telnet.c - fp2-dev/platform/external/busybox - Gitiles

 /*
  * $Id: telnet.c,v 1.3 2000/05/12 19:41:47 erik Exp $
  * Mini telnet implementation for busybox
  *
  * Copyright (C) 2000 by Randolph Chung <tausq@debian.org>
  *
  * 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
  *
  * This version of telnet is adapted (but very heavily modified) from the
  * telnet in netkit-telnet 0.16, which is:
  *
  * Copyright (c) 1989 The Regents of the University of California.
  * All rights reserved.
  *
  * Original copyright notice is retained at the end of this file.
  */

 #include "internal.h"
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
 #include <ctype.h>
 #include <signal.h>
 #include <errno.h>
 #include <netdb.h>
 #include <termios.h>
 #include <netinet/in.h>
 #include <sys/types.h>
 #include <sys/socket.h>
 #include <sys/ioctl.h>
 #define TELOPTS
 #include <arpa/telnet.h>
 #include <arpa/inet.h>

 static int STDIN = 0;
 static int STDOUT = 1;
 static const char *telnet_usage = "telnet host [port]\n"
 #ifndef BB_FEATURE_TRIVIAL_HELP
 	"\nProvides interactive communication with another\n"
 	"networked host using the TELNET protocol\n"
 #endif
 	;
 static struct termios saved_tc;
 static unsigned char options[NTELOPTS];
 static char tr_state = 0; /* telnet send and receive state */
 static unsigned char subbuffer[256];
 static unsigned char *subpointer, *subend;
 #define	SB_CLEAR()	subpointer = subbuffer;
 #define	SB_TERM()	{ subend = subpointer; SB_CLEAR(); }
 #define	SB_ACCUM(c)	if (subpointer < (subbuffer+sizeof subbuffer)) { *subpointer++ = (c); }
 #define	SB_GET()	(*subpointer++)
 #define	SB_PEEK()	(*subpointer)
 #define	SB_EOF()	(subpointer >= subend)
 #define	SB_LEN()	(subend - subpointer)

 #define TELNETPORT		23
 #define MASK_WILL		0x01
 #define MASK_WONT		0x04
 #define MASK_DO			0x10
 #define MASK_DONT		0x40

 #define TFLAG_ISSET(opt, flag) (options[opt] & MASK_##flag)
 #define TFLAG_SET(opt, flag) (options[opt] |= MASK_##flag)
 #define TFLAG_CLR(opt, flag) (options[opt] &= ~MASK_##flag)

 #define PERROR(ctx) do { fprintf(stderr, "%s: %s\n", ctx, strerror(errno)); \
                          return; } while (0)

 #define	TS_DATA		0
 #define	TS_IAC		1
 #define	TS_WILL		2
 #define	TS_WONT		3
 #define	TS_DO		4
 #define	TS_DONT		5
 #define	TS_CR		6
 #define	TS_SB		7		/* sub-option collection */
 #define	TS_SE		8		/* looking for sub-option end */

 /* prototypes */
 static void telnet_init(void);
 static void telnet_start(char *host, int port);
 static void telnet_shutdown(void);
 /* ******************************************************************* */
 #define SENDCOMMAND(c,o) \
 	char buf[3]; \
 	buf[0] = IAC; buf[1] = c; buf[2] = o; \
 	write(s, buf, sizeof(buf));

 static inline void telnet_sendwill(int s, int c) { SENDCOMMAND(WILL, c); }
 static inline void telnet_sendwont(int s, int c) { SENDCOMMAND(WONT, c); }
 static inline void telnet_senddo(int s, int c) { SENDCOMMAND(DO, c); }
 static inline void telnet_senddont(int s, int c) { SENDCOMMAND(DONT, c); }

