/*
 * Copyright (c) Contributors, http://opensimulator.org/
 * See CONTRIBUTORS.TXT for a full list of copyright holders.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name of the OpenSimulator Project nor the
 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Net;
using System.Net.Sockets;
using System.Reflection;
using System.Threading;
using log4net;
using NDesk.Options;
using Nini.Config;
using OpenMetaverse.Packets;
using OpenSim.Framework;
using OpenSim.Framework.Console;
using OpenSim.Framework.Monitoring;
using OpenSim.Region.Framework.Scenes;
using OpenMetaverse;

using TokenBucket = OpenSim.Region.ClientStack.LindenUDP.TokenBucket;

namespace OpenSim.Region.ClientStack.LindenUDP
{
    /// <summary>
    /// A shim around LLUDPServer that implements the IClientNetworkServer interface
    /// </summary>
    public sealed class LLUDPServerShim : IClientNetworkServer
    {
        LLUDPServer m_udpServer;

        public LLUDPServerShim()
        {
        }

        public void Initialise(IPAddress listenIP, ref uint port, int proxyPortOffsetParm, bool allow_alternate_port, IConfigSource configSource, AgentCircuitManager circuitManager)
        {
            m_udpServer = new LLUDPServer(listenIP, ref port, proxyPortOffsetParm, allow_alternate_port, configSource, circuitManager);
        }

        public void AddScene(IScene scene)
        {
            m_udpServer.AddScene(scene);

            StatsManager.RegisterStat(
                new Stat(
                    "ClientLogoutsDueToNoReceives",
                    "Number of times a client has been logged out because no packets were received before the timeout.",
                    "",
                    "",
                    "clientstack",
                    scene.Name,
                    StatType.Pull,
                    MeasuresOfInterest.None,
                    stat => stat.Value = m_udpServer.ClientLogoutsDueToNoReceives,
                    StatVerbosity.Debug));

            StatsManager.RegisterStat(
                new Stat(
                    "IncomingUDPReceivesCount",
                    "Number of UDP receives performed",
                    "",
                    "",
                    "clientstack",
                    scene.Name,
                    StatType.Pull,
                    MeasuresOfInterest.AverageChangeOverTime,
                    stat => stat.Value = m_udpServer.UdpReceives,
                    StatVerbosity.Debug));

            StatsManager.RegisterStat(
                new Stat(
                    "IncomingPacketsProcessedCount",
                    "Number of inbound LL protocol packets processed",
                    "",
                    "",
                    "clientstack",
                    scene.Name,
                    StatType.Pull,
                    MeasuresOfInterest.AverageChangeOverTime,
                    stat => stat.Value = m_udpServer.IncomingPacketsProcessed,
                    StatVerbosity.Debug));

            StatsManager.RegisterStat(
                new Stat(
                    "IncomingPacketsMalformedCount",
                    "Number of inbound UDP packets that could not be recognized as LL protocol packets.",
                    "",
                    "",
                    "clientstack",
                    scene.Name,
                    StatType.Pull,
                    MeasuresOfInterest.AverageChangeOverTime,
                    stat => stat.Value = m_udpServer.IncomingMalformedPacketCount,
                    StatVerbosity.Info));

            StatsManager.RegisterStat(
                new Stat(
                    "IncomingPacketsOrphanedCount",
                    "Number of inbound packets that were not initial connections packets and could not be associated with a viewer.",
                    "",
                    "",
                    "clientstack",
                    scene.Name,
                    StatType.Pull,
                    MeasuresOfInterest.AverageChangeOverTime,
                    stat => stat.Value = m_udpServer.IncomingOrphanedPacketCount,
                    StatVerbosity.Info));

            StatsManager.RegisterStat(
                new Stat(
                    "IncomingPacketsResentCount",
                    "Number of inbound packets that clients indicate are resends.",
                    "",
                    "",
                    "clientstack",
                    scene.Name,
                    StatType.Pull,
                    MeasuresOfInterest.AverageChangeOverTime,
                    stat => stat.Value = m_udpServer.IncomingPacketsResentCount,
                    StatVerbosity.Debug));

            StatsManager.RegisterStat(
                new Stat(
                    "OutgoingUDPSendsCount",
                    "Number of UDP sends performed",
                    "",
                    "",
                    "clientstack",
                    scene.Name,
                    StatType.Pull,
                    MeasuresOfInterest.AverageChangeOverTime,
                    stat => stat.Value = m_udpServer.UdpSends,
                    StatVerbosity.Debug));

            StatsManager.RegisterStat(
                new Stat(
                    "OutgoingPacketsResentCount",
                    "Number of packets resent because a client did not acknowledge receipt",
                    "",
                    "",
                    "clientstack",
                    scene.Name,
                    StatType.Pull,
                    MeasuresOfInterest.AverageChangeOverTime,
                    stat => stat.Value = m_udpServer.PacketsResentCount,
                    StatVerbosity.Debug));

            StatsManager.RegisterStat(
                new Stat(
                    "AverageUDPProcessTime",
                    "Average number of milliseconds taken to process each incoming UDP packet in a sample.",
                    "This is for initial receive processing which is separate from the later client LL packet processing stage.",
                    "ms",
                    "clientstack",
                    scene.Name,
                    StatType.Pull,
                    MeasuresOfInterest.None,
                    stat => stat.Value = m_udpServer.AverageReceiveTicksForLastSamplePeriod / TimeSpan.TicksPerMillisecond,
//                    stat => 
//                        stat.Value = Math.Round(m_udpServer.AverageReceiveTicksForLastSamplePeriod / TimeSpan.TicksPerMillisecond, 7),
                    StatVerbosity.Debug));
        }

        public bool HandlesRegion(Location x)
        {
            return m_udpServer.HandlesRegion(x);
        }

        public void Start()
        {
            m_udpServer.Start();
        }

        public void Stop()
        {
            m_udpServer.Stop();
        }
    }

    /// <summary>
    /// The LLUDP server for a region. This handles incoming and outgoing
    /// packets for all UDP connections to the region
    /// </summary>
    public class LLUDPServer : OpenSimUDPBase
    {
        private static readonly ILog m_log = LogManager.GetLogger(MethodBase.GetCurrentMethod().DeclaringType);

        /// <summary>Maximum transmission unit, or UDP packet size, for the LLUDP protocol</summary>
        public const int MTU = 1400;

        /// <summary>Number of forced client logouts due to no receipt of packets before timeout.</summary>
        public int ClientLogoutsDueToNoReceives { get; private set; }

        /// <summary>
        /// Default packet debug level given to new clients
        /// </summary>
        public int DefaultClientPacketDebugLevel { get; set; }

        /// <summary>The measured resolution of Environment.TickCount</summary>
        public readonly float TickCountResolution;

        /// <summary>Number of prim updates to put on the queue each time the 
        /// OnQueueEmpty event is triggered for updates</summary>
        public readonly int PrimUpdatesPerCallback;

        /// <summary>Number of texture packets to put on the queue each time the
        /// OnQueueEmpty event is triggered for textures</summary>
        public readonly int TextureSendLimit;

        /// <summary>Handlers for incoming packets</summary>
        //PacketEventDictionary packetEvents = new PacketEventDictionary();
        /// <summary>Incoming packets that are awaiting handling</summary>
        private OpenMetaverse.BlockingQueue<IncomingPacket> packetInbox = new OpenMetaverse.BlockingQueue<IncomingPacket>();

        /// <summary></summary>
        //private UDPClientCollection m_clients = new UDPClientCollection();
        /// <summary>Bandwidth throttle for this UDP server</summary>
        protected TokenBucket m_throttle;
        
        /// <summary>Bandwidth throttle rates for this UDP server</summary>
        public ThrottleRates ThrottleRates { get; private set; }
        
        /// <summary>Manages authentication for agent circuits</summary>
        private AgentCircuitManager m_circuitManager;

        /// <summary>Reference to the scene this UDP server is attached to</summary>
        public Scene Scene { get; private set; }

        /// <summary>The X/Y coordinates of the scene this UDP server is attached to</summary>
        private Location m_location;

        /// <summary>The size of the receive buffer for the UDP socket. This value
        /// is passed up to the operating system and used in the system networking
        /// stack. Use zero to leave this value as the default</summary>
        private int m_recvBufferSize;

        /// <summary>Flag to process packets asynchronously or synchronously</summary>
        private bool m_asyncPacketHandling;

        /// <summary>Tracks whether or not a packet was sent each round so we know
        /// whether or not to sleep</summary>
        private bool m_packetSent;

        /// <summary>Environment.TickCount of the last time that packet stats were reported to the scene</summary>
        private int m_elapsedMSSinceLastStatReport = 0;

        /// <summary>Environment.TickCount of the last time the outgoing packet handler executed</summary>
        private int m_tickLastOutgoingPacketHandler;

        /// <summary>Keeps track of the number of elapsed milliseconds since the last time the outgoing packet handler looped</summary>
        private int m_elapsedMSOutgoingPacketHandler;

        /// <summary>Keeps track of the number of 100 millisecond periods elapsed in the outgoing packet handler executed</summary>
        private int m_elapsed100MSOutgoingPacketHandler;

        /// <summary>Keeps track of the number of 500 millisecond periods elapsed in the outgoing packet handler executed</summary>
        private int m_elapsed500MSOutgoingPacketHandler;

        /// <summary>Flag to signal when clients should check for resends</summary>
        protected bool m_resendUnacked;

        /// <summary>Flag to signal when clients should send ACKs</summary>
        protected bool m_sendAcks;

        /// <summary>Flag to signal when clients should send pings</summary>
        protected bool m_sendPing;

        /// <summary>
        /// Event used to signal when queued packets are available for sending.
        /// </summary>
        /// <remarks>
        /// This allows the outbound loop to only operate when there is data to send rather than continuously polling.
        /// Some data is sent immediately and not queued.  That data would not trigger this event.
        /// </remarks>
        private AutoResetEvent m_dataPresentEvent = new AutoResetEvent(false);

        private Pool<IncomingPacket> m_incomingPacketPool;

        /// <summary>
        /// Stat for number of packets in the main pool awaiting use.
        /// </summary>
        private Stat m_poolCountStat;

