networking/telnet.c - codeaurora/busybox - Gitiles

 /* vi: set sw=4 ts=4: */
 /*
  * telnet implementation for busybox
  *
  * Author: Tomi Ollila <too@iki.fi>
  * Copyright (C) 1994-2000 by Tomi Ollila
  *
  * Created: Thu Apr  7 13:29:41 1994 too
  * Last modified: Fri Jun  9 14:34:24 2000 too
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 2 of the License, or
  * (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  * General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  *
  * HISTORY
  * Revision 3.1  1994/04/17  11:31:54  too
  * initial revision
  * Modified 2000/06/13 for inclusion into BusyBox by Erik Andersen <andersee@debian.org>
  * Modified 2001/05/07 to add ability to pass TTYPE to remote host by Jim McQuillan
  * <jam@ltsp.org>
  *
  */

 #include <termios.h>
 #include <unistd.h>
 #include <errno.h>
 #include <stdlib.h>
 #include <stdarg.h>
 #include <string.h>
 #include <signal.h>
 #include <arpa/telnet.h>
 #include <sys/types.h>
 #include <sys/socket.h>
 #include <netinet/in.h>
 #include "busybox.h"

 #ifdef CONFIG_FEATURE_AUTOWIDTH
 #   include <sys/ioctl.h>
 #endif

 #if 0
 static const int DOTRACE = 1;
 #endif

 #ifdef DOTRACE
 #include <arpa/inet.h> /* for inet_ntoa()... */
 #define TRACE(x, y) do { if (x) printf y; } while (0)
 #else
 #define TRACE(x, y)
 #endif

 #if 0
 #define USE_POLL
 #include <sys/poll.h>
 #else
 #include <sys/time.h>
 #endif

 #define DATABUFSIZE  128
 #define IACBUFSIZE   128

 static const int CHM_TRY = 0;
 static const int CHM_ON = 1;
 static const int CHM_OFF = 2;

 static const int UF_ECHO = 0x01;
 static const int UF_SGA = 0x02;

 enum {
 	TS_0 = 1,
 	TS_IAC = 2,
 	TS_OPT = 3,
 	TS_SUB1 = 4,
 	TS_SUB2 = 5,
 };

 #define WriteCS(fd, str) write(fd, str, sizeof str -1)

 typedef unsigned char byte;

 /* use globals to reduce size ??? */ /* test this hypothesis later */
 static struct Globalvars {
 	int		netfd; /* console fd:s are 0 and 1 (and 2) */
     /* same buffer used both for network and console read/write */
 	char    buf[DATABUFSIZE]; /* allocating so static size is smaller */
 	byte	telstate; /* telnet negotiation state from network input */
 	byte	telwish;  /* DO, DONT, WILL, WONT */
 	byte    charmode;
 	byte    telflags;
 	byte	gotsig;
 	/* buffer to handle telnet negotiations */
 	char    iacbuf[IACBUFSIZE];
 	short	iaclen; /* could even use byte */
 	struct termios termios_def;
 	struct termios termios_raw;
 } G;

 #define xUSE_GLOBALVAR_PTR /* xUSE... -> don't use :D (makes smaller code) */

 #ifdef USE_GLOBALVAR_PTR
 struct Globalvars * Gptr;
 #define G (*Gptr)
 #endif

 static inline void iacflush(void)
 {
 	write(G.netfd, G.iacbuf, G.iaclen);
 	G.iaclen = 0;
 }

 /* Function prototypes */
 static void rawmode(void);
 static void cookmode(void);
 static void do_linemode(void);
 static void will_charmode(void);
 static void telopt(byte c);
 static int subneg(byte c);

 /* Some globals */
 static int one = 1;

 #ifdef CONFIG_FEATURE_TELNET_TTYPE
 static char *ttype;
 #endif

 #ifdef CONFIG_FEATURE_AUTOWIDTH
 static int win_width, win_height;
 #endif

 static void doexit(int ev)
 {
 	cookmode();
 	exit(ev);
 }

 static void conescape(void)
 {
 	char b;

 	if (G.gotsig)	/* came from line  mode... go raw */
 		rawmode();

