Merge pull request #827 from Rhefew/feature/ip-connection-limit

feat(plugins): implement customizable maximum concurrent connections

(cherry picked from commit 0e30df9ae22a265c3486dea1eba259567631eb87)

src/GameLogic/IHasIpAddress.cs

@@ -0,0 +1,16 @@
+// <copyright file="IHasIpAddress.cs" company="MUnique">
+// Licensed under the MIT License. See LICENSE file in the project root for full license information.
+// </copyright>
+
+namespace MUnique.OpenMU.GameLogic;
+
+/// <summary>
+/// Interface for objects that expose a remote IP address.
+/// </summary>
+public interface IHasIpAddress
+{
+    /// <summary>
+    /// Gets the IP address of the remote connection.
+    /// </summary>
+    string? IpAddress { get; }
+}

src/GameLogic/Player.cs

@@ -203,6 +203,11 @@ public class Player : AsyncDisposable, IBucketMapObserver, IAttackable, IAttacke
     /// <inheritdoc/>
     public ushort Id { get; set; }
 
+    /// <summary>
+    /// Gets or sets a custom login result to override the default when login fails.
+    /// </summary>
+    public Views.Login.LoginResult? LoginResultOverride { get; set; }
+
     /// <inheritdoc cref="IPartyMember" />
     public string Name => this.SelectedCharacter?.Name ?? string.Empty;
 

src/GameLogic/PlayerActions/LoginAction.cs

@@ -189,7 +189,9 @@ public class LoginAction
 
     private async ValueTask HandleAlreadyConnectedAsync(Player player, string username)
     {
-        await player.InvokeViewPlugInAsync<IShowLoginResultPlugIn>(p => p.ShowLoginResultAsync(LoginResult.AccountAlreadyConnected)).ConfigureAwait(false);
+        var result = player.LoginResultOverride ?? LoginResult.AccountAlreadyConnected;
+        player.LoginResultOverride = null;
+        await player.InvokeViewPlugInAsync<IShowLoginResultPlugIn>(p => p.ShowLoginResultAsync(result)).ConfigureAwait(false);
         if (player.GameContext is IGameServerContext gameServerContext)
         {
             await gameServerContext.EventPublisher.PlayerAlreadyLoggedInAsync(gameServerContext.Id, username).ConfigureAwait(false);

src/GameLogic/PlugIns/MaximumConnectionsPerIpPlugIn.cs

@@ -0,0 +1,68 @@
+// <copyright file="MaximumConnectionsPerIpPlugIn.cs" company="MUnique">
+// Licensed under the MIT License. See LICENSE file in the project root for full license information.
+// </copyright>
+
+namespace MUnique.OpenMU.GameLogic.PlugIns;
+
+using System.ComponentModel.DataAnnotations;
+using System.Linq;
+using System.Runtime.InteropServices;
+using System.Threading.Tasks;
+using Microsoft.Extensions.Logging;
+using MUnique.OpenMU.PlugIns;
+
+/// <summary>
+/// A plugin that limits the number of simultaneous active player sessions connected from the same IP address.
+/// </summary>
+[PlugIn]
+[Display(Name = "Maximum Connections Per IP", Description = "Limits the maximum number of parallel connections from the same IP address.")]
+[Guid("2C779F5E-379E-4CE0-BFCC-CA6455D757B3")]
+public class MaximumConnectionsPerIpPlugIn : IPlayerStateChangingPlugIn, ISupportCustomConfiguration<MaximumConnectionsPerIpPlugInConfiguration>, ISupportDefaultCustomConfiguration, IDisabledByDefault
+{
+    /// <inheritdoc />
+    public MaximumConnectionsPerIpPlugInConfiguration? Configuration { get; set; }
+
+    /// <inheritdoc />
+    public async ValueTask PlayerStateChangingAsync(Player player, StateMachine.StateChangeEventArgs eventArgs)
+    {
+        if (eventArgs.NextState != PlayerState.Authenticated)
+        {
+            return;
+        }
+
+        var ipAddress = (player as IHasIpAddress)?.IpAddress;
+        if (string.IsNullOrEmpty(ipAddress))
+        {
+            return;
+        }
+
+        var config = this.Configuration ?? CreateDefaultConfiguration();
+        var players = await player.GameContext.GetPlayersAsync().ConfigureAwait(false);
+        var sameIpCount = players.Count(p =>
+            (p as IHasIpAddress)?.IpAddress == ipAddress
+            && p != player
+            && p.PlayerState.CurrentState != PlayerState.Initial
+            && p.PlayerState.CurrentState != PlayerState.LoginScreen);
+
+        if (sameIpCount >= config.MaximumConnectionsPerIp)
+        {
+            player.Logger.LogWarning(
+                "Login request for IP '{IpAddress}' was cancelled. It exceeded the maximum connection limit of {Limit}.",
+                ipAddress,
+                config.MaximumConnectionsPerIp);
+            player.LoginResultOverride = Views.Login.LoginResult.ServerIsFull;
+            eventArgs.Cancel = true;
+        }
+    }
+
+    /// <inheritdoc />
+    public object CreateDefaultConfig()
+    {
+        return CreateDefaultConfiguration();
+    }
+
+    private static MaximumConnectionsPerIpPlugInConfiguration CreateDefaultConfiguration()
+    {
+        return new MaximumConnectionsPerIpPlugInConfiguration();
+    }
+}

src/GameLogic/PlugIns/MaximumConnectionsPerIpPlugInConfiguration.cs

@@ -0,0 +1,16 @@
+// <copyright file="MaximumConnectionsPerIpPlugInConfiguration.cs" company="MUnique">
+// Licensed under the MIT License. See LICENSE file in the project root for full license information.
+// </copyright>
+
+namespace MUnique.OpenMU.GameLogic.PlugIns;
+
+/// <summary>
+/// Configuration for the <see cref="MaximumConnectionsPerIpPlugIn"/>.
+/// </summary>
+public class MaximumConnectionsPerIpPlugInConfiguration
+{
+    /// <summary>
+    /// Gets or sets the maximum number of concurrent connections per IP address.
+    /// </summary>
+    public int MaximumConnectionsPerIp { get; set; } = 3;
+}