1 files changed, 697 insertions, 0 deletions

diff --git a/OpenSim/Region/ClientStack/Linden/UDP/LLUDPClient.cs b/OpenSim/Region/ClientStack/Linden/UDP/LLUDPClient.cs
new file mode 100644
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--- /dev/null
+++ b/OpenSim/Region/ClientStack/Linden/UDP/LLUDPClient.cs
@@ -0,0 +1,697 @@
+/*
+ * 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.Net;
+using System.Threading;
+using log4net;
+using OpenSim.Framework;
+using OpenMetaverse;
+using OpenMetaverse.Packets;
+
+using TokenBucket = OpenSim.Region.ClientStack.LindenUDP.TokenBucket;
+
+namespace OpenSim.Region.ClientStack.LindenUDP
+{
+    #region Delegates
+
+    /// <summary>
+    /// Fired when updated networking stats are produced for this client
+    /// </summary>
+    /// <param name="inPackets">Number of incoming packets received since this
+    /// event was last fired</param>
+    /// <param name="outPackets">Number of outgoing packets sent since this
+    /// event was last fired</param>
+    /// <param name="unAckedBytes">Current total number of bytes in packets we
+    /// are waiting on ACKs for</param>
+    public delegate void PacketStats(int inPackets, int outPackets, int unAckedBytes);
+    /// <summary>
+    /// Fired when the queue for one or more packet categories is empty. This 
+    /// event can be hooked to put more data on the empty queues
+    /// </summary>
+    /// <param name="category">Categories of the packet queues that are empty</param>
+    public delegate void QueueEmpty(ThrottleOutPacketTypeFlags categories);
+
+    #endregion Delegates
+
+    /// <summary>
+    /// Tracks state for a client UDP connection and provides client-specific methods
+    /// </summary>
+    public sealed class LLUDPClient
+    {
+        // TODO: Make this a config setting
+        /// <summary>Percentage of the task throttle category that is allocated to avatar and prim
+        /// state updates</summary>
+        const float STATE_TASK_PERCENTAGE = 0.8f;
+
+        private static readonly ILog m_log = LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);
+
+        /// <summary>The number of packet categories to throttle on. If a throttle category is added
+        /// or removed, this number must also change</summary>
+        const int THROTTLE_CATEGORY_COUNT = 8;
+
+        /// <summary>Fired when updated networking stats are produced for this client</summary>
+        public event PacketStats OnPacketStats;
+        /// <summary>Fired when the queue for a packet category is empty. This event can be
+        /// hooked to put more data on the empty queue</summary>
+        public event QueueEmpty OnQueueEmpty;
+
+        /// <summary>AgentID for this client</summary>
+        public readonly UUID AgentID;
+        /// <summary>The remote address of the connected client</summary>
+        public readonly IPEndPoint RemoteEndPoint;
+        /// <summary>Circuit code that this client is connected on</summary>
+        public readonly uint CircuitCode;
+        /// <summary>Sequence numbers of packets we've received (for duplicate checking)</summary>
+        public readonly IncomingPacketHistoryCollection PacketArchive = new IncomingPacketHistoryCollection(200);
+        /// <summary>Packets we have sent that need to be ACKed by the client</summary>
+        public readonly UnackedPacketCollection NeedAcks = new UnackedPacketCollection();
+        /// <summary>ACKs that are queued up, waiting to be sent to the client</summary>
+        public readonly OpenSim.Framework.LocklessQueue<uint> PendingAcks = new OpenSim.Framework.LocklessQueue<uint>();
+
+        /// <summary>Current packet sequence number</summary>
+        public int CurrentSequence;
+        /// <summary>Current ping sequence number</summary>
+        public byte CurrentPingSequence;
+        /// <summary>True when this connection is alive, otherwise false</summary>
+        public bool IsConnected = true;
+        /// <summary>True when this connection is paused, otherwise false</summary>
+        public bool IsPaused;
+        /// <summary>Environment.TickCount when the last packet was received for this client</summary>
+        public int TickLastPacketReceived;
+
+        /// <summary>Smoothed round-trip time. A smoothed average of the round-trip time for sending a
