telnet.c

putty

    telnet->state = TOP_LEVEL;
    telnet->ldisc = NULL;
    telnet->pinger = NULL;
    *backend_handle = telnet;

    /*
     * Try to find host.
     */
    {
	char *buf;
	buf = dupprintf("Looking up host \"%s\"%s", host,
			(cfg->addressfamily == ADDRTYPE_IPV4 ? " (IPv4)" :
			 (cfg->addressfamily == ADDRTYPE_IPV6 ? " (IPv6)" :
			  "")));
	logevent(telnet->frontend, buf);
	sfree(buf);
    }
    addr = name_lookup(host, port, realhost, &telnet->cfg, cfg->addressfamily);
    if ((err = sk_addr_error(addr)) != NULL) {
	sk_addr_free(addr);
	return err;
    }

    if (port < 0)
	port = 23;		       /* default telnet port */

    /*
     * Open socket.
     */
    telnet->s = new_connection(addr, *realhost, port, 0, 1,
			       nodelay, keepalive, (Plug) telnet, &telnet->cfg);
    if ((err = sk_socket_error(telnet->s)) != NULL)
	return err;

    telnet->pinger = pinger_new(&telnet->cfg, &telnet_backend, telnet);

    /*
     * Initialise option states.
     */
    if (telnet->cfg.passive_telnet) {
	const struct Opt *const *o;

	for (o = opts; *o; o++)
	    telnet->opt_states[(*o)->index] = INACTIVE;
    } else {
	const struct Opt *const *o;

	for (o = opts; *o; o++) {
	    telnet->opt_states[(*o)->index] = (*o)->initial_state;
	    if (telnet->opt_states[(*o)->index] == REQUESTED)
		send_opt(telnet, (*o)->send, (*o)->option);
	}
	telnet->activated = TRUE;
    }

    /*
     * Set up SYNCH state.
     */
    telnet->in_synch = FALSE;

    /*
     * We can send special commands from the start.
     */
    update_specials_menu(telnet->frontend);

    return NULL;
}

static void telnet_free(void *handle)
{
    Telnet telnet = (Telnet) handle;

    sfree(telnet->sb_buf);
    if (telnet->s)
	sk_close(telnet->s);
    if (telnet->pinger)
	pinger_free(telnet->pinger);
    sfree(telnet);
}
/*
 * Reconfigure the Telnet backend. There's no immediate action
 * necessary, in this backend: we just save the fresh config for
 * any subsequent negotiations.
 */
static void telnet_reconfig(void *handle, Config *cfg)
{
    Telnet telnet = (Telnet) handle;
    pinger_reconfig(telnet->pinger, &telnet->cfg, cfg);
    telnet->cfg = *cfg;		       /* STRUCTURE COPY */
}

/*
 * Called to send data down the Telnet connection.
 */
static int telnet_send(void *handle, char *buf, int len)
{
    Telnet telnet = (Telnet) handle;
    unsigned char *p, *end;
    static const unsigned char iac[2] = { IAC, IAC };
    static const unsigned char cr[2] = { CR, NUL };
#if 0
    static const unsigned char nl[2] = { CR, LF };
#endif

    if (telnet->s == NULL)
	return 0;

    p = (unsigned char *)buf;
    end = (unsigned char *)(buf + len);
    while (p < end) {
	unsigned char *q = p;

	while (p < end && iswritable(*p))
	    p++;
	telnet->bufsize = sk_write(telnet->s, (char *)q, p - q);

	while (p < end && !iswritable(*p)) {
	    telnet->bufsize = 
		sk_write(telnet->s, (char *)(*p == IAC ? iac : cr), 2);
	    p++;
	}
    }

    return telnet->bufsize;
}

/*
 * Called to query the current socket sendability status.
 */
static int telnet_sendbuffer(void *handle)
{
    Telnet telnet = (Telnet) handle;
    return telnet->bufsize;
}

/*
 * Called to set the size of the window from Telnet's POV.
 */
static void telnet_size(void *handle, int width, int height)
{
    Telnet telnet = (Telnet) handle;
    unsigned char b[24];
    int n;
    char *logbuf;

    telnet->term_width = width;
    telnet->term_height = height;

    if (telnet->s == NULL || telnet->opt_states[o_naws.index] != ACTIVE)
	return;
    n = 0;
    b[n++] = IAC;
    b[n++] = SB;
    b[n++] = TELOPT_NAWS;
    b[n++] = telnet->term_width >> 8;
    if (b[n-1] == IAC) b[n++] = IAC;   /* duplicate any IAC byte occurs */
    b[n++] = telnet->term_width & 0xFF;
    if (b[n-1] == IAC) b[n++] = IAC;   /* duplicate any IAC byte occurs */
    b[n++] = telnet->term_height >> 8;
    if (b[n-1] == IAC) b[n++] = IAC;   /* duplicate any IAC byte occurs */
    b[n++] = telnet->term_height & 0xFF;
    if (b[n-1] == IAC) b[n++] = IAC;   /* duplicate any IAC byte occurs */
    b[n++] = IAC;
    b[n++] = SE;
    telnet->bufsize = sk_write(telnet->s, (char *)b, n);
    logbuf = dupprintf("client:\tSB NAWS %d,%d",
		       telnet->term_width, telnet->term_height);
    logevent(telnet->frontend, logbuf);
    sfree(logbuf);
}

