libtelnet.h man page

libtelnet.h — libtelnet — TELNET protocol handling library

Synopsis

#include <stdarg.h>

Data Structures

struct telnet_environ_t

union telnet_event_t

struct telnet_event_t::data_t

struct telnet_event_t::error_t

struct telnet_event_t::iac_t

struct telnet_event_t::negotiate_t

struct telnet_event_t::subnegotiate_t

struct telnet_event_t::zmp_t

struct telnet_event_t::ttype_t

struct telnet_event_t::compress_t

struct telnet_event_t::environ_t

struct telnet_event_t::mssp_t

struct telnet_telopt_t

Macros

#define TELNET_GNU_PRINTF(f, a)

#define TELNET_GNU_SENTINEL

#define telnet_finish_sb(telnet) telnet_iac((telnet), TELNET_SE)
Finish a sub-negotiation command.
#define telnet_finish_newenviron(telnet) telnet_finish_sb((telnet))
Finish a NEW-ENVIRON command.
#define telnet_finish_zmp(telnet) telnet_finish_sb((telnet))
Finish a ZMP command.

Telnet commands

#define TELNET_IAC 255

#define TELNET_DONT 254

#define TELNET_DO 253

#define TELNET_WONT 252

#define TELNET_WILL 251

#define TELNET_SB 250

#define TELNET_GA 249

#define TELNET_EL 248

#define TELNET_EC 247

#define TELNET_AYT 246

#define TELNET_AO 245

#define TELNET_IP 244

#define TELNET_BREAK 243

#define TELNET_DM 242

#define TELNET_NOP 241

#define TELNET_SE 240

#define TELNET_EOR 239

#define TELNET_ABORT 238

#define TELNET_SUSP 237

#define TELNET_EOF 236

Telnet option values.

#define TELNET_TELOPT_BINARY 0

#define TELNET_TELOPT_ECHO 1

#define TELNET_TELOPT_RCP 2

#define TELNET_TELOPT_SGA 3

#define TELNET_TELOPT_NAMS 4

#define TELNET_TELOPT_STATUS 5

#define TELNET_TELOPT_TM 6

#define TELNET_TELOPT_RCTE 7

#define TELNET_TELOPT_NAOL 8

#define TELNET_TELOPT_NAOP 9

#define TELNET_TELOPT_NAOCRD 10

#define TELNET_TELOPT_NAOHTS 11

#define TELNET_TELOPT_NAOHTD 12

#define TELNET_TELOPT_NAOFFD 13

#define TELNET_TELOPT_NAOVTS 14

#define TELNET_TELOPT_NAOVTD 15

#define TELNET_TELOPT_NAOLFD 16

#define TELNET_TELOPT_XASCII 17

#define TELNET_TELOPT_LOGOUT 18

#define TELNET_TELOPT_BM 19

#define TELNET_TELOPT_DET 20

#define TELNET_TELOPT_SUPDUP 21

#define TELNET_TELOPT_SUPDUPOUTPUT 22

#define TELNET_TELOPT_SNDLOC 23

#define TELNET_TELOPT_TTYPE 24

#define TELNET_TELOPT_EOR 25

#define TELNET_TELOPT_TUID 26

#define TELNET_TELOPT_OUTMRK 27

#define TELNET_TELOPT_TTYLOC 28

#define TELNET_TELOPT_3270REGIME 29

#define TELNET_TELOPT_X3PAD 30

#define TELNET_TELOPT_NAWS 31

#define TELNET_TELOPT_TSPEED 32

#define TELNET_TELOPT_LFLOW 33

#define TELNET_TELOPT_LINEMODE 34

#define TELNET_TELOPT_XDISPLOC 35

#define TELNET_TELOPT_ENVIRON 36

#define TELNET_TELOPT_AUTHENTICATION 37

#define TELNET_TELOPT_ENCRYPT 38

#define TELNET_TELOPT_NEW_ENVIRON 39

#define TELNET_TELOPT_MSSP 70

#define TELNET_TELOPT_COMPRESS2 86

#define TELNET_TELOPT_ZMP 93

#define TELNET_TELOPT_EXOPL 255

#define TELNET_TELOPT_MCCP2 86

Protocol codes for TERMINAL-TYPE commands.