+        /// reliable packet to the client and receiving an ACK</summary>
+        public float SRTT;
+        /// <summary>Round-trip time variance. Measures the consistency of round-trip times</summary>
+        public float RTTVAR;
+        /// <summary>Retransmission timeout. Packets that have not been acknowledged in this number of
+        /// milliseconds or longer will be resent</summary>
+        /// <remarks>Calculated from <seealso cref="SRTT"/> and <seealso cref="RTTVAR"/> using the
+        /// guidelines in RFC 2988</remarks>
+        public int RTO;
+        /// <summary>Number of bytes received since the last acknowledgement was sent out. This is used
+        /// to loosely follow the TCP delayed ACK algorithm in RFC 1122 (4.2.3.2)</summary>
+        public int BytesSinceLastACK;
+        /// <summary>Number of packets received from this client</summary>
+        public int PacketsReceived;
+        /// <summary>Number of packets sent to this client</summary>
+        public int PacketsSent;
+        /// <summary>Number of packets resent to this client</summary>
+        public int PacketsResent;        
+        /// <summary>Total byte count of unacked packets sent to this client</summary>
+        public int UnackedBytes;
+
+        /// <summary>Total number of received packets that we have reported to the OnPacketStats event(s)</summary>
+        private int m_packetsReceivedReported;
+        /// <summary>Total number of sent packets that we have reported to the OnPacketStats event(s)</summary>
+        private int m_packetsSentReported;
+        /// <summary>Holds the Environment.TickCount value of when the next OnQueueEmpty can be fired</summary>
+        private int m_nextOnQueueEmpty = 1;
+
+        /// <summary>Throttle bucket for this agent's connection</summary>
+        private readonly AdaptiveTokenBucket m_throttleClient;
+        public AdaptiveTokenBucket FlowThrottle
+        {
+            get { return m_throttleClient; }
+        }
+
+        /// <summary>Throttle bucket for this agent's connection</summary>
+        private readonly TokenBucket m_throttleCategory;
+        /// <summary>Throttle buckets for each packet category</summary>
+        private readonly TokenBucket[] m_throttleCategories;
+        /// <summary>Outgoing queues for throttled packets</summary>
+        private readonly OpenSim.Framework.LocklessQueue<OutgoingPacket>[] m_packetOutboxes = new OpenSim.Framework.LocklessQueue<OutgoingPacket>[THROTTLE_CATEGORY_COUNT];
+        /// <summary>A container that can hold one packet for each outbox, used to store
+        /// dequeued packets that are being held for throttling</summary>
+        private readonly OutgoingPacket[] m_nextPackets = new OutgoingPacket[THROTTLE_CATEGORY_COUNT];
+        /// <summary>A reference to the LLUDPServer that is managing this client</summary>
+        private readonly LLUDPServer m_udpServer;
+
+        /// <summary>Caches packed throttle information</summary>
+        private byte[] m_packedThrottles;
+
+        private int m_defaultRTO = 1000; // 1sec is the recommendation in the RFC
+        private int m_maxRTO = 60000;
+
+        /// <summary>
+        /// Default constructor
+        /// </summary>
+        /// <param name="server">Reference to the UDP server this client is connected to</param>
+        /// <param name="rates">Default throttling rates and maximum throttle limits</param>
+        /// <param name="parentThrottle">Parent HTB (hierarchical token bucket)
+        /// that the child throttles will be governed by</param>
+        /// <param name="circuitCode">Circuit code for this connection</param>
+        /// <param name="agentID">AgentID for the connected agent</param>
+        /// <param name="remoteEndPoint">Remote endpoint for this connection</param>
+        public LLUDPClient(LLUDPServer server, ThrottleRates rates, TokenBucket parentThrottle, uint circuitCode, UUID agentID, IPEndPoint remoteEndPoint, int defaultRTO, int maxRTO)
+        {
+            AgentID = agentID;
+            RemoteEndPoint = remoteEndPoint;
+            CircuitCode = circuitCode;
+            m_udpServer = server;
+            if (defaultRTO != 0)
+                m_defaultRTO = defaultRTO;
+            if (maxRTO != 0)
