A telnet library (including ipaccess-telnet)
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libtelnet/libtelnet.c

1177 lines
32 KiB

/*
* libtelnet - TELNET protocol handling library
*
* Sean Middleditch
* sean@sourcemud.org
*
* 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.
*/
#include <malloc.h>
#include <string.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <stdarg.h>
#if defined(HAVE_ALLOCA)
# include <alloca.h>
#endif
#if defined(HAVE_ZLIB)
# include <zlib.h>
#endif
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#include "libtelnet.h"
/* inlinable functions */
#if defined(__GNUC__) || __STDC_VERSION__ >= 199901L
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# define INLINE __inline__
#else
# define INLINE
#endif
/* telnet state codes */
enum telnet_state_t {
TELNET_STATE_DATA = 0,
TELNET_STATE_IAC,
TELNET_STATE_WILL,
TELNET_STATE_WONT,
TELNET_STATE_DO,
TELNET_STATE_DONT,
TELNET_STATE_SB,
TELNET_STATE_SB_DATA,
TELNET_STATE_SB_DATA_IAC
};
typedef enum telnet_state_t telnet_state_t;
/* telnet state tracker */
struct telnet_t {
/* user data */
void *ud;
/* telopt support table */
const telnet_telopt_t *telopts;
/* event handler */
telnet_event_handler_t eh;
#if defined(HAVE_ZLIB)
/* zlib (mccp2) compression */
z_stream *z;
#endif
/* RFC1143 option negotiation states */
struct telnet_rfc1143_t *q;
/* sub-request buffer */
char *buffer;
/* current size of the buffer */
size_t buffer_size;
/* current buffer write position (also length of buffer data) */
size_t buffer_pos;
/* current state */
enum telnet_state_t state;
/* option flags */
unsigned char flags;
/* current subnegotiation telopt */
unsigned char sb_telopt;
/* length of RFC1143 queue */
unsigned char q_size;
};
/* RFC1143 option negotiation state */
typedef struct telnet_rfc1143_t {
unsigned char telopt;
char us:4, him:4;
} telnet_rfc1143_t;
/* RFC1143 state names */
#define Q_NO 0
#define Q_YES 1
#define Q_WANTNO 2
#define Q_WANTYES 3
#define Q_WANTNO_OP 4
#define Q_WANTYES_OP 5
/* buffer sizes */
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static const size_t _buffer_sizes[] = { 0, 512, 2048, 8192, 16384, };
static const size_t _buffer_sizes_count = sizeof(_buffer_sizes) /
sizeof(_buffer_sizes[0]);
/* event dispatch helper */
static INLINE void _event(telnet_t *telnet, telnet_event_type_t type,
unsigned char command, unsigned char telopt,
const char *buffer, size_t size, const char **argv, size_t argc) {
telnet_event_t ev;
ev.argv = argv;
ev.argc = argc;
ev.buffer = buffer;
ev.size = size;
ev.type = type;
ev.command = command;
ev.telopt = telopt;
telnet->eh(telnet, &ev, telnet->ud);
}
/* error generation function */
static telnet_error_t _error(telnet_t *telnet, unsigned line,
const char* func, telnet_error_t err, int fatal, const char *fmt,
...) {
char buffer[512];
va_list va;
/* format error intro */
snprintf(buffer, sizeof(buffer), "%s:%u in %s: ", __FILE__, line, func);
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/* format informational text */
va_start(va, fmt);
vsnprintf(buffer + strlen(buffer), sizeof(buffer) - strlen(buffer),
fmt, va);
va_end(va);
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/* send error event to the user */
_event(telnet, fatal ? TELNET_EV_ERROR : TELNET_EV_WARNING, err,
0, buffer, strlen(buffer), 0, 0);
return err;
}
#if defined(HAVE_ZLIB)
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/* initialize the zlib box for a telnet box; if deflate is non-zero, it
* initializes zlib for delating (compression), otherwise for inflating
* (decompression). returns TELNET_EOK on success, something else on
* failure.