 	WriteCS(1, "\r\nConsole escape. Commands are:\r\n\n"
 			" l	go to line mode\r\n"
 			" c	go to character mode\r\n"
 			" z	suspend telnet\r\n"
 			" e	exit telnet\r\n");

 	if (read(0, &b, 1) <= 0)
 		doexit(1);

 	switch (b)
 	{
 	case 'l':
 		if (!G.gotsig)
 		{
 			do_linemode();
 			goto rrturn;
 		}
 		break;
 	case 'c':
 		if (G.gotsig)
 		{
 			will_charmode();
 			goto rrturn;
 		}
 		break;
 	case 'z':
 		cookmode();
 		kill(0, SIGTSTP);
 		rawmode();
 		break;
 	case 'e':
 		doexit(0);
 	}

 	WriteCS(1, "continuing...\r\n");

 	if (G.gotsig)
 		cookmode();

  rrturn:
 	G.gotsig = 0;

 }
 static void handlenetoutput(int len)
 {
 	/*	here we could do smart tricks how to handle 0xFF:s in output
 	 *	stream  like writing twice every sequence of FF:s (thus doing
 	 *	many write()s. But I think interactive telnet application does
 	 *	not need to be 100% 8-bit clean, so changing every 0xff:s to
 	 *	0x7f:s
 	 *
 	 *	2002-mar-21, Przemyslaw Czerpak (druzus@polbox.com)
 	 *	I don't agree.
 	 *	first - I cannot use programs like sz/rz
 	 *	second - the 0x0D is sent as one character and if the next
 	 *	         char is 0x0A then it's eaten by a server side.
 	 *	third - whay doy you have to make 'many write()s'?
 	 *	        I don't understand.
 	 *	So I implemented it. It's realy useful for me. I hope that
 	 *	others people will find it interesting to.
 	 */

 	int i, j;
 	byte * p = G.buf;
 	byte outbuf[4*DATABUFSIZE];

 	for (i = len, j = 0; i > 0; i--, p++)
 	{
 		if (*p == 0x1d)
 		{
 			conescape();
 			return;
 		}
 		outbuf[j++] = *p;
 		if (*p == 0xff)
 		    outbuf[j++] = 0xff;
 		else if (*p == 0x0d)
 		    outbuf[j++] = 0x00;
 	}
 	if (j > 0 )
 	    write(G.netfd, outbuf, j);
 }


 static void handlenetinput(int len)
 {
 	int i;
 	int cstart = 0;

 	for (i = 0; i < len; i++)
 	{
 		byte c = G.buf[i];

 		if (G.telstate == 0) /* most of the time state == 0 */
 		{
 			if (c == IAC)
 			{
 				cstart = i;
 				G.telstate = TS_IAC;
 			}
 		}
 		else
 			switch (G.telstate)
 			 {
 			 case TS_0:
 				 if (c == IAC)
 					 G.telstate = TS_IAC;
 				 else
 					 G.buf[cstart++] = c;
 				 break;

 			 case TS_IAC:
 				 if (c == IAC) /* IAC IAC -> 0xFF */
 				 {
 					 G.buf[cstart++] = c;
 					 G.telstate = TS_0;
 					 break;
 				 }
 				 /* else */
 				 switch (c)
 				 {
 				 case SB:
 					 G.telstate = TS_SUB1;
 					 break;
 				 case DO:
 				 case DONT:
 				 case WILL:
 				 case WONT:
 					 G.telwish =  c;
 					 G.telstate = TS_OPT;
 					 break;
 				 default:
 					 G.telstate = TS_0;	/* DATA MARK must be added later */
 				 }
 				 break;
 			 case TS_OPT: /* WILL, WONT, DO, DONT */
 				 telopt(c);
 				 G.telstate = TS_0;
 				 break;
 			 case TS_SUB1: /* Subnegotiation */
 			 case TS_SUB2: /* Subnegotiation */
 				 if (subneg(c))
 					 G.telstate = TS_0;
 				 break;
 			 }
 	}
 	if (G.telstate)
 	{
 		if (G.iaclen)			iacflush();
 		if (G.telstate == TS_0)	G.telstate = 0;

 		len = cstart;
 	}

 	if (len)
 		write(1, G.buf, len);
 }


 /* ******************************* */

 static inline void putiac(int c)
 {
 	G.iacbuf[G.iaclen++] = c;
 }


 static void putiac2(byte wwdd, byte c)
 {
 	if (G.iaclen + 3 > IACBUFSIZE)
 		iacflush();

 	putiac(IAC);
 	putiac(wwdd);
 	putiac(c);
 }

 #if 0
 static void putiac1(byte c)
 {
 	if (G.iaclen + 2 > IACBUFSIZE)
 		iacflush();