 static void telnet_setoptions(int s)
 {
 	/*
 	telnet_sendwill(s, TELOPT_NAWS); TFLAG_SET(TELOPT_NAWS, WILL);
 	telnet_sendwill(s, TELOPT_TSPEED); TFLAG_SET(TELOPT_TSPEED, WILL);
 	telnet_sendwill(s, TELOPT_NEW_ENVIRON); TFLAG_SET(TELOPT_NEW_ENVIRON, WILL);
 	telnet_senddo(s, TELOPT_STATUS); TFLAG_SET(TELOPT_STATUS, DO);
 	telnet_sendwill(s, TELOPT_TTYPE); TFLAG_SET(TELOPT_TTYPE, WILL);
 	*/
 	telnet_senddo(s, TELOPT_SGA); TFLAG_SET(TELOPT_SGA, DO);
 	telnet_sendwill(s, TELOPT_LFLOW); TFLAG_SET(TELOPT_LFLOW, WILL);
 	telnet_sendwill(s, TELOPT_LINEMODE); TFLAG_SET(TELOPT_LINEMODE, WILL);
 	telnet_senddo(s, TELOPT_BINARY); TFLAG_SET(TELOPT_BINARY, DO);
 	telnet_sendwill(s, TELOPT_BINARY); TFLAG_SET(TELOPT_BINARY, WILL);
 }

 static void telnet_suboptions(int net)
 {
 	char buf[256];
 	switch (SB_GET()) {
 		case TELOPT_TTYPE:
 			if (TFLAG_ISSET(TELOPT_TTYPE, WONT)) return;
 			if (SB_EOF() || SB_GET() != TELQUAL_SEND) {
       			return;
     		} else {
       			const char *name = getenv("TERM");
 				if (name) {
 					snprintf(buf, sizeof(buf), "%c%c%c%c%s%c%c", IAC, SB,
 						TELOPT_TTYPE, TELQUAL_IS, name, IAC, SE);
 					write(net, buf, strlen(name)+6);
 				}
 			}
     		break;
   		case TELOPT_TSPEED:
 			if (TFLAG_ISSET(TELOPT_TSPEED, WONT)) return;
     		if (SB_EOF()) return;
     		if (SB_GET() == TELQUAL_SEND) {
 				/*
       			long oospeed, iispeed;
       			netoring.printf("%c%c%c%c%ld,%ld%c%c", IAC, SB, TELOPT_TSPEED,
 		      TELQUAL_IS, oospeed, iispeed, IAC, SE);
     		    */
 			}
     		break;
 		/*
 		case TELOPT_LFLOW:
 			if (TFLAG_ISSET(TELOPT_LFLOW, WONT)) return;
 			if (SB_EOF()) return;
     		switch(SB_GET()) {
     			case 1: localflow = 1; break;
 				case 0: localflow = 0; break;
 				default: return;
 			}
     		break;
   		case TELOPT_LINEMODE:
 			if (TFLAG_ISSET(TELOPT_LINEMODE, WONT)) return;
 			if (SB_EOF()) return;
 			switch (SB_GET()) {
     			case WILL: lm_will(subpointer, SB_LEN()); break;
 				case WONT: lm_wont(subpointer, SB_LEN()); break;
 				case DO: lm_do(subpointer, SB_LEN()); break;
 				case DONT: lm_dont(subpointer, SB_LEN()); break;
 				case LM_SLC: slc(subpointer, SB_LEN()); break;
 				case LM_MODE: lm_mode(subpointer, SB_LEN(), 0); break;
 				default: break;
 			}
     		break;
 		case TELOPT_ENVIRON:
 			if (SB_EOF()) return;
 			switch(SB_PEEK()) {
 				case TELQUAL_IS:
 				case TELQUAL_INFO:
 					if (TFLAG_ISSET(TELOPT_ENVIRON, DONT)) return;
 					break;
 				case TELQUAL_SEND:
 					if (TFLAG_ISSET(TELOPT_ENVIRON, WONT)) return;
 					break;
 				default:
 					return;
 			}
 			env_opt(subpointer, SB_LEN());
 			break;
 		*/
 		case TELOPT_XDISPLOC:
 			if (TFLAG_ISSET(TELOPT_XDISPLOC, WONT)) return;
     		if (SB_EOF()) return;
 			if (SB_GET() == TELQUAL_SEND) {
 				const char *dp = getenv("DISPLAY");
 				if (dp) {
 					snprintf(buf, sizeof(buf), "%c%c%c%c%s%c%c", IAC, SB,
 						TELOPT_XDISPLOC, TELQUAL_IS, dp, IAC, SE);
 					write(net, buf, strlen(dp)+6);
 				}
 			}
     		break;
     	default:
 			break;
 	}
 }

 static void sighandler(int sig)
 {
 	telnet_shutdown();
 	exit(0);
 }

 static int telnet_send(int tty, int net)
 {
 	int ret;
 	unsigned char ch;

