common functions:

tac_connect -
  initiate connect to tacacs server
  return struct session* value

  struct session* 
  tac_connect(	const char *peer,     - IP address of TACACS+ server
		int timeout,          - connection timeout (sec)
		const char *key,      - MD5 key
		int port)             - port, if 0 its set to 49

tac_close -
  close connection from server
  tac_close(struct session *session);	



authentication

  authentication scene consists several questions/answers between
  client and server

  --------------------------------------------------------------------
  Example:  - simple ascii login check
     You can see it in /samples/tac_authen_c.c
  --------------------------------------------------------------------

  functions:

   int 
   tac_authen_send_start (
	 struct session *session,
	 const char *port,
	 const char *username,
	 int type,
	 const char *data
   )
   Where:
       session - session identificator from tac_connect
       port - string with port name
       username - username
       type - type of authentication
	   TACACS_ENABLE_REQUEST  1     Enable Requests
	   TACACS_ASCII_LOGIN     2     Inbound ASCII Login
	   TACACS_PAP_LOGIN       3     Inbound PAP Login
	   TACACS_CHAP_LOGIN      4     Inbound CHAP login
	   TACACS_ARAP_LOGIN      5     Inbound ARAP login
	   TACACS_PAP_OUT         6     Outbound PAP request
	   TACACS_CHAP_OUT        7     Outbound CHAP request
	   TACACS_ASCII_ARAP_OUT  8     Outbound ASCII and ARAP request
	   TACACS_ASCII_CHPASS    9     ASCII change password request
	   TACACS_PPP_CHPASS      10    PPP change password request
	   TACACS_ARAP_CHPASS     11    ARAP change password request
	   TACACS_MSCHAP_LOGIN    12    MS-CHAP inbound login
	   TACACS_MSCHAP_OUT      13    MS-CHAP outbound login
       data - string, that transmit to server
    Return: 0 - fail   1 - success

   int
   tac_authen_get_reply(session,serv_msg,data_msg);
      char server_msg[256];
      char data_msg[256];
   get reply from server
     returns status and message/data from server
	  TAC_PLUS_AUTHEN_STATUS_PASS     1
	  TAC_PLUS_AUTHEN_STATUS_FAIL     2
	  TAC_PLUS_AUTHEN_STATUS_GETDATA  3
	  TAC_PLUS_AUTHEN_STATUS_GETUSER  4
	  TAC_PLUS_AUTHEN_STATUS_GETPASS  5
	  TAC_PLUS_AUTHEN_STATUS_RESTART  6
	  TAC_PLUS_AUTHEN_STATUS_ERROR    7
	  TAC_PLUS_AUTHEN_STATUS_FOLLOW   0x21

   int
   tac_authen_send_cont(
	      struct session *session,   - session
	      const char *user_msg,      - message to server
	      const char *data           - data to server
   )
   send continue packet to server


  if we are wish get login question from tacacs server,
  when we are need set <username> to "" (void)
      /samples/tac_authen_c.c

  if we are set username in tac_authen_send_start,
  then we are get response with password request string
      /samples/tac_authen_c2.c