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*/
telnet_error_t _init_zlib(telnet_t *telnet, int deflate, int err_fatal) {
z_stream *z;
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int rs;
/* if compression is already enabled, fail loudly */
if (telnet->z != 0)
return _error(telnet, __LINE__, __func__, TELNET_EBADVAL,
err_fatal, "cannot initialize compression twice");
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/* allocate zstream box */
if ((z= (z_stream *)calloc(1, sizeof(z_stream))) == 0)
return _error(telnet, __LINE__, __func__, TELNET_ENOMEM, err_fatal,
"malloc() failed: %s", strerror(errno));
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/* initialize */
if (deflate) {
if ((rs = deflateInit(z, Z_DEFAULT_COMPRESSION)) != Z_OK) {
free(z);
return _error(telnet, __LINE__, __func__, TELNET_ECOMPRESS,
err_fatal, "deflateInit() failed: %s", zError(rs));
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}
telnet->flags |= TELNET_PFLAG_DEFLATE;
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} else {
if ((rs = inflateInit(z)) != Z_OK) {
free(z);
return _error(telnet, __LINE__, __func__, TELNET_ECOMPRESS,
err_fatal, "inflateInit() failed: %s", zError(rs));
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}
telnet->flags &= ~TELNET_PFLAG_DEFLATE;
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}
telnet->z = z;
return TELNET_EOK;
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}
#endif /* defined(HAVE_ZLIB) */
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/* push bytes out, compressing them first if need be */
static void _send(telnet_t *telnet, const char *buffer,
size_t size) {
#if defined(HAVE_ZLIB)
/* if we have a deflate (compression) zlib box, use it */
if (telnet->z != 0 && telnet->flags & TELNET_PFLAG_DEFLATE) {
char deflate_buffer[1024];
int rs;
/* initialize z state */
telnet->z->next_in = (unsigned char *)buffer;
telnet->z->avail_in = size;
telnet->z->next_out = (unsigned char *)deflate_buffer;
telnet->z->avail_out = sizeof(deflate_buffer);
/* deflate until buffer exhausted and all output is produced */
while (telnet->z->avail_in > 0 || telnet->z->avail_out == 0) {
/* compress */
if ((rs = deflate(telnet->z, Z_SYNC_FLUSH)) != Z_OK) {
_error(telnet, __LINE__, __func__, TELNET_ECOMPRESS, 1,
"deflate() failed: %s", zError(rs));
deflateEnd(telnet->z);
free(telnet->z);
telnet->z = 0;
break;
}
_event(telnet, TELNET_EV_SEND, 0, 0, deflate_buffer,
sizeof(deflate_buffer) - telnet->z->avail_out, 0, 0);
/* prepare output buffer for next run */
telnet->z->next_out = (unsigned char *)deflate_buffer;
telnet->z->avail_out = sizeof(deflate_buffer);
}
/* COMPRESS2 is not negotiated, just send */
} else
#endif /* defined(HAVE_ZLIB) */
_event(telnet, TELNET_EV_SEND, 0, 0, buffer, size, 0, 0);
}
/* to send bags of unsigned chars */
#define _sendu(t, d, s) _send((t), (const char*)(d), (s))
/* check if we support a particular telopt; if us is non-zero, we
* check if we (local) supports it, otherwise we check if he (remote)
* supports it. return non-zero if supported, zero if not supported.
