opensim-development – Blame information for rev 1

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1 eva 1 /*
2 * Copyright (c) Contributors, http://opensimulator.org/
3 * See CONTRIBUTORS.TXT for a full list of copyright holders.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions are met:
7 * * Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * * Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 * * Neither the name of the OpenSimulator Project nor the
13 * names of its contributors may be used to endorse or promote products
14 * derived from this software without specific prior written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY
17 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
18 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
19 * DISCLAIMED. IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY
20 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
21 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
22 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
23 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
25 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26 */
27  
28 using System;
29 using System.Collections.Generic;
30 using System.Net;
31 using System.Threading;
32 using OpenMetaverse;
33  
34 namespace OpenSim.Region.ClientStack.LindenUDP
35 {
36 /// <summary>
37 /// Special collection that is optimized for tracking unacknowledged packets
38 /// </summary>
39 public sealed class UnackedPacketCollection
40 {
41 /// <summary>
42 /// Holds information about a pending acknowledgement
43 /// </summary>
44 private struct PendingAck
45 {
46 /// <summary>Sequence number of the packet to remove</summary>
47 public uint SequenceNumber;
48 /// <summary>Environment.TickCount value when the remove was queued.
49 /// This is used to update round-trip times for packets</summary>
50 public int RemoveTime;
51 /// <summary>Whether or not this acknowledgement was attached to a
52 /// resent packet. If so, round-trip time will not be calculated</summary>
53 public bool FromResend;
54  
55 public PendingAck(uint sequenceNumber, int currentTime, bool fromResend)
56 {
57 SequenceNumber = sequenceNumber;
58 RemoveTime = currentTime;
59 FromResend = fromResend;
60 }
61 }
62  
63 /// <summary>Holds the actual unacked packet data, sorted by sequence number</summary>
64 private Dictionary<uint, OutgoingPacket> m_packets = new Dictionary<uint, OutgoingPacket>();
65 /// <summary>Holds packets that need to be added to the unacknowledged list</summary>
66 private LocklessQueue<OutgoingPacket> m_pendingAdds = new LocklessQueue<OutgoingPacket>();
67 /// <summary>Holds information about pending acknowledgements</summary>
68 private LocklessQueue<PendingAck> m_pendingAcknowledgements = new LocklessQueue<PendingAck>();
69 /// <summary>Holds information about pending removals</summary>
70 private LocklessQueue<uint> m_pendingRemoves = new LocklessQueue<uint>();
71  
72 /// <summary>
73 /// Add an unacked packet to the collection
74 /// </summary>
75 /// <param name="packet">Packet that is awaiting acknowledgement</param>
76 /// <returns>True if the packet was successfully added, false if the
77 /// packet already existed in the collection</returns>
78 /// <remarks>This does not immediately add the ACK to the collection,
79 /// it only queues it so it can be added in a thread-safe way later</remarks>
80 public void Add(OutgoingPacket packet)
81 {
82 m_pendingAdds.Enqueue(packet);
83 Interlocked.Add(ref packet.Client.UnackedBytes, packet.Buffer.DataLength);
84 }
85  
86 /// <summary>
87 /// Marks a packet as acknowledged
88 /// This method is used when an acknowledgement is received from the network for a previously
89 /// sent packet. Effects of removal this way are to update unacked byte count, adjust RTT
90 /// and increase throttle to the coresponding client.
91 /// </summary>
92 /// <param name="sequenceNumber">Sequence number of the packet to
93 /// acknowledge</param>
94 /// <param name="currentTime">Current value of Environment.TickCount</param>
95 /// <remarks>This does not immediately acknowledge the packet, it only
96 /// queues the ack so it can be handled in a thread-safe way later</remarks>
97 public void Acknowledge(uint sequenceNumber, int currentTime, bool fromResend)
98 {
99 m_pendingAcknowledgements.Enqueue(new PendingAck(sequenceNumber, currentTime, fromResend));
100 }
101  
102 /// <summary>
103 /// Marks a packet as no longer needing acknowledgement without a received acknowledgement.
104 /// This method is called when a packet expires and we no longer need an acknowledgement.
105 /// When some reliable packet types expire, they are handled in a way other than simply
106 /// resending them. The only effect of removal this way is to update unacked byte count.