        /// <summary>
        /// Stat for number of packets in the inbound packet pool awaiting use.
        /// </summary>
        private Stat m_incomingPacketPoolStat;

        private int m_defaultRTO = 0;
        private int m_maxRTO = 0;
        private int m_ackTimeout = 0;
        private int m_pausedAckTimeout = 0;
        private bool m_disableFacelights = false;

        public Socket Server { get { return null; } }

        /// <summary>
        /// Record how many packets have been resent
        /// </summary>
        internal int PacketsResentCount { get; set; }

        /// <summary>
        /// Record how many packets have been sent
        /// </summary>
        internal int PacketsSentCount { get; set; }

        /// <summary>
        /// Record how many incoming packets are indicated as resends by clients.
        /// </summary>
        internal int IncomingPacketsResentCount { get; set; }

        /// <summary>
        /// Record how many inbound packets could not be recognized as LLUDP packets.
        /// </summary>
        public int IncomingMalformedPacketCount { get; private set; }

        /// <summary>
        /// Record how many inbound packets could not be associated with a simulator circuit.
        /// </summary>
        public int IncomingOrphanedPacketCount { get; private set; }

        /// <summary>
        /// Record current outgoing client for monitoring purposes.
        /// </summary>
        private IClientAPI m_currentOutgoingClient;

        /// <summary>
        /// Recording current incoming client for monitoring purposes.
        /// </summary>
        private IClientAPI m_currentIncomingClient;

        /// <summary>
        /// Experimental facility to run queue empty processing within a controlled number of threads rather than
        /// requiring massive numbers of short-lived threads from the threadpool when there are a high number of 
        /// connections.
        /// </summary>
        public OutgoingQueueRefillEngine OqrEngine { get; private set; }

        public LLUDPServer(
            IPAddress listenIP, ref uint port, int proxyPortOffsetParm, bool allow_alternate_port,
            IConfigSource configSource, AgentCircuitManager circuitManager)
            : base(listenIP, (int)port)
        {
            #region Environment.TickCount Measurement

            // Measure the resolution of Environment.TickCount
            TickCountResolution = 0f;
            for (int i = 0; i < 5; i++)
            {
                int start = Environment.TickCount;
                int now = start;
                while (now == start)
                    now = Environment.TickCount;
                TickCountResolution += (float)(now - start) * 0.2f;
            }
            m_log.Info("[LLUDPSERVER]: Average Environment.TickCount resolution: " + TickCountResolution + "ms");
            TickCountResolution = (float)Math.Ceiling(TickCountResolution);

            #endregion Environment.TickCount Measurement

            m_circuitManager = circuitManager;
            int sceneThrottleBps = 0;
            bool usePools = false;

            IConfig config = configSource.Configs["ClientStack.LindenUDP"];
            if (config != null)
            {
                m_asyncPacketHandling = config.GetBoolean("async_packet_handling", true);
                m_recvBufferSize = config.GetInt("client_socket_rcvbuf_size", 0);
                sceneThrottleBps = config.GetInt("scene_throttle_max_bps", 0);

                PrimUpdatesPerCallback = config.GetInt("PrimUpdatesPerCallback", 100);
                TextureSendLimit = config.GetInt("TextureSendLimit", 20);

                m_defaultRTO = config.GetInt("DefaultRTO", 0);
                m_maxRTO = config.GetInt("MaxRTO", 0);
                m_disableFacelights = config.GetBoolean("DisableFacelights", false);
                m_ackTimeout = 1000 * config.GetInt("AckTimeout", 60);
                m_pausedAckTimeout = 1000 * config.GetInt("PausedAckTimeout", 300);
            }
            else
            {
                PrimUpdatesPerCallback = 100;
                TextureSendLimit = 20;
                m_ackTimeout = 1000 * 60; // 1 minute
                m_pausedAckTimeout = 1000 * 300; // 5 minutes
            }

            // FIXME: This actually only needs to be done once since the PacketPool is shared across all servers.
            // However, there is no harm in temporarily doing it multiple times.
            IConfig packetConfig = configSource.Configs["PacketPool"];
            if (packetConfig != null)
            {
                PacketPool.Instance.RecyclePackets = packetConfig.GetBoolean("RecyclePackets", true);
                PacketPool.Instance.RecycleDataBlocks = packetConfig.GetBoolean("RecycleDataBlocks", true);
                usePools = packetConfig.GetBoolean("RecycleBaseUDPPackets", usePools);
            }

            #region BinaryStats
            config = configSource.Configs["Statistics.Binary"];
            m_shouldCollectStats = false;
            if (config != null)
            {
                m_shouldCollectStats = config.GetBoolean("Enabled", false);
                binStatsMaxFilesize = TimeSpan.FromSeconds(config.GetInt("packet_headers_period_seconds", 300));
                binStatsDir = config.GetString("stats_dir", ".");
                m_aggregatedBWStats = config.GetBoolean("aggregatedBWStats", false);
            }
            #endregion BinaryStats

            m_throttle = new TokenBucket(null, sceneThrottleBps);
            ThrottleRates = new ThrottleRates(configSource);

            if (usePools)
                EnablePools();

            OqrEngine = new OutgoingQueueRefillEngine(this);
        }

        public void Start()
        {
            StartInbound();
            StartOutbound();

            m_elapsedMSSinceLastStatReport = Environment.TickCount;
        }

        private void StartInbound()
        {
            m_log.InfoFormat(
                "[LLUDPSERVER]: Starting inbound packet processing for the LLUDP server in {0} mode with UsePools = {1}",
                m_asyncPacketHandling ? "asynchronous" : "synchronous", UsePools);

            base.StartInbound(m_recvBufferSize, m_asyncPacketHandling);

            // This thread will process the packets received that are placed on the packetInbox
            Watchdog.StartThread(
                IncomingPacketHandler,
                string.Format("Incoming Packets ({0})", Scene.Name),
                ThreadPriority.Normal,
                false,
                true,
                GetWatchdogIncomingAlarmData,
                Watchdog.DEFAULT_WATCHDOG_TIMEOUT_MS);
        }

        private new void StartOutbound()
        {
            m_log.Info("[LLUDPSERVER]: Starting outbound packet processing for the LLUDP server");

            base.StartOutbound();

            Watchdog.StartThread(
                OutgoingPacketHandler,
                string.Format("Outgoing Packets ({0})", Scene.Name),
                ThreadPriority.Normal,
                false,
                true,
                GetWatchdogOutgoingAlarmData,
                Watchdog.DEFAULT_WATCHDOG_TIMEOUT_MS);
        }

        public void Stop()
        {
            m_log.Info("[LLUDPSERVER]: Shutting down the LLUDP server for " + Scene.Name);
            base.StopOutbound();
            base.StopInbound();
        }

        protected override bool EnablePools()
        {
            if (!UsePools)
            {
                base.EnablePools();

                m_incomingPacketPool = new Pool<IncomingPacket>(() => new IncomingPacket(), 500);

                return true;
            }

            return false;
        }

        protected override bool DisablePools()
        {
            if (UsePools)
            {
                base.DisablePools();

                StatsManager.DeregisterStat(m_incomingPacketPoolStat);

                // We won't null out the pool to avoid a race condition with code that may be in the middle of using it.

                return true;
            }

            return false;
        }

        /// <summary>
        /// This is a seperate method so that it can be called once we have an m_scene to distinguish different scene
        /// stats.
        /// </summary>
        private void EnablePoolStats()
        {
            m_poolCountStat
                = new Stat(
                    "UDPPacketBufferPoolCount",
                    "Objects within the UDPPacketBuffer pool",
                    "The number of objects currently stored within the UDPPacketBuffer pool",
                    "",
                    "clientstack",
                    Scene.Name,
                    StatType.Pull,
                    stat => stat.Value = Pool.Count,
                    StatVerbosity.Debug);

            StatsManager.RegisterStat(m_poolCountStat);

            m_incomingPacketPoolStat
                = new Stat(
                    "IncomingPacketPoolCount",
                    "Objects within incoming packet pool",
                    "The number of objects currently stored within the incoming packet pool",
                    "",
                    "clientstack",
                    Scene.Name,
                    StatType.Pull,
                    stat => stat.Value = m_incomingPacketPool.Count,
                    StatVerbosity.Debug);

            StatsManager.RegisterStat(m_incomingPacketPoolStat);
        }

        /// <summary>
        /// Disables pool stats.
        /// </summary>
        private void DisablePoolStats()
        {
            StatsManager.DeregisterStat(m_poolCountStat);
            m_poolCountStat = null;

            StatsManager.DeregisterStat(m_incomingPacketPoolStat);
            m_incomingPacketPoolStat = null;
        }

        /// <summary>
        /// If the outgoing UDP thread times out, then return client that was being processed to help with debugging.
        /// </summary>
        /// <returns></returns>
        private string GetWatchdogIncomingAlarmData()
        {
            return string.Format(
                "Client is {0}",
                m_currentIncomingClient != null ? m_currentIncomingClient.Name : "none");
        }

        /// <summary>
        /// If the outgoing UDP thread times out, then return client that was being processed to help with debugging.
        /// </summary>
        /// <returns></returns>
        private string GetWatchdogOutgoingAlarmData()
        {
            return string.Format(
                "Client is {0}",
                m_currentOutgoingClient != null ? m_currentOutgoingClient.Name : "none");
        }

        public void AddScene(IScene scene)
        {
            if (Scene != null)
            {
                m_log.Error("[LLUDPSERVER]: AddScene() called on an LLUDPServer that already has a scene");
                return;
            }

            if (!(scene is Scene))
            {
                m_log.Error("[LLUDPSERVER]: AddScene() called with an unrecognized scene type " + scene.GetType());
                return;
            }

            Scene = (Scene)scene;
            m_location = new Location(Scene.RegionInfo.RegionHandle);

            StatsManager.RegisterStat(
                new Stat(
                    "InboxPacketsCount",
                    "Number of LL protocol packets waiting for the second stage of processing after initial receive.",
                    "Number of LL protocol packets waiting for the second stage of processing after initial receive.",
                    "",
                    "clientstack",
                    scene.Name,
                    StatType.Pull,
                    MeasuresOfInterest.AverageChangeOverTime,
                    stat => stat.Value = packetInbox.Count,
                    StatVerbosity.Debug));

            // XXX: These stats are also pool stats but we register them separately since they are currently not
            // turned on and off by EnablePools()/DisablePools()
            StatsManager.RegisterStat(
                new PercentageStat(
                    "PacketsReused",
                    "Packets reused",
                    "Number of packets reused out of all requests to the packet pool",
                    "clientstack",
                    Scene.Name,
                    StatType.Pull,
                    stat => 
                        { PercentageStat pstat = (PercentageStat)stat; 
                          pstat.Consequent = PacketPool.Instance.PacketsRequested; 
                          pstat.Antecedent = PacketPool.Instance.PacketsReused; },
                    StatVerbosity.Debug));