*/
static INLINE int _check_telopt(telnet_t *telnet, unsigned char telopt,
int us) {
int i;
/* if we have no telopts table, we obviously don't support it */
if (telnet->telopts == 0)
return 0;
/* loop unti found or end marker (us and him both 0) */
for (i = 0; telnet->telopts[i].telopt != -1; ++i) {
if (telnet->telopts[i].telopt == telopt) {
if (us && telnet->telopts[i].us == TELNET_WILL)
return 1;
else if (!us && telnet->telopts[i].him == TELNET_DO)
return 1;
else
return 0;
}
}
/* not found, so not supported */
return 0;
}
/* retrieve RFC1143 option state */
static INLINE telnet_rfc1143_t _get_rfc1143(telnet_t *telnet,
unsigned char telopt) {
const telnet_rfc1143_t empty = { telopt, 0, 0};
int i;
/* search for entry */
for (i = 0; i != telnet->q_size; ++i)
if (telnet->q[i].telopt == telopt)
return telnet->q[i];
/* not found, return empty value */
return empty;
}
/* save RFC1143 option state */
static INLINE void _set_rfc1143(telnet_t *telnet, unsigned char telopt,
char us, char him) {
telnet_rfc1143_t *qtmp;
int i;
/* search for entry */
for (i = 0; i != telnet->q_size; ++i) {
if (telnet->q[i].telopt == telopt) {
telnet->q[i].us = us;
telnet->q[i].him = him;
return;
}
}
/* we're going to need to track state for it, so grow the queue
* by 4 (four) elements and put the telopt into it; bail on allocation
* error. we go by four because it seems like a reasonable guess as
* to the number of enabled options for most simple code, and it
* allows for an acceptable number of reallocations for complex code.
*/
if ((qtmp = (telnet_rfc1143_t *)realloc(telnet->q,
sizeof(telnet_rfc1143_t) * (telnet->q_size + 4))) == 0) {
_error(telnet, __LINE__, __func__, TELNET_ENOMEM, 0,
"malloc() failed: %s", strerror(errno));
return;
}
memset(&qtmp[telnet->q_size], 0, sizeof(telnet_rfc1143_t) * 4);
telnet->q = qtmp;
telnet->q[telnet->q_size].telopt = telopt;
telnet->q[telnet->q_size].us = us;
telnet->q[telnet->q_size].him = him;
telnet->q_size += 4;
}
/* send negotiation bytes */
static INLINE void _send_negotiate(telnet_t *telnet, unsigned char cmd,
unsigned char telopt) {
const unsigned char bytes[3] = { TELNET_IAC, cmd, telopt };
_sendu(telnet, bytes, 3);
}
/* negotiation handling magic for RFC1143 */
static void _negotiate(telnet_t *telnet, unsigned char telopt) {
telnet_rfc1143_t q;
/* in PROXY mode, just pass it thru and do nothing */
if (telnet->flags & TELNET_FLAG_PROXY) {
switch ((int)telnet->state) {
case TELNET_STATE_WILL:
_event(telnet, TELNET_EV_WILL, 0, telopt, 0, 0, 0, 0);
break;
case TELNET_STATE_WONT:
_event(telnet, TELNET_EV_WONT, 0, telopt, 0, 0, 0, 0);
break;
case TELNET_STATE_DO:
_event(telnet, TELNET_EV_DO, 0, telopt, 0, 0, 0, 0);
break;
case TELNET_STATE_DONT:
_event(telnet, TELNET_EV_DONT, 0, telopt, 0, 0, 0, 0);
break;
}
return;
}
/* lookup the current state of the option */
q = _get_rfc1143(telnet, telopt);
/* start processing... */
switch ((int)telnet->state) {
/* request to enable option on remote end or confirm DO */
case TELNET_STATE_WILL:
switch (q.him) {
case Q_NO:
if (_check_telopt(telnet, telopt, 0)) {
_set_rfc1143(telnet, telopt, q.us, Q_YES);
_send_negotiate(telnet, TELNET_DO, telopt);
_event(telnet, TELNET_EV_WILL, 0, telopt, 0, 0, 0, 0);
} else
_send_negotiate(telnet, TELNET_DONT, telopt);
break;
case Q_WANTNO:
_set_rfc1143(telnet, telopt, q.us, Q_NO);