107 /// </summary>
108 /// <param name="sequenceNumber">Sequence number of the packet to
109 /// acknowledge</param>
110 /// <remarks>The does not immediately remove the packet, it only queues the removal
111 /// so it can be handled in a thread safe way later</remarks>
112 public void Remove(uint sequenceNumber)
113 {
114 m_pendingRemoves.Enqueue(sequenceNumber);
115 }
116  
117 /// <summary>
118 /// Returns a list of all of the packets with a TickCount older than
119 /// the specified timeout
120 /// </summary>
121 /// <remarks>
122 /// This function is not thread safe, and cannot be called
123 /// multiple times concurrently
124 /// </remarks>
125 /// <param name="timeoutMS">Number of ticks (milliseconds) before a
126 /// packet is considered expired
127 /// </param>
128 /// <returns>
129 /// A list of all expired packets according to the given
130 /// expiration timeout
131 /// </returns>
132 public List<OutgoingPacket> GetExpiredPackets(int timeoutMS)
133 {
134 ProcessQueues();
135  
136 List<OutgoingPacket> expiredPackets = null;
137  
138 if (m_packets.Count > 0)
139 {
140 int now = Environment.TickCount & Int32.MaxValue;
141  
142 foreach (OutgoingPacket packet in m_packets.Values)
143 {
144 // TickCount of zero means a packet is in the resend queue
145 // but hasn't actually been sent over the wire yet
146 if (packet.TickCount == 0)
147 continue;
148  
149 if (now - packet.TickCount >= timeoutMS)
150 {
151 if (expiredPackets == null)
152 expiredPackets = new List<OutgoingPacket>();
153  
154 // The TickCount will be set to the current time when the packet
155 // is actually sent out again
156 packet.TickCount = 0;
157  
158 // As with other network applications, assume that an expired packet is
159 // an indication of some network problem, slow transmission
160 packet.Client.FlowThrottle.ExpirePackets(1);
161  
162 expiredPackets.Add(packet);
163 }
164 }
165 }
166  
167 //if (expiredPackets != null)
168 // m_log.DebugFormat("[UNACKED PACKET COLLECTION]: Found {0} expired packets on timeout of {1}", expiredPackets.Count, timeoutMS);
169  
170 return expiredPackets;
171 }
172  
173 private void ProcessQueues()
174 {
175 // Process all the pending adds
176 OutgoingPacket pendingAdd;
177 while (m_pendingAdds.TryDequeue(out pendingAdd))
178 if (pendingAdd != null)
179 m_packets[pendingAdd.SequenceNumber] = pendingAdd;
180  
181 // Process all the pending removes, including updating statistics and round-trip times
182 PendingAck pendingAcknowledgement;
183 while (m_pendingAcknowledgements.TryDequeue(out pendingAcknowledgement))
184 {
185 //m_log.DebugFormat("[UNACKED PACKET COLLECTION]: Processing ack {0}", pendingAcknowledgement.SequenceNumber);
186 OutgoingPacket ackedPacket;
187 if (m_packets.TryGetValue(pendingAcknowledgement.SequenceNumber, out ackedPacket))
188 {
189 if (ackedPacket != null)
190 {
191 m_packets.Remove(pendingAcknowledgement.SequenceNumber);
192  
193 // As with other network applications, assume that an acknowledged packet is an
194 // indication that the network can handle a little more load, speed up the transmission
195 ackedPacket.Client.FlowThrottle.AcknowledgePackets(ackedPacket.Buffer.DataLength);
196  
197 // Update stats
198 Interlocked.Add(ref ackedPacket.Client.UnackedBytes, -ackedPacket.Buffer.DataLength);
199  
200 if (!pendingAcknowledgement.FromResend)
201 {
202 // Calculate the round-trip time for this packet and its ACK
203 int rtt = pendingAcknowledgement.RemoveTime - ackedPacket.TickCount;
204 if (rtt > 0)
205 ackedPacket.Client.UpdateRoundTrip(rtt);
206 }
207 }
208 else
209 {
210 //m_log.WarnFormat("[UNACKED PACKET COLLECTION]: Could not find packet with sequence number {0} to ack", pendingAcknowledgement.SequenceNumber);
211 }
212 }
213 }
214  
215 uint pendingRemove;
216 while(m_pendingRemoves.TryDequeue(out pendingRemove))
217 {
218 OutgoingPacket removedPacket;
219 if (m_packets.TryGetValue(pendingRemove, out removedPacket))
220 {
221 if (removedPacket != null)
222 {
223 m_packets.Remove(pendingRemove);
224  
225 // Update stats
226 Interlocked.Add(ref removedPacket.Client.UnackedBytes, -removedPacket.Buffer.DataLength);
227 }
228 }
229 }
230 }
231 }
232 }