Add vote kick

OpenRA.Game/Server/Server.cs

@@ -148,6 +148,8 @@ namespace OpenRA.Server
 		GameInformation gameInfo;
 		readonly List<GameInformation.Player> worldPlayers = new();
 		readonly Stopwatch pingUpdated = Stopwatch.StartNew();
+
+		public readonly VoteKickTracker VoteKickTracker;
 		readonly PlayerMessageTracker playerMessageTracker;
 
 		public ServerState State
@@ -318,6 +320,7 @@ namespace OpenRA.Server
 			MapStatusCache = new MapStatusCache(modData, MapStatusChanged, type == ServerType.Dedicated && settings.EnableLintChecks);
 
 			playerMessageTracker = new PlayerMessageTracker(this, DispatchOrdersToClient, SendLocalizedMessageTo);
+			VoteKickTracker = new VoteKickTracker(this);
 
 			LobbyInfo = new Session
 			{
@@ -1162,15 +1165,8 @@ namespace OpenRA.Server
 			return LobbyInfo.ClientWithIndex(conn.PlayerIndex);
 		}
 
-		/// <summary>Does not check if client is admin.</summary>
-		public bool CanKickClient(Session.Client kickee)
-		{
-			if (State != ServerState.GameStarted || kickee.IsObserver)
-				return true;
-
-			var player = worldPlayers.FirstOrDefault(p => p?.ClientIndex == kickee.Index);
-			return player != null && player.Outcome != WinState.Undefined;
-		}
+		public bool HasClientWonOrLost(Session.Client client) =>
+			worldPlayers.FirstOrDefault(p => p?.ClientIndex == client.Index)?.Outcome != WinState.Undefined;
 