#define TELNET_TTYPE_IS 0

#define TELNET_TTYPE_SEND 1

Protocol codes for NEW-ENVIRON/ENVIRON commands.

#define TELNET_ENVIRON_IS 0

#define TELNET_ENVIRON_SEND 1

#define TELNET_ENVIRON_INFO 2

#define TELNET_ENVIRON_VAR 0

#define TELNET_ENVIRON_VALUE 1

#define TELNET_ENVIRON_ESC 2

#define TELNET_ENVIRON_USERVAR 3

Protocol codes for MSSP commands.

#define TELNET_MSSP_VAR 1

#define TELNET_MSSP_VAL 2

Telnet state tracker flags.

#define TELNET_FLAG_PROXY (1<<0)

#define TELNET_PFLAG_DEFLATE (1<<7)

Typedefs

typedef struct telnet_t telnet_t

typedef union telnet_event_t telnet_event_t

typedef struct telnet_telopt_t telnet_telopt_t

typedef enum telnet_error_t telnet_error_t

typedef enum telnet_event_type_t telnet_event_type_t

typedef void(* telnet_event_handler_t) (telnet_t *telnet, telnet_event_t *event, void *user_data)
event handler

Enumerations

enum telnet_error_t { TELNET_EOK = 0, TELNET_EBADVAL, TELNET_ENOMEM, TELNET_EOVERFLOW, TELNET_EPROTOCOL, TELNET_ECOMPRESS }

enum telnet_event_type_t { TELNET_EV_DATA = 0, TELNET_EV_SEND, TELNET_EV_IAC, TELNET_EV_WILL, TELNET_EV_WONT, TELNET_EV_DO, TELNET_EV_DONT, TELNET_EV_SUBNEGOTIATION, TELNET_EV_COMPRESS, TELNET_EV_ZMP, TELNET_EV_TTYPE, TELNET_EV_ENVIRON, TELNET_EV_MSSP, TELNET_EV_WARNING, TELNET_EV_ERROR }

Functions

telnet_t * telnet_init (const telnet_telopt_t *telopts, telnet_event_handler_t eh, unsigned char flags, void *user_data)
Initialize a telnet state tracker.
void telnet_free (telnet_t *telnet)
Free up any memory allocated by a state tracker.
void telnet_recv (telnet_t *telnet, const char *buffer, size_t size)
Push a byte buffer into the state tracker.
void telnet_iac (telnet_t *telnet, unsigned char cmd)
Send a telnet command.
void telnet_negotiate (telnet_t *telnet, unsigned char cmd, unsigned char opt)
Send negotiation command.
void telnet_send (telnet_t *telnet, const char *buffer, size_t size)

void telnet_begin_sb (telnet_t *telnet, unsigned char telopt)
Begin a sub-negotiation command.
void telnet_subnegotiation (telnet_t *telnet, unsigned char telopt, const char *buffer, size_t size)
Shortcut for sending a complete subnegotiation buffer.
void telnet_begin_compress2 (telnet_t *telnet)
Begin sending compressed data.
int telnet_printf (telnet_t *telnet, const char *fmt,...) TELNET_GNU_PRINTF(2
Send formatted data.
int int telnet_vprintf (telnet_t *telnet, const char *fmt, va_list va)
Send formatted data.
int telnet_raw_printf (telnet_t *telnet, const char *fmt,...) TELNET_GNU_PRINTF(2
Send formatted data (no newline escaping).
int int telnet_raw_vprintf (telnet_t *telnet, const char *fmt, va_list va)
Send formatted data (no newline escaping).
void telnet_begin_newenviron (telnet_t *telnet, unsigned char type)
Begin a new set of NEW-ENVIRON values to request or send.
void telnet_newenviron_value (telnet_t *telnet, unsigned char type, const char *string)
Send a NEW-ENVIRON variable name or value.
void telnet_ttype_send (telnet_t *telnet)
Send the TERMINAL-TYPE SEND command.
void telnet_ttype_is (telnet_t *telnet, const char *ttype)
Send the TERMINAL-TYPE IS command.
void telnet_send_zmp (telnet_t *telnet, size_t argc, const char **argv)
Send a ZMP command.
void telnet_send_zmpv (telnet_t *telnet,...) TELNET_GNU_SENTINEL
Send a ZMP command.
void telnet_send_vzmpv (telnet_t *telnet, va_list va)
Send a ZMP command.
void telnet_begin_zmp (telnet_t *telnet, const char *cmd)
Begin sending a ZMP command.
void telnet_zmp_arg (telnet_t *telnet, const char *arg)
Send a ZMP command argument.

