* Added a Basic DOS protection container/base object for the most common HTTP Server handlers. XMLRPC Handler, GenericHttpHandler and <Various>StreamHandler

* Applied the XmlRpcBasicDOSProtector.cs to the login service as both an example, and good practice.
* Applied the BaseStreamHandlerBasicDOSProtector.cs to the friends service as an example of the DOS Protector on StreamHandlers
* Added CircularBuffer, used for CPU and Memory friendly rate monitoring.
* DosProtector has 2 states, 1. Just Check for blocked users and check general velocity, 2. Track velocity per user,     It only jumps to 2 if it's getting a lot of requests, and state 1 is about as resource friendly as if it wasn't even there.

OpenSim/Framework/CircularBuffer.cs

@@ -0,0 +1,312 @@
+/*
+Copyright (c) 2012, Alex Regueiro 
+All rights reserved.
+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.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "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 COPYRIGHT HOLDER OR 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;
+using System.Collections.Generic;
+using System.Threading;
+
+namespace OpenSim.Framework
+{
+    public class CircularBuffer<T> : ICollection<T>, IEnumerable<T>, ICollection, IEnumerable
+    {
+        private int capacity;
+        private int size;
+        private int head;
+        private int tail;
+        private T[] buffer;
+
+        [NonSerialized()]
+        private object syncRoot;
+
+        public CircularBuffer(int capacity)
+            : this(capacity, false)
+        {
+        }
+
+        public CircularBuffer(int capacity, bool allowOverflow)
+        {
+            if (capacity < 0)
+                throw new ArgumentException("Needs to have at least 1","capacity");
+
+            this.capacity = capacity;
+            size = 0;
+            head = 0;
+            tail = 0;
+            buffer = new T[capacity];
+            AllowOverflow = allowOverflow;
+        }
+
+        public bool AllowOverflow
+        {
+            get;
+            set;
+        }
+
+        public int Capacity
+        {
+            get { return capacity; }
+            set
+            {
+                if (value == capacity)
+                    return;
+
+                if (value < size)
+                    throw new ArgumentOutOfRangeException("value","Capacity is too small.");
+
+                var dst = new T[value];
+                if (size > 0)
+                    CopyTo(dst);
+                buffer = dst;
+
+                capacity = value;
+            }
+        }
+
+        public int Size
+        {
+            get { return size; }
+        }
+
+        public bool Contains(T item)
+        {
+            int bufferIndex = head;
+            var comparer = EqualityComparer<T>.Default;
+            for (int i = 0; i < size; i++, bufferIndex++)
+            {
+                if (bufferIndex == capacity)
+                    bufferIndex = 0;
+
+                if (item == null && buffer[bufferIndex] == null)
+                    return true;
+                else if ((buffer[bufferIndex] != null) &&
+                    comparer.Equals(buffer[bufferIndex], item))
+                    return true;
+            }
+
+            return false;
+        }
+
+        public void Clear()
+        {
+            size = 0;
+            head = 0;
+            tail = 0;
+        }
+
+        public int Put(T[] src)
+        {
+            return Put(src, 0, src.Length);
+        }
+
+        public int Put(T[] src, int offset, int count)
+        {
+            if (!AllowOverflow && count > capacity - size)
+                throw new InvalidOperationException("Buffer Overflow");
+
+            int srcIndex = offset;
+            for (int i = 0; i < count; i++, tail++, srcIndex++)
+            {
+                if (tail == capacity)
+                    tail = 0;
+                buffer[tail] = src[srcIndex];
+            }
+            size = Math.Min(size + count, capacity);
+            return count;
+        }
+
+        public void Put(T item)
+        {
+            if (!AllowOverflow && size == capacity)
+                throw new InvalidOperationException("Buffer Overflow");
+
+            buffer[tail] = item;
+            if (++tail == capacity)
+                tail = 0;
+            size++;
+        }
+
+        public void Skip(int count)
+        {
+            head += count;
+            if (head >= capacity)
+                head -= capacity;
+        }
+
+        public T[] Get(int count)
+        {
+            var dst = new T[count];
+            Get(dst);
+            return dst;
+        }
+
+        public int Get(T[] dst)
+        {
+            return Get(dst, 0, dst.Length);
+        }
+
+        public int Get(T[] dst, int offset, int count)
+        {
+            int realCount = Math.Min(count, size);
+            int dstIndex = offset;
+            for (int i = 0; i < realCount; i++, head++, dstIndex++)
+            {
+                if (head == capacity)
+                    head = 0;
+                dst[dstIndex] = buffer[head];
+            }
+            size -= realCount;
+            return realCount;
+        }
+
+        public T Get()
+        {
+            if (size == 0)
+                throw new InvalidOperationException("Buffer Empty");
+
+            var item = buffer[head];
+            if (++head == capacity)
+                head = 0;
+            size--;
+            return item;
+        }
+
+        public void CopyTo(T[] array)
+        {
+            CopyTo(array, 0);
+        }
+
+        public void CopyTo(T[] array, int arrayIndex)
+        {
+            CopyTo(0, array, arrayIndex, size);
+        }
+
+        public void CopyTo(int index, T[] array, int arrayIndex, int count)
+        {
+            if (count > size)
+                throw new ArgumentOutOfRangeException("count", "Count Too Large");
+
+            int bufferIndex = head;
+            for (int i = 0; i < count; i++, bufferIndex++, arrayIndex++)
+            {
+                if (bufferIndex == capacity)
+                    bufferIndex = 0;
+                array[arrayIndex] = buffer[bufferIndex];
+            }
+        }
+
+        public IEnumerator<T> GetEnumerator()
+        {
+            int bufferIndex = head;
+            for (int i = 0; i < size; i++, bufferIndex++)
+            {
+                if (bufferIndex == capacity)
+                    bufferIndex = 0;
+
+                yield return buffer[bufferIndex];
+            }
+        }
+
+        public T[] GetBuffer()
+        {
+            return buffer;
+        }
+
+        public T[] ToArray()
+        {
+            var dst = new T[size];
+            CopyTo(dst);
+            return dst;
+        }
+
+        #region ICollection<T> Members
+
+        int ICollection<T>.Count
+        {
+            get { return Size; }
+        }
+
+        bool ICollection<T>.IsReadOnly
+        {
+            get { return false; }
+        }
+
+        void ICollection<T>.Add(T item)
+        {
+            Put(item);
+        }
+
+        bool ICollection<T>.Remove(T item)
+        {
+            if (size == 0)
+                return false;
+
+            Get();
+            return true;
+        }
+
+        #endregion
+
+        #region IEnumerable<T> Members
+
+        IEnumerator<T> IEnumerable<T>.GetEnumerator()
+        {
+            return GetEnumerator();
+        }
+
+        #endregion
+
+        #region ICollection Members
+
+        int ICollection.Count
+        {
+            get { return Size; }
+        }
+
+        bool ICollection.IsSynchronized
+        {
+            get { return false; }
+        }
+
+        object ICollection.SyncRoot
+        {
+            get
+            {
+                if (syncRoot == null)
+                    Interlocked.CompareExchange(ref syncRoot, new object(), null);
+                return syncRoot;
+            }
+        }
+
+        void ICollection.CopyTo(Array array, int arrayIndex)
+        {
+            CopyTo((T[])array, arrayIndex);
+        }
+
+        #endregion
+
+        #region IEnumerable Members
+
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            return (IEnumerator)GetEnumerator();
+        }
+
+        #endregion
+    }
+}