 	while ((ret = read(tty, &ch, 1)) > 0) {
 		if (ch == 29) { /* 29 -- ctrl-] */
 			/* do something here? */
 			exit(0);
 		} else {
 			ret = write(net, &ch, 1);
 			break;
 		}
 	}
 	if (ret == -1 && errno == EWOULDBLOCK) return 1;
 	return ret;
 }

 static int telnet_recv(int net, int tty)
 {
 	/* globals: tr_state - telnet receive state */
 	int ret, c = 0;
 	unsigned char ch;

 	while ((ret = read(net, &ch, 1)) > 0) {
 		c = ch;
 		/* printf("%02X ", c); fflush(stdout); */
 		switch (tr_state) {
 			case TS_DATA:
 				if (c == IAC) {
 					tr_state = TS_IAC;
 					break;
 				} else {
 					write(tty, &c, 1);
 				}
 				break;
 			case TS_IAC:
 				switch (c) {
 					case WILL:
 						tr_state = TS_WILL; break;
 					case WONT:
 						tr_state = TS_WONT; break;
 					case DO:
 						tr_state = TS_DO; break;
 					case DONT:
 						tr_state = TS_DONT; break;
 					case SB:
 						SB_CLEAR();
 						tr_state = TS_SB; break;
 					case IAC:
 						write(tty, &c, 1); /* fallthrough */
 					default:
 						tr_state = TS_DATA;
 				}

 			/* subnegotiation -- ignored for now */
 			case TS_SB:
 				if (c == IAC) tr_state = TS_SE;
 				else SB_ACCUM(c);
 				break;
 			case TS_SE:
 				if (c == IAC) {
 					SB_ACCUM(IAC);
 					tr_state = TS_SB;
 				} else if (c == SE) {
 					SB_ACCUM(IAC);
 					SB_ACCUM(SE);
 					subpointer -= 2;
 					SB_TERM();
 					telnet_suboptions(net);
 					tr_state = TS_DATA;
 				}
 			    /* otherwise this is an error, but we ignore it for now */
 				break;
 			/* handle incoming requests */
 			case TS_WILL:
 				printf("WILL %s\n", telopts[c]);
 				if (!TFLAG_ISSET(c, DO)) {
 					if (c == TELOPT_BINARY) {
 						TFLAG_SET(c, DO);
 						TFLAG_CLR(c, DONT);
 						telnet_senddo(net, c);
 					} else {
 						TFLAG_SET(c, DONT);
 						telnet_senddont(net, c);
 					}
 				}
 				telnet_senddont(net, c);
 				tr_state = TS_DATA;
 				break;
 			case TS_WONT:
 				printf("WONT %s\n", telopts[c]);
 				if (!TFLAG_ISSET(c, DONT)) {
 					TFLAG_SET(c, DONT);
 					TFLAG_CLR(c, DO);
 					telnet_senddont(net, c);
 				}
 				tr_state = TS_DATA;
 				break;
 			case TS_DO:
 				printf("DO %s\n", telopts[c]);
 				if (!TFLAG_ISSET(c, WILL)) {
 					if (c == TELOPT_BINARY) {
 						TFLAG_SET(c, WILL);
 						TFLAG_CLR(c, WONT);
 						telnet_sendwill(net, c);
 					} else {
 						TFLAG_SET(c, WONT);
 						telnet_sendwont(net, c);
 					}
 				}
 				tr_state = TS_DATA;
 				break;
 			case TS_DONT:
 				printf("DONT %s\n", telopts[c]);
 				if (!TFLAG_ISSET(c, WONT)) {
 					TFLAG_SET(c, WONT);
 					TFLAG_CLR(c, WILL);
 					telnet_sendwont(net, c);
 				}
 				tr_state = TS_DATA;
 				break;
 		}

 	}
 	if (ret == -1 && errno == EWOULDBLOCK) return 1;
 	return ret;
 }

 /* ******************************************************************* */
 static void telnet_init(void)
 {
 	struct termios tmp_tc;
 	cc_t esc = (']' & 0x1f); /* ctrl-] */

 	memset(options, 0, sizeof(options));
 	SB_CLEAR();

 	tcgetattr(STDIN, &saved_tc);

 	tmp_tc = saved_tc;
     tmp_tc.c_lflag &= ~ECHO; /* echo */
 	tmp_tc.c_oflag |= ONLCR; /* NL->CRLF translation */
 	tmp_tc.c_iflag |= ICRNL;
 	tmp_tc.c_iflag &= ~(IXANY|IXOFF|IXON); /* no flow control */
 	tmp_tc.c_lflag |= ISIG; /* trap signals */
 	tmp_tc.c_lflag &= ~ICANON; /* edit mode  */

