aboutsummaryrefslogtreecommitdiffstatshomepage
path: root/OpenSim/Region/ClientStack/Linden/UDP/UnackedPacketCollection.cs
blob: b546a99603eb1f650db5047d480dcb3b2d111403 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
/*
 * 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 OpenMetaverse;

//using System.Reflection;
//using log4net;

namespace OpenSim.Region.ClientStack.LindenUDP
{
    /// <summary>
    /// Special collection that is optimized for tracking unacknowledged packets
    /// </summary>
    public sealed class UnackedPacketCollection
    {
        /// <summary>
        /// Holds information about a pending acknowledgement
        /// </summary>
        private struct PendingAck
        {
            /// <summary>Sequence number of the packet to remove</summary>
            public uint SequenceNumber;
            /// <summary>Environment.TickCount value when the remove was queued.
            /// This is used to update round-trip times for packets</summary>
            public int RemoveTime;
            /// <summary>Whether or not this acknowledgement was attached to a
            /// resent packet. If so, round-trip time will not be calculated</summary>
            public bool FromResend;

            public PendingAck(uint sequenceNumber, int currentTime, bool fromResend)
            {
                SequenceNumber = sequenceNumber;
                RemoveTime = currentTime;
                FromResend = fromResend;
            }
        }

        //private static readonly ILog m_log = LogManager.GetLogger(MethodBase.GetCurrentMethod().DeclaringType);

        /// <summary>Holds the actual unacked packet data, sorted by sequence number</summary>
        private Dictionary<uint, OutgoingPacket> m_packets = new Dictionary<uint, OutgoingPacket>();
        /// <summary>Holds packets that need to be added to the unacknowledged list</summary>
        private LocklessQueue<OutgoingPacket> m_pendingAdds = new LocklessQueue<OutgoingPacket>();
        /// <summary>Holds information about pending acknowledgements</summary>
        private LocklessQueue<PendingAck> m_pendingAcknowledgements = new LocklessQueue<PendingAck>();
        /// <summary>Holds information about pending removals</summary>
        private LocklessQueue<uint> m_pendingRemoves = new LocklessQueue<uint>();

        /// <summary>
        /// Add an unacked packet to the collection
        /// </summary>
        /// <param name="packet">Packet that is awaiting acknowledgement</param>
        /// <returns>True if the packet was successfully added, false if the
        /// packet already existed in the collection</returns>
        /// <remarks>This does not immediately add the ACK to the collection,
        /// it only queues it so it can be added in a thread-safe way later</remarks>
        public void Add(OutgoingPacket packet)
        {
            m_pendingAdds.Enqueue(packet);
            Interlocked.Add(ref packet.Client.UnackedBytes, packet.Buffer.DataLength);            
        }

        /// <summary>
        /// Marks a packet as acknowledged
        /// This method is used when an acknowledgement is received from the network for a previously
        /// sent packet. Effects of removal this way are to update unacked byte count, adjust RTT
        /// and increase throttle to the coresponding client.
        /// </summary>
        /// <param name="sequenceNumber">Sequence number of the packet to
        /// acknowledge</param>
        /// <param name="currentTime">Current value of Environment.TickCount</param>
        /// <remarks>This does not immediately acknowledge the packet, it only
        /// queues the ack so it can be handled in a thread-safe way later</remarks>
        public void Acknowledge(uint sequenceNumber, int currentTime, bool fromResend)
        {
            m_pendingAcknowledgements.Enqueue(new PendingAck(sequenceNumber, currentTime, fromResend));
        }

        /// <summary>
        /// Marks a packet as no longer needing acknowledgement without a received acknowledgement.
        /// This method is called when a packet expires and we no longer need an acknowledgement.
        /// When some reliable packet types expire, they are handled in a way other than simply 
        /// resending them. The only effect of removal this way is to update unacked byte count.
        /// </summary>
        /// <param name="sequenceNumber">Sequence number of the packet to
        /// acknowledge</param>
        /// <remarks>The does not immediately remove the packet, it only queues the removal
        /// so it can be handled in a thread safe way later</remarks>
        public void Remove(uint sequenceNumber)
        {
            m_pendingRemoves.Enqueue(sequenceNumber);
        }

