From 1df06f459aa506ee3c60ef3b58bd5e5e5e4622c0 Mon Sep 17 00:00:00 2001
From: UbitUmarov <ajlduarte@sapo.pt>
Date: Wed, 4 Mar 2020 22:39:44 +0000
Subject: [PATCH] avoid duplicated udpbuffer free that may still happen

---
 OpenSim/Region/ClientStack/Linden/UDP/LLClientView.cs       | 4 +---
 OpenSim/Region/ClientStack/Linden/UDP/LLUDPServer.cs        | 3 +--
 OpenSim/Region/ClientStack/Linden/UDP/OpenSimUDPBase.cs     | 6 +++++-
 .../ClientStack/Linden/UDP/UnackedPacketCollection.cs       | 2 +-
 4 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/OpenSim/Region/ClientStack/Linden/UDP/LLClientView.cs b/OpenSim/Region/ClientStack/Linden/UDP/LLClientView.cs
index 83f5c4f4e9..0810071b4c 100755
--- a/OpenSim/Region/ClientStack/Linden/UDP/LLClientView.cs
+++ b/OpenSim/Region/ClientStack/Linden/UDP/LLClientView.cs
@@ -4831,11 +4831,9 @@ namespace OpenSim.Region.ClientStack.LindenUDP
             // because we are requeuing the list of updates. They will be resent in new packets
             // with the most recent state and priority.
             m_udpClient.NeedAcks.Remove(oPacket.SequenceNumber);
-            if(oPacket.Buffer == null)
+            if (oPacket.Buffer == null)
                 return;
 
-            m_udpClient.FreeUDPBuffer(oPacket.Buffer);
-
             // Count this as a resent packet since we are going to requeue all of the updates contained in it
             Interlocked.Increment(ref m_udpClient.PacketsResent);
 
diff --git a/OpenSim/Region/ClientStack/Linden/UDP/LLUDPServer.cs b/OpenSim/Region/ClientStack/Linden/UDP/LLUDPServer.cs
index b09ab9e9ce..414bbd4008 100755
--- a/OpenSim/Region/ClientStack/Linden/UDP/LLUDPServer.cs
+++ b/OpenSim/Region/ClientStack/Linden/UDP/LLUDPServer.cs
@@ -1188,8 +1188,7 @@ namespace OpenSim.Region.ClientStack.LindenUDP
             SyncSend(buffer);
 
             // Keep track of when this packet was sent out (right now)
-            int enow = Environment.TickCount & Int32.MaxValue;
-            Interlocked.Exchange(ref outgoingPacket.TickCount, enow);
+            Interlocked.Exchange(ref outgoingPacket.TickCount, Environment.TickCount & Int32.MaxValue);
 
             if (outgoingPacket.UnackedMethod == null)
                 FreeUDPBuffer(buffer);
diff --git a/OpenSim/Region/ClientStack/Linden/UDP/OpenSimUDPBase.cs b/OpenSim/Region/ClientStack/Linden/UDP/OpenSimUDPBase.cs
index 8b2f84f04a..a5d12d1c2f 100644
--- a/OpenSim/Region/ClientStack/Linden/UDP/OpenSimUDPBase.cs
+++ b/OpenSim/Region/ClientStack/Linden/UDP/OpenSimUDPBase.cs
@@ -192,6 +192,7 @@ namespace OpenMetaverse
                     m_udpBuffersPool[m_udpBuffersPoolPtr] = null;
                     m_udpBuffersPoolPtr--;
                     buf.RemoteEndPoint = remoteEndpoint;
+                    buf.DataLength = 0;
                     return buf;
                 }
             }
@@ -202,10 +203,13 @@ namespace OpenMetaverse
         {
             lock (m_udpBuffersPoolLock)
             {
+                if(buf.DataLength < 0)
+                    return; // avoid duplicated free that may still happen
+
                 if (m_udpBuffersPoolPtr < 999)
                 {
                     buf.RemoteEndPoint = null;
-                    buf.DataLength = 0;
+                    buf.DataLength = -1;
                     m_udpBuffersPoolPtr++;
                     m_udpBuffersPool[m_udpBuffersPoolPtr] = buf;
                 }
diff --git a/OpenSim/Region/ClientStack/Linden/UDP/UnackedPacketCollection.cs b/OpenSim/Region/ClientStack/Linden/UDP/UnackedPacketCollection.cs
index af5b2ae425..db937021df 100644
--- a/OpenSim/Region/ClientStack/Linden/UDP/UnackedPacketCollection.cs
+++ b/OpenSim/Region/ClientStack/Linden/UDP/UnackedPacketCollection.cs
@@ -215,7 +215,7 @@ namespace OpenSim.Region.ClientStack.LindenUDP
                 if (m_packets.TryGetValue(pendingRemove, out OutgoingPacket removedPacket))
                 {
                     m_packets.Remove(pendingRemove);
-                    if (removedPacket != null)
+                    if (removedPacket != null && removedPacket.Buffer != null)
                     {
                         // Update stats
                         Interlocked.Add(ref removedPacket.Client.UnackedBytes, -removedPacket.Buffer.DataLength);