 	putiac(IAC);
 	putiac(c);
 }
 #endif

 #ifdef CONFIG_FEATURE_TELNET_TTYPE
 static void putiac_subopt(byte c, char *str)
 {
 	int	len = strlen(str) + 6;   // ( 2 + 1 + 1 + strlen + 2 )

 	if (G.iaclen + len > IACBUFSIZE)
 		iacflush();

 	putiac(IAC);
 	putiac(SB);
 	putiac(c);
 	putiac(0);

 	while(*str)
 		putiac(*str++);

 	putiac(IAC);
 	putiac(SE);
 }
 #endif

 #ifdef CONFIG_FEATURE_AUTOWIDTH
 static void putiac_naws(byte c, int x, int y)
 {
 	if (G.iaclen + 9 > IACBUFSIZE)
 		iacflush();

 	putiac(IAC);
 	putiac(SB);
 	putiac(c);

 	putiac((x >> 8) & 0xff);
 	putiac(x & 0xff);
 	putiac((y >> 8) & 0xff);
 	putiac(y & 0xff);

 	putiac(IAC);
 	putiac(SE);
 }
 #endif

 /* void putiacstring (subneg strings) */

 /* ******************************* */

 static char const escapecharis[] = "\r\nEscape character is ";

 static void setConMode(void)
 {
 	if (G.telflags & UF_ECHO)
 	{
 		if (G.charmode == CHM_TRY) {
 			G.charmode = CHM_ON;
 			printf("\r\nEntering character mode%s'^]'.\r\n", escapecharis);
 			rawmode();
 		}
 	}
 	else
 	{
 		if (G.charmode != CHM_OFF) {
 			G.charmode = CHM_OFF;
 			printf("\r\nEntering line mode%s'^C'.\r\n", escapecharis);
 			cookmode();
 		}
 	}
 }

 /* ******************************* */

 static void will_charmode(void)
 {
 	G.charmode = CHM_TRY;
 	G.telflags |= (UF_ECHO | UF_SGA);
 	setConMode();

 	putiac2(DO, TELOPT_ECHO);
 	putiac2(DO, TELOPT_SGA);
 	iacflush();
 }

 static void do_linemode(void)
 {
 	G.charmode = CHM_TRY;
 	G.telflags &= ~(UF_ECHO | UF_SGA);
 	setConMode();

 	putiac2(DONT, TELOPT_ECHO);
 	putiac2(DONT, TELOPT_SGA);
 	iacflush();
 }

 /* ******************************* */

 static inline void to_notsup(char c)
 {
 	if      (G.telwish == WILL)	putiac2(DONT, c);
 	else if (G.telwish == DO)	putiac2(WONT, c);
 }

 static inline void to_echo(void)
 {
 	/* if server requests ECHO, don't agree */
 	if      (G.telwish == DO) {	putiac2(WONT, TELOPT_ECHO);	return; }
 	else if (G.telwish == DONT)	return;

 	if (G.telflags & UF_ECHO)
 	{
 		if (G.telwish == WILL)
 			return;
 	}
 	else
 		if (G.telwish == WONT)
 			return;

 	if (G.charmode != CHM_OFF)
 		G.telflags ^= UF_ECHO;

 	if (G.telflags & UF_ECHO)
 		putiac2(DO, TELOPT_ECHO);
 	else
 		putiac2(DONT, TELOPT_ECHO);

 	setConMode();
 	WriteCS(1, "\r\n");  /* sudden modec */
 }

 static inline void to_sga(void)
 {
 	/* daemon always sends will/wont, client do/dont */

 	if (G.telflags & UF_SGA)
 	{
 		if (G.telwish == WILL)
 			return;
 	}
 	else
 		if (G.telwish == WONT)
 			return;

 	if ((G.telflags ^= UF_SGA) & UF_SGA) /* toggle */
 		putiac2(DO, TELOPT_SGA);
 	else
 		putiac2(DONT, TELOPT_SGA);

 	return;
 }

 #ifdef CONFIG_FEATURE_TELNET_TTYPE
 static inline void to_ttype(void)
 {
 	/* Tell server we will (or won't) do TTYPE */

 	if(ttype)
 		putiac2(WILL, TELOPT_TTYPE);
 	else
 		putiac2(WONT, TELOPT_TTYPE);