+                m_maxRTO = maxRTO;
+
+            // Create a token bucket throttle for this client that has the scene token bucket as a parent
+            m_throttleClient = new AdaptiveTokenBucket(parentThrottle, rates.Total, rates.AdaptiveThrottlesEnabled);
+            // Create a token bucket throttle for the total categary with the client bucket as a throttle
+            m_throttleCategory = new TokenBucket(m_throttleClient, 0);
+            // Create an array of token buckets for this clients different throttle categories
+            m_throttleCategories = new TokenBucket[THROTTLE_CATEGORY_COUNT];
+
+            for (int i = 0; i < THROTTLE_CATEGORY_COUNT; i++)
+            {
+                ThrottleOutPacketType type = (ThrottleOutPacketType)i;
+
+                // Initialize the packet outboxes, where packets sit while they are waiting for tokens
+                m_packetOutboxes[i] = new OpenSim.Framework.LocklessQueue<OutgoingPacket>();
+                // Initialize the token buckets that control the throttling for each category
+                m_throttleCategories[i] = new TokenBucket(m_throttleCategory, rates.GetRate(type));
+            }
+
+            // Default the retransmission timeout to three seconds
+            RTO = m_defaultRTO;
+
+            // Initialize this to a sane value to prevent early disconnects
+            TickLastPacketReceived = Environment.TickCount & Int32.MaxValue;
+        }
+
+        /// <summary>
+        /// Shuts down this client connection
+        /// </summary>
+        public void Shutdown()
+        {
+            IsConnected = false;
+            for (int i = 0; i < THROTTLE_CATEGORY_COUNT; i++)
+            {
+                m_packetOutboxes[i].Clear();
+                m_nextPackets[i] = null;
+            }
+
+            // pull the throttle out of the scene throttle
+            m_throttleClient.Parent.UnregisterRequest(m_throttleClient);
+            OnPacketStats = null;
+            OnQueueEmpty = null;
+        }
+
+        /// <summary>
+        /// Gets information about this client connection
+        /// </summary>
+        /// <returns>Information about the client connection</returns>
+        public ClientInfo GetClientInfo()
+        {
+            // TODO: This data structure is wrong in so many ways. Locking and copying the entire lists
+            // of pending and needed ACKs for every client every time some method wants information about
+            // this connection is a recipe for poor performance
+            ClientInfo info = new ClientInfo();
+            info.pendingAcks = new Dictionary<uint, uint>();
+            info.needAck = new Dictionary<uint, byte[]>();
+
+            info.resendThrottle = (int)m_throttleCategories[(int)ThrottleOutPacketType.Resend].DripRate;
+            info.landThrottle = (int)m_throttleCategories[(int)ThrottleOutPacketType.Land].DripRate;
+            info.windThrottle = (int)m_throttleCategories[(int)ThrottleOutPacketType.Wind].DripRate;
+            info.cloudThrottle = (int)m_throttleCategories[(int)ThrottleOutPacketType.Cloud].DripRate;
+            info.taskThrottle = (int)m_throttleCategories[(int)ThrottleOutPacketType.Task].DripRate;
+            info.assetThrottle = (int)m_throttleCategories[(int)ThrottleOutPacketType.Asset].DripRate;
+            info.textureThrottle = (int)m_throttleCategories[(int)ThrottleOutPacketType.Texture].DripRate;
+            info.totalThrottle = (int)m_throttleCategory.DripRate;
+
+            return info;
+        }
+
+        /// <summary>
+        /// Modifies the UDP throttles
+        /// </summary>
+        /// <param name="info">New throttling values</param>
+        public void SetClientInfo(ClientInfo info)
+        {
+            // TODO: Allowing throttles to be manually set from this function seems like a reasonable
+            // idea. On the other hand, letting external code manipulate our ACK accounting is not
+            // going to happen
+            throw new NotImplementedException();
+        }
+
+        /// <summary>
+        /// Return statistics information about client packet queues.
+        /// </summary>
+        /// 
+        /// FIXME: This should really be done in a more sensible manner rather than sending back a formatted string.
