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General Version

Data structure and function description

• class ToaFetcher
  A subject class used to manage the acquisition and release of TOA.
• InitUpToaFetcher

1. Function description
   This function is used to initialize TOA fetcher.

   bool InitUpToaFetcher(char *ncard_ip_str, char *svr_ip_str, u_short svr_port[], u_short svr_port_num, u_short cache_secs=TIMER_CACHE_SECS)
   

2. Input parameters description

   • ncard_ip_str: This is used to identify the IP address string of the network interface, for example, 10.75.132.39. This is the NIC that communicates with the client.
     
   • svr_ip_str: The IP address string of the server, such as 10.75.132.39, used to filter TCP flows.
   • svr_port: The port list of the server, used to filter TCP flows. Up to three ports can be added. Either svr_port or port_range_ptr must be configured.
   • svr_port_num: The number of server ports.
   • port_range_ptr: The array of server port range pointers, where the elements are pointers pointing to a string. A port range string is in the format of 10001-10005, and up to three ranges can be added. This parameter is used to filter TCP flows. Either svr_port or port_range_ptr must be configured.
   • port_range_num: The number of port ranges of the server.
   • cache_secs: The length of cache in seconds. The default value is 15 seconds. For more information, see toa_fetcher.h: TIMER_CACHE_SECS. The TOA will no longer be saved after the cache expires.

3. Returned value

   • TRUE: Successfully created an additional thread to obtain TOA
   • FALSE: Failed to create an additional thread to obtain TOA

• FetchToaValue

1. Function description
   This function is used to get the TOA value. After the tcp-syn packet interacts, TOA can be obtained after 1 ms. Normally, a three-way handshake takes more than 1 ms.

   bool FetchToaValue(u_long fake_client_ip_addr, u_short fake_client_port, u_long &real_client_ip_addr, u_short &real_client_port)
   

2. Input parameters description

   • fake_client_ip_addr: The fake IP address of the client stored in network byte order and can be obtained from the opposite address returned by the accept function of the server.
   • fake_client_port: The fake port number of the client stored in network byte order and can be obtained from the opposite address returned by the accept function of the server.
   • real_client_ip_addr: The real IP address of the client stored in network byte order and can be obtained from TOA.
   • real_client_port: The real port number of the client stored in network byte order and can be obtained from TOA.

3. Returned value

   • TRUE: TOA obtained successfully.
   • FALSE: Failed to obtain TOA. Normally, the reason is TOA has been cleared because the cache expires.

• StopToaFetcher

1. Function description
   This function is used to stop TOA fetcher.

   void StopToaFetcher()
   

2. Input parameters description

-
3. Returned value
-

• GetFetcherStatus

1. Function description
   This function is used to obtain the Fetcher status.

   int GetFetcherStatus()
   

2. Input parameters description

-
3. Returned value
0: initial status. An instance will be in this status after it is created. During fetcher initialization, this status will remain unchanged. If an error occurs, -1 will be returned. If the execution succeeds, 1 will be returned.
-1: an exception occurs.
1: normal operation.

• FetchThreadHandler

1. Function description
   This function is used to obtain the TOA additional thread handler.

   HANDLE FetchThreadHandler()
   

2. Input parameters description

-
3. Returned value
The TOA additional thread handler. When ToaFetcher instance is terminated, this handler will be closed.

• FetchErrorInfo

1. Function description
   This function is used to obtain the error code.

   bool FetchErrorInfo(int* err_code_ptr, char* err_msg_ptr)
   

2. Input parameters description

   • err_code_ptr: An integer-type pointer to the error code, used to return the error code.
   • err_msg_ptr: A character-type pointer to a string buffer. It contains at least 50 bytes of data and is used to return the error message.

3. Returned value

   • TRUE: Obtained successfully.
   • FALSE: Failed to obtain.

Error codes

Example

• Initialize ToaFetcher:

  char ncard_ip_str[] = "1.1.1.1";
  char svr_ip_str[] = "1.1.1.1";
  char port_range[3][100] = {"10001-10005", "20001-20005", "30001-30005"};
  char* port_range_ptr[3] = {port_range[0], port_range[1], port_range[2]};
       u_short svr_port_list[3] = {1111, 2222, 3333};
       ToaFetcher inst = ToaFetcher();
       inst.InitUpToaFetcher((char*)ncard_ip_str, (char*)svr_ip_str, svr_port_list, 3);
  

• Obtain TOA:

  void GetToa(SOCKADDR_IN client_addr, ToaFetcher * toa_fetcher_ptr)
  {
  u_long fake_client_ip_addr = 0;
  u_short fake_client_port = 0;
  u_long real_client_ip_addr = 0;
  u_short real_client_port = 0;
  memcpy(&fake_client_ip_addr, &client_addr.sin_addr, 4);
  memcpy(&fake_client_port, &client_addr.sin_port, 2);
  bool ret = toa_fetcher_ptr->FetchToaValue(fake_client_ip_addr, fake_client_port, real_client_ip_addr, real_client_port);
  if(ret == FALSE){
    printf("No toa found\n");
  }else{
       //fpp: Custom print function
    fpp("real_client_ip_addr", &real_client_ip_addr, 4);    
  　fpp("real_client_port", &real_client_port, 2);
  }
  }
  

Go Version

TOA obtaining program obtains the real IP address from toa_win.exe through UDP communication.

Protocol format

• Request: | ID（4Bytes）| FakeIPAddress（4Bytes）| FakePort（2Bytes）|

The fields are described as follows:

• ID: The unique ID of the request and will be returned as it is in the response. It contains 4 bytes of data.

• FakeIPAddrss: The fake IP address of the client stored in the network byte order and can be obtained from the opposite address returned by the accept function of the server. It contains 4 bytes of data.

• FakePort: The fake port number of the client stored in the network byte order and can be obtained from the opposite address returned by the accept function of the server. It contains 2 bytes of data.

• Response: | ID（4Bytes）| Code（1Byte）| RealIPAddress（4Bytes）| RealPort（2Bytes）|

The fields are described as follows:

• ID: The unique ID of the request and is the same as that in the request. It contains 4 bytes of data.
• Code: It contains 1 byte of data. 0: real IP and port obtained successfully. 1: failed to obtain.
• RealIPAddress: If Code is 0, it indicates the real client IP address. It contains 4 bytes of data in network byte order.
• RealPort: If Code is 0, it indicates the real client port. It contains 2 bytes of data in network byte order.

Example

For more information, see demo.go. You can develop a TOA obtaining client on your own, or use the queryToa function in demo.go to obtain TOA.

1. Function description

   func queryToa(serverAddr string, fakeIp string, fakePort uint16)(int32, string, uint16)
   

2. Input parameters description

• serverAddr: The string-type service communication address of toa_win.exe in the format of 127.0.0.1:9999.
• fakeIp: the string-type fake IP address in the format of 1.2.3.4.
• fakePort: The uint16-type fake port in the format of 8899.

3. Returned value

• The first returned value: It is in int32 type and used to indicate the error code.
  • 0: Obtained successfully
  • -1: Failed to get TOA. This may happen if fakeIP or fakePort is incorrect or the cache has expired.
  • -2: Failed due to a network communication exception.
• The second returned value: It is in string type and will return the real IP if TOA is obtained successfully, otherwise an empty string is returned.
• The third returned value: It is in uint16 type and will return the real port if TOA is obtained successfully, otherwise 0 is returned.