1 files changed, 123 insertions, 0 deletions
diff --git a/Tools/Hazel-Networking/Hazel/Dtls/Record.cs b/Tools/Hazel-Networking/Hazel/Dtls/Record.cs
new file mode 100644
index 0000000..23eaa95
--- /dev/null
+++ b/Tools/Hazel-Networking/Hazel/Dtls/Record.cs
@@ -0,0 +1,123 @@
+namespace Hazel.Dtls
+{
+    /// <summary>
+    /// DTLS version constants
+    /// </summary>
+    public enum ProtocolVersion : ushort
+    {
+        /// <summary>
+        /// Use to obfuscate DTLS as regular UDP packets
+        /// </summary>
+        UDP = 0,
+
+        /// <summary>
+        /// DTLS 1.2
+        /// </summary>
+        DTLS1_2 = 0xFEFD,
+    }
+
+    /// <summary>
+    /// DTLS record content type
+    /// </summary>
+    public enum ContentType : byte
+    {
+        ChangeCipherSpec = 20,
+        Alert = 21,
+        Handshake = 22,
+        ApplicationData = 23,
+    }
+
+    /// <summary>
+    /// Encode/decode DTLS record header
+    /// </summary>
+    public struct Record
+    {
+        public ContentType ContentType;
+        public ProtocolVersion ProtocolVersion;
+        public ushort Epoch;
+        public ulong SequenceNumber;
+        public ushort Length;
+
+        public const int Size = 13;
+
+        /// <summary>
+        /// Parse a DTLS record from wire format
+        /// </summary>
+        /// <returns>True if we successfully parse the record header. Otherwise false</returns>
+        public static bool Parse(out Record record, ProtocolVersion? expectedProtocolVersion, ByteSpan span)
+        {
+            record = new Record();
+
+            if (span.Length < Size)
+            {
+                return false;
+            }
+
+            record.ContentType = (ContentType)span[0];
+            record.ProtocolVersion = (ProtocolVersion)span.ReadBigEndian16(1);
+            record.Epoch = span.ReadBigEndian16(3);
+            record.SequenceNumber = span.ReadBigEndian48(5);
+            record.Length = span.ReadBigEndian16(11);
+
+            if (expectedProtocolVersion.HasValue && record.ProtocolVersion != expectedProtocolVersion.Value)
+            {
+                return false;
+            }
+
+            return true;
+        }
+
+        /// <summary>
+        /// Encode a DTLS record to wire format
+        /// </summary>
+        public void Encode(ByteSpan span)
+        {
+            span[0] = (byte)this.ContentType;
+            span.WriteBigEndian16((ushort)this.ProtocolVersion, 1);
+            span.WriteBigEndian16(this.Epoch, 3);
+            span.WriteBigEndian48(this.SequenceNumber, 5);
+            span.WriteBigEndian16(this.Length, 11);
+        }
+    }
+
+    public struct ChangeCipherSpec
+    {
+        public const int Size = 1;
+
+        enum Value : byte
+        {
+            ChangeCipherSpec = 1,
+        }
+
+        /// <summary>
+        /// Parse a ChangeCipherSpec record from wire format
+        /// </summary>
+        /// <returns>
+        /// True if we successfully parse the ChangeCipherSpec
+        /// record. Otherwise, false.
+        /// </returns>
+        public static bool Parse(ByteSpan span)
+        {
+            if (span.Length != 1)
+            {
+                return false;
+            }
+
+            Value value = (Value)span[0];
+            if (value != Value.ChangeCipherSpec)
+            {
+                return false;
+            }
+
+            return true;
+        }
+
+        /// <summary>
+        /// Encode a ChangeCipherSpec record to wire format
+        /// </summary>
+        public static void Encode(ByteSpan span)
+        {
+            span[0] = (byte)Value.ChangeCipherSpec;
+        }
+    }
+}