+        /// 
+        /// <returns></returns>
+        public string GetStats()
+        {
+            return string.Format(
+                "{0,7} {1,7} {2,7} {3,9} {4,7} {5,7} {6,7} {7,7} {8,7} {9,8} {10,7} {11,7}",
+                PacketsReceived,                                 
+                PacketsSent,
+                PacketsResent,
+                UnackedBytes,
+                m_packetOutboxes[(int)ThrottleOutPacketType.Resend].Count,
+                m_packetOutboxes[(int)ThrottleOutPacketType.Land].Count,
+                m_packetOutboxes[(int)ThrottleOutPacketType.Wind].Count,
+                m_packetOutboxes[(int)ThrottleOutPacketType.Cloud].Count,
+                m_packetOutboxes[(int)ThrottleOutPacketType.Task].Count,
+                m_packetOutboxes[(int)ThrottleOutPacketType.Texture].Count,
+                m_packetOutboxes[(int)ThrottleOutPacketType.Asset].Count,
+                m_packetOutboxes[(int)ThrottleOutPacketType.State].Count);                                
+        }
+
+        public void SendPacketStats()
+        {
+            PacketStats callback = OnPacketStats;
+            if (callback != null)
+            {
+                int newPacketsReceived = PacketsReceived - m_packetsReceivedReported;
+                int newPacketsSent = PacketsSent - m_packetsSentReported;
+
+                callback(newPacketsReceived, newPacketsSent, UnackedBytes);
+
+                m_packetsReceivedReported += newPacketsReceived;
+                m_packetsSentReported += newPacketsSent;
+            }
+        }
+
+        public void SetThrottles(byte[] throttleData)
+        {
+            byte[] adjData;
+            int pos = 0;
+
+            if (!BitConverter.IsLittleEndian)
+            {
+                byte[] newData = new byte[7 * 4];
+                Buffer.BlockCopy(throttleData, 0, newData, 0, 7 * 4);
+
+                for (int i = 0; i < 7; i++)
+                    Array.Reverse(newData, i * 4, 4);
+
+                adjData = newData;
+            }
+            else
+            {
+                adjData = throttleData;
+            }
+
+            // 0.125f converts from bits to bytes
+            int resend = (int)(BitConverter.ToSingle(adjData, pos) * 0.125f); pos += 4;
+            int land = (int)(BitConverter.ToSingle(adjData, pos) * 0.125f); pos += 4;
+            int wind = (int)(BitConverter.ToSingle(adjData, pos) * 0.125f); pos += 4;
+            int cloud = (int)(BitConverter.ToSingle(adjData, pos) * 0.125f); pos += 4;
+            int task = (int)(BitConverter.ToSingle(adjData, pos) * 0.125f); pos += 4;
+            int texture = (int)(BitConverter.ToSingle(adjData, pos) * 0.125f); pos += 4;
+            int asset = (int)(BitConverter.ToSingle(adjData, pos) * 0.125f);
+            // State is a subcategory of task that we allocate a percentage to
+            int state = 0;
+
+            // Make sure none of the throttles are set below our packet MTU,
+            // otherwise a throttle could become permanently clogged
+            resend = Math.Max(resend, LLUDPServer.MTU);
+            land = Math.Max(land, LLUDPServer.MTU);
+            wind = Math.Max(wind, LLUDPServer.MTU);
+            cloud = Math.Max(cloud, LLUDPServer.MTU);
+            task = Math.Max(task, LLUDPServer.MTU);
+            texture = Math.Max(texture, LLUDPServer.MTU);
+            asset = Math.Max(asset, LLUDPServer.MTU);
+
+            //int total = resend + land + wind + cloud + task + texture + asset;
+            //m_log.DebugFormat("[LLUDPCLIENT]: {0} is setting throttles. Resend={1}, Land={2}, Wind={3}, Cloud={4}, Task={5}, Texture={6}, Asset={7}, Total={8}",
+            //                  AgentID, resend, land, wind, cloud, task, texture, asset, total);
+
+            // Update the token buckets with new throttle values
+            TokenBucket bucket;
+
+            bucket = m_throttleCategories[(int)ThrottleOutPacketType.Resend];
+            bucket.RequestedDripRate = resend;
+
+            bucket = m_throttleCategories[(int)ThrottleOutPacketType.Land];
+            bucket.RequestedDripRate = land;
+
+            bucket = m_throttleCategories[(int)ThrottleOutPacketType.Wind];
+            bucket.RequestedDripRate = wind;
+
+            bucket = m_throttleCategories[(int)ThrottleOutPacketType.Cloud];
+            bucket.RequestedDripRate = cloud;
+
+            bucket = m_throttleCategories[(int)ThrottleOutPacketType.Asset];
+            bucket.RequestedDripRate = asset;
+
+            bucket = m_throttleCategories[(int)ThrottleOutPacketType.Task];
+            bucket.RequestedDripRate = task;
+
+            bucket = m_throttleCategories[(int)ThrottleOutPacketType.State];