 	return;
 }
 #endif

 #ifdef CONFIG_FEATURE_AUTOWIDTH
 static inline void to_naws(void)
 {
 	/* Tell server we will do NAWS */
 	putiac2(WILL, TELOPT_NAWS);
 	return;
 }
 #endif

 static void telopt(byte c)
 {
 	switch (c)
 	{
 		case TELOPT_ECHO:		to_echo();	break;
 		case TELOPT_SGA:		to_sga();	break;
 #ifdef CONFIG_FEATURE_TELNET_TTYPE
 		case TELOPT_TTYPE:		to_ttype();break;
 #endif
 #ifdef CONFIG_FEATURE_AUTOWIDTH
 		case TELOPT_NAWS:		to_naws();
 								putiac_naws(c, win_width, win_height);
 								break;
 #endif
 		default:				to_notsup(c);
 								break;
 	}
 }


 /* ******************************* */

 /* subnegotiation -- ignore all (except TTYPE,NAWS) */

 static int subneg(byte c)
 {
 	switch (G.telstate)
 	{
 	case TS_SUB1:
 		if (c == IAC)
 			G.telstate = TS_SUB2;
 #ifdef CONFIG_FEATURE_TELNET_TTYPE
 		else
 		if (c == TELOPT_TTYPE)
 			putiac_subopt(TELOPT_TTYPE,ttype);
 #endif
 		break;
 	case TS_SUB2:
 		if (c == SE)
 			return TRUE;
 		G.telstate = TS_SUB1;
 		/* break; */
 	}
 	return FALSE;
 }

 /* ******************************* */

 static void fgotsig(int sig)
 {
 	G.gotsig = sig;
 }


 static void rawmode(void)
 {
 	tcsetattr(0, TCSADRAIN, &G.termios_raw);
 }

 static void cookmode(void)
 {
 	tcsetattr(0, TCSADRAIN, &G.termios_def);
 }

 extern int telnet_main(int argc, char** argv)
 {
 	char *host;
 	char *port;
 	int len;
 #ifdef USE_POLL
 	struct pollfd ufds[2];
 #else
 	fd_set readfds;
 	int maxfd;
 #endif

 #ifdef CONFIG_FEATURE_AUTOWIDTH
     struct winsize winp;
     if( ioctl(0, TIOCGWINSZ, &winp) == 0 ) {
 	win_width  = winp.ws_col;
 	win_height = winp.ws_row;
     }
 #endif

 #ifdef CONFIG_FEATURE_TELNET_TTYPE
     ttype = getenv("TERM");
 #endif

 	memset(&G, 0, sizeof G);

 	if (tcgetattr(0, &G.termios_def) < 0)
 		exit(1);

 	G.termios_raw = G.termios_def;
 	cfmakeraw(&G.termios_raw);

 	if (argc < 2)	bb_show_usage();
 	port = (argc > 2)? argv[2] : "23";

 	host = argv[1];

 	G.netfd = xconnect(host, port);

 	setsockopt(G.netfd, SOL_SOCKET, SO_KEEPALIVE, &one, sizeof one);

 	signal(SIGINT, fgotsig);

 #ifdef USE_POLL
 	ufds[0].fd = 0; ufds[1].fd = G.netfd;
 	ufds[0].events = ufds[1].events = POLLIN;
 #else
 	FD_ZERO(&readfds);
 	FD_SET(0, &readfds);
 	FD_SET(G.netfd, &readfds);
 	maxfd = G.netfd + 1;
 #endif

 	while (1)
 	{
 #ifndef USE_POLL
 		fd_set rfds = readfds;

 		switch (select(maxfd, &rfds, NULL, NULL, NULL))
 #else
 		switch (poll(ufds, 2, -1))
 #endif
 		{
 		case 0:
 			/* timeout */
 		case -1:
 			/* error, ignore and/or log something, bay go to loop */
 			if (G.gotsig)
 				conescape();
 			else
 				sleep(1);
 			break;
 		default:

 #ifdef USE_POLL
 			if (ufds[0].revents) /* well, should check POLLIN, but ... */
 #else
 			if (FD_ISSET(0, &rfds))
 #endif
 			{
 				len = read(0, G.buf, DATABUFSIZE);

 				if (len <= 0)
 					doexit(0);

