save out-of-sequence fragments

SSU.h

@@ -31,7 +31,6 @@ namespace ssu
 	};
 #pragma pack()
 
-	const size_t SSU_MTU = 1484;
 	const int SSU_CONNECT_TIMEOUT = 5; // 5 seconds
 	const int SSU_TERMINATION_TIMEOUT = 330; // 5.5 minutes
 

SSUData.cpp

@@ -82,55 +82,73 @@ namespace ssu
 			bool isLast = fragmentInfo & 0x010000; // bit 16	
 			uint8_t fragmentNum = fragmentInfo >> 17; // bits 23 - 17
 			LogPrint ("SSU data fragment ", (int)fragmentNum, " of message ", msgID, " size=", (int)fragmentSize, isLast ? " last" : " non-last"); 		
+
+			//  find message with msgID
 			I2NPMessage * msg = nullptr;
-			if (fragmentNum > 0) // follow-up fragment
-			{
+			IncompleteMessage * incompleteMessage = nullptr;
 			auto it = m_IncomleteMessages.find (msgID);
 			if (it != m_IncomleteMessages.end ()) 
 			{	
-					if (fragmentNum == it->second->nextFragmentNum)
+				// message exists
+				incompleteMessage = it->second;
+				msg = incompleteMessage->msg;
+			}	
+			else
+			{
+				// create new message
+				msg = NewI2NPMessage ();
+				msg->len -= sizeof (I2NPHeaderShort);
+				incompleteMessage = new IncompleteMessage (msg);
+				m_IncomleteMessages[msgID] = incompleteMessage;
+			}	
+
+			// handle current fragment
+			if (fragmentNum == incompleteMessage->nextFragmentNum)
 			{
 				// expected fragment
-						msg = it->second->msg;
 				memcpy (msg->buf + msg->len, buf, fragmentSize);
 				msg->len += fragmentSize;
-						it->second->nextFragmentNum++;
+				incompleteMessage->nextFragmentNum++;
+				if (!isLast && !incompleteMessage->savedFragments.empty ())
+				{
+					// try saved fragments
+					for (auto it1 = incompleteMessage->savedFragments.begin (); it1 != incompleteMessage->savedFragments.end ();)
+					{
+						auto savedFragment = *it1;
+						if (savedFragment->fragmentNum == incompleteMessage->nextFragmentNum)
+						{
+							memcpy (msg->buf + msg->len, savedFragment->buf, savedFragment->len);
+							msg->len += savedFragment->len;
+							isLast = savedFragment->isLast;
+							incompleteMessage->nextFragmentNum++;
+							incompleteMessage->savedFragments.erase (it1++);
+							delete savedFragment;
 						}
-					else if (fragmentNum < it->second->nextFragmentNum)
-						// duplicate fragment
-						LogPrint ("Duplicate fragment ", (int)fragmentNum, " of message ", msgID, ". Ignored");	
 						else
-					{
-						// missing fragment
-						LogPrint ("Missing fragments from ", it->second->nextFragmentNum, " to ", fragmentNum - 1, " of message ", msgID);	
-						//TODO
+							break;
 					}	
- 						
-					if (isLast)
-					{
-						if (!msg)	
-							DeleteI2NPMessage (it->second->msg);
-						delete it->second;
-						m_IncomleteMessages.erase (it);
 				}	
 			}	
 			else
-					// TODO:
-					LogPrint ("Unexpected follow-on fragment ", (int)fragmentNum, " of message ", msgID);	
-			}
-			else // first fragment
 			{	
-				msg = NewI2NPMessage ();
-				memcpy (msg->GetSSUHeader (), buf, fragmentSize);
-				msg->len += fragmentSize - sizeof (I2NPHeaderShort);
+				if (fragmentNum < incompleteMessage->nextFragmentNum)
+					// duplicate fragment
+					LogPrint ("Duplicate fragment ", (int)fragmentNum, " of message ", msgID, ". Ignored");	
+				else
+				{
+					// missing fragment
+					LogPrint ("Missing fragments from ", (int)incompleteMessage->nextFragmentNum, " to ", fragmentNum - 1, " of message ", msgID);	
+					incompleteMessage->savedFragments.insert (new Fragment (fragmentNum, buf, fragmentSize, isLast));
+				}
+				isLast = false;
 			}	
 
-			if (msg)
-			{					
-				if (!fragmentNum && !isLast)
-					m_IncomleteMessages[msgID] = new IncompleteMessage (msg);
 			if (isLast)
 			{
+				// delete incomplete message
+				delete incompleteMessage;
+				m_IncomleteMessages.erase (msgID);				
+				// process message
 				SendMsgAck (msgID);
 				msg->FromSSU (msgID);
 				if (m_Session.GetState () == eSessionStateEstablished)
@@ -148,7 +166,6 @@ namespace ssu
 					DeleteI2NPMessage (msg);
 				}	
 			}				
-			}
 			buf += fragmentSize;
 		}	
 	}

SSUData.h

@@ -2,8 +2,10 @@
 #define SSU_DATA_H__
 
 #include <inttypes.h>
+#include <string.h>
 #include <map>
 #include <vector>
+#include <set>
 #include "I2NPProtocol.h"
 
 namespace i2p
@@ -11,6 +13,7 @@ namespace i2p
 namespace ssu
 {
 
+	const size_t SSU_MTU = 1484;
 	// data flags
 	const uint8_t DATA_FLAG_EXTENDED_DATA_INCLUDED = 0x02;
 	const uint8_t DATA_FLAG_WANT_REPLY = 0x04;
@@ -19,6 +22,34 @@ namespace ssu
 	const uint8_t DATA_FLAG_ACK_BITFIELDS_INCLUDED = 0x40;
 	const uint8_t DATA_FLAG_EXPLICIT_ACKS_INCLUDED = 0x80;	
 
+	struct Fragment
+	{
+		int fragmentNum, len;
+		bool isLast;
+		uint8_t buf[SSU_MTU];
+
+		Fragment (int n, const uint8_t * b, int l, bool last): 
+			fragmentNum (n), len (l), isLast (last) { memcpy (buf, b, len); };		
+	};	
+
+	struct FragmentCmp
+	{
+		bool operator() (const Fragment * f1, const Fragment * f2) const
+  		{	
+			return f1->fragmentNum < f2->fragmentNum; 
+		};
+	};	
+	
+	struct IncompleteMessage
+	{
+		I2NPMessage * msg;
+		int nextFragmentNum;	
+		std::set<Fragment *, FragmentCmp> savedFragments;
+		
+		IncompleteMessage (I2NPMessage * m): msg (m), nextFragmentNum (0) {};
+		~IncompleteMessage () { for (auto it: savedFragments) { delete it; }; };
+	};
+	
 	class SSUSession;
 	class SSUData
 	{
@@ -37,13 +68,7 @@ namespace ssu
 
 		private:
 
-			struct IncompleteMessage
-			{
-				I2NPMessage * msg;
-				uint8_t nextFragmentNum;	
 			
-				IncompleteMessage (I2NPMessage * m): msg (m), nextFragmentNum (1) {};
-			};
 
 			SSUSession& m_Session;
 			std::map<uint32_t, IncompleteMessage *> m_IncomleteMessages;