            StatsManager.RegisterStat(
                new PercentageStat(
                    "PacketDataBlocksReused",
                    "Packet data blocks reused",
                    "Number of data blocks reused out of all requests to the packet pool",
                    "clientstack",
                    Scene.Name,
                    StatType.Pull,
                    stat =>
                        { PercentageStat pstat = (PercentageStat)stat; 
                          pstat.Consequent = PacketPool.Instance.BlocksRequested; 
                          pstat.Antecedent = PacketPool.Instance.BlocksReused; },
                    StatVerbosity.Debug));

            StatsManager.RegisterStat(
                new Stat(
                    "PacketsPoolCount",
                    "Objects within the packet pool",
                    "The number of objects currently stored within the packet pool",
                    "",
                    "clientstack",
                    Scene.Name,
                    StatType.Pull,
                    stat => stat.Value = PacketPool.Instance.PacketsPooled,
                    StatVerbosity.Debug));

            StatsManager.RegisterStat(
                new Stat(
                    "PacketDataBlocksPoolCount",
                    "Objects within the packet data block pool",
                    "The number of objects currently stored within the packet data block pool",
                    "",
                    "clientstack",
                    Scene.Name,
                    StatType.Pull,
                    stat => stat.Value = PacketPool.Instance.BlocksPooled,
                    StatVerbosity.Debug));
        
            // We delay enabling pool stats to AddScene() instead of Initialize() so that we can distinguish pool stats by
            // scene name
            if (UsePools)
                EnablePoolStats();

            MainConsole.Instance.Commands.AddCommand(
                "Debug", false, "debug lludp packet",
                 "debug lludp packet [--default | --all] <level> [<avatar-first-name> <avatar-last-name>]",
                 "Turn on packet debugging",
                   "If level >  255 then all incoming and outgoing packets are logged.\n"
                 + "If level <= 255 then incoming AgentUpdate and outgoing SimStats and SimulatorViewerTimeMessage packets are not logged.\n"
                 + "If level <= 200 then incoming RequestImage and outgoing ImagePacket, ImageData, LayerData and CoarseLocationUpdate packets are not logged.\n"
                 + "If level <= 100 then incoming ViewerEffect and AgentAnimation and outgoing ViewerEffect and AvatarAnimation packets are not logged.\n"
                 + "If level <=  50 then outgoing ImprovedTerseObjectUpdate packets are not logged.\n"
                 + "If level <= 0 then no packets are logged.\n"
                 + "If --default is specified then the level becomes the default logging level for all subsequent agents.\n"
                 + "If --all is specified then the level becomes the default logging level for all current and subsequent agents.\n"
                 + "In these cases, you cannot also specify an avatar name.\n"
                 + "If an avatar name is given then only packets from that avatar are logged.",
                 HandlePacketCommand);

            MainConsole.Instance.Commands.AddCommand(
                "Debug", false, "debug lludp drop",
                "debug lludp drop <in|out> <add|remove> <packet-name>",
                "Drop all in or outbound packets that match the given name",
                "For test purposes.",
                HandleDropCommand);

            MainConsole.Instance.Commands.AddCommand(
                "Debug",
                false,
                "debug lludp start",
                "debug lludp start <in|out|all>",
                "Control LLUDP packet processing.",
                "No effect if packet processing has already started.\n"
                    + "in  - start inbound processing.\n"
                    + "out - start outbound processing.\n"
                    + "all - start in and outbound processing.\n",
                HandleStartCommand);

            MainConsole.Instance.Commands.AddCommand(
                "Debug",
                false,
                "debug lludp stop",
                "debug lludp stop <in|out|all>",
                "Stop LLUDP packet processing.",
                "No effect if packet processing has already stopped.\n"
                    + "in  - stop inbound processing.\n"
                    + "out - stop outbound processing.\n"
                    + "all - stop in and outbound processing.\n",
                HandleStopCommand);

            MainConsole.Instance.Commands.AddCommand(
                "Debug",
                false,
                "debug lludp pool",
                "debug lludp pool <on|off>",
                "Turn object pooling within the lludp component on or off.",
                HandlePoolCommand);

            MainConsole.Instance.Commands.AddCommand(
                "Debug",
                false,
                "debug lludp status",
                "debug lludp status",
                "Return status of LLUDP packet processing.",
                HandleStatusCommand);

            MainConsole.Instance.Commands.AddCommand(
                "Debug",
                false,
                "debug lludp toggle agentupdate",
                "debug lludp toggle agentupdate",
                "Toggle whether agentupdate packets are processed or simply discarded.",
                HandleAgentUpdateCommand);
        }

        private void HandlePacketCommand(string module, string[] args)
        {
            if (SceneManager.Instance.CurrentScene != null && SceneManager.Instance.CurrentScene != Scene)
                return;

            bool setAsDefaultLevel = false;
            bool setAll = false;
            OptionSet optionSet = new OptionSet()
                .Add("default", o => setAsDefaultLevel = (o != null))
                .Add("all", o => setAll = (o != null));
            List<string> filteredArgs = optionSet.Parse(args);

            string name = null;

            if (filteredArgs.Count == 6)
            {
                if (!(setAsDefaultLevel || setAll))
                {
                    name = string.Format("{0} {1}", filteredArgs[4], filteredArgs[5]);
                }
                else
                {
                    MainConsole.Instance.OutputFormat("ERROR: Cannot specify a user name when setting default/all logging level");
                    return;
                }
            }

            if (filteredArgs.Count > 3)
            {
                int newDebug;
                if (int.TryParse(filteredArgs[3], out newDebug))
                {
                    if (setAsDefaultLevel || setAll)
                    {
                        DefaultClientPacketDebugLevel = newDebug;

                        MainConsole.Instance.OutputFormat(
                            "Packet debug for {0} clients set to {1} in {2}",
                            (setAll ? "all" : "future"), DefaultClientPacketDebugLevel, Scene.Name);

                        if (setAll)
                        {
                            Scene.ForEachScenePresence(sp =>
                            {
                                MainConsole.Instance.OutputFormat(
                                    "Packet debug for {0} ({1}) set to {2} in {3}",
                                    sp.Name, sp.IsChildAgent ? "child" : "root", newDebug, Scene.Name);

                                sp.ControllingClient.DebugPacketLevel = newDebug;
                            });
                        }
                    }
                    else
                    {
                        Scene.ForEachScenePresence(sp =>
                        {
                            if (name == null || sp.Name == name)
                            {
                                MainConsole.Instance.OutputFormat(
                                    "Packet debug for {0} ({1}) set to {2} in {3}",
                                    sp.Name, sp.IsChildAgent ? "child" : "root", newDebug, Scene.Name);

                                sp.ControllingClient.DebugPacketLevel = newDebug;
                            }
                        });
                    }
                }
                else
                {
                    MainConsole.Instance.Output("Usage: debug lludp packet [--default | --all] 0..255 [<first-name> <last-name>]");
                }
            }
        }

        private void HandleDropCommand(string module, string[] args)
        {
            if (SceneManager.Instance.CurrentScene != null && SceneManager.Instance.CurrentScene != Scene)
                return;

            if (args.Length != 6)
            {
                MainConsole.Instance.Output("Usage: debug lludp drop <in|out> <add|remove> <packet-name>");
                return;
            }

            string direction = args[3];
            string subCommand = args[4];
            string packetName = args[5];           

            if (subCommand == "add")
            {
                MainConsole.Instance.OutputFormat(
                    "Adding packet {0} to {1} drop list for all connections in {2}", direction, packetName, Scene.Name);

                Scene.ForEachScenePresence(
                    sp =>
                    {
                        LLClientView llcv = (LLClientView)sp.ControllingClient;

                        if (direction == "in")
                            llcv.AddInPacketToDropSet(packetName);
                        else if (direction == "out")
                            llcv.AddOutPacketToDropSet(packetName);
                    }
                );
            }
            else if (subCommand == "remove")
            {
                MainConsole.Instance.OutputFormat(
                    "Removing packet {0} from {1} drop list for all connections in {2}", direction, packetName, Scene.Name);

                Scene.ForEachScenePresence(
                    sp =>
                    {
                        LLClientView llcv = (LLClientView)sp.ControllingClient;

                        if (direction == "in")
                            llcv.RemoveInPacketFromDropSet(packetName);
                        else if (direction == "out")
                            llcv.RemoveOutPacketFromDropSet(packetName);
                    }
                );
            }
        }

        private void HandleStartCommand(string module, string[] args)
        {
            if (SceneManager.Instance.CurrentScene != null && SceneManager.Instance.CurrentScene != Scene)
                return;

            if (args.Length != 4)
            {
                MainConsole.Instance.Output("Usage: debug lludp start <in|out|all>");
                return;
            }

            string subCommand = args[3];

            if (subCommand == "in" || subCommand == "all")
                StartInbound();

            if (subCommand == "out" || subCommand == "all")
                StartOutbound();
        }

        private void HandleStopCommand(string module, string[] args)
        {
            if (SceneManager.Instance.CurrentScene != null && SceneManager.Instance.CurrentScene != Scene)
                return;

            if (args.Length != 4)
            {
                MainConsole.Instance.Output("Usage: debug lludp stop <in|out|all>");
                return;
            }

            string subCommand = args[3];

            if (subCommand == "in" || subCommand == "all")
                StopInbound();

            if (subCommand == "out" || subCommand == "all")
                StopOutbound();
        }

        private void HandlePoolCommand(string module, string[] args)
        {
            if (SceneManager.Instance.CurrentScene != null && SceneManager.Instance.CurrentScene != Scene)
                return;

            if (args.Length != 4)
            {
                MainConsole.Instance.Output("Usage: debug lludp pool <on|off>");
                return;
            }

            string enabled = args[3];

            if (enabled == "on")
            {
                if (EnablePools())
                {
                    EnablePoolStats();
                    MainConsole.Instance.OutputFormat("Packet pools enabled on {0}", Scene.Name);
                }
            }
            else if (enabled == "off")
            {
                if (DisablePools())
                {
                    DisablePoolStats();
                    MainConsole.Instance.OutputFormat("Packet pools disabled on {0}", Scene.Name);
                }
            }
            else
            {
                MainConsole.Instance.Output("Usage: debug lludp pool <on|off>");
            }
        }

        bool m_discardAgentUpdates;

        private void HandleAgentUpdateCommand(string module, string[] args)
        {
            if (SceneManager.Instance.CurrentScene != null && SceneManager.Instance.CurrentScene != Scene)
                return;

            m_discardAgentUpdates = !m_discardAgentUpdates;