 	/* misc settings, compat with default telnet stuff */
 	tmp_tc.c_oflag &= ~TABDLY;

 	/* 8-bit clean */
 	tmp_tc.c_iflag &= ~ISTRIP;
 	tmp_tc.c_cflag &= ~(CSIZE|PARENB);
 	tmp_tc.c_cflag |= saved_tc.c_cflag & (CSIZE|PARENB);
 	tmp_tc.c_oflag |= OPOST;

 	/* set escape character */
 	tmp_tc.c_cc[VEOL] = esc;
 	tcsetattr(STDIN, TCSADRAIN, &tmp_tc);
 }

 static void telnet_start(char *hostname, int port)
 {
     struct hostent *host = 0;
 	struct sockaddr_in addr;
     int s, c;
 	fd_set rfds, wfds;

 	memset(&addr, 0, sizeof(addr));
 	host = gethostbyname(hostname);
 	if (!host) {
 		fprintf(stderr, "Unknown host: %s\n", hostname);
 		return;
 	}
 	addr.sin_family = host->h_addrtype;
 	memcpy(&addr.sin_addr, host->h_addr, sizeof(addr.sin_addr));
 	addr.sin_port = htons(port);

 	printf("Trying %s...\n", inet_ntoa(addr.sin_addr));

 	if ((s = socket(AF_INET, SOCK_STREAM, 0)) < 0) PERROR("socket");
 	if (connect(s, (struct sockaddr *)&addr, sizeof(addr)) < 0)
 	    PERROR("connect");
 	printf("Connected to %s\n", hostname);
 	printf("Escape character is ^]\n");

 	signal(SIGINT, sighandler);
 	signal(SIGQUIT, sighandler);
 	signal(SIGPIPE, sighandler);
 	signal(SIGWINCH, sighandler);

 	/* make inputs nonblocking */
 	c = 1;
  	ioctl(s, FIONBIO, &c);
 	ioctl(STDIN, FIONBIO, &c);

 	if (port == TELNETPORT) telnet_setoptions(s);

 	/* shuttle data back and forth between tty and socket */
 	while (1) {
 		FD_ZERO(&rfds);
 		FD_ZERO(&wfds);

 		FD_SET(s, &rfds);
 		/* FD_SET(s, &wfds); */
 		FD_SET(STDIN, &rfds);
 		/* FD_SET(STDOUT, &wfds); */

 		if ((c = select(s+1, &rfds, &wfds, 0, 0))) {
 			if (c == -1) {
 			    /* handle errors */
 				PERROR("select");
 			}
 			if (FD_ISSET(s, &rfds)) {
 				/* input from network */
 				FD_CLR(s, &rfds);
 				c = telnet_recv(s, STDOUT);
 				if (c == 0) break;
 				if (c < 0) PERROR("telnet_recv");
 			}
 			if (FD_ISSET(STDIN, &rfds)) {
 				/* input from tty */
 				FD_CLR(STDIN, &rfds);
 				c = telnet_send(STDIN, s);
 				if (c == 0) break;
 				if (c < 0) PERROR("telnet_send");
 			}
 		}
 	}

     return;
 }

 static void telnet_shutdown(void)
 {
 	printf("\n");
 	tcsetattr(STDIN, TCSANOW, &saved_tc);
 }