+            bucket.RequestedDripRate = state;
+
+            bucket = m_throttleCategories[(int)ThrottleOutPacketType.Texture];
+            bucket.RequestedDripRate = texture;
+
+            // Reset the packed throttles cached data
+            m_packedThrottles = null;
+        }
+
+        public byte[] GetThrottlesPacked(float multiplier)
+        {
+            byte[] data = m_packedThrottles;
+
+            if (data == null)
+            {
+                float rate;
+
+                data = new byte[7 * 4];
+                int i = 0;
+
+                // multiply by 8 to convert bytes back to bits
+                rate = (float)m_throttleCategories[(int)ThrottleOutPacketType.Resend].RequestedDripRate * 8 * multiplier;
+                Buffer.BlockCopy(Utils.FloatToBytes(rate), 0, data, i, 4); i += 4;
+
+                rate = (float)m_throttleCategories[(int)ThrottleOutPacketType.Land].RequestedDripRate * 8 * multiplier;
+                Buffer.BlockCopy(Utils.FloatToBytes(rate), 0, data, i, 4); i += 4;
+
+                rate = (float)m_throttleCategories[(int)ThrottleOutPacketType.Wind].RequestedDripRate * 8 * multiplier;
+                Buffer.BlockCopy(Utils.FloatToBytes(rate), 0, data, i, 4); i += 4;
+
+                rate = (float)m_throttleCategories[(int)ThrottleOutPacketType.Cloud].RequestedDripRate * 8 * multiplier;
+                Buffer.BlockCopy(Utils.FloatToBytes(rate), 0, data, i, 4); i += 4;
+
+                rate = (float)m_throttleCategories[(int)ThrottleOutPacketType.Task].RequestedDripRate * 8 * multiplier;
+                Buffer.BlockCopy(Utils.FloatToBytes(rate), 0, data, i, 4); i += 4;
+
+                rate = (float)m_throttleCategories[(int)ThrottleOutPacketType.Texture].RequestedDripRate * 8 * multiplier;
+                Buffer.BlockCopy(Utils.FloatToBytes(rate), 0, data, i, 4); i += 4;
+
+                rate = (float)m_throttleCategories[(int)ThrottleOutPacketType.Asset].RequestedDripRate * 8 * multiplier;
+                Buffer.BlockCopy(Utils.FloatToBytes(rate), 0, data, i, 4); i += 4;
+
+                m_packedThrottles = data;
+            }
+
+            return data;
+        }
+
+        /// <summary>
+        /// Queue an outgoing packet if appropriate.
+        /// </summary>
+        /// <param name="packet"></param>
+        /// <param name="forceQueue">Always queue the packet if at all possible.</param>
+        /// <returns>
+        /// true if the packet has been queued, 
+        /// false if the packet has not been queued and should be sent immediately.
+        /// </returns>
+        public bool EnqueueOutgoing(OutgoingPacket packet, bool forceQueue)
+        {
+            int category = (int)packet.Category;
+
+            if (category >= 0 && category < m_packetOutboxes.Length)
+            {
+                OpenSim.Framework.LocklessQueue<OutgoingPacket> queue = m_packetOutboxes[category];
+                TokenBucket bucket = m_throttleCategories[category];
+
+                // Don't send this packet if there is already a packet waiting in the queue
+                // even if we have the tokens to send it, tokens should go to the already
+                // queued packets
+                if (queue.Count > 0)
+                {
+                    queue.Enqueue(packet);
+                    return true;
+                }
+                
+                    
+                if (!forceQueue && bucket.RemoveTokens(packet.Buffer.DataLength))
+                {
+                    // Enough tokens were removed from the bucket, the packet will not be queued
+                    return false;
+                }
+                else
+                {
+                    // Force queue specified or not enough tokens in the bucket, queue this packet
+                    queue.Enqueue(packet);
+                    return true;
+                }
+            }
+            else
+            {
+                // We don't have a token bucket for this category, so it will not be queued
+                return false;
+            }
+        }
+
+        /// <summary>
+        /// Loops through all of the packet queues for this client and tries to send
+        /// an outgoing packet from each, obeying the throttling bucket limits
+        /// </summary>
+        /// 
+        /// <remarks>
+        /// Packet queues are inspected in ascending numerical order starting from 0.  Therefore, queues with a lower 
+        /// ThrottleOutPacketType number will see their packet get sent first (e.g. if both Land and Wind queues have
+        /// packets, then the packet at the front of the Land queue will be sent before the packet at the front of the
+        /// wind queue).
