Stop LLUDPServer sending updates after object deletes by always queueing deletes

If an LL 1.23.5 client (and possibly earlier and later) receives an object update after a kill object packet, it leaves the deleted prim in the scene until client relog
This is possible in LLUDPServer if an object update packet is queued but a kill packet sent immediately.
Beyond invasive tracking of kill sending, most expedient solution is to always queue kills, so that they always arrive after updates.
In tests, this doesn't appear to affect performance.
There is probably still an issue present where an update packet might not be acked and then resent after the kill packet.

3 files changed, 28 insertions, 19 deletions

diff --git a/OpenSim/Region/ClientStack/LindenUDP/LLClientView.cs b/OpenSim/Region/ClientStack/LindenUDP/LLClientView.cs
index 7851c4d..f125822 100644
--- a/OpenSim/Region/ClientStack/LindenUDP/LLClientView.cs
+++ b/OpenSim/Region/ClientStack/LindenUDP/LLClientView.cs
@@ -3562,24 +3562,28 @@ namespace OpenSim.Region.ClientStack.LindenUDP
                 EntityUpdate update;
                 while (updatesThisCall < maxUpdates && m_entityUpdates.TryDequeue(out update))
                 {
-                    // Please do not remove this unless you can demonstrate on the OpenSim mailing list that a client
-                    // will never receive an update after a prim kill.  Even then, keeping the kill record may be a good
-                    // safety measure.
-                    //
-                    // Receiving updates after kills results in undeleteable prims that persist until relog and
-                    // currently occurs because prims can be deleted before all queued updates are sent.
-                    if (m_killRecord.Contains(update.Entity.LocalId))
-                    {
-//                        m_log.WarnFormat(
-//                            "[CLIENT]: Preventing full update for prim with local id {0} after client for user {1} told it was deleted",
-//                            update.Entity.LocalId, Name);
-                        continue;
-                    }
-
                     if (update.Entity is SceneObjectPart)
                     {
                         SceneObjectPart part = (SceneObjectPart)update.Entity;
 
+                        // Please do not remove this unless you can demonstrate on the OpenSim mailing list that a client
+                        // will never receive an update after a prim kill.  Even then, keeping the kill record may be a good
+                        // safety measure.
+                        //
+                        // If a Linden Lab 1.23.5 client (and possibly later and earlier) receives an object update
+                        // after a kill, it will keep displaying the deleted object until relog.  OpenSim currently performs
+                        // updates and kills on different threads with different scheduling strategies, hence this protection.
+                        // 
+                        // This doesn't appear to apply to child prims - a client will happily ignore these updates
+                        // after the root prim has been deleted.
+                        if (m_killRecord.Contains(part.LocalId))
+                        {
+        //                        m_log.WarnFormat(
+        //                            "[CLIENT]: Preventing update for prim with local id {0} after client for user {1} told it was deleted",
+        //                            part.LocalId, Name);
+                            continue;
+                        }                        
+                        
                         if (part.ParentGroup.IsAttachment && m_disableFacelights)
                         {
                             if (part.ParentGroup.RootPart.Shape.State != (byte)AttachmentPoint.LeftHand &&
diff --git a/OpenSim/Region/ClientStack/LindenUDP/LLUDPClient.cs b/OpenSim/Region/ClientStack/LindenUDP/LLUDPClient.cs
index 5bf36e6..e02783a 100644
--- a/OpenSim/Region/ClientStack/LindenUDP/LLUDPClient.cs
+++ b/OpenSim/Region/ClientStack/LindenUDP/LLUDPClient.cs
@@ -403,11 +403,12 @@ namespace OpenSim.Region.ClientStack.LindenUDP
         /// 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)
+        public bool EnqueueOutgoing(OutgoingPacket packet, bool forceQueue)
         {
             int category = (int)packet.Category;
 
@@ -416,14 +417,14 @@ namespace OpenSim.Region.ClientStack.LindenUDP
                 OpenSim.Framework.LocklessQueue<OutgoingPacket> queue = m_packetOutboxes[category];
                 TokenBucket bucket = m_throttleCategories[category];
 
-                if (bucket.RemoveTokens(packet.Buffer.DataLength))
+                if (!forceQueue && bucket.RemoveTokens(packet.Buffer.DataLength))
                 {
                     // Enough tokens were removed from the bucket, the packet will not be queued
                     return false;
                 }
                 else
                 {
-                    // Not enough tokens in the bucket, queue this packet
+                    // Force queue specified or not enough tokens in the bucket, queue this packet
                     queue.Enqueue(packet);
                     return true;
                 }
diff --git a/OpenSim/Region/ClientStack/LindenUDP/LLUDPServer.cs b/OpenSim/Region/ClientStack/LindenUDP/LLUDPServer.cs
index ff4abf8..e54cfc2 100644
--- a/OpenSim/Region/ClientStack/LindenUDP/LLUDPServer.cs
+++ b/OpenSim/Region/ClientStack/LindenUDP/LLUDPServer.cs
@@ -410,7 +410,11 @@ namespace OpenSim.Region.ClientStack.LindenUDP
 
             OutgoingPacket outgoingPacket = new OutgoingPacket(udpClient, buffer, category);
 
-            if (!outgoingPacket.Client.EnqueueOutgoing(outgoingPacket))
+            // 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 requestQueue = type == PacketType.KillObject;
+            if (!outgoingPacket.Client.EnqueueOutgoing(outgoingPacket, requestQueue))
                 SendPacketFinal(outgoingPacket);
 
             #endregion Queue or Send
@@ -503,7 +507,7 @@ namespace OpenSim.Region.ClientStack.LindenUDP
                     //Interlocked.Increment(ref Stats.ResentPackets);
 
                     // Requeue or resend the packet
-                    if (!outgoingPacket.Client.EnqueueOutgoing(outgoingPacket))
+                    if (!outgoingPacket.Client.EnqueueOutgoing(outgoingPacket, false))
                         SendPacketFinal(outgoingPacket);
                 }
             }