 				TRACE(0, ("Read con: %d\n", len));

 				handlenetoutput(len);
 			}

 #ifdef USE_POLL
 			if (ufds[1].revents) /* well, should check POLLIN, but ... */
 #else
 			if (FD_ISSET(G.netfd, &rfds))
 #endif
 			{
 				len = read(G.netfd, G.buf, DATABUFSIZE);

 				if (len <= 0)
 				{
 					WriteCS(1, "Connection closed by foreign host.\r\n");
 					doexit(1);
 				}
 				TRACE(0, ("Read netfd (%d): %d\n", G.netfd, len));

 				handlenetinput(len);
 			}
 		}
 	}
 }

 /*
 Local Variables:
 c-file-style: "linux"
 c-basic-offset: 4
 tab-width: 4
 End:
 */
	/* vi: set sw=4 ts=4: */
	/*
	* telnet implementation for busybox
	*
	* Author: Tomi Ollila <too@iki.fi>
	* Copyright (C) 1994-2000 by Tomi Ollila
	*
	* Created: Thu Apr 7 13:29:41 1994 too
	* Last modified: Fri Jun 9 14:34:24 2000 too
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License as published by
	* the Free Software Foundation; either version 2 of the License, or
	* (at your option) any later version.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	* General Public License for more details.
	*
	* You should have received a copy of the GNU General Public License
	* along with this program; if not, write to the Free Software
	* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
	*
	* HISTORY
	* Revision 3.1 1994/04/17 11:31:54 too
	* initial revision
	* Modified 2000/06/13 for inclusion into BusyBox by Erik Andersen <andersee@debian.org>
	* Modified 2001/05/07 to add ability to pass TTYPE to remote host by Jim McQuillan
	* <jam@ltsp.org>
	*
	*/

	#include <termios.h>
	#include <unistd.h>
	#include <errno.h>
	#include <stdlib.h>
	#include <stdarg.h>
	#include <string.h>
	#include <signal.h>
	#include <arpa/telnet.h>
	#include <sys/types.h>
	#include <sys/socket.h>
	#include <netinet/in.h>
	#include "busybox.h"

	#ifdef CONFIG_FEATURE_AUTOWIDTH
	# include <sys/ioctl.h>
	#endif

	#if 0
	static const int DOTRACE = 1;
	#endif

	#ifdef DOTRACE
	#include <arpa/inet.h> /* for inet_ntoa()... */
	#define TRACE(x, y) do { if (x) printf y; } while (0)
	#else
	#define TRACE(x, y)
	#endif

	#if 0
	#define USE_POLL
	#include <sys/poll.h>
	#else
	#include <sys/time.h>
	#endif

	#define DATABUFSIZE 128
	#define IACBUFSIZE 128

	static const int CHM_TRY = 0;
	static const int CHM_ON = 1;
	static const int CHM_OFF = 2;

	static const int UF_ECHO = 0x01;
	static const int UF_SGA = 0x02;

	enum {
	TS_0 = 1,
	TS_IAC = 2,
	TS_OPT = 3,
	TS_SUB1 = 4,
	TS_SUB2 = 5,
	};

	#define WriteCS(fd, str) write(fd, str, sizeof str -1)

	typedef unsigned char byte;

	/* use globals to reduce size ??? / / test this hypothesis later */
	static struct Globalvars {
	int netfd; /* console fd:s are 0 and 1 (and 2) */
	/* same buffer used both for network and console read/write */
	char buf[DATABUFSIZE]; /* allocating so static size is smaller */
	byte telstate; /* telnet negotiation state from network input */
	byte telwish; /* DO, DONT, WILL, WONT */
	byte charmode;
	byte telflags;
	byte gotsig;
	/* buffer to handle telnet negotiations */
	char iacbuf[IACBUFSIZE];
	short iaclen; /* could even use byte */
	struct termios termios_def;
	struct termios termios_raw;
	} G;

	#define xUSE_GLOBALVAR_PTR /* xUSE... -> don't use :D (makes smaller code) */

	#ifdef USE_GLOBALVAR_PTR
	struct Globalvars * Gptr;
	#define G (*Gptr)
	#endif

	static inline void iacflush(void)
	{
	write(G.netfd, G.iacbuf, G.iaclen);
	G.iaclen = 0;
	}

	/* Function prototypes */
	static void rawmode(void);
	static void cookmode(void);
	static void do_linemode(void);
	static void will_charmode(void);
	static void telopt(byte c);
	static int subneg(byte c);

	/* Some globals */
	static int one = 1;