+        /// 
+        /// This function is only called from a synchronous loop in the
+        /// UDPServer so we don't need to bother making this thread safe
+        /// </remarks>
+        /// 
+        /// <returns>True if any packets were sent, otherwise false</returns>
+        public bool DequeueOutgoing()
+        {
+            OutgoingPacket packet;
+            OpenSim.Framework.LocklessQueue<OutgoingPacket> queue;
+            TokenBucket bucket;
+            bool packetSent = false;
+            ThrottleOutPacketTypeFlags emptyCategories = 0;
+
+            //string queueDebugOutput = String.Empty; // Serious debug business
+
+            for (int i = 0; i < THROTTLE_CATEGORY_COUNT; i++)
+            {
+                bucket = m_throttleCategories[i];
+                //queueDebugOutput += m_packetOutboxes[i].Count + " ";  // Serious debug business
+
+                if (m_nextPackets[i] != null)
+                {
+                    // This bucket was empty the last time we tried to send a packet,
+                    // leaving a dequeued packet still waiting to be sent out. Try to
+                    // send it again
+                    OutgoingPacket nextPacket = m_nextPackets[i];
+                    if (bucket.RemoveTokens(nextPacket.Buffer.DataLength))
+                    {
+                        // Send the packet
+                        m_udpServer.SendPacketFinal(nextPacket);
+                        m_nextPackets[i] = null;
+                        packetSent = true;
+                    }
+                }
+                else
+                {
+                    // No dequeued packet waiting to be sent, try to pull one off
+                    // this queue
+                    queue = m_packetOutboxes[i];
+                    if (queue.Dequeue(out packet))
+                    {
+                        // A packet was pulled off the queue. See if we have
+                        // enough tokens in the bucket to send it out
+                        if (bucket.RemoveTokens(packet.Buffer.DataLength))
+                        {
+                            // Send the packet
+                            m_udpServer.SendPacketFinal(packet);
+                            packetSent = true;
+                        }
+                        else
+                        {
+                            // Save the dequeued packet for the next iteration
+                            m_nextPackets[i] = packet;
+                        }
+
+                        // If the queue is empty after this dequeue, fire the queue
+                        // empty callback now so it has a chance to fill before we 
+                        // get back here
+                        if (queue.Count == 0)
+                            emptyCategories |= CategoryToFlag(i);
+                    }
+                    else
+                    {
+                        // No packets in this queue. Fire the queue empty callback
+                        // if it has not been called recently
+                        emptyCategories |= CategoryToFlag(i);
+                    }
+                }
+            }
+
+            if (emptyCategories != 0)
+                BeginFireQueueEmpty(emptyCategories);
+
+            //m_log.Info("[LLUDPCLIENT]: Queues: " + queueDebugOutput); // Serious debug business
+            return packetSent;
+        }
+
+        /// <summary>
+        /// Called when an ACK packet is received and a round-trip time for a
+        /// packet is calculated. This is used to calculate the smoothed
+        /// round-trip time, round trip time variance, and finally the
+        /// retransmission timeout
+        /// </summary>
+        /// <param name="r">Round-trip time of a single packet and its
+        /// acknowledgement</param>
+        public void UpdateRoundTrip(float r)
+        {
+            const float ALPHA = 0.125f;
+            const float BETA = 0.25f;
+            const float K = 4.0f;
+
+            if (RTTVAR == 0.0f)
+            {
+                // First RTT measurement
+                SRTT = r;
+                RTTVAR = r * 0.5f;
+            }
+            else
+            {
+                // Subsequence RTT measurement
+                RTTVAR = (1.0f - BETA) * RTTVAR + BETA * Math.Abs(SRTT - r);
+                SRTT = (1.0f - ALPHA) * SRTT + ALPHA * r;
+            }
+
+            int rto = (int)(SRTT + Math.Max(m_udpServer.TickCountResolution, K * RTTVAR));
+
+            // Clamp the retransmission timeout to manageable values