            MainConsole.Instance.OutputFormat(
                "Discard AgentUpdates now {0} for {1}", m_discardAgentUpdates, Scene.Name);
        }

        private void HandleStatusCommand(string module, string[] args)
        {
            if (SceneManager.Instance.CurrentScene != null && SceneManager.Instance.CurrentScene != Scene)
                return;

            MainConsole.Instance.OutputFormat(
                "IN  LLUDP packet processing for {0} is {1}", Scene.Name, IsRunningInbound ? "enabled" : "disabled");

            MainConsole.Instance.OutputFormat(
                "OUT LLUDP packet processing for {0} is {1}", Scene.Name, IsRunningOutbound ? "enabled" : "disabled");

            MainConsole.Instance.OutputFormat("LLUDP pools in {0} are {1}", Scene.Name, UsePools ? "on" : "off");

            MainConsole.Instance.OutputFormat(
                "Packet debug level for new clients is {0}", DefaultClientPacketDebugLevel);
        }

        public bool HandlesRegion(Location x)
        {
            return x == m_location;
        }

//        public void BroadcastPacket(Packet packet, ThrottleOutPacketType category, bool sendToPausedAgents, bool allowSplitting)
//        {
//            // CoarseLocationUpdate and AvatarGroupsReply packets cannot be split in an automated way
//            if ((packet.Type == PacketType.CoarseLocationUpdate || packet.Type == PacketType.AvatarGroupsReply) && allowSplitting)
//                allowSplitting = false;
//
//            if (allowSplitting && packet.HasVariableBlocks)
//            {
//                byte[][] datas = packet.ToBytesMultiple();
//                int packetCount = datas.Length;
//
//                if (packetCount < 1)
//                    m_log.Error("[LLUDPSERVER]: Failed to split " + packet.Type + " with estimated length " + packet.Length);
//
//                for (int i = 0; i < packetCount; i++)
//                {
//                    byte[] data = datas[i];
//                    m_scene.ForEachClient(
//                        delegate(IClientAPI client)
//                        {
//                            if (client is LLClientView)
//                                SendPacketData(((LLClientView)client).UDPClient, data, packet.Type, category, null);
//                        }
//                    );
//                }
//            }
//            else
//            {
//                byte[] data = packet.ToBytes();
//                m_scene.ForEachClient(
//                    delegate(IClientAPI client)
//                    {
//                        if (client is LLClientView)
//                            SendPacketData(((LLClientView)client).UDPClient, data, packet.Type, category, null);
//                    }
//                );
//            }
//        }

        /// <summary>
        /// Start the process of sending a packet to the client.
        /// </summary>
        /// <param name="udpClient"></param>
        /// <param name="packet"></param>
        /// <param name="category"></param>
        /// <param name="allowSplitting"></param>
        /// <param name="method">
        /// The method to call if the packet is not acked by the client.  If null, then a standard
        /// resend of the packet is done.
        /// </param>
        public virtual void SendPacket(
            LLUDPClient udpClient, Packet packet, ThrottleOutPacketType category, bool allowSplitting, UnackedPacketMethod method)
        {
            // CoarseLocationUpdate packets cannot be split in an automated way
            if (packet.Type == PacketType.CoarseLocationUpdate && allowSplitting)
                allowSplitting = false;

            bool packetQueued = false;

            if (allowSplitting && packet.HasVariableBlocks)
            {
                byte[][] datas = packet.ToBytesMultiple();
                int packetCount = datas.Length;

                if (packetCount < 1)
                    m_log.Error("[LLUDPSERVER]: Failed to split " + packet.Type + " with estimated length " + packet.Length);

                for (int i = 0; i < packetCount; i++)
                {
                    byte[] data = datas[i];
                    if (!SendPacketData(udpClient, data, packet.Type, category, method))
                        packetQueued = true;
                }
            }
            else
            {
                byte[] data = packet.ToBytes();
                if (!SendPacketData(udpClient, data, packet.Type, category, method))
                    packetQueued = true;
            }

            PacketPool.Instance.ReturnPacket(packet);

            if (packetQueued)
                m_dataPresentEvent.Set();
        }

        /// <summary>
        /// Start the process of sending a packet to the client.
        /// </summary>
        /// <param name="udpClient"></param>
        /// <param name="data"></param>
        /// <param name="type"></param>
        /// <param name="category"></param>
        /// <param name="method">
        /// The method to call if the packet is not acked by the client.  If null, then a standard
        /// resend of the packet is done.
        /// </param>
        /// <returns>true if the data was sent immediately, false if it was queued for sending</returns>
        public bool SendPacketData(
            LLUDPClient udpClient, byte[] data, PacketType type, ThrottleOutPacketType category, UnackedPacketMethod method)
        {
            int dataLength = data.Length;
            bool doZerocode = (data[0] & Helpers.MSG_ZEROCODED) != 0;
            bool doCopy = true;

            // Frequency analysis of outgoing packet sizes shows a large clump of packets at each end of the spectrum.
            // The vast majority of packets are less than 200 bytes, although due to asset transfers and packet splitting
            // there are a decent number of packets in the 1000-1140 byte range. We allocate one of two sizes of data here
            // to accomodate for both common scenarios and provide ample room for ACK appending in both
            int bufferSize = (dataLength > 180) ? LLUDPServer.MTU : 200;

            UDPPacketBuffer buffer = new UDPPacketBuffer(udpClient.RemoteEndPoint, bufferSize);

            // Zerocode if needed
            if (doZerocode)
            {
                try
                {
                    dataLength = Helpers.ZeroEncode(data, dataLength, buffer.Data);
                    doCopy = false;
                }
                catch (IndexOutOfRangeException)
                {
                    // The packet grew larger than the bufferSize while zerocoding.
                    // Remove the MSG_ZEROCODED flag and send the unencoded data
                    // instead
                    m_log.Debug("[LLUDPSERVER]: Packet exceeded buffer size during zerocoding for " + type + ". DataLength=" + dataLength +
                        " and BufferLength=" + buffer.Data.Length + ". Removing MSG_ZEROCODED flag");
                    data[0] = (byte)(data[0] & ~Helpers.MSG_ZEROCODED);
                }
            }

            // If the packet data wasn't already copied during zerocoding, copy it now
            if (doCopy)
            {
                if (dataLength <= buffer.Data.Length)
                {
                    Buffer.BlockCopy(data, 0, buffer.Data, 0, dataLength);
                }
                else
                {
                    bufferSize = dataLength;
                    buffer = new UDPPacketBuffer(udpClient.RemoteEndPoint, bufferSize);

                    // m_log.Error("[LLUDPSERVER]: Packet exceeded buffer size! This could be an indication of packet assembly not obeying the MTU. Type=" +
                    //     type + ", DataLength=" + dataLength + ", BufferLength=" + buffer.Data.Length + ". Dropping packet");
                    Buffer.BlockCopy(data, 0, buffer.Data, 0, dataLength);
                }
            }

            buffer.DataLength = dataLength;

            #region Queue or Send

            OutgoingPacket outgoingPacket = new OutgoingPacket(udpClient, buffer, category, null);

            // If we were not provided a method for handling unacked, use the UDPServer default method
            if ((outgoingPacket.Buffer.Data[0] & Helpers.MSG_RELIABLE) != 0)
                outgoingPacket.UnackedMethod = ((method == null) ? delegate(OutgoingPacket oPacket) { ResendUnacked(oPacket); } : method);

            // If a Linden Lab 1.23.5 client receives an update packet after a kill packet for an object, it will 
            // continue to display the deleted object until relog.  Therefore, we need to always queue a kill object
            // packet so that it isn't sent before a queued update packet.
            bool forceQueue = (type == PacketType.KillObject);

            if (!outgoingPacket.Client.EnqueueOutgoing(outgoingPacket, forceQueue))
            {
                SendPacketFinal(outgoingPacket);
                return true;
            }
            else
            {
                return false;
            }

            #endregion Queue or Send
        }

        public void SendAcks(LLUDPClient udpClient)
        {
            uint ack;

            if (udpClient.PendingAcks.Dequeue(out ack))
            {
                List<PacketAckPacket.PacketsBlock> blocks = new List<PacketAckPacket.PacketsBlock>();
                PacketAckPacket.PacketsBlock block = new PacketAckPacket.PacketsBlock();
                block.ID = ack;
                blocks.Add(block);

                while (udpClient.PendingAcks.Dequeue(out ack))
                {
                    block = new PacketAckPacket.PacketsBlock();
                    block.ID = ack;
                    blocks.Add(block);
                }

                PacketAckPacket packet = new PacketAckPacket();
                packet.Header.Reliable = false;
                packet.Packets = blocks.ToArray();

                SendPacket(udpClient, packet, ThrottleOutPacketType.Unknown, true, null);
            }
        }

        public void SendPing(LLUDPClient udpClient)
        {
            StartPingCheckPacket pc = (StartPingCheckPacket)PacketPool.Instance.GetPacket(PacketType.StartPingCheck);
            pc.Header.Reliable = false;

            pc.PingID.PingID = (byte)udpClient.CurrentPingSequence++;
            // We *could* get OldestUnacked, but it would hurt performance and not provide any benefit
            pc.PingID.OldestUnacked = 0;

            SendPacket(udpClient, pc, ThrottleOutPacketType.Unknown, false, null);
        }

        public void CompletePing(LLUDPClient udpClient, byte pingID)
        {
            CompletePingCheckPacket completePing = new CompletePingCheckPacket();
            completePing.PingID.PingID = pingID;
            SendPacket(udpClient, completePing, ThrottleOutPacketType.Unknown, false, null);
        }

        public void HandleUnacked(LLClientView client)
        {
            LLUDPClient udpClient = client.UDPClient;

            if (!udpClient.IsConnected)
                return;

            // Disconnect an agent if no packets are received for some time
            int timeoutTicks = m_ackTimeout;