Detailed Description

libtelnet - TELNET protocol handling library

SUMMARY:

libtelnet is a library for handling the TELNET protocol. It includes routines for parsing incoming data from a remote peer as well as formatting data to send to the remote peer.

libtelnet uses a callback-oriented API, allowing application-specific handling of various events. The callback system is also used for buffering outgoing protocol data, allowing the application to maintain control over the actual socket connection.

Features supported include the full TELNET protocol, Q-method option negotiation, ZMP, MCCP2, MSSP, and NEW-ENVIRON.

CONFORMS TO:

RFC854 - http://www.faqs.org/rfcs/rfc854.html RFC855 - http://www.faqs.org/rfcs/rfc855.html RFC1091 - http://www.faqs.org/rfcs/rfc1091.html RFC1143 - http://www.faqs.org/rfcs/rfc1143.html RFC1408 - http://www.faqs.org/rfcs/rfc1408.html RFC1572 - http://www.faqs.org/rfcs/rfc1572.html

LICENSE:

The author or authors of this code dedicate any and all copyright interest in this code to the public domain. We make this dedication for the benefit of the public at large and to the detriment of our heirs and successors. We intend this dedication to be an overt act of relinquishment in perpetuity of all present and future rights to this code under copyright law.

Version:

0.20

Author:

Sean Middleditch sean@sourcemud.org

Macro Definition Documentation

#define TELNET_ENVIRON_IS 0

NEW-ENVIRON/ENVIRON codes.

#define telnet_finish_newenviron(telnet) telnet_finish_sb((telnet))

Finish a NEW-ENVIRON command. This must be called after a call to telnet_begin_newenviron() to finish a NEW-ENVIRON variable list.

Parameters:

telnet Telnet state tracker object.

#define telnet_finish_sb(telnet) telnet_iac((telnet), TELNET_SE)

Finish a sub-negotiation command. This must be called after a call to telnet_begin_sb() to finish a sub-negotiation command.

Parameters:

telnet Telnet state tracker object.

#define telnet_finish_zmp(telnet) telnet_finish_sb((telnet))

Finish a ZMP command. This must be called after a call to telnet_begin_zmp() to finish a ZMP argument list.

Parameters:

telnet Telnet state tracker object.

#define TELNET_FLAG_PROXY (1<<0)

Control behavior of telnet state tracker.

#define TELNET_GNU_PRINTF(f, a)

internal helper

#define TELNET_GNU_SENTINEL

internal helper

#define TELNET_IAC 255

Telnet commands and special values.

#define TELNET_MSSP_VAR 1

MSSP codes.

#define TELNET_TELOPT_BINARY 0

Telnet options.

#define TELNET_TTYPE_IS 0

TERMINAL-TYPE codes.

Typedef Documentation

typedef enum telnet_error_t telnet_error_t

Error code type.

typedef void(* telnet_event_handler_t) (telnet_t *telnet, telnet_event_t *event, void *user_data)

event handler This is the type of function that must be passed to telnet_init() when creating a new telnet object. The function will be invoked once for every event generated by the libtelnet protocol parser.

Parameters:

telnet The telnet object that generated the event
event Event structure with details about the event
user_data User-supplied pointer

typedef union telnet_event_t telnet_event_t

Telnet event object type.

typedef enum telnet_event_type_t telnet_event_type_t

Telnet event type.

typedef struct telnet_t telnet_t

Telnet state tracker object type.

typedef struct telnet_telopt_t telnet_telopt_t

Telnet option table element type.