        /// <summary>
        /// Returns a list of all of the packets with a TickCount older than
        /// the specified timeout
        /// </summary>
        /// <remarks>
        /// This function is not thread safe, and cannot be called
        /// multiple times concurrently
        /// </remarks>
        /// <param name="timeoutMS">Number of ticks (milliseconds) before a
        /// packet is considered expired
        /// </param>
        /// <returns>
        /// A list of all expired packets according to the given
        /// expiration timeout
        /// </returns>
        public List<OutgoingPacket> GetExpiredPackets(int timeoutMS)
        {
            ProcessQueues();

            List<OutgoingPacket> expiredPackets = null;

            if (m_packets.Count > 0)
            {
                int now = Environment.TickCount & Int32.MaxValue;

                foreach (OutgoingPacket packet in m_packets.Values)
                {
                    // TickCount of zero means a packet is in the resend queue 
                    // but hasn't actually been sent over the wire yet
                    if (packet.TickCount == 0)
                        continue;

                    if (now - packet.TickCount >= timeoutMS)
                    {
                        if (expiredPackets == null)
                            expiredPackets = new List<OutgoingPacket>();

                        // The TickCount will be set to the current time when the packet
                        // is actually sent out again
                        packet.TickCount = 0;

                        // As with other network applications, assume that an expired packet is
                        // an indication of some network problem, slow transmission
                        packet.Client.FlowThrottle.ExpirePackets(1);
                        
                        expiredPackets.Add(packet);
                    }
                }
            }

            // if (expiredPackets != null)
            //     m_log.DebugFormat("[UNACKED PACKET COLLECTION]: Found {0} expired packets on timeout of {1}", expiredPackets.Count, timeoutMS);

            return expiredPackets;
        }

        private void ProcessQueues()
        {
            // Process all the pending adds
            OutgoingPacket pendingAdd;
            while (m_pendingAdds.TryDequeue(out pendingAdd))
                if (pendingAdd != null)
                    m_packets[pendingAdd.SequenceNumber] = pendingAdd;
            
            // Process all the pending removes, including updating statistics and round-trip times
            PendingAck pendingAcknowledgement;
            while (m_pendingAcknowledgements.TryDequeue(out pendingAcknowledgement))
            {
                //m_log.DebugFormat("[UNACKED PACKET COLLECTION]: Processing ack {0}", pendingAcknowledgement.SequenceNumber);
                OutgoingPacket ackedPacket;
                if (m_packets.TryGetValue(pendingAcknowledgement.SequenceNumber, out ackedPacket))
                {
                    if (ackedPacket != null)
                    {
                        m_packets.Remove(pendingAcknowledgement.SequenceNumber);

                        // As with other network applications, assume that an acknowledged packet is an
                        // indication that the network can handle a little more load, speed up the transmission
                        ackedPacket.Client.FlowThrottle.AcknowledgePackets(1);

                        // Update stats
                        Interlocked.Add(ref ackedPacket.Client.UnackedBytes, -ackedPacket.Buffer.DataLength);

                        if (!pendingAcknowledgement.FromResend)
                        {
                            // Calculate the round-trip time for this packet and its ACK
                            int rtt = pendingAcknowledgement.RemoveTime - ackedPacket.TickCount;
                            if (rtt > 0)
                                ackedPacket.Client.UpdateRoundTrip(rtt);
                        }
                    }
                    else
                    {
                        // m_log.WarnFormat("[UNACKED PACKET COLLECTION]: found null packet for sequence number {0} to ack",
                        //                  pendingAcknowledgement.SequenceNumber);
                    }
                }
                else
                {
                    // m_log.WarnFormat("[UNACKED PACKET COLLECTION]: Could not find packet with sequence number {0} to ack",
                    //                  pendingAcknowledgement.SequenceNumber);                    
                }
            }

            uint pendingRemove;
            while(m_pendingRemoves.TryDequeue(out pendingRemove))
            {
                OutgoingPacket removedPacket;
                if (m_packets.TryGetValue(pendingRemove, out removedPacket))
                {
                    if (removedPacket != null)
                    {
                        m_packets.Remove(pendingRemove);

                        // Update stats
                        Interlocked.Add(ref removedPacket.Client.UnackedBytes, -removedPacket.Buffer.DataLength);
                    }
                }
            }
        }
    }
}