            // Allow more slack if the client is "paused" eg file upload dialogue is open
            // Some sort of limit is needed in case the client crashes, loses its network connection
            // or some other disaster prevents it from sendung the AgentResume
            if (udpClient.IsPaused)
                timeoutTicks = m_pausedAckTimeout;

            if (client.IsActive &&
                (Environment.TickCount & Int32.MaxValue) - udpClient.TickLastPacketReceived > timeoutTicks)
            {
                // We must set IsActive synchronously so that we can stop the packet loop reinvoking this method, even
                // though it's set later on by LLClientView.Close()
                client.IsActive = false;

                // Fire this out on a different thread so that we don't hold up outgoing packet processing for
                // everybody else if this is being called due to an ack timeout.
                // This is the same as processing as the async process of a logout request.
                Util.FireAndForget(o => DeactivateClientDueToTimeout(client, timeoutTicks));

                return;
            }

            // Get a list of all of the packets that have been sitting unacked longer than udpClient.RTO
            List<OutgoingPacket> expiredPackets = udpClient.NeedAcks.GetExpiredPackets(udpClient.RTO);

            if (expiredPackets != null)
            {
                //m_log.Debug("[LLUDPSERVER]: Handling " + expiredPackets.Count + " packets to " + udpClient.AgentID + ", RTO=" + udpClient.RTO);
                // Exponential backoff of the retransmission timeout
                udpClient.BackoffRTO();
                for (int i = 0; i < expiredPackets.Count; ++i)
                    expiredPackets[i].UnackedMethod(expiredPackets[i]);
            }
        }

        public void ResendUnacked(OutgoingPacket outgoingPacket)
        {
            //m_log.DebugFormat("[LLUDPSERVER]: Resending packet #{0} (attempt {1}), {2}ms have passed",
            //    outgoingPacket.SequenceNumber, outgoingPacket.ResendCount, Environment.TickCount - outgoingPacket.TickCount);

            // Set the resent flag
            outgoingPacket.Buffer.Data[0] = (byte)(outgoingPacket.Buffer.Data[0] | Helpers.MSG_RESENT);
            outgoingPacket.Category = ThrottleOutPacketType.Resend;

            // Bump up the resend count on this packet
            Interlocked.Increment(ref outgoingPacket.ResendCount);

            // Requeue or resend the packet
            if (!outgoingPacket.Client.EnqueueOutgoing(outgoingPacket, false))
                SendPacketFinal(outgoingPacket);
        }

        public void Flush(LLUDPClient udpClient)
        {
            // FIXME: Implement?
        }

        /// <summary>
        /// Actually send a packet to a client.
        /// </summary>
        /// <param name="outgoingPacket"></param>
        internal void SendPacketFinal(OutgoingPacket outgoingPacket)
        {
            UDPPacketBuffer buffer = outgoingPacket.Buffer;
            byte flags = buffer.Data[0];
            bool isResend = (flags & Helpers.MSG_RESENT) != 0;
            bool isReliable = (flags & Helpers.MSG_RELIABLE) != 0;
            bool isZerocoded = (flags & Helpers.MSG_ZEROCODED) != 0;
            LLUDPClient udpClient = outgoingPacket.Client;

            if (!udpClient.IsConnected)
                return;

            #region ACK Appending

            int dataLength = buffer.DataLength;

            // NOTE: I'm seeing problems with some viewers when ACKs are appended to zerocoded packets so I've disabled that here
            if (!isZerocoded)
            {
                // Keep appending ACKs until there is no room left in the buffer or there are
                // no more ACKs to append
                uint ackCount = 0;
                uint ack;
                while (dataLength + 5 < buffer.Data.Length && udpClient.PendingAcks.Dequeue(out ack))
                {
                    Utils.UIntToBytesBig(ack, buffer.Data, dataLength);
                    dataLength += 4;
                    ++ackCount;
                }

                if (ackCount > 0)
                {
                    // Set the last byte of the packet equal to the number of appended ACKs
                    buffer.Data[dataLength++] = (byte)ackCount;
                    // Set the appended ACKs flag on this packet
                    buffer.Data[0] = (byte)(buffer.Data[0] | Helpers.MSG_APPENDED_ACKS);
                }
            }

            buffer.DataLength = dataLength;

            #endregion ACK Appending

            #region Sequence Number Assignment

            if (!isResend)
            {
                // Not a resend, assign a new sequence number
                uint sequenceNumber = (uint)Interlocked.Increment(ref udpClient.CurrentSequence);
                Utils.UIntToBytesBig(sequenceNumber, buffer.Data, 1);
                outgoingPacket.SequenceNumber = sequenceNumber;

                if (isReliable)
                {
                    // Add this packet to the list of ACK responses we are waiting on from the server
                    udpClient.NeedAcks.Add(outgoingPacket);
                }
            }
            else
            {
                Interlocked.Increment(ref udpClient.PacketsResent);

                // We're not going to worry about interlock yet since its not currently critical that this total count
                // is 100% correct
                PacketsResentCount++;
            }

            #endregion Sequence Number Assignment

            // Stats tracking
            Interlocked.Increment(ref udpClient.PacketsSent);

            // We're not going to worry about interlock yet since its not currently critical that this total count
            // is 100% correct
            PacketsSentCount++;

            // Put the UDP payload on the wire
            AsyncBeginSend(buffer);

            // Keep track of when this packet was sent out (right now)
            outgoingPacket.TickCount = Environment.TickCount & Int32.MaxValue;
        }

        private void RecordMalformedInboundPacket(IPEndPoint endPoint)
        {
//                if (m_malformedCount < 100)
//                    m_log.DebugFormat("[LLUDPSERVER]: Dropped malformed packet: " + e.ToString());

            IncomingMalformedPacketCount++;

            if ((IncomingMalformedPacketCount % 10000) == 0)
                m_log.WarnFormat(
                    "[LLUDPSERVER]: Received {0} malformed packets so far, probable network attack.  Last was from {1}", 
                    IncomingMalformedPacketCount, endPoint);
        }

        public override void PacketReceived(UDPPacketBuffer buffer)
        {
            // Debugging/Profiling
            //try { Thread.CurrentThread.Name = "PacketReceived (" + m_scene.RegionInfo.RegionName + ")"; }
            //catch (Exception) { }
//            m_log.DebugFormat(
//                "[LLUDPSERVER]: Packet received from {0} in {1}", buffer.RemoteEndPoint, m_scene.RegionInfo.RegionName);

            LLUDPClient udpClient = null;
            Packet packet = null;
            int packetEnd = buffer.DataLength - 1;
            IPEndPoint endPoint = (IPEndPoint)buffer.RemoteEndPoint;

            #region Decoding

            if (buffer.DataLength < 7)
            {
//                m_log.WarnFormat(
//                    "[LLUDPSERVER]: Dropping undersized packet with {0} bytes received from {1} in {2}",
//                    buffer.DataLength, buffer.RemoteEndPoint, m_scene.RegionInfo.RegionName);

                RecordMalformedInboundPacket(endPoint);

                return; // Drop undersized packet
            }

            int headerLen = 7;
            if (buffer.Data[6] == 0xFF)
            {
                if (buffer.Data[7] == 0xFF)
                    headerLen = 10;
                else
                    headerLen = 8;
            }

            if (buffer.DataLength < headerLen)
            {
//                m_log.WarnFormat(
//                    "[LLUDPSERVER]: Dropping packet with malformed header received from {0} in {1}",
//                    buffer.RemoteEndPoint, m_scene.RegionInfo.RegionName);

                RecordMalformedInboundPacket(endPoint);

                return; // Malformed header
            }

            try
            {
//                packet = Packet.BuildPacket(buffer.Data, ref packetEnd,
//                    // Only allocate a buffer for zerodecoding if the packet is zerocoded
//                    ((buffer.Data[0] & Helpers.MSG_ZEROCODED) != 0) ? new byte[4096] : null);
                // If OpenSimUDPBase.UsePool == true (which is currently separate from the PacketPool) then we
                // assume that packet construction does not retain a reference to byte[] buffer.Data (instead, all
                // bytes are copied out).
                packet = PacketPool.Instance.GetPacket(buffer.Data, ref packetEnd,
                    // Only allocate a buffer for zerodecoding if the packet is zerocoded
                    ((buffer.Data[0] & Helpers.MSG_ZEROCODED) != 0) ? new byte[4096] : null);
            }
            catch (Exception e)
            {
                if (IncomingMalformedPacketCount < 100)
                    m_log.DebugFormat("[LLUDPSERVER]: Dropped malformed packet: " + e.ToString());
            }

            // Fail-safe check
            if (packet == null)
            {
                if (IncomingMalformedPacketCount < 100)
                {
                    m_log.WarnFormat("[LLUDPSERVER]: Malformed data, cannot parse {0} byte packet from {1}, data {2}:",
                        buffer.DataLength, buffer.RemoteEndPoint, Utils.BytesToHexString(buffer.Data, buffer.DataLength, null));
                }

                RecordMalformedInboundPacket(endPoint);

                return;
            }

            #endregion Decoding

            #region Packet to Client Mapping

            // UseCircuitCode handling
            if (packet.Type == PacketType.UseCircuitCode)
            {
                // We need to copy the endpoint so that it doesn't get changed when another thread reuses the
                // buffer.
                object[] array = new object[] { new IPEndPoint(endPoint.Address, endPoint.Port), packet };

                Util.FireAndForget(HandleUseCircuitCode, array);

                return;
            }
            else if (packet.Type == PacketType.CompleteAgentMovement)
            {
                // Send ack straight away to let the viewer know that we got it.
                SendAckImmediate(endPoint, packet.Header.Sequence);

                // We need to copy the endpoint so that it doesn't get changed when another thread reuses the
                // buffer.
                object[] array = new object[] { new IPEndPoint(endPoint.Address, endPoint.Port), packet };

                Util.FireAndForget(HandleCompleteMovementIntoRegion, array);

                return;
            }

            // Determine which agent this packet came from
            IClientAPI client;
            if (!Scene.TryGetClient(endPoint, out client) || !(client is LLClientView))
            {
                //m_log.Debug("[LLUDPSERVER]: Received a " + packet.Type + " packet from an unrecognized source: " + address + " in " + m_scene.RegionInfo.RegionName);

                IncomingOrphanedPacketCount++;

                if ((IncomingOrphanedPacketCount % 10000) == 0)
                    m_log.WarnFormat(
                        "[LLUDPSERVER]: Received {0} orphaned packets so far.  Last was from {1}", 
                        IncomingOrphanedPacketCount, endPoint);

                return;
            }

            udpClient = ((LLClientView)client).UDPClient;

            if (!udpClient.IsConnected)
                return;