_event(telnet, TELNET_EV_WONT, 0, telopt, 0, 0, 0, 0);
_error(telnet, __LINE__, __func__, TELNET_EPROTOCOL, 0,
"DONT answered by WILL");
break;
case Q_WANTNO_OP:
_set_rfc1143(telnet, telopt, q.us, Q_YES);
_event(telnet, TELNET_EV_WILL, 0, telopt, 0, 0, 0, 0);
_error(telnet, __LINE__, __func__, TELNET_EPROTOCOL, 0,
"DONT answered by WILL");
break;
case Q_WANTYES:
_set_rfc1143(telnet, telopt, q.us, Q_YES);
_event(telnet, TELNET_EV_WILL, 0, telopt, 0, 0, 0, 0);
break;
case Q_WANTYES_OP:
_set_rfc1143(telnet, telopt, q.us, Q_WANTNO);
_send_negotiate(telnet, TELNET_DONT, telopt);
_event(telnet, TELNET_EV_WILL, 0, telopt, 0, 0, 0, 0);
break;
}
break;
/* request to disable option on remote end, confirm DONT, reject DO */
case TELNET_STATE_WONT:
switch (q.him) {
case Q_YES:
_set_rfc1143(telnet, telopt, q.us, Q_NO);
_send_negotiate(telnet, TELNET_DONT, telopt);
_event(telnet, TELNET_EV_WONT, 0, telopt, 0, 0, 0, 0);
break;
case Q_WANTNO:
_set_rfc1143(telnet, telopt, q.us, Q_NO);
_event(telnet, TELNET_EV_WONT, 0, telopt, 0, 0, 0, 0);
break;
case Q_WANTNO_OP:
_set_rfc1143(telnet, telopt, q.us, Q_WANTYES);
_event(telnet, TELNET_EV_DO, 0, telopt, 0, 0, 0, 0);
break;
case Q_WANTYES:
case Q_WANTYES_OP:
_set_rfc1143(telnet, telopt, q.us, Q_NO);
break;
}
break;
/* request to enable option on local end or confirm WILL */
case TELNET_STATE_DO:
switch (q.us) {
case Q_NO:
if (_check_telopt(telnet, telopt, 1)) {
_set_rfc1143(telnet, telopt, Q_YES, q.him);
_send_negotiate(telnet, TELNET_WILL, telopt);
_event(telnet, TELNET_EV_DO, 0, telopt, 0, 0, 0, 0);
} else
_send_negotiate(telnet, TELNET_WONT, telopt);
break;
case Q_WANTNO:
_set_rfc1143(telnet, telopt, Q_NO, q.him);
_event(telnet, TELNET_EV_DONT, 0, telopt, 0, 0, 0, 0);
_error(telnet, __LINE__, __func__, TELNET_EPROTOCOL, 0,
"WONT answered by DO");
break;
case Q_WANTNO_OP:
_set_rfc1143(telnet, telopt, Q_YES, q.him);
_event(telnet, TELNET_EV_DO, 0, telopt, 0, 0, 0, 0);
_error(telnet, __LINE__, __func__, TELNET_EPROTOCOL, 0,
"WONT answered by DO");
break;
case Q_WANTYES:
_set_rfc1143(telnet, telopt, Q_YES, q.him);
_event(telnet, TELNET_EV_DO, 0, telopt, 0, 0, 0, 0);
break;
case Q_WANTYES_OP:
_set_rfc1143(telnet, telopt, Q_WANTNO, q.him);
_send_negotiate(telnet, TELNET_WONT, telopt);
_event(telnet, TELNET_EV_DO, 0, telopt, 0, 0, 0, 0);
break;
}
break;
/* request to disable option on local end, confirm WONT, reject WILL */
case TELNET_STATE_DONT:
switch (q.us) {
case Q_YES:
_set_rfc1143(telnet, telopt, Q_NO, q.him);
_send_negotiate(telnet, TELNET_WONT, telopt);
_event(telnet, TELNET_EV_DONT, 0, telopt, 0, 0, 0, 0);
break;
case Q_WANTNO:
_set_rfc1143(telnet, telopt, Q_NO, q.him);
_event(telnet, TELNET_EV_WONT, 0, telopt, 0, 0, 0, 0);
break;
case Q_WANTNO_OP:
_set_rfc1143(telnet, telopt, Q_WANTYES, q.him);
_event(telnet, TELNET_EV_WILL, 0, telopt, 0, 0, 0, 0);
break;
case Q_WANTYES:
case Q_WANTYES_OP:
_set_rfc1143(telnet, telopt, Q_NO, q.him);
break;
}
break;
}
}
/* process a subnegotiation buffer; return non-zero if the current buffer
* must be aborted and reprocessed due to COMPRESS2 being activated
*/
static int _subnegotiate(telnet_t *telnet) {
switch (telnet->sb_telopt) {
#if defined(HAVE_ZLIB)
/* received COMPRESS2 begin marker, setup our zlib box and
* start handling the compressed stream if it's not already.
