check for SSU packet size

SSUData.cpp

@@ -148,6 +148,11 @@ namespace transport
 			bool isLast = fragmentInfo & 0x010000; // bit 16	
 			uint8_t fragmentNum = fragmentInfo >> 17; // bits 23 - 17
 			LogPrint (eLogDebug, "SSU data fragment ", (int)fragmentNum, " of message ", msgID, " size=", (int)fragmentSize, isLast ? " last" : " non-last"); 		
+			if (fragmentSize >= SSU_V4_MAX_PACKET_SIZE)
+			{
+				LogPrint (eLogError, "Fragment size ", fragmentSize, "exceeds max SSU packet size");
+				return;
+			}
 
 			//  find message with msgID
 			I2NPMessage * msg = nullptr;