/*
 * Send Telnet special codes.
 */
static void telnet_special(void *handle, Telnet_Special code)
{
    Telnet telnet = (Telnet) handle;
    unsigned char b[2];

    if (telnet->s == NULL)
	return;

    b[0] = IAC;
    switch (code) {
      case TS_AYT:
	b[1] = AYT;
	telnet->bufsize = sk_write(telnet->s, (char *)b, 2);
	break;
      case TS_BRK:
	b[1] = BREAK;
	telnet->bufsize = sk_write(telnet->s, (char *)b, 2);
	break;
      case TS_EC:
	b[1] = EC;
	telnet->bufsize = sk_write(telnet->s, (char *)b, 2);
	break;
      case TS_EL:
	b[1] = EL;
	telnet->bufsize = sk_write(telnet->s, (char *)b, 2);
	break;
      case TS_GA:
	b[1] = GA;
	telnet->bufsize = sk_write(telnet->s, (char *)b, 2);
	break;
      case TS_NOP:
	b[1] = NOP;
	telnet->bufsize = sk_write(telnet->s, (char *)b, 2);
	break;
      case TS_ABORT:
	b[1] = ABORT;
	telnet->bufsize = sk_write(telnet->s, (char *)b, 2);
	break;
      case TS_AO:
	b[1] = AO;
	telnet->bufsize = sk_write(telnet->s, (char *)b, 2);
	break;
      case TS_IP:
	b[1] = IP;
	telnet->bufsize = sk_write(telnet->s, (char *)b, 2);
	break;
      case TS_SUSP:
	b[1] = SUSP;
	telnet->bufsize = sk_write(telnet->s, (char *)b, 2);
	break;
      case TS_EOR:
	b[1] = EOR;
	telnet->bufsize = sk_write(telnet->s, (char *)b, 2);
	break;
      case TS_EOF:
	b[1] = xEOF;
	telnet->bufsize = sk_write(telnet->s, (char *)b, 2);
	break;
      case TS_EOL:
	/* In BINARY mode, CR-LF becomes just CR -
	 * and without the NUL suffix too. */
	if (telnet->opt_states[o_we_bin.index] == ACTIVE)
	    telnet->bufsize = sk_write(telnet->s, "\r", 1);
	else
	    telnet->bufsize = sk_write(telnet->s, "\r\n", 2);
	break;
      case TS_SYNCH:
	b[1] = DM;
	telnet->bufsize = sk_write(telnet->s, (char *)b, 1);
	telnet->bufsize = sk_write_oob(telnet->s, (char *)(b + 1), 1);
	break;
      case TS_RECHO:
	if (telnet->opt_states[o_echo.index] == INACTIVE ||
	    telnet->opt_states[o_echo.index] == REALLY_INACTIVE) {
	    telnet->opt_states[o_echo.index] = REQUESTED;
	    send_opt(telnet, o_echo.send, o_echo.option);
	}
	break;
      case TS_LECHO:
	if (telnet->opt_states[o_echo.index] == ACTIVE) {
	    telnet->opt_states[o_echo.index] = REQUESTED;
	    send_opt(telnet, o_echo.nsend, o_echo.option);
	}
	break;
      case TS_PING:
	if (telnet->opt_states[o_they_sga.index] == ACTIVE) {
	    b[1] = NOP;
	    telnet->bufsize = sk_write(telnet->s, (char *)b, 2);
	}
	break;
      default:
	break;	/* never heard of it */
    }
}

static const struct telnet_special *telnet_get_specials(void *handle)
{
    static const struct telnet_special specials[] = {
	{"Are You There", TS_AYT},
	{"Break", TS_BRK},
	{"Synch", TS_SYNCH},
	{"Erase Character", TS_EC},
	{"Erase Line", TS_EL},
	{"Go Ahead", TS_GA},
	{"No Operation", TS_NOP},
	{NULL, TS_SEP},
	{"Abort Process", TS_ABORT},
	{"Abort Output", TS_AO},
	{"Interrupt Process", TS_IP},
	{"Suspend Process", TS_SUSP},
	{NULL, TS_SEP},
	{"End Of Record", TS_EOR},
	{"End Of File", TS_EOF},
	{NULL, TS_EXITMENU}
    };
    return specials;
}

static int telnet_connected(void *handle)
{
    Telnet telnet = (Telnet) handle;
    return telnet->s != NULL;
}

static int telnet_sendok(void *handle)
{
    /* Telnet telnet = (Telnet) handle; */
    return 1;
}

static void telnet_unthrottle(void *handle, int backlog)
{
    Telnet telnet = (Telnet) handle;
    sk_set_frozen(telnet->s, backlog > TELNET_MAX_BACKLOG);
}

static int telnet_ldisc(void *handle, int option)
{
    Telnet telnet = (Telnet) handle;
    if (option == LD_ECHO)
	return telnet->echoing;
    if (option == LD_EDIT)
	return telnet->editing;
    return FALSE;
}

static void telnet_provide_ldisc(void *handle, void *ldisc)
{
    Telnet telnet = (Telnet) handle;
    telnet->ldisc = ldisc;
}

static void telnet_provide_logctx(void *handle, void *logctx)
{
    /* This is a stub. */
}

static int telnet_exitcode(void *handle)
{
    Telnet telnet = (Telnet) handle;
    if (telnet->s != NULL)
        return -1;                     /* still connected */
    else
        /* Telnet doesn't transmit exit codes back to the client */
        return 0;
}

/*
 * cfg_info for Telnet does nothing at all.
 */
static int telnet_cfg_info(void *handle)
{
    return 0;
}

Backend telnet_backend = {
    telnet_init,
    telnet_free,
    telnet_reconfig,
    telnet_send,
    telnet_sendbuffer,
    telnet_size,
    telnet_special,
    telnet_get_specials,
    telnet_connected,
    telnet_exitcode,
    telnet_sendok,
    telnet_ldisc,
    telnet_provide_ldisc,
    telnet_provide_logctx,
    telnet_unthrottle,
    telnet_cfg_info,
    23
};