 #ifdef STANDALONE_TELNET
 void usage(const char *msg)
 {
 	printf("%s", msg);
 	exit(0);
 }

 int main(int argc, char **argv)
 #else
 int telnet_main(int argc, char **argv)
 #endif
 {
     int port = TELNETPORT;

     argc--; argv++;
     if (argc < 1) usage(telnet_usage);
     if (argc > 1) port = atoi(argv[1]);
     telnet_init();
     atexit(telnet_shutdown);

     telnet_start(argv[0], port);
     return 0;
 }

 /*
  * Copyright (c) 1988, 1990 Regents of the University of California.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  * 3. All advertising materials mentioning features or use of this software
  *    must display the following acknowledgement:
  *	This product includes software developed by the University of
  *	California, Berkeley and its contributors.
  * 4. Neither the name of the University nor the names of its contributors
  *    may be used to endorse or promote products derived from this software
  *    without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  */
	/*
	* $Id: telnet.c,v 1.3 2000/05/12 19:41:47 erik Exp $
	* Mini telnet implementation for busybox
	*
	* Copyright (C) 2000 by Randolph Chung <tausq@debian.org>
	*
	* 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
	*
	* This version of telnet is adapted (but very heavily modified) from the
	* telnet in netkit-telnet 0.16, which is:
	*
	* Copyright (c) 1989 The Regents of the University of California.
	* All rights reserved.
	*
	* Original copyright notice is retained at the end of this file.
	*/

	#include "internal.h"
	#include <stdio.h>
	#include <stdlib.h>
	#include <unistd.h>
	#include <ctype.h>
	#include <signal.h>
	#include <errno.h>
	#include <netdb.h>
	#include <termios.h>
	#include <netinet/in.h>
	#include <sys/types.h>
	#include <sys/socket.h>
	#include <sys/ioctl.h>
	#define TELOPTS
	#include <arpa/telnet.h>
	#include <arpa/inet.h>

	static int STDIN = 0;
	static int STDOUT = 1;
	static const char *telnet_usage = "telnet host [port]\n"
	#ifndef BB_FEATURE_TRIVIAL_HELP
	"\nProvides interactive communication with another\n"
	"networked host using the TELNET protocol\n"
	#endif
	;
	static struct termios saved_tc;
	static unsigned char options[NTELOPTS];
	static char tr_state = 0; /* telnet send and receive state */
	static unsigned char subbuffer[256];
	static unsigned char subpointer, subend;
	#define SB_CLEAR() subpointer = subbuffer;
	#define SB_TERM() { subend = subpointer; SB_CLEAR(); }
	#define SB_ACCUM(c) if (subpointer < (subbuffer+sizeof subbuffer)) { *subpointer++ = (c); }
	#define SB_GET() (*subpointer++)
	#define SB_PEEK() (*subpointer)
	#define SB_EOF() (subpointer >= subend)
	#define SB_LEN() (subend - subpointer)

	#define TELNETPORT 23
	#define MASK_WILL 0x01
	#define MASK_WONT 0x04
	#define MASK_DO 0x10
	#define MASK_DONT 0x40

	#define TFLAG_ISSET(opt, flag) (options[opt] & MASK_##flag)
	#define TFLAG_SET(opt, flag) (options[opt] \|= MASK_##flag)
	#define TFLAG_CLR(opt, flag) (options[opt] &= ~MASK_##flag)

	#define PERROR(ctx) do { fprintf(stderr, "%s: %s\n", ctx, strerror(errno)); \
	return; } while (0)

	#define TS_DATA 0
	#define TS_IAC 1
	#define TS_WILL 2
	#define TS_WONT 3
	#define TS_DO 4
	#define TS_DONT 5
	#define TS_CR 6
	#define TS_SB 7 /* sub-option collection */
	#define TS_SE 8 /* looking for sub-option end */

	/* prototypes */
	static void telnet_init(void);
	static void telnet_start(char *host, int port);
	static void telnet_shutdown(void);
	/* ******************************************************************* */
	#define SENDCOMMAND(c,o) \
	char buf[3]; \
	buf[0] = IAC; buf[1] = c; buf[2] = o; \
	write(s, buf, sizeof(buf));

	static inline void telnet_sendwill(int s, int c) { SENDCOMMAND(WILL, c); }
	static inline void telnet_sendwont(int s, int c) { SENDCOMMAND(WONT, c); }
	static inline void telnet_senddo(int s, int c) { SENDCOMMAND(DO, c); }
	static inline void telnet_senddont(int s, int c) { SENDCOMMAND(DONT, c); }

