Stop it being possible for an agent to teleport back to its source region before the source region has finished cleaning up old agent data and structures.

If this is allowed, then the client usually gets forcibly logged out and data structures might be put into bad states.
To prevent this, the binary state machine of EMT.m_agentsInTransit is replaced with a 4 state machine (Preparing, Transferring, ReceivedAtDestination, CleaningUp).
This is necessary because the source region needs to know when the destination region has received the user but a teleport back cannot happen until the source region has cleaned up.
Tested on standalone, grid and with v1 and v3 clients.

2 files changed, 4 insertions, 4 deletions

diff --git a/OpenSim/Region/Framework/Interfaces/IEntityTransferModule.cs b/OpenSim/Region/Framework/Interfaces/IEntityTransferModule.cs
index 75c44d5..69be83e 100644
--- a/OpenSim/Region/Framework/Interfaces/IEntityTransferModule.cs
+++ b/OpenSim/Region/Framework/Interfaces/IEntityTransferModule.cs
@@ -77,8 +77,8 @@ namespace OpenSim.Region.Framework.Interfaces
         /// <summary>
         /// Show whether the given agent is being teleported.
         /// </summary>
-        /// <returns>true if the agent is in the process of being teleported, false otherwise.</returns>
         /// <param name='id'>The agent ID</para></param>
+        /// <returns>true if the agent is in the process of being teleported, false otherwise.</returns>
         bool IsInTransit(UUID id);        
 
         bool Cross(ScenePresence agent, bool isFlying);
diff --git a/OpenSim/Region/Framework/Scenes/Scene.cs b/OpenSim/Region/Framework/Scenes/Scene.cs
index 755b1e6..98a75e4 100644
--- a/OpenSim/Region/Framework/Scenes/Scene.cs
+++ b/OpenSim/Region/Framework/Scenes/Scene.cs
@@ -5212,10 +5212,10 @@ namespace OpenSim.Region.Framework.Scenes
         {
             if (EntityTransferModule.IsInTransit(agentID))
             {
-                reason = "Agent is already in transit on this region";
+                reason = "Agent is still in transit from this region";
 
-                m_log.DebugFormat(
-                    "[SCENE]: Denying agent {0} entry into {1} since region already has them registered as in transit",
+                m_log.WarnFormat(
+                    "[SCENE]: Denying agent {0} entry into {1} since region still has them registered as in transit",
                     agentID, RegionInfo.RegionName);
 
                 return false;