	#ifdef CONFIG_FEATURE_TELNET_TTYPE
	static char *ttype;
	#endif

	#ifdef CONFIG_FEATURE_AUTOWIDTH
	static int win_width, win_height;
	#endif

	static void doexit(int ev)
	{
	cookmode();
	exit(ev);
	}

	static void conescape(void)
	{
	char b;

	if (G.gotsig) /* came from line mode... go raw */
	rawmode();

	WriteCS(1, "\r\nConsole escape. Commands are:\r\n\n"
	" l go to line mode\r\n"
	" c go to character mode\r\n"
	" z suspend telnet\r\n"
	" e exit telnet\r\n");

	if (read(0, &b, 1) <= 0)
	doexit(1);

	switch (b)
	{
	case 'l':
	if (!G.gotsig)
	{
	do_linemode();
	goto rrturn;
	}
	break;
	case 'c':
	if (G.gotsig)
	{
	will_charmode();
	goto rrturn;
	}
	break;
	case 'z':
	cookmode();
	kill(0, SIGTSTP);
	rawmode();
	break;
	case 'e':
	doexit(0);
	}

	WriteCS(1, "continuing...\r\n");

	if (G.gotsig)
	cookmode();

	rrturn:
	G.gotsig = 0;

	}
	static void handlenetoutput(int len)
	{
	/* here we could do smart tricks how to handle 0xFF:s in output
	* stream like writing twice every sequence of FF:s (thus doing
	* many write()s. But I think interactive telnet application does
	* not need to be 100% 8-bit clean, so changing every 0xff:s to
	* 0x7f:s
	*
	* 2002-mar-21, Przemyslaw Czerpak (druzus@polbox.com)
	* I don't agree.
	* first - I cannot use programs like sz/rz
	* second - the 0x0D is sent as one character and if the next
	* char is 0x0A then it's eaten by a server side.
	* third - whay doy you have to make 'many write()s'?
	* I don't understand.
	* So I implemented it. It's realy useful for me. I hope that
	* others people will find it interesting to.
	*/

	int i, j;
	byte * p = G.buf;
	byte outbuf[4*DATABUFSIZE];

	for (i = len, j = 0; i > 0; i--, p++)
	{
	if (*p == 0x1d)
	{
	conescape();
	return;
	}
	outbuf[j++] = *p;
	if (*p == 0xff)
	outbuf[j++] = 0xff;
	else if (*p == 0x0d)
	outbuf[j++] = 0x00;
	}
	if (j > 0 )
	write(G.netfd, outbuf, j);
	}


	static void handlenetinput(int len)
	{
	int i;
	int cstart = 0;

	for (i = 0; i < len; i++)
	{
	byte c = G.buf[i];

	if (G.telstate == 0) /* most of the time state == 0 */
	{
	if (c == IAC)
	{
	cstart = i;
	G.telstate = TS_IAC;
	}
	}
	else
	switch (G.telstate)
	{
	case TS_0:
	if (c == IAC)
	G.telstate = TS_IAC;
	else
	G.buf[cstart++] = c;
	break;

	case TS_IAC:
	if (c == IAC) /* IAC IAC -> 0xFF */
	{
	G.buf[cstart++] = c;
	G.telstate = TS_0;
	break;
	}
	/* else */
	switch (c)
	{
	case SB:
	G.telstate = TS_SUB1;
	break;
	case DO:
	case DONT:
	case WILL:
	case WONT:
	G.telwish = c;
	G.telstate = TS_OPT;
	break;
	default:
	G.telstate = TS_0; /* DATA MARK must be added later */
	}
	break;
	case TS_OPT: /* WILL, WONT, DO, DONT */
	telopt(c);
	G.telstate = TS_0;
	break;
	case TS_SUB1: /* Subnegotiation */
	case TS_SUB2: /* Subnegotiation */
	if (subneg(c))
	G.telstate = TS_0;
	break;
	}
	}
	if (G.telstate)
	{
	if (G.iaclen) iacflush();
	if (G.telstate == TS_0) G.telstate = 0;

	len = cstart;
	}

	if (len)
	write(1, G.buf, len);
	}


	/* ******************************* */

	static inline void putiac(int c)
	{
	G.iacbuf[G.iaclen++] = c;
	}


	static void putiac2(byte wwdd, byte c)
	{
	if (G.iaclen + 3 > IACBUFSIZE)
	iacflush();

	putiac(IAC);
	putiac(wwdd);
	putiac(c);
	}

	#if 0
	static void putiac1(byte c)
	{
	if (G.iaclen + 2 > IACBUFSIZE)
	iacflush();