            #endregion Packet to Client Mapping

            // Stats tracking
            Interlocked.Increment(ref udpClient.PacketsReceived);

            int now = Environment.TickCount & Int32.MaxValue;
            udpClient.TickLastPacketReceived = now;

            #region ACK Receiving

            // Handle appended ACKs
            if (packet.Header.AppendedAcks && packet.Header.AckList != null)
            {
//                m_log.DebugFormat(
//                    "[LLUDPSERVER]: Handling {0} appended acks from {1} in {2}",
//                    packet.Header.AckList.Length, client.Name, m_scene.Name);

                for (int i = 0; i < packet.Header.AckList.Length; i++)
                    udpClient.NeedAcks.Acknowledge(packet.Header.AckList[i], now, packet.Header.Resent);
            }

            // Handle PacketAck packets
            if (packet.Type == PacketType.PacketAck)
            {
                PacketAckPacket ackPacket = (PacketAckPacket)packet;

//                m_log.DebugFormat(
//                    "[LLUDPSERVER]: Handling {0} packet acks for {1} in {2}",
//                    ackPacket.Packets.Length, client.Name, m_scene.Name);

                for (int i = 0; i < ackPacket.Packets.Length; i++)
                    udpClient.NeedAcks.Acknowledge(ackPacket.Packets[i].ID, now, packet.Header.Resent);

                // We don't need to do anything else with PacketAck packets
                return;
            }

            #endregion ACK Receiving

            #region ACK Sending

            if (packet.Header.Reliable)
            {
//                m_log.DebugFormat(
//                    "[LLUDPSERVER]: Adding ack request for {0} {1} from {2} in {3}",
//                    packet.Type, packet.Header.Sequence, client.Name, m_scene.Name);

                udpClient.PendingAcks.Enqueue(packet.Header.Sequence);

                // This is a somewhat odd sequence of steps to pull the client.BytesSinceLastACK value out,
                // add the current received bytes to it, test if 2*MTU bytes have been sent, if so remove
                // 2*MTU bytes from the value and send ACKs, and finally add the local value back to
                // client.BytesSinceLastACK. Lockless thread safety
                int bytesSinceLastACK = Interlocked.Exchange(ref udpClient.BytesSinceLastACK, 0);
                bytesSinceLastACK += buffer.DataLength;
                if (bytesSinceLastACK > LLUDPServer.MTU * 2)
                {
                    bytesSinceLastACK -= LLUDPServer.MTU * 2;
                    SendAcks(udpClient);
                }
                Interlocked.Add(ref udpClient.BytesSinceLastACK, bytesSinceLastACK);
            }

            #endregion ACK Sending

            #region Incoming Packet Accounting

            // We're not going to worry about interlock yet since its not currently critical that this total count
            // is 100% correct
            if (packet.Header.Resent)
                IncomingPacketsResentCount++;

            // Check the archive of received reliable packet IDs to see whether we already received this packet
            if (packet.Header.Reliable && !udpClient.PacketArchive.TryEnqueue(packet.Header.Sequence))
            {
                if (packet.Header.Resent)
                    m_log.DebugFormat(
                        "[LLUDPSERVER]: Received a resend of already processed packet #{0}, type {1} from {2}", 
                        packet.Header.Sequence, packet.Type, client.Name);
                 else
                    m_log.WarnFormat(
                        "[LLUDPSERVER]: Received a duplicate (not marked as resend) of packet #{0}, type {1} from {2}",
                        packet.Header.Sequence, packet.Type, client.Name);

                // Avoid firing a callback twice for the same packet
                return;
            }

            #endregion Incoming Packet Accounting

            #region BinaryStats
            LogPacketHeader(true, udpClient.CircuitCode, 0, packet.Type, (ushort)packet.Length);
            #endregion BinaryStats

            if (packet.Type == PacketType.AgentUpdate)
            {
                if (m_discardAgentUpdates)
                    return;

                ((LLClientView)client).TotalAgentUpdates++;

                AgentUpdatePacket agentUpdate = (AgentUpdatePacket)packet;

                LLClientView llClient = client as LLClientView;
                if (agentUpdate.AgentData.SessionID != client.SessionId 
                    || agentUpdate.AgentData.AgentID != client.AgentId
                    || !(llClient == null || llClient.CheckAgentUpdateSignificance(agentUpdate.AgentData)) )
                {
                    PacketPool.Instance.ReturnPacket(packet);
                    return;
                }
            }

            #region Ping Check Handling

            if (packet.Type == PacketType.StartPingCheck)
            {
//                m_log.DebugFormat("[LLUDPSERVER]: Handling ping from {0} in {1}", client.Name, m_scene.Name);

                // We don't need to do anything else with ping checks
                StartPingCheckPacket startPing = (StartPingCheckPacket)packet;
                CompletePing(udpClient, startPing.PingID.PingID);

                if ((Environment.TickCount - m_elapsedMSSinceLastStatReport) >= 3000)
                {
                    udpClient.SendPacketStats();
                    m_elapsedMSSinceLastStatReport = Environment.TickCount;
                }
                return;
            }
            else if (packet.Type == PacketType.CompletePingCheck)
            {
                // We don't currently track client ping times
                return;
            }

            #endregion Ping Check Handling

            IncomingPacket incomingPacket;

            // Inbox insertion
            if (UsePools)
            {
                incomingPacket = m_incomingPacketPool.GetObject();
                incomingPacket.Client = (LLClientView)client;
                incomingPacket.Packet = packet;
            }
            else
            {
                incomingPacket = new IncomingPacket((LLClientView)client, packet);
            }

            packetInbox.Enqueue(incomingPacket);
        }

        #region BinaryStats

        public class PacketLogger
        {
            public DateTime StartTime;
            public string Path = null;
            public System.IO.BinaryWriter Log = null;
        }

        public static PacketLogger PacketLog;

        protected static bool m_shouldCollectStats = false;
        // Number of seconds to log for
        static TimeSpan binStatsMaxFilesize = TimeSpan.FromSeconds(300);
        static object binStatsLogLock = new object();
        static string binStatsDir = "";

        //for Aggregated In/Out BW logging
        static bool m_aggregatedBWStats = false;
        static long m_aggregatedBytesIn = 0;
        static long m_aggregatedByestOut = 0;
        static object aggBWStatsLock = new object();

        public static long AggregatedLLUDPBytesIn
        {
            get { return m_aggregatedBytesIn; }
        }
        public static long AggregatedLLUDPBytesOut
        {
            get {return m_aggregatedByestOut;}
        }

        public static void LogPacketHeader(bool incoming, uint circuit, byte flags, PacketType packetType, ushort size)
        {
            if (m_aggregatedBWStats)
            {
                lock (aggBWStatsLock)
                {
                    if (incoming)
                        m_aggregatedBytesIn += size;
                    else
                        m_aggregatedByestOut += size;
                }
            }

            if (!m_shouldCollectStats) return;

            // Binary logging format is TTTTTTTTCCCCFPPPSS, T=Time, C=Circuit, F=Flags, P=PacketType, S=size

            // Put the incoming bit into the least significant bit of the flags byte
            if (incoming)
                flags |= 0x01;
            else
                flags &= 0xFE;

            // Put the flags byte into the most significant bits of the type integer
            uint type = (uint)packetType;
            type |= (uint)flags << 24;

            // m_log.Debug("1 LogPacketHeader(): Outside lock");
            lock (binStatsLogLock)
            {
                DateTime now = DateTime.Now;

                // m_log.Debug("2 LogPacketHeader(): Inside lock. now is " + now.Ticks);
                try
                {
                    if (PacketLog == null || (now > PacketLog.StartTime + binStatsMaxFilesize))
                    {
                        if (PacketLog != null && PacketLog.Log != null)
                        {
                            PacketLog.Log.Close();
                        }

                        // First log file or time has expired, start writing to a new log file
                        PacketLog = new PacketLogger();
                        PacketLog.StartTime = now;
                        PacketLog.Path = (binStatsDir.Length > 0 ? binStatsDir + System.IO.Path.DirectorySeparatorChar.ToString() : "")
                                + String.Format("packets-{0}.log", now.ToString("yyyyMMddHHmmss"));
                        PacketLog.Log = new BinaryWriter(File.Open(PacketLog.Path, FileMode.Append, FileAccess.Write));
                    }

                    // Serialize the data
                    byte[] output = new byte[18];
                    Buffer.BlockCopy(BitConverter.GetBytes(now.Ticks), 0, output, 0, 8);
                    Buffer.BlockCopy(BitConverter.GetBytes(circuit), 0, output, 8, 4);
                    Buffer.BlockCopy(BitConverter.GetBytes(type), 0, output, 12, 4);
                    Buffer.BlockCopy(BitConverter.GetBytes(size), 0, output, 16, 2);

                    // Write the serialized data to disk
                    if (PacketLog != null && PacketLog.Log != null)
                        PacketLog.Log.Write(output);
                }
                catch (Exception ex)
                {
                    m_log.Error("Packet statistics gathering failed: " + ex.Message, ex);
                    if (PacketLog.Log != null)
                    {
                        PacketLog.Log.Close();
                    }
                    PacketLog = null;
                }
            }
        }

        #endregion BinaryStats

        private void HandleUseCircuitCode(object o)
        {
            IPEndPoint endPoint = null;
            IClientAPI client = null;

            try
            {
    //            DateTime startTime = DateTime.Now;
                object[] array = (object[])o;
                endPoint = (IPEndPoint)array[0];
                UseCircuitCodePacket uccp = (UseCircuitCodePacket)array[1];

                m_log.DebugFormat(
                    "[LLUDPSERVER]: Handling UseCircuitCode request for circuit {0} to {1} from IP {2}",
                    uccp.CircuitCode.Code, Scene.RegionInfo.RegionName, endPoint);
    
                AuthenticateResponse sessionInfo;
                if (IsClientAuthorized(uccp, out sessionInfo))
                {
                    // Begin the process of adding the client to the simulator
                    client
                        = AddClient(
                            uccp.CircuitCode.Code,
                            uccp.CircuitCode.ID,
                            uccp.CircuitCode.SessionID,
                            endPoint,
                            sessionInfo);
            
                    // Send ack straight away to let the viewer know that the connection is active.
                    // The client will be null if it already exists (e.g. if on a region crossing the client sends a use
                    // circuit code to the existing child agent.  This is not particularly obvious.
                    SendAckImmediate(endPoint, uccp.Header.Sequence);
            