*/
case TELNET_TELOPT_COMPRESS2:
if (telnet->sb_telopt == TELNET_TELOPT_COMPRESS2) {
if (_init_zlib(telnet, 0, 1) != TELNET_EOK)
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return 0;
/* standard SB notification */
_event(telnet, TELNET_EV_SUBNEGOTIATION, 0, telnet->sb_telopt,
telnet->buffer, telnet->buffer_pos, 0, 0);
/* notify app that compression was enabled */
_event(telnet, TELNET_EV_COMPRESS, 1, 0, 0, 0, 0, 0);
return 1;
}
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return 0;
#endif /* defined(HAVE_ZLIB) */
#if defined(HAVE_ALLOCA)
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/* ZMP command */
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case TELNET_TELOPT_ZMP: {
const char **argv, *c;
size_t i, argc;
/* make sure this is a valid ZMP buffer */
if (telnet->buffer_pos == 0 ||
telnet->buffer[telnet->buffer_pos - 1] != 0) {
_error(telnet, __LINE__, __func__, TELNET_EPROTOCOL, 0,
"incomplete ZMP frame");
_event(telnet, TELNET_EV_SUBNEGOTIATION, 0, telnet->sb_telopt,
telnet->buffer, telnet->buffer_pos, 0, 0);
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return 0;
}
/* count arguments */
for (argc = 0, c = telnet->buffer; c != telnet->buffer +
telnet->buffer_pos; ++argc)
c += strlen(c) + 1;
/* allocate argument array, bail on error */
if ((argv = (const char **)alloca(sizeof(char *) * argc)) == 0) {
_error(telnet, __LINE__, __func__, TELNET_ENOMEM, 0,
"alloca() failed: %s", strerror(errno));
_event(telnet, TELNET_EV_SUBNEGOTIATION, 0, telnet->sb_telopt,
telnet->buffer, telnet->buffer_pos, 0, 0);
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return 0;
}
/* populate argument array */
for (i = 0, c = telnet->buffer; i != argc; ++i) {
argv[i] = c;
c += strlen(c) + 1;
}
/* invoke event with our arguments */
_event(telnet, TELNET_EV_SUBNEGOTIATION, 0, telnet->sb_telopt,
telnet->buffer, telnet->buffer_pos, argv, argc);
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return 0;
}
/* any of a number of commands that use the form <BYTE>data<BYTE>data,
* including TTYPE, ENVIRON, NEW-ENVIRON, and MSSP
*/
case TELNET_TELOPT_TTYPE:
case TELNET_TELOPT_ENVIRON:
case TELNET_TELOPT_NEW_ENVIRON:
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case TELNET_TELOPT_MSSP: {
char **argv, *c, *l;
size_t i, argc;
/* if we have no data, just pass it through */
if (telnet->buffer_pos == 0) {
_event(telnet, TELNET_EV_SUBNEGOTIATION, 0, telnet->sb_telopt,
telnet->buffer, telnet->buffer_pos, 0, 0);
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return 0;
}
/* very first byte must be in range 0-3 */
if ((unsigned)telnet->buffer[0] > 3) {
_error(telnet, __LINE__, __func__, TELNET_EPROTOCOL, 0,
"telopt %d subneg has invalid data", telnet->sb_telopt);
_event(telnet, TELNET_EV_SUBNEGOTIATION, 0, telnet->sb_telopt,
telnet->buffer, telnet->buffer_pos, 0, 0);
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return 0;
}
/* count arguments; each argument is preceded by a byte in the
* range 0-3, so just count those.