 		public void DropClient(Connection toDrop)
 		{

OpenRA.Game/Server/VoteKickTracker.cs

@@ -0,0 +1,223 @@
+#region Copyright & License Information
+/*
+ * Copyright (c) The OpenRA Developers and Contributors
+ * This file is part of OpenRA, which is free software. It is made
+ * available to you under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, either version 3 of
+ * the License, or (at your option) any later version. For more
+ * information, see COPYING.
+ */
+#endregion
+
+using System.Collections.Generic;
+using System.Diagnostics;
+using OpenRA.Network;
+
+namespace OpenRA.Server
+{
+	public sealed class VoteKickTracker
+	{
+		[TranslationReference("kickee")]
+		const string InsufficientVotes = "notification-insufficient-votes-to-kick";
+
+		[TranslationReference]
+		const string AlreadyVoted = "notification-kick-already-voted";
+
+		[TranslationReference("kicker", "kickee")]
+		const string VoteKickStarted = "notification-vote-kick-started";
+
+		[TranslationReference]
+		const string UnableToStartAVote = "notification-unable-to-start-a-vote";
+
+		[TranslationReference("kickee", "percentage")]
+		const string VoteKickProgress = "notification-vote-kick-in-progress";
+
+		[TranslationReference("kickee")]
+		const string VoteKickEnded = "notification-vote-kick-ended";
+
+		readonly Dictionary<int, bool> voteTracker = new();
+		readonly Dictionary<Session.Client, long> failedVoteKickers = new();
+		readonly Server server;
+
+		Stopwatch voteKickTimer;
+		(Session.Client Client, Connection Conn) kickee;
+		(Session.Client Client, Connection Conn) voteKickerStarter;
+
+		public VoteKickTracker(Server server)
+		{
+			this.server = server;
+		}
+
+		// Only admins and alive players can participate in a vote kick.
+		bool ClientHasPower(Session.Client client) => client.IsAdmin || (!client.IsObserver && !server.HasClientWonOrLost(client));
+
+		public void Tick()
+		{
+			if (voteKickTimer == null)
+				return;
+
+			if (!server.Conns.Contains(kickee.Conn))
+			{
+				EndKickVote();
+				return;
+			}
+
+			if (voteKickTimer.ElapsedMilliseconds > server.Settings.VoteKickTimer)
+				EndKickVoteAndBlockKicker();
+		}
+
+		public bool VoteKick(Connection conn, Session.Client kicker, Connection kickeeConn, Session.Client kickee, int kickeeID, bool vote)
+		{
+			var voteInProgress = voteKickTimer != null;
+
+			if (server.State != ServerState.GameStarted
+				|| (kickee.IsAdmin && server.Type != ServerType.Dedicated)
+				|| (!voteInProgress && !vote) // Disallow starting a vote with a downvote
+				|| (voteInProgress && this.kickee.Client != kickee) // Disallow starting new votes when one is already ongoing.
+				|| !ClientHasPower(kicker))
+			{
+				server.SendLocalizedMessageTo(conn, UnableToStartAVote);
+				return false;
+			}
+
+			short eligiblePlayers = 0;
+			var isKickeeOnline = false;
+			var adminIsDeadButOnline = false;
+			foreach (var c in server.Conns)
+			{
+				var client = server.GetClient(c);
+				if (client != kickee && ClientHasPower(client))
+					eligiblePlayers++;
+
+				if (c == kickeeConn)
+					isKickeeOnline = true;
+
+				if (client.IsAdmin && (client.IsObserver || server.HasClientWonOrLost(client)))
+					adminIsDeadButOnline = true;
+			}
+
+			if (!isKickeeOnline)
+			{
+				EndKickVote();
+				return false;
+			}
+
+			if (eligiblePlayers < 2 || (adminIsDeadButOnline && !kickee.IsAdmin && eligiblePlayers < 3))
+			{
+				if (!kickee.IsObserver && !server.HasClientWonOrLost(kickee))
+				{
+					// Vote kick cannot be the sole deciding factor for a game.
+					server.SendLocalizedMessageTo(conn, InsufficientVotes, Translation.Arguments("kickee", kickee.Name));
+					EndKickVote();
+					return false;
+				}
+				else if (vote)
+				{
+					// If only a single player is playing, allow him to kick observers.
+					EndKickVote(false);
+					return true;
+				}
+			}
+
+			if (!voteInProgress)
+			{
+				// Prevent vote kick spam abuse.
+				if (failedVoteKickers.TryGetValue(kicker, out var time))
+				{
+					if (time + server.Settings.VoteKickerCooldown > kickeeConn.ConnectionTimer.ElapsedMilliseconds)
+					{
+						server.SendLocalizedMessageTo(conn, UnableToStartAVote);
+						return false;
+					}
+					else
+						failedVoteKickers.Remove(kicker);
+				}
+
+				Log.Write("server", $"Vote kick started on {kickeeID}.");
+				voteKickTimer = Stopwatch.StartNew();
+				server.SendLocalizedMessage(VoteKickStarted, Translation.Arguments("kicker", kicker.Name, "kickee", kickee.Name));
+				server.DispatchServerOrdersToClients(new Order("StartKickVote", null, false) { ExtraData = (uint)kickeeID }.Serialize());
+				this.kickee = (kickee, kickeeConn);
+				voteKickerStarter = (kicker, conn);
+			}
+
+			if (!voteTracker.ContainsKey(conn.PlayerIndex))
+				voteTracker[conn.PlayerIndex] = vote;
+			else
+			{
+				server.SendLocalizedMessageTo(conn, AlreadyVoted, null);
+				return false;
+			}
+
+			short votesFor = 0;
+			short votesAgainst = 0;
+			foreach (var c in voteTracker)
+			{
+				if (c.Value)
+					votesFor++;
+				else
+					votesAgainst++;
+			}
+
+			// Include the kickee in eligeablePlayers, so that in a 2v2 or any other even team
+			// matchup one team could not vote out the other team's player.
+			if (ClientHasPower(kickee))
+			{
+				eligiblePlayers++;
+				votesAgainst++;
+			}
+
+			var votesNeeded = eligiblePlayers / 2 + 1;
+			server.SendLocalizedMessage(VoteKickProgress, Translation.Arguments(
+				"kickee", kickee.Name,
+				"percentage", votesFor * 100 / eligiblePlayers));
+
+			// If a player or players during a vote lose or disconnect, it is possible that a downvote will
+			// kick a client. Guard against that situation.
+			if (vote && (votesFor >= votesNeeded))
+			{
+				EndKickVote(false);
+				return true;
+			}
+
+			// End vote if it can never succeed.
+			if (eligiblePlayers - votesAgainst < votesNeeded)
+			{
+				EndKickVoteAndBlockKicker();
+				return false;
+			}
+
+			voteKickTimer.Restart();
+			return false;
+		}
+
+		void EndKickVoteAndBlockKicker()
+		{
+			// Make sure vote kick is in progress.
+			if (voteKickTimer == null)
+				return;
+
+			if (server.Conns.Contains(voteKickerStarter.Conn))
+				failedVoteKickers[voteKickerStarter.Client] = voteKickerStarter.Conn.ConnectionTimer.ElapsedMilliseconds;
+
+			EndKickVote();
+		}
+
+		void EndKickVote(bool sendMessage = true)
+		{
+			// Make sure vote kick is in progress.
+			if (voteKickTimer == null)
+				return;
+
+			if (sendMessage)
+				server.SendLocalizedMessage(VoteKickEnded, Translation.Arguments("kickee", kickee.Client.Name));
+
+			server.DispatchServerOrdersToClients(new Order("EndKickVote", null, false) { ExtraData = (uint)kickee.Client.Index }.Serialize());
+
+			voteKickTimer = null;
+			voteKickerStarter = (null, null);
+			kickee = (null, null);
+			voteTracker.Clear();
+		}
+	}
+}