                    // We only want to send initial data to new clients, not ones which are being converted from child to root.
                    if (client != null)
                    {
                        AgentCircuitData aCircuit = Scene.AuthenticateHandler.GetAgentCircuitData(uccp.CircuitCode.Code);
                        bool tp = (aCircuit.teleportFlags > 0);
                        // Let's delay this for TP agents, otherwise the viewer doesn't know where to get resources from
                        if (!tp && !client.SceneAgent.SentInitialDataToClient)
                            client.SceneAgent.SendInitialDataToClient();
                    }
                }
                else
                {
                    // Don't create clients for unauthorized requesters.
                    m_log.WarnFormat(
                        "[LLUDPSERVER]: Ignoring connection request for {0} to {1} with unknown circuit code {2} from IP {3}",
                        uccp.CircuitCode.ID, Scene.RegionInfo.RegionName, uccp.CircuitCode.Code, endPoint);
                }
    
                //            m_log.DebugFormat(
    //                "[LLUDPSERVER]: Handling UseCircuitCode request from {0} took {1}ms", 
    //                buffer.RemoteEndPoint, (DateTime.Now - startTime).Milliseconds);

            }
            catch (Exception e)
            {
                m_log.ErrorFormat(
                    "[LLUDPSERVER]: UseCircuitCode handling from endpoint {0}, client {1} {2} failed.  Exception {3}{4}",
                    endPoint != null ? endPoint.ToString() : "n/a",
                    client != null ? client.Name : "unknown",
                    client != null ? client.AgentId.ToString() : "unknown",
                    e.Message,
                    e.StackTrace);
            }
        }

        private void HandleCompleteMovementIntoRegion(object o)
        {
            IPEndPoint endPoint = null;
            IClientAPI client = null;

            try
            {
                object[] array = (object[])o;
                endPoint = (IPEndPoint)array[0];
                CompleteAgentMovementPacket packet = (CompleteAgentMovementPacket)array[1];

                m_log.DebugFormat(
                    "[LLUDPSERVER]: Handling CompleteAgentMovement request from {0} in {1}", endPoint, Scene.Name);

                // Determine which agent this packet came from
                // We need to wait here because in when using the OpenSimulator V2 teleport protocol to travel to a destination
                // simulator with no existing child presence, the viewer (at least LL 3.3.4) will send UseCircuitCode 
                // and then CompleteAgentMovement immediately without waiting for an ack.  As we are now handling these
                // packets asynchronously, we need to account for this thread proceeding more quickly than the 
                // UseCircuitCode thread.
                int count = 40;
                while (count-- > 0)
                {
                    if (Scene.TryGetClient(endPoint, out client))
                    {
                        if (!client.IsActive)
                        {
                            // This check exists to catch a condition where the client has been closed by another thread
                            // but has not yet been removed from the client manager (and possibly a new connection has
                            // not yet been established).
                            m_log.DebugFormat(
                                "[LLUDPSERVER]: Received a CompleteAgentMovement from {0} for {1} in {2} but client is not active yet.  Waiting.",
                                endPoint, client.Name, Scene.Name);
                        }
                        else if (client.SceneAgent == null)
                        {
                            // This check exists to catch a condition where the new client has been added to the client
                            // manager but the SceneAgent has not yet been set in Scene.AddNewAgent().  If we are too
                            // eager, then the new ScenePresence may not have registered a listener for this messsage
                            // before we try to process it.
                            // XXX: A better long term fix may be to add the SceneAgent before the client is added to 
                            // the client manager
                            m_log.DebugFormat(
                                "[LLUDPSERVER]: Received a CompleteAgentMovement from {0} for {1} in {2} but client SceneAgent not set yet.  Waiting.",
                                endPoint, client.Name, Scene.Name);
                        }
                        else
                        {
                            break;
                        }
                    }
                    else
                    {
                        m_log.DebugFormat(
                            "[LLUDPSERVER]: Received a CompleteAgentMovement from {0} in {1} but no client exists yet.  Waiting.", 
                            endPoint, Scene.Name);
                    }

                    Thread.Sleep(200);
                }

                if (client == null)
                {
                    m_log.DebugFormat(
                        "[LLUDPSERVER]: No client found for CompleteAgentMovement from {0} in {1} after wait.  Dropping.",
                        endPoint, Scene.Name);

                    return;
                }
                else if (!client.IsActive || client.SceneAgent == null)
                {
                    // This check exists to catch a condition where the client has been closed by another thread
                    // but has not yet been removed from the client manager.
                    // The packet could be simply ignored but it is useful to know if this condition occurred for other debugging
                    // purposes.
                    m_log.DebugFormat(
                        "[LLUDPSERVER]: Received a CompleteAgentMovement from {0} for {1} in {2} but client is not active after wait.  Dropping.",
                        endPoint, client.Name, Scene.Name);

                    return;
                }

                IncomingPacket incomingPacket1;

                // Inbox insertion
                if (UsePools)
                {
                    incomingPacket1 = m_incomingPacketPool.GetObject();
                    incomingPacket1.Client = (LLClientView)client;
                    incomingPacket1.Packet = packet;
                }
                else
                {
                    incomingPacket1 = new IncomingPacket((LLClientView)client, packet);
                }

                packetInbox.Enqueue(incomingPacket1);
            }
            catch (Exception e)
            {
                m_log.ErrorFormat(
                    "[LLUDPSERVER]: CompleteAgentMovement handling from endpoint {0}, client {1} {2} failed.  Exception {3}{4}",
                    endPoint != null ? endPoint.ToString() : "n/a",
                    client != null ? client.Name : "unknown",
                    client != null ? client.AgentId.ToString() : "unknown",
                    e.Message,
                    e.StackTrace);
            }
        }

        /// <summary>
        /// Send an ack immediately to the given endpoint.
        /// </summary>
        /// <remarks>
        /// FIXME: Might be possible to use SendPacketData() like everything else, but this will require refactoring so
        /// that we can obtain the UDPClient easily at this point.
        /// </remarks>
        /// <param name="remoteEndpoint"></param>
        /// <param name="sequenceNumber"></param>
        private void SendAckImmediate(IPEndPoint remoteEndpoint, uint sequenceNumber)
        {
            PacketAckPacket ack = new PacketAckPacket();
            ack.Header.Reliable = false;
            ack.Packets = new PacketAckPacket.PacketsBlock[1];
            ack.Packets[0] = new PacketAckPacket.PacketsBlock();
            ack.Packets[0].ID = sequenceNumber;

            SendAckImmediate(remoteEndpoint, ack);
        }

        public virtual void SendAckImmediate(IPEndPoint remoteEndpoint, PacketAckPacket ack)
        {
            byte[] packetData = ack.ToBytes();
            int length = packetData.Length;

            UDPPacketBuffer buffer = new UDPPacketBuffer(remoteEndpoint, length);
            buffer.DataLength = length;

            Buffer.BlockCopy(packetData, 0, buffer.Data, 0, length);

            AsyncBeginSend(buffer);
        }

        private bool IsClientAuthorized(UseCircuitCodePacket useCircuitCode, out AuthenticateResponse sessionInfo)
        {
            UUID agentID = useCircuitCode.CircuitCode.ID;
            UUID sessionID = useCircuitCode.CircuitCode.SessionID;
            uint circuitCode = useCircuitCode.CircuitCode.Code;

            sessionInfo = m_circuitManager.AuthenticateSession(sessionID, agentID, circuitCode);
            return sessionInfo.Authorised;
        }

        /// <summary>
        /// Add a client.
        /// </summary>
        /// <param name="circuitCode"></param>
        /// <param name="agentID"></param>
        /// <param name="sessionID"></param>
        /// <param name="remoteEndPoint"></param>
        /// <param name="sessionInfo"></param>
        /// <returns>The client if it was added.  Null if the client already existed.</returns>
        protected virtual IClientAPI AddClient(
            uint circuitCode, UUID agentID, UUID sessionID, IPEndPoint remoteEndPoint, AuthenticateResponse sessionInfo)
        {
            IClientAPI client = null;

            // We currently synchronize this code across the whole scene to avoid issues such as
            // http://opensimulator.org/mantis/view.php?id=5365  However, once locking per agent circuit can be done
            // consistently, this lock could probably be removed.
            lock (this)
            {
                if (!Scene.TryGetClient(agentID, out client))
                {
                    LLUDPClient udpClient = new LLUDPClient(this, ThrottleRates, m_throttle, circuitCode, agentID, remoteEndPoint, m_defaultRTO, m_maxRTO);
    
                    client = new LLClientView(Scene, this, udpClient, sessionInfo, agentID, sessionID, circuitCode);
                    client.OnLogout += LogoutHandler;
                    client.DebugPacketLevel = DefaultClientPacketDebugLevel;
    
                    ((LLClientView)client).DisableFacelights = m_disableFacelights;
    
                    client.Start();
                }
            }

            return client;
        }

        /// <summary>
        /// Deactivates the client if we don't receive any packets within a certain amount of time (default 60 seconds).
        /// </summary>
        /// <remarks>
        /// If a connection is active then we will always receive packets even if nothing else is happening, due to
        /// regular client pings.
        /// </remarks>
        /// <param name='client'></param>
        /// <param name='timeoutTicks'></param>
        private void DeactivateClientDueToTimeout(LLClientView client, int timeoutTicks)
        {
            lock (client.CloseSyncLock)
            {    
                ClientLogoutsDueToNoReceives++;

                m_log.WarnFormat(
                    "[LLUDPSERVER]: No packets received from {0} agent of {1} for {2}ms in {3}.  Disconnecting.",
                    client.SceneAgent.IsChildAgent ? "child" : "root", client.Name, timeoutTicks, Scene.Name);
    
                if (!client.SceneAgent.IsChildAgent)
                     client.Kick("Simulator logged you out due to connection timeout.");
            }

            Scene.CloseAgent(client.AgentId, true);
        }

        private void IncomingPacketHandler()
        {
            // Set this culture for the thread that incoming packets are received
            // on to en-US to avoid number parsing issues
            Culture.SetCurrentCulture();

            while (IsRunningInbound)
            {
                try
                {
                    IncomingPacket incomingPacket = null;

