Stop a scene object from attempting to link with itself (which results in an exception and constant complaints in v3 viewers).

Aims to address http://opensimulator.org/mantis/view.php?id=5878

OpenSim/Region/Framework/Scenes/Scene.Inventory.cs

@@ -2170,7 +2170,24 @@ namespace OpenSim.Region.Framework.Scenes
             m_sceneGraph.DelinkObjects(parts);
         }
 
+        /// <summary>
+        /// Link the scene objects containing the indicated parts to a root object.
+        /// </summary>
+        /// <param name="client"></param>
+        /// <param name="parentPrimId">A root prim id of the object which will be the root prim of the resulting linkset.</param>
+        /// <param name="childPrimIds">A list of child prims for the objects that should be linked in.</param>
         public void LinkObjects(IClientAPI client, uint parentPrimId, List<uint> childPrimIds)
+        {
+            LinkObjects(client.AgentId, parentPrimId, childPrimIds);
+        }
+
+        /// <summary>
+        /// Link the scene objects containing the indicated parts to a root object.
+        /// </summary>
+        /// <param name="agentId">The ID of the user linking.</param>
+        /// <param name="parentPrimId">A root prim id of the object which will be the root prim of the resulting linkset.</param>
+        /// <param name="childPrimIds">A list of child prims for the objects that should be linked in.</param>
+        public void LinkObjects(UUID agentId, uint parentPrimId, List<uint> childPrimIds)
         {
             List<UUID> owners = new List<UUID>();
 
@@ -2183,7 +2200,7 @@ namespace OpenSim.Region.Framework.Scenes
                 return;
             }
 
-            if (!Permissions.CanLinkObject(client.AgentId, root.ParentGroup.RootPart.UUID))
+            if (!Permissions.CanLinkObject(agentId, root.ParentGroup.RootPart.UUID))
             {
                 m_log.DebugFormat("[LINK]: Refusing link. No permissions on root prim");
                 return;
@@ -2199,7 +2216,7 @@ namespace OpenSim.Region.Framework.Scenes
                 if (!owners.Contains(part.OwnerID))
                     owners.Add(part.OwnerID);
 
-                if (Permissions.CanLinkObject(client.AgentId, part.ParentGroup.RootPart.UUID))
+                if (Permissions.CanLinkObject(agentId, part.ParentGroup.RootPart.UUID))
                     children.Add(part);
             }
 

OpenSim/Region/Framework/Scenes/SceneGraph.cs

@@ -1662,6 +1662,10 @@ namespace OpenSim.Region.Framework.Scenes
                 {
                     SceneObjectGroup child = children[i].ParentGroup;
 
+                    // Don't try and add a group to itself - this will only cause severe problems later on.
+                    if (child == parentGroup)
+                        continue;
+
                     // Make sure no child prim is set for sale
                     // So that, on delink, no prims are unwittingly
                     // left for sale and sold off
@@ -1684,11 +1688,13 @@ namespace OpenSim.Region.Framework.Scenes
 
                 // We need to explicitly resend the newly link prim's object properties since no other actions
                 // occur on link to invoke this elsewhere (such as object selection)
+                if (childGroups.Count > 0)
+                {
                     parentGroup.RootPart.CreateSelected = true;
                     parentGroup.TriggerScriptChangedEvent(Changed.LINK);
                     parentGroup.HasGroupChanged = true;
                     parentGroup.ScheduleGroupForFullUpdate();
-                
+                }
             }
             finally
             {

OpenSim/Region/Framework/Scenes/SceneObjectGroup.cs

@@ -1961,6 +1961,10 @@ namespace OpenSim.Region.Framework.Scenes
 //                "[SCENE OBJECT GROUP]: Linking group with root part {0}, {1} to group with root part {2}, {3}",
 //                objectGroup.RootPart.Name, objectGroup.RootPart.UUID, RootPart.Name, RootPart.UUID);
 
+            // Linking to ourselves is not a valid operation.
+            if (objectGroup == this)
+                return;
+
             SceneObjectPart linkPart = objectGroup.m_rootPart;
 
             Vector3 oldGroupPosition = linkPart.GroupPosition;

OpenSim/Region/Framework/Scenes/Tests/SceneObjectLinkingTests.cs

@@ -39,14 +39,31 @@ using log4net;
 
 namespace OpenSim.Region.Framework.Scenes.Tests
 {
-    /// <summary>
-    /// Linking tests
-    /// </summary>
     [TestFixture]
     public class SceneObjectLinkingTests
     {
         private static readonly ILog m_log = LogManager.GetLogger(MethodBase.GetCurrentMethod().DeclaringType);
 
+        /// <summary>
+        /// Links to self should be ignored.
+        /// </summary>
+        [Test]
+        public void TestLinkToSelf()
+        {
+            TestHelpers.InMethod();
+
+            UUID ownerId = TestHelpers.ParseTail(0x1);
+            int nParts = 3;
+
+            TestScene scene = SceneHelpers.SetupScene();
+            SceneObjectGroup sog1 = SceneHelpers.CreateSceneObject(nParts, ownerId, "TestLinkToSelf_", 0x10);
+            scene.AddSceneObject(sog1);
+            scene.LinkObjects(ownerId, sog1.LocalId, new List<uint>() { sog1.Parts[1].LocalId });
+//            sog1.LinkToGroup(sog1);
+
+            Assert.That(sog1.Parts.Length, Is.EqualTo(nParts));
+        }
+
         [Test]
         public void TestLinkDelink2SceneObjects()
         {