	putiac(IAC);
	putiac(c);
	}
	#endif

	#ifdef CONFIG_FEATURE_TELNET_TTYPE
	static void putiac_subopt(byte c, char *str)
	{
	int len = strlen(str) + 6; // ( 2 + 1 + 1 + strlen + 2 )

	if (G.iaclen + len > IACBUFSIZE)
	iacflush();

	putiac(IAC);
	putiac(SB);
	putiac(c);
	putiac(0);

	while(*str)
	putiac(*str++);

	putiac(IAC);
	putiac(SE);
	}
	#endif

	#ifdef CONFIG_FEATURE_AUTOWIDTH
	static void putiac_naws(byte c, int x, int y)
	{
	if (G.iaclen + 9 > IACBUFSIZE)
	iacflush();

	putiac(IAC);
	putiac(SB);
	putiac(c);

	putiac((x >> 8) & 0xff);
	putiac(x & 0xff);
	putiac((y >> 8) & 0xff);
	putiac(y & 0xff);

	putiac(IAC);
	putiac(SE);
	}
	#endif

	/* void putiacstring (subneg strings) */

	/* ******************************* */

	static char const escapecharis[] = "\r\nEscape character is ";

	static void setConMode(void)
	{
	if (G.telflags & UF_ECHO)
	{
	if (G.charmode == CHM_TRY) {
	G.charmode = CHM_ON;
	printf("\r\nEntering character mode%s'^]'.\r\n", escapecharis);
	rawmode();
	}
	}
	else
	{
	if (G.charmode != CHM_OFF) {
	G.charmode = CHM_OFF;
	printf("\r\nEntering line mode%s'^C'.\r\n", escapecharis);
	cookmode();
	}
	}
	}

	/* ******************************* */

	static void will_charmode(void)
	{
	G.charmode = CHM_TRY;
	G.telflags \|= (UF_ECHO \| UF_SGA);
	setConMode();

	putiac2(DO, TELOPT_ECHO);
	putiac2(DO, TELOPT_SGA);
	iacflush();
	}

	static void do_linemode(void)
	{
	G.charmode = CHM_TRY;
	G.telflags &= ~(UF_ECHO \| UF_SGA);
	setConMode();

	putiac2(DONT, TELOPT_ECHO);
	putiac2(DONT, TELOPT_SGA);
	iacflush();
	}

	/* ******************************* */

	static inline void to_notsup(char c)
	{
	if (G.telwish == WILL) putiac2(DONT, c);
	else if (G.telwish == DO) putiac2(WONT, c);
	}

	static inline void to_echo(void)
	{
	/* if server requests ECHO, don't agree */
	if (G.telwish == DO) { putiac2(WONT, TELOPT_ECHO); return; }
	else if (G.telwish == DONT) return;

	if (G.telflags & UF_ECHO)
	{
	if (G.telwish == WILL)
	return;
	}
	else
	if (G.telwish == WONT)
	return;

	if (G.charmode != CHM_OFF)
	G.telflags ^= UF_ECHO;

	if (G.telflags & UF_ECHO)
	putiac2(DO, TELOPT_ECHO);
	else
	putiac2(DONT, TELOPT_ECHO);

	setConMode();
	WriteCS(1, "\r\n"); /* sudden modec */
	}

	static inline void to_sga(void)
	{
	/* daemon always sends will/wont, client do/dont */

	if (G.telflags & UF_SGA)
	{
	if (G.telwish == WILL)
	return;
	}
	else
	if (G.telwish == WONT)
	return;

	if ((G.telflags ^= UF_SGA) & UF_SGA) /* toggle */
	putiac2(DO, TELOPT_SGA);
	else
	putiac2(DONT, TELOPT_SGA);

	return;
	}

	#ifdef CONFIG_FEATURE_TELNET_TTYPE
	static inline void to_ttype(void)
	{
	/* Tell server we will (or won't) do TTYPE */

	if(ttype)
	putiac2(WILL, TELOPT_TTYPE);
	else
	putiac2(WONT, TELOPT_TTYPE);

	return;
	}
	#endif

	#ifdef CONFIG_FEATURE_AUTOWIDTH
	static inline void to_naws(void)
	{
	/* Tell server we will do NAWS */
	putiac2(WILL, TELOPT_NAWS);
	return;
	}
	#endif

	static void telopt(byte c)
	{
	switch (c)
	{
	case TELOPT_ECHO: to_echo(); break;
	case TELOPT_SGA: to_sga(); break;
	#ifdef CONFIG_FEATURE_TELNET_TTYPE
	case TELOPT_TTYPE: to_ttype();break;
	#endif
	#ifdef CONFIG_FEATURE_AUTOWIDTH
	case TELOPT_NAWS: to_naws();
	putiac_naws(c, win_width, win_height);
	break;
	#endif
	default: to_notsup(c);
	break;
	}
	}