                    /*
                    // HACK: This is a test to try and rate limit packet handling on Mono.
                    // If it works, a more elegant solution can be devised
                    if (Util.FireAndForgetCount() < 2)
                    {
                        //m_log.Debug("[LLUDPSERVER]: Incoming packet handler is sleeping");
                        Thread.Sleep(30);
                    }
                     */

                    if (packetInbox.Dequeue(100, ref incomingPacket))
                    {
                        ProcessInPacket(incomingPacket);//, incomingPacket); Util.FireAndForget(ProcessInPacket, incomingPacket);

                        if (UsePools)
                            m_incomingPacketPool.ReturnObject(incomingPacket);
                    }
                }
                catch (Exception ex)
                {
                    m_log.Error("[LLUDPSERVER]: Error in the incoming packet handler loop: " + ex.Message, ex);
                }

                Watchdog.UpdateThread();
            }

            if (packetInbox.Count > 0)
                m_log.Warn("[LLUDPSERVER]: IncomingPacketHandler is shutting down, dropping " + packetInbox.Count + " packets");
            packetInbox.Clear();

            Watchdog.RemoveThread();
        }

        private void OutgoingPacketHandler()
        {
            // Set this culture for the thread that outgoing packets are sent
            // on to en-US to avoid number parsing issues
            Culture.SetCurrentCulture();

            // Typecast the function to an Action<IClientAPI> once here to avoid allocating a new
            // Action generic every round
            Action<IClientAPI> clientPacketHandler = ClientOutgoingPacketHandler;

            while (base.IsRunningOutbound)
            {
                try
                {
                    m_packetSent = false;

                    #region Update Timers

                    m_resendUnacked = false;
                    m_sendAcks = false;
                    m_sendPing = false;

                    // Update elapsed time
                    int thisTick = Environment.TickCount & Int32.MaxValue;
                    if (m_tickLastOutgoingPacketHandler > thisTick)
                        m_elapsedMSOutgoingPacketHandler += ((Int32.MaxValue - m_tickLastOutgoingPacketHandler) + thisTick);
                    else
                        m_elapsedMSOutgoingPacketHandler += (thisTick - m_tickLastOutgoingPacketHandler);

                    m_tickLastOutgoingPacketHandler = thisTick;

                    // Check for pending outgoing resends every 100ms
                    if (m_elapsedMSOutgoingPacketHandler >= 100)
                    {
                        m_resendUnacked = true;
                        m_elapsedMSOutgoingPacketHandler = 0;
                        m_elapsed100MSOutgoingPacketHandler += 1;
                    }

                    // Check for pending outgoing ACKs every 500ms
                    if (m_elapsed100MSOutgoingPacketHandler >= 5)
                    {
                        m_sendAcks = true;
                        m_elapsed100MSOutgoingPacketHandler = 0;
                        m_elapsed500MSOutgoingPacketHandler += 1;
                    }

                    // Send pings to clients every 5000ms
                    if (m_elapsed500MSOutgoingPacketHandler >= 10)
                    {
                        m_sendPing = true;
                        m_elapsed500MSOutgoingPacketHandler = 0;
                    }

                    #endregion Update Timers

                    // Use this for emergency monitoring -- bug hunting
                    //if (m_scene.EmergencyMonitoring)
                    //    clientPacketHandler = MonitoredClientOutgoingPacketHandler;
                    //else
                    //    clientPacketHandler = ClientOutgoingPacketHandler;

                    // Handle outgoing packets, resends, acknowledgements, and pings for each
                    // client. m_packetSent will be set to true if a packet is sent
                    Scene.ForEachClient(clientPacketHandler);

                    m_currentOutgoingClient = null;

                    // If nothing was sent, sleep for the minimum amount of time before a
                    // token bucket could get more tokens
                    //if (!m_packetSent)
                    //    Thread.Sleep((int)TickCountResolution);
                    //
                    // Instead, now wait for data present to be explicitly signalled.  Evidence so far is that with
                    // modern mono it reduces CPU base load since there is no more continuous polling.
                    if (!m_packetSent)
                        m_dataPresentEvent.WaitOne(100);

                    Watchdog.UpdateThread();
                }
                catch (Exception ex)
                {
                    m_log.Error("[LLUDPSERVER]: OutgoingPacketHandler loop threw an exception: " + ex.Message, ex);
                }
            }

            Watchdog.RemoveThread();
        }

        protected void ClientOutgoingPacketHandler(IClientAPI client)
        {
            m_currentOutgoingClient = client;

            try
            {
                if (client is LLClientView)
                {
                    LLClientView llClient = (LLClientView)client;
                    LLUDPClient udpClient = llClient.UDPClient;

                    if (udpClient.IsConnected)
                    {
                        if (m_resendUnacked)
                            HandleUnacked(llClient);

                        if (m_sendAcks)
                            SendAcks(udpClient);

                        if (m_sendPing)
                            SendPing(udpClient);

                        // Dequeue any outgoing packets that are within the throttle limits
                        if (udpClient.DequeueOutgoing())
                            m_packetSent = true;
                    }
                }
            }
            catch (Exception ex)
            {
                m_log.Error(
                    string.Format("[LLUDPSERVER]: OutgoingPacketHandler iteration for {0} threw ", client.Name), ex);
            }
        }

        #region Emergency Monitoring
        // Alternative packet handler fuull of instrumentation
        // Handy for hunting bugs
        private Stopwatch watch1 = new Stopwatch();
        private Stopwatch watch2 = new Stopwatch();

        private float avgProcessingTicks = 0;
        private float avgResendUnackedTicks = 0;
        private float avgSendAcksTicks = 0;
        private float avgSendPingTicks = 0;
        private float avgDequeueTicks = 0;
        private long nticks = 0;
        private long nticksUnack = 0;
        private long nticksAck = 0;
        private long nticksPing = 0;
        private int npacksSent = 0;
        private int npackNotSent = 0;

        /// <summary>
        /// Number of inbound packets processed since startup.
        /// </summary>
        public long IncomingPacketsProcessed { get; private set; }

        private void MonitoredClientOutgoingPacketHandler(IClientAPI client)
        {
            nticks++;
            watch1.Start();
            m_currentOutgoingClient = client;

            try
            {
                if (client is LLClientView)
                {
                    LLClientView llClient = (LLClientView)client;
                    LLUDPClient udpClient = llClient.UDPClient;

                    if (udpClient.IsConnected)
                    {
                        if (m_resendUnacked)
                        {
                            nticksUnack++;
                            watch2.Start();

                            HandleUnacked(llClient);

                            watch2.Stop();
                            avgResendUnackedTicks = (nticksUnack - 1)/(float)nticksUnack * avgResendUnackedTicks + (watch2.ElapsedTicks / (float)nticksUnack);
                            watch2.Reset();
                        }

                        if (m_sendAcks)
                        {
                            nticksAck++;
                            watch2.Start();
                            
                            SendAcks(udpClient);

                            watch2.Stop();
                            avgSendAcksTicks = (nticksAck - 1) / (float)nticksAck * avgSendAcksTicks + (watch2.ElapsedTicks / (float)nticksAck);
                            watch2.Reset();
                        }

                        if (m_sendPing)
                        {
                            nticksPing++;
                            watch2.Start();
                            
                            SendPing(udpClient);

                            watch2.Stop();
                            avgSendPingTicks = (nticksPing - 1) / (float)nticksPing * avgSendPingTicks + (watch2.ElapsedTicks / (float)nticksPing);
                            watch2.Reset();
                        }

                        watch2.Start();
                        // Dequeue any outgoing packets that are within the throttle limits
                        if (udpClient.DequeueOutgoing())
                        {
                            m_packetSent = true;
                            npacksSent++;
                        }
                        else
                        {
                            npackNotSent++;
                        }

                        watch2.Stop();
                        avgDequeueTicks = (nticks - 1) / (float)nticks * avgDequeueTicks + (watch2.ElapsedTicks / (float)nticks);
                        watch2.Reset();

                    }
                    else
                    {
                        m_log.WarnFormat("[LLUDPSERVER]: Client is not connected");
                    }
                }
            }
            catch (Exception ex)
            {
                m_log.Error("[LLUDPSERVER]: OutgoingPacketHandler iteration for " + client.Name +
                    " threw an exception: " + ex.Message, ex);
            }
            watch1.Stop();
            avgProcessingTicks = (nticks - 1) / (float)nticks * avgProcessingTicks + (watch1.ElapsedTicks / (float)nticks);
            watch1.Reset();

            // reuse this -- it's every ~100ms
            if (Scene.EmergencyMonitoring && nticks % 100 == 0)
            {
                m_log.InfoFormat("[LLUDPSERVER]: avg processing ticks: {0} avg unacked: {1} avg acks: {2} avg ping: {3} avg dequeue: {4} (TickCountRes: {5} sent: {6} notsent: {7})", 
                    avgProcessingTicks, avgResendUnackedTicks, avgSendAcksTicks, avgSendPingTicks, avgDequeueTicks, TickCountResolution, npacksSent, npackNotSent);
                npackNotSent = npacksSent = 0;
            }

        }

        #endregion 

        private void ProcessInPacket(IncomingPacket incomingPacket)
        {
            Packet packet = incomingPacket.Packet;
            LLClientView client = incomingPacket.Client;

            if (client.IsActive)
            {
                m_currentIncomingClient = client;

                try
                {
                    // Process this packet
                    client.ProcessInPacket(packet);
                }
                catch (ThreadAbortException)
                {
                    // If something is trying to abort the packet processing thread, take that as a hint that it's time to shut down
                    m_log.Info("[LLUDPSERVER]: Caught a thread abort, shutting down the LLUDP server");
                    Stop();
                }
                catch (Exception e)
                {
                    // Don't let a failure in an individual client thread crash the whole sim.
                    m_log.Error(
                        string.Format(
                            "[LLUDPSERVER]: Client packet handler for {0} for packet {1} threw ",
                            client.Name, packet.Type),
                        e);
                }
                finally
                {
                    m_currentIncomingClient = null;
                }
            }
            else
            {
                m_log.DebugFormat(
                    "[LLUDPSERVER]: Dropped incoming {0} for dead client {1} in {2}",
                    packet.Type, client.Name, Scene.RegionInfo.RegionName);
            }

            IncomingPacketsProcessed++;
        }

        protected void LogoutHandler(IClientAPI client)
        {
            client.SendLogoutPacket();

            if (!client.IsLoggingOut)
            {
                client.IsLoggingOut = true;
                Scene.CloseAgent(client.AgentId, false);
            }
        }
    }
}