+            rto = Utils.Clamp(rto, m_defaultRTO, m_maxRTO);
+
+            RTO = rto;
+
+            //m_log.Debug("[LLUDPCLIENT]: Setting agent " + this.Agent.FullName + "'s RTO to " + RTO + "ms with an RTTVAR of " +
+            //    RTTVAR + " based on new RTT of " + r + "ms");
+        }
+
+        /// <summary>
+        /// Exponential backoff of the retransmission timeout, per section 5.5
+        /// of RFC 2988
+        /// </summary>
+        public void BackoffRTO()
+        {
+            // Reset SRTT and RTTVAR, we assume they are bogus since things
+            // didn't work out and we're backing off the timeout
+            SRTT = 0.0f;
+            RTTVAR = 0.0f;
+
+            // Double the retransmission timeout
+            RTO = Math.Min(RTO * 2, m_maxRTO);
+        }
+
+        /// <summary>
+        /// Does an early check to see if this queue empty callback is already
+        /// running, then asynchronously firing the event
+        /// </summary>
+        /// <param name="throttleIndex">Throttle category to fire the callback
+        /// for</param>
+        private void BeginFireQueueEmpty(ThrottleOutPacketTypeFlags categories)
+        {
+            if (m_nextOnQueueEmpty != 0 && (Environment.TickCount & Int32.MaxValue) >= m_nextOnQueueEmpty)
+            {
+                // Use a value of 0 to signal that FireQueueEmpty is running
+                m_nextOnQueueEmpty = 0;
+                // Asynchronously run the callback
+                Util.FireAndForget(FireQueueEmpty, categories);
+            }
+        }
+
+        /// <summary>
+        /// Fires the OnQueueEmpty callback and sets the minimum time that it
+        /// can be called again
+        /// </summary>
+        /// <param name="o">Throttle categories to fire the callback for,
+        /// stored as an object to match the WaitCallback delegate
+        /// signature</param>
+        private void FireQueueEmpty(object o)
+        {
+            const int MIN_CALLBACK_MS = 30;
+
+            ThrottleOutPacketTypeFlags categories = (ThrottleOutPacketTypeFlags)o;
+            QueueEmpty callback = OnQueueEmpty;
+            
+            int start = Environment.TickCount & Int32.MaxValue;
+
+            if (callback != null)
+            {
+                try { callback(categories); }
+                catch (Exception e) { m_log.Error("[LLUDPCLIENT]: OnQueueEmpty(" + categories + ") threw an exception: " + e.Message, e); }
+            }
+
+            m_nextOnQueueEmpty = start + MIN_CALLBACK_MS;
+            if (m_nextOnQueueEmpty == 0)
+                m_nextOnQueueEmpty = 1;
+        }
+
+        /// <summary>
+        /// Converts a <seealso cref="ThrottleOutPacketType"/> integer to a
+        /// flag value
+        /// </summary>
+        /// <param name="i">Throttle category to convert</param>
+        /// <returns>Flag representation of the throttle category</returns>
+        private static ThrottleOutPacketTypeFlags CategoryToFlag(int i)
+        {
+            ThrottleOutPacketType category = (ThrottleOutPacketType)i;
+
+            /*
+             * Land = 1,
+        /// <summary>Wind data</summary>
+        Wind = 2,
+        /// <summary>Cloud data</summary>
+        Cloud = 3,
+        /// <summary>Any packets that do not fit into the other throttles</summary>
+        Task = 4,
+        /// <summary>Texture assets</summary>
+        Texture = 5,
+        /// <summary>Non-texture assets</summary>
+        Asset = 6,
+        /// <summary>Avatar and primitive data</summary>
+        /// <remarks>This is a sub-category of Task</remarks>
+        State = 7,
+             */
+
+            switch (category)
+            {
+                case ThrottleOutPacketType.Land:
+                    return ThrottleOutPacketTypeFlags.Land;
+                case ThrottleOutPacketType.Wind:
+                    return ThrottleOutPacketTypeFlags.Wind;
+                case ThrottleOutPacketType.Cloud:
+                    return ThrottleOutPacketTypeFlags.Cloud;
+                case ThrottleOutPacketType.Task:
+                    return ThrottleOutPacketTypeFlags.Task;
+                case ThrottleOutPacketType.Texture:
+                    return ThrottleOutPacketTypeFlags.Texture;
+                case ThrottleOutPacketType.Asset:
+                    return ThrottleOutPacketTypeFlags.Asset;
+                case ThrottleOutPacketType.State:
+                    return ThrottleOutPacketTypeFlags.State;
+                default:
+                    return 0;
+            }
+        }
+    }
+}