	/* ******************************* */

	/* subnegotiation -- ignore all (except TTYPE,NAWS) */

	static int subneg(byte c)
	{
	switch (G.telstate)
	{
	case TS_SUB1:
	if (c == IAC)
	G.telstate = TS_SUB2;
	#ifdef CONFIG_FEATURE_TELNET_TTYPE
	else
	if (c == TELOPT_TTYPE)
	putiac_subopt(TELOPT_TTYPE,ttype);
	#endif
	break;
	case TS_SUB2:
	if (c == SE)
	return TRUE;
	G.telstate = TS_SUB1;
	/* break; */
	}
	return FALSE;
	}

	/* ******************************* */

	static void fgotsig(int sig)
	{
	G.gotsig = sig;
	}


	static void rawmode(void)
	{
	tcsetattr(0, TCSADRAIN, &G.termios_raw);
	}

	static void cookmode(void)
	{
	tcsetattr(0, TCSADRAIN, &G.termios_def);
	}

	extern int telnet_main(int argc, char** argv)
	{
	char *host;
	char *port;
	int len;
	#ifdef USE_POLL
	struct pollfd ufds[2];
	#else
	fd_set readfds;
	int maxfd;
	#endif

	#ifdef CONFIG_FEATURE_AUTOWIDTH
	struct winsize winp;
	if( ioctl(0, TIOCGWINSZ, &winp) == 0 ) {
	win_width = winp.ws_col;
	win_height = winp.ws_row;
	}
	#endif

	#ifdef CONFIG_FEATURE_TELNET_TTYPE
	ttype = getenv("TERM");
	#endif

	memset(&G, 0, sizeof G);

	if (tcgetattr(0, &G.termios_def) < 0)
	exit(1);

	G.termios_raw = G.termios_def;
	cfmakeraw(&G.termios_raw);

	if (argc < 2) bb_show_usage();
	port = (argc > 2)? argv[2] : "23";

	host = argv[1];

	G.netfd = xconnect(host, port);

	setsockopt(G.netfd, SOL_SOCKET, SO_KEEPALIVE, &one, sizeof one);

	signal(SIGINT, fgotsig);

	#ifdef USE_POLL
	ufds[0].fd = 0; ufds[1].fd = G.netfd;
	ufds[0].events = ufds[1].events = POLLIN;
	#else
	FD_ZERO(&readfds);
	FD_SET(0, &readfds);
	FD_SET(G.netfd, &readfds);
	maxfd = G.netfd + 1;
	#endif

	while (1)
	{
	#ifndef USE_POLL
	fd_set rfds = readfds;

	switch (select(maxfd, &rfds, NULL, NULL, NULL))
	#else
	switch (poll(ufds, 2, -1))
	#endif
	{
	case 0:
	/* timeout */
	case -1:
	/* error, ignore and/or log something, bay go to loop */
	if (G.gotsig)
	conescape();
	else
	sleep(1);
	break;
	default:

	#ifdef USE_POLL
	if (ufds[0].revents) /* well, should check POLLIN, but ... */
	#else
	if (FD_ISSET(0, &rfds))
	#endif
	{
	len = read(0, G.buf, DATABUFSIZE);

	if (len <= 0)
	doexit(0);

	TRACE(0, ("Read con: %d\n", len));

	handlenetoutput(len);
	}

	#ifdef USE_POLL
	if (ufds[1].revents) /* well, should check POLLIN, but ... */
	#else
	if (FD_ISSET(G.netfd, &rfds))
	#endif
	{
	len = read(G.netfd, G.buf, DATABUFSIZE);

	if (len <= 0)
	{
	WriteCS(1, "Connection closed by foreign host.\r\n");
	doexit(1);
	}
	TRACE(0, ("Read netfd (%d): %d\n", G.netfd, len));

	handlenetinput(len);
	}
	}
	}
	}

	/*
	Local Variables:
	c-file-style: "linux"
	c-basic-offset: 4
	tab-width: 4
	End:
	*/