Enumeration Type Documentation

enum telnet_error_t

error codes

Enumerator

TELNET_EOK
no error
TELNET_EBADVAL
invalid parameter, or API misuse
TELNET_ENOMEM
memory allocation failure
TELNET_EOVERFLOW
data exceeds buffer size
TELNET_EPROTOCOL
invalid sequence of special bytes
TELNET_ECOMPRESS
error handling compressed streams

enum telnet_event_type_t

event codes

Enumerator

TELNET_EV_DATA
raw text data has been received
TELNET_EV_SEND
data needs to be sent to the peer
TELNET_EV_IAC
generic IAC code received
TELNET_EV_WILL
WILL option negotiation received
TELNET_EV_WONT
WONT option neogitation received
TELNET_EV_DO
DO option negotiation received
TELNET_EV_DONT
DONT option negotiation received
TELNET_EV_SUBNEGOTIATION
sub-negotiation data received
TELNET_EV_COMPRESS
compression has been enabled
TELNET_EV_ZMP
ZMP command has been received
TELNET_EV_TTYPE
TTYPE command has been received
TELNET_EV_ENVIRON
ENVIRON command has been received
TELNET_EV_MSSP
MSSP command has been received
TELNET_EV_WARNING
recoverable error has occured
TELNET_EV_ERROR
non-recoverable error has occured

Function Documentation

void telnet_begin_compress2 (telnet_t * telnet)

Begin sending compressed data. This function will begein sending data using the COMPRESS2 option, which enables the use of zlib to compress data sent to the client. The client must offer support for COMPRESS2 with option negotiation, and zlib support must be compiled into libtelnet.

Only the server may call this command.

Parameters:

telnet Telnet state tracker object.

void telnet_begin_newenviron (telnet_t * telnet, unsigned char type)

Begin a new set of NEW-ENVIRON values to request or send. This function will begin the sub-negotiation block for sending or requesting NEW-ENVIRON values.

The telnet_finish_newenviron() macro must be called after this function to terminate the NEW-ENVIRON command.

Parameters:

telnet Telnet state tracker object.
type One of TELNET_ENVIRON_SEND, TELNET_ENVIRON_IS, or TELNET_ENVIRON_INFO.

void telnet_begin_sb (telnet_t * telnet, unsigned char telopt)

Begin a sub-negotiation command. Sends IAC SB followed by the telopt code. All following data sent will be part of the sub-negotiation, until telnet_finish_sb() is called.

Parameters:

telnet Telnet state tracker object.
telopt One of the TELNET_TELOPT_* values.

void telnet_begin_zmp (telnet_t * telnet, const char * cmd)

Begin sending a ZMP command.

Parameters:

telnet Telnet state tracker object.
cmd The first argument (command name) for the ZMP command.

void telnet_free (telnet_t * telnet)

Free up any memory allocated by a state tracker. This function must be called when a telnet state tracker is no longer needed (such as after the connection has been closed) to release any memory resources used by the state tracker.

Parameters:

telnet Telnet state tracker object.

void telnet_iac (telnet_t * telnet, unsigned char cmd)

Send a telnet command.

Parameters:

telnet Telnet state tracker object.
cmd Command to send.

telnet_t* telnet_init (const telnet_telopt_t * telopts, telnet_event_handler_t eh, unsigned char flags, void * user_data)

Initialize a telnet state tracker. This function initializes a new state tracker, which is used for all other libtelnet functions. Each connection must have its own telnet state tracker object.

Parameters:

telopts Table of TELNET options the application supports.
eh Event handler function called for every event.
flags 0 or TELNET_FLAG_PROXY.
user_data Optional data pointer that will be passsed to eh.

Returns:

Telent state tracker object.

void telnet_negotiate (telnet_t * telnet, unsigned char cmd, unsigned char opt)

Send negotiation command. Internally, libtelnet uses RFC1143 option negotiation rules. The negotiation commands sent with this function may be ignored if they are determined to be redundant.

Parameters:

telnet Telnet state tracker object.
cmd TELNET_WILL, TELNET_WONT, TELNET_DO, or TELNET_DONT.
opt One of the TELNET_TELOPT_* values.

void telnet_newenviron_value (telnet_t * telnet, unsigned char type, const char * string)

Send a NEW-ENVIRON variable name or value. This can only be called between calls to telnet_begin_newenviron() and telnet_finish_newenviron().

Parameters:

telnet Telnet state tracker object.
type One of TELNET_ENVIRON_VAR, TELNET_ENVIRON_USERVAR, or TELNET_ENVIRON_VALUE.
string Variable name or value.

int telnet_printf (telnet_t * telnet, const char * fmt, ...)

