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

feat(plugins): implement customizable maximum concurrent connections

(cherry picked from commit 0e30df9ae22a265c3486dea1eba259567631eb87)

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();
+    }
+}