* NOTE: we don't support the ENVIRON/NEW-ENVIRON ESC handling
* properly at all. guess that's a FIXME.
*/
for (argc = 0, i = 0; i != telnet->buffer_pos; ++i)
if ((unsigned)telnet->buffer[i] <= 3)
++argc;
/* allocate argument array, bail on error */
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if ((argv = (char **)alloca(sizeof(char *) * argc)) == 0) {
_error(telnet, __LINE__, __func__, TELNET_ENOMEM, 0,
"alloca() failed: %s", strerror(errno));
_event(telnet, TELNET_EV_SUBNEGOTIATION, 0, telnet->sb_telopt,
telnet->buffer, telnet->buffer_pos, 0, 0);
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return 0;
}
/* allocate strings in argument array */
for (i = 0, l = telnet->buffer; i != argc; ++i) {
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/* search for end marker */
c = l + 1;
while (c != telnet->buffer + telnet->buffer_pos &&
(unsigned)*c > 3)
++c;
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/* allocate space; bail on error */
if ((argv[i] = (char *)alloca(c - l + 1)) == 0) {
_error(telnet, __LINE__, __func__, TELNET_ENOMEM, 0,
"alloca() failed: %s", strerror(errno));
_event(telnet, TELNET_EV_SUBNEGOTIATION, 0, telnet->sb_telopt,
telnet->buffer, telnet->buffer_pos, 0, 0);
return 0;
}
/* copy data */
memcpy(argv[i], l, c - l);
argv[i][c - l] = 0;
/* prepare for next loop */
l = c;
}
/* invoke event with our arguments */
_event(telnet, TELNET_EV_SUBNEGOTIATION, 0, telnet->sb_telopt,
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telnet->buffer, telnet->buffer_pos, (const char **)argv, argc);
return 0;
}
#endif /* defined(HAVE_ALLOCA) */
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/* other generic subnegotiation */
default:
_event(telnet, TELNET_EV_SUBNEGOTIATION, 0, telnet->sb_telopt,
telnet->buffer, telnet->buffer_pos, 0, 0);
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return 0;
}
}
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/* initialize a telnet state tracker */
telnet_t *telnet_init(const telnet_telopt_t *telopts,
telnet_event_handler_t eh, unsigned char flags, void *user_data) {
/* allocate structure */
struct telnet_t *telnet = (telnet_t*)calloc(1, sizeof(telnet_t));
if (telnet == 0)
return 0;
/* initialize data */
telnet->ud = user_data;
telnet->telopts = telopts;
telnet->eh = eh;
telnet->flags = flags;
return telnet;
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}
/* free up any memory allocated by a state tracker */
void telnet_free(telnet_t *telnet) {
/* free sub-request buffer */
if (telnet->buffer != 0) {
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free(telnet->buffer);
telnet->buffer = 0;
telnet->buffer_size = 0;
telnet->buffer_pos = 0;
}
#if defined(HAVE_ZLIB)
/* free zlib box */
if (telnet->z != 0) {
if (telnet->flags & TELNET_PFLAG_DEFLATE)
deflateEnd(telnet->z);
else
inflateEnd(telnet->z);
free(telnet->z);
telnet->z = 0;
}
#endif /* defined(HAVE_ZLIB) */
/* free RFC1143 queue */
if (telnet->q) {
free(telnet->q);
telnet->q = 0;
telnet->q_size = 0;
}