	static void telnet_setoptions(int s)
	{
	/*
	telnet_sendwill(s, TELOPT_NAWS); TFLAG_SET(TELOPT_NAWS, WILL);
	telnet_sendwill(s, TELOPT_TSPEED); TFLAG_SET(TELOPT_TSPEED, WILL);
	telnet_sendwill(s, TELOPT_NEW_ENVIRON); TFLAG_SET(TELOPT_NEW_ENVIRON, WILL);
	telnet_senddo(s, TELOPT_STATUS); TFLAG_SET(TELOPT_STATUS, DO);
	telnet_sendwill(s, TELOPT_TTYPE); TFLAG_SET(TELOPT_TTYPE, WILL);
	*/
	telnet_senddo(s, TELOPT_SGA); TFLAG_SET(TELOPT_SGA, DO);
	telnet_sendwill(s, TELOPT_LFLOW); TFLAG_SET(TELOPT_LFLOW, WILL);
	telnet_sendwill(s, TELOPT_LINEMODE); TFLAG_SET(TELOPT_LINEMODE, WILL);
	telnet_senddo(s, TELOPT_BINARY); TFLAG_SET(TELOPT_BINARY, DO);
	telnet_sendwill(s, TELOPT_BINARY); TFLAG_SET(TELOPT_BINARY, WILL);
	}

	static void telnet_suboptions(int net)
	{
	char buf[256];
	switch (SB_GET()) {
	case TELOPT_TTYPE:
	if (TFLAG_ISSET(TELOPT_TTYPE, WONT)) return;
	if (SB_EOF() \|\| SB_GET() != TELQUAL_SEND) {
	return;
	} else {
	const char *name = getenv("TERM");
	if (name) {
	snprintf(buf, sizeof(buf), "%c%c%c%c%s%c%c", IAC, SB,
	TELOPT_TTYPE, TELQUAL_IS, name, IAC, SE);
	write(net, buf, strlen(name)+6);
	}
	}
	break;
	case TELOPT_TSPEED:
	if (TFLAG_ISSET(TELOPT_TSPEED, WONT)) return;
	if (SB_EOF()) return;
	if (SB_GET() == TELQUAL_SEND) {
	/*
	long oospeed, iispeed;
	netoring.printf("%c%c%c%c%ld,%ld%c%c", IAC, SB, TELOPT_TSPEED,
	TELQUAL_IS, oospeed, iispeed, IAC, SE);
	*/
	}
	break;
	/*
	case TELOPT_LFLOW:
	if (TFLAG_ISSET(TELOPT_LFLOW, WONT)) return;
	if (SB_EOF()) return;
	switch(SB_GET()) {
	case 1: localflow = 1; break;
	case 0: localflow = 0; break;
	default: return;
	}
	break;
	case TELOPT_LINEMODE:
	if (TFLAG_ISSET(TELOPT_LINEMODE, WONT)) return;
	if (SB_EOF()) return;
	switch (SB_GET()) {
	case WILL: lm_will(subpointer, SB_LEN()); break;
	case WONT: lm_wont(subpointer, SB_LEN()); break;
	case DO: lm_do(subpointer, SB_LEN()); break;
	case DONT: lm_dont(subpointer, SB_LEN()); break;
	case LM_SLC: slc(subpointer, SB_LEN()); break;
	case LM_MODE: lm_mode(subpointer, SB_LEN(), 0); break;
	default: break;
	}
	break;
	case TELOPT_ENVIRON:
	if (SB_EOF()) return;
	switch(SB_PEEK()) {
	case TELQUAL_IS:
	case TELQUAL_INFO:
	if (TFLAG_ISSET(TELOPT_ENVIRON, DONT)) return;
	break;
	case TELQUAL_SEND:
	if (TFLAG_ISSET(TELOPT_ENVIRON, WONT)) return;
	break;
	default:
	return;
	}
	env_opt(subpointer, SB_LEN());
	break;
	*/
	case TELOPT_XDISPLOC:
	if (TFLAG_ISSET(TELOPT_XDISPLOC, WONT)) return;
	if (SB_EOF()) return;
	if (SB_GET() == TELQUAL_SEND) {
	const char *dp = getenv("DISPLAY");
	if (dp) {
	snprintf(buf, sizeof(buf), "%c%c%c%c%s%c%c", IAC, SB,
	TELOPT_XDISPLOC, TELQUAL_IS, dp, IAC, SE);
	write(net, buf, strlen(dp)+6);
	}
	}
	break;
	default:
	break;
	}
	}

	static void sighandler(int sig)
	{
	telnet_shutdown();
	exit(0);
	}

	static int telnet_send(int tty, int net)
	{
	int ret;
	unsigned char ch;