Send formatted data. This function is a wrapper around telnet_send(). It allows using printf-style formatting.

Additionally, this function will translate \r to the CR NUL construct and \n with CR LF, as well as automatically escaping IAC bytes like telnet_send().

Parameters:

telnet Telnet state tracker object.
fmt Format string.

Returns:

Number of bytes sent.

int telnet_raw_printf (telnet_t * telnet, const char * fmt, ...)

Send formatted data (no newline escaping). This behaves identically to telnet_printf(), except that the \r and \n characters are not translated. The IAC byte is still escaped as normal with telnet_send().

Parameters:

telnet Telnet state tracker object.
fmt Format string.

Returns:

Number of bytes sent.

int int telnet_raw_vprintf (telnet_t * telnet, const char * fmt, va_list va)

Send formatted data (no newline escaping). See telnet_raw_printf().

void telnet_recv (telnet_t * telnet, const char * buffer, size_t size)

Push a byte buffer into the state tracker. Passes one or more bytes to the telnet state tracker for protocol parsing. The byte buffer is most often going to be the buffer that recv() was called for while handling the connection.

Parameters:

telnet Telnet state tracker object.
buffer Pointer to byte buffer.
size Number of bytes pointed to by buffer.

void telnet_send (telnet_t * telnet, const char * buffer, size_t size)

Send non-command data (escapes IAC bytes).

Parameters:

telnet Telnet state tracker object.
buffer Buffer of bytes to send.
size Number of bytes to send.

void telnet_send_vzmpv (telnet_t * telnet, va_list va)

Send a ZMP command. See telnet_send_zmpv().

void telnet_send_zmp (telnet_t * telnet, size_t argc, const char ** argv)

Send a ZMP command.

Parameters:

telnet Telnet state tracker object.
argc Number of ZMP commands being sent.
argv Array of argument strings.

void telnet_send_zmpv (telnet_t * telnet, ...)

Send a ZMP command. Arguments are listed out in var-args style. After the last argument, a NULL pointer must be passed in as a sentinel value.

Parameters:

telnet Telnet state tracker object.

void telnet_subnegotiation (telnet_t * telnet, unsigned char telopt, const char * buffer, size_t size)

Shortcut for sending a complete subnegotiation buffer. Equivalent to: telnet_begin_sb(telnet, telopt); telnet_send(telnet, buffer, size); telnet_finish_sb(telnet);

Parameters:

telnet Telnet state tracker format.
telopt One of the TELNET_TELOPT_* values.
buffer Byte buffer for sub-negotiation data.
size Number of bytes to use for sub-negotiation data.

void telnet_ttype_is (telnet_t * telnet, const char * ttype)

Send the TERMINAL-TYPE IS command. Sends the sequence IAC TERMINAL-TYPE IS 'string'.

According to the RFC, the recipient of a TERMINAL-TYPE SEND shall send the next possible terminal-type the client supports. Upon sending the type, the client should switch modes to begin acting as the terminal type is just sent.

The server may continue sending TERMINAL-TYPE IS until it receives a terminal type is understands. To indicate to the server that it has reached the end of the available optoins, the client must send the last terminal type a second time. When the server receives the same terminal type twice in a row, it knows it has seen all available terminal types.

After the last terminal type is sent, if the client receives another TERMINAL-TYPE SEND command, it must begin enumerating the available terminal types from the very beginning. This allows the server to scan the available types for a preferred terminal type and, if none is found, to then ask the client to switch to an acceptable alternative.

Note that if the client only supports a single terminal type, then simply sending that one type in response to every SEND will satisfy the behavior requirements.

Parameters:

telnet Telnet state tracker object.
ttype Name of the terminal-type being sent.

void telnet_ttype_send (telnet_t * telnet)

Send the TERMINAL-TYPE SEND command. Sends the sequence IAC TERMINAL-TYPE SEND.

Parameters:

telnet Telnet state tracker object.

int int telnet_vprintf (telnet_t * telnet, const char * fmt, va_list va)

Send formatted data. See telnet_printf().

void telnet_zmp_arg (telnet_t * telnet, const char * arg)

Send a ZMP command argument.

Parameters:

telnet Telnet state tracker object.
arg Telnet argument string.

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