullException(nameof(timestamper));
+    private readonly IEvictionManager _evictionManager = evictionManager ?? throw new ArgumentNullException(nameof(evictionManager));
+    private readonly INodeStatsManager _nodeStatsManager = nodeStatsManager ?? throw new ArgumentNullException(nameof(nodeStatsManager));
+    private readonly NodeRecord _selfNodeRecord = (nodeRecordProvider ?? throw new ArgumentNullException(nameof(nodeRecordProvider))).Current;
+
+    public IDiscoveryManager? DiscoveryManager { private get; set; }
+    public NodeRecord SelfNodeRecord => _selfNodeRecord;
+
+    public INodeLifecycleManager CreateNodeLifecycleManager(Node node)
+    {
+        if (DiscoveryManager is null)
+            throw new Exception($"{nameof(DiscoveryManager)} has to be set");
+
+        return new XdcNodeLifecycleManager(
+            node,
+            DiscoveryManager,
+            _nodeTable,
+            _evictionManager,
+            _nodeStatsManager.GetOrAdd(node),
+            _selfNodeRecord,
+            _discoveryConfig,
+            _timestamper,
+            _logger);
+    }
+}

src/Nethermind/Nethermind.Xdc/Discovery/XdcPingMsgSerializer.cs

@@ -0,0 +1,15 @@
+// SPDX-FileCopyrightText: 2026 Demerzel Solutions Limited
+// SPDX-License-Identifier: LGPL-3.0-only
+
+using Autofac.Features.AttributeFilters;
+using Nethermind.Crypto;
+using Nethermind.Network.Discovery.Messages;
+using Nethermind.Network.Discovery.Serializers;
+
+namespace Nethermind.Xdc.Discovery;
+
+public class XdcPingMsgSerializer(IEcdsa ecdsa, [KeyFilter(IProtectedPrivateKey.NodeKey)] IPrivateKeyGenerator nodeKey, INodeIdResolver nodeIdResolver)
+    : PingMsgSerializer(ecdsa, nodeKey, nodeIdResolver)
+{
+    protected override byte MsgTypeByte => 5;
+}

src/Nethermind/Nethermind.Xdc/Nethermind.Xdc.csproj

@@ -17,6 +17,7 @@
     <ProjectReference Include="..\Nethermind.Consensus\Nethermind.Consensus.csproj" />
     <ProjectReference Include="..\Nethermind.Core\Nethermind.Core.csproj" />
     <ProjectReference Include="..\Nethermind.Init\Nethermind.Init.csproj" />
+    <ProjectReference Include="..\Nethermind.Network.Discovery\Nethermind.Network.Discovery.csproj" />
   </ItemGroup>
 
 </Project>