	while ((ret = read(tty, &ch, 1)) > 0) {
	if (ch == 29) { /* 29 -- ctrl-] */
	/* do something here? */
	exit(0);
	} else {
	ret = write(net, &ch, 1);
	break;
	}
	}
	if (ret == -1 && errno == EWOULDBLOCK) return 1;
	return ret;
	}

	static int telnet_recv(int net, int tty)
	{
	/* globals: tr_state - telnet receive state */
	int ret, c = 0;
	unsigned char ch;

	while ((ret = read(net, &ch, 1)) > 0) {
	c = ch;
	/* printf("%02X ", c); fflush(stdout); */
	switch (tr_state) {
	case TS_DATA:
	if (c == IAC) {
	tr_state = TS_IAC;
	break;
	} else {
	write(tty, &c, 1);
	}
	break;
	case TS_IAC:
	switch (c) {
	case WILL:
	tr_state = TS_WILL; break;
	case WONT:
	tr_state = TS_WONT; break;
	case DO:
	tr_state = TS_DO; break;
	case DONT:
	tr_state = TS_DONT; break;
	case SB:
	SB_CLEAR();
	tr_state = TS_SB; break;
	case IAC:
	write(tty, &c, 1); /* fallthrough */
	default:
	tr_state = TS_DATA;
	}

	/* subnegotiation -- ignored for now */
	case TS_SB:
	if (c == IAC) tr_state = TS_SE;
	else SB_ACCUM(c);
	break;
	case TS_SE:
	if (c == IAC) {
	SB_ACCUM(IAC);
	tr_state = TS_SB;
	} else if (c == SE) {
	SB_ACCUM(IAC);
	SB_ACCUM(SE);
	subpointer -= 2;
	SB_TERM();
	telnet_suboptions(net);
	tr_state = TS_DATA;
	}
	/* otherwise this is an error, but we ignore it for now */
	break;
	/* handle incoming requests */
	case TS_WILL:
	printf("WILL %s\n", telopts[c]);
	if (!TFLAG_ISSET(c, DO)) {
	if (c == TELOPT_BINARY) {
	TFLAG_SET(c, DO);
	TFLAG_CLR(c, DONT);
	telnet_senddo(net, c);
	} else {
	TFLAG_SET(c, DONT);
	telnet_senddont(net, c);
	}
	}
	telnet_senddont(net, c);
	tr_state = TS_DATA;
	break;
	case TS_WONT:
	printf("WONT %s\n", telopts[c]);
	if (!TFLAG_ISSET(c, DONT)) {
	TFLAG_SET(c, DONT);
	TFLAG_CLR(c, DO);
	telnet_senddont(net, c);
	}
	tr_state = TS_DATA;
	break;
	case TS_DO:
	printf("DO %s\n", telopts[c]);
	if (!TFLAG_ISSET(c, WILL)) {
	if (c == TELOPT_BINARY) {
	TFLAG_SET(c, WILL);
	TFLAG_CLR(c, WONT);
	telnet_sendwill(net, c);
	} else {
	TFLAG_SET(c, WONT);
	telnet_sendwont(net, c);
	}
	}
	tr_state = TS_DATA;
	break;
	case TS_DONT:
	printf("DONT %s\n", telopts[c]);
	if (!TFLAG_ISSET(c, WONT)) {
	TFLAG_SET(c, WONT);
	TFLAG_CLR(c, WILL);
	telnet_sendwont(net, c);
	}
	tr_state = TS_DATA;
	break;
	}

	}
	if (ret == -1 && errno == EWOULDBLOCK) return 1;
	return ret;
	}

	/* ******************************************************************* */
	static void telnet_init(void)
	{
	struct termios tmp_tc;
	cc_t esc = (']' & 0x1f); /* ctrl-] */

	memset(options, 0, sizeof(options));
	SB_CLEAR();

	tcgetattr(STDIN, &saved_tc);

	tmp_tc = saved_tc;
	tmp_tc.c_lflag &= ~ECHO; /* echo */
	tmp_tc.c_oflag \|= ONLCR; /* NL->CRLF translation */
	tmp_tc.c_iflag \|= ICRNL;
	tmp_tc.c_iflag &= ~(IXANY\|IXOFF\|IXON); /* no flow control */
	tmp_tc.c_lflag \|= ISIG; /* trap signals */
	tmp_tc.c_lflag &= ~ICANON; /* edit mode */

