opensim-development – Rev 1
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/*
* 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;
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;
}
}
/// <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(ackedPacket.Buffer.DataLength);
// 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]: 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);
}
}
}
}
}
}
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