handle SSU I2NP header

I2NPProtocol.h

@@ -4,6 +4,7 @@
 #include <inttypes.h>
 #include <set>
 #include <string.h>
+#include "I2PEndian.h"
 #include "RouterInfo.h"
 
 namespace i2p
@@ -19,6 +20,12 @@ namespace i2p
 		uint8_t chks;
 	};	
 
+	struct I2NPHeaderShort
+	{
+		uint8_t typeID;
+		uint32_t shortExpiration;
+	};	
+
 	struct I2NPDatabaseStoreMsg
 	{
 		uint8_t key[32];
@@ -101,6 +108,19 @@ namespace i2p
 			len = offset + other.GetLength ();
 			return *this;
 		}	
+
+		// for SSU only
+		uint8_t * GetSSUHeader () { return buf + offset + sizeof(I2NPHeader) - sizeof(I2NPHeaderShort); };	
+		void FromSSU (uint32_t msgID) // we have received SSU message and convert it to regular
+		{
+			I2NPHeaderShort ssu = *(I2NPHeaderShort *)GetSSUHeader ();
+			I2NPHeader * header = GetHeader ();
+			header->typeID = ssu.typeID;
+			header->msgID = htobe32 (msgID);
+			header->expiration = htobe64 (be32toh (ssu.shortExpiration)*1000LL);
+			header->size = htobe16 (len - offset - sizeof (I2NPHeader));
+			header->chks = 0;
+		}
 	};	
 	I2NPMessage * NewI2NPMessage ();
 	void DeleteI2NPMessage (I2NPMessage * msg);

SSU.cpp

@@ -388,23 +388,31 @@ namespace ssu
 			{
 				auto it = m_IncomleteMessages.find (msgID);
 				if (it != m_IncomleteMessages.end ())
+				{
 					msg = it->second;
+					memcpy (msg->buf + msg->len, buf, fragmentSize);
+					msg->len += fragmentSize;
+				}
 				else
 					// TODO:
 					LogPrint ("Unexpected follow-on fragment ", fragmentNum, " of message ", msgID);	
 			}
 			else // first fragment
+			{
 				msg = NewI2NPMessage ();
+				memcpy (msg->GetSSUHeader (), buf, fragmentSize);
+				msg->len += fragmentSize - sizeof (I2NPHeaderShort);
+			}
+
 			if (msg)
-			{
-				memcpy (msg->buf + msg->len, buf, fragmentSize);
-				msg->len += fragmentSize;	
+			{					
 				if (!fragmentNum && !isLast)
 					m_IncomleteMessages[msgID] = msg;
 				if (isLast)
 				{
 					if (fragmentNum > 0)	
 						m_IncomleteMessages.erase (msgID);
+					msg->FromSSU (msgID);
 					i2p::HandleI2NPMessage (msg, false);	
 				}
 			}