	/* misc settings, compat with default telnet stuff */
	tmp_tc.c_oflag &= ~TABDLY;

	/* 8-bit clean */
	tmp_tc.c_iflag &= ~ISTRIP;
	tmp_tc.c_cflag &= ~(CSIZE\|PARENB);
	tmp_tc.c_cflag \|= saved_tc.c_cflag & (CSIZE\|PARENB);
	tmp_tc.c_oflag \|= OPOST;

	/* set escape character */
	tmp_tc.c_cc[VEOL] = esc;
	tcsetattr(STDIN, TCSADRAIN, &tmp_tc);
	}

	static void telnet_start(char *hostname, int port)
	{
	struct hostent *host = 0;
	struct sockaddr_in addr;
	int s, c;
	fd_set rfds, wfds;

	memset(&addr, 0, sizeof(addr));
	host = gethostbyname(hostname);
	if (!host) {
	fprintf(stderr, "Unknown host: %s\n", hostname);
	return;
	}
	addr.sin_family = host->h_addrtype;
	memcpy(&addr.sin_addr, host->h_addr, sizeof(addr.sin_addr));
	addr.sin_port = htons(port);

	printf("Trying %s...\n", inet_ntoa(addr.sin_addr));

	if ((s = socket(AF_INET, SOCK_STREAM, 0)) < 0) PERROR("socket");
	if (connect(s, (struct sockaddr *)&addr, sizeof(addr)) < 0)
	PERROR("connect");
	printf("Connected to %s\n", hostname);
	printf("Escape character is ^]\n");

	signal(SIGINT, sighandler);
	signal(SIGQUIT, sighandler);
	signal(SIGPIPE, sighandler);
	signal(SIGWINCH, sighandler);

	/* make inputs nonblocking */
	c = 1;
	ioctl(s, FIONBIO, &c);
	ioctl(STDIN, FIONBIO, &c);

	if (port == TELNETPORT) telnet_setoptions(s);

	/* shuttle data back and forth between tty and socket */
	while (1) {
	FD_ZERO(&rfds);
	FD_ZERO(&wfds);

	FD_SET(s, &rfds);
	/* FD_SET(s, &wfds); */
	FD_SET(STDIN, &rfds);
	/* FD_SET(STDOUT, &wfds); */

	if ((c = select(s+1, &rfds, &wfds, 0, 0))) {
	if (c == -1) {
	/* handle errors */
	PERROR("select");
	}
	if (FD_ISSET(s, &rfds)) {
	/* input from network */
	FD_CLR(s, &rfds);
	c = telnet_recv(s, STDOUT);
	if (c == 0) break;
	if (c < 0) PERROR("telnet_recv");
	}
	if (FD_ISSET(STDIN, &rfds)) {
	/* input from tty */
	FD_CLR(STDIN, &rfds);
	c = telnet_send(STDIN, s);
	if (c == 0) break;
	if (c < 0) PERROR("telnet_send");
	}
	}
	}

	return;
	}

	static void telnet_shutdown(void)
	{
	printf("\n");
	tcsetattr(STDIN, TCSANOW, &saved_tc);
	}

	#ifdef STANDALONE_TELNET
	void usage(const char *msg)
	{
	printf("%s", msg);
	exit(0);
	}

	int main(int argc, char **argv)
	#else
	int telnet_main(int argc, char **argv)
	#endif
	{
	int port = TELNETPORT;

	argc--; argv++;
	if (argc < 1) usage(telnet_usage);
	if (argc > 1) port = atoi(argv[1]);
	telnet_init();
	atexit(telnet_shutdown);

	telnet_start(argv[0], port);
	return 0;
	}

	/*
	* Copyright (c) 1988, 1990 Regents of the University of California.
	* All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions
	* are met:
	* 1. Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* 2. Redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in the
	* documentation and/or other materials provided with the distribution.
	* 3. All advertising materials mentioning features or use of this software
	* must display the following acknowledgement:
	* This product includes software developed by the University of
	* California, Berkeley and its contributors.
	* 4. Neither the name of the University nor the names of its contributors
	* may be used to endorse or promote products derived from this software
	* without specific prior written permission.
	*
	* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	* SUCH DAMAGE.
	*/