tty.c

经典的ppp程序

/*
 * tty.c - code for handling serial ports in pppd.
 *
 * Copyright (C) 2000 Paul Mackerras.
 * All rights reserved.
 *
 * Portions Copyright (c) 1989 Carnegie Mellon University.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms are permitted
 * provided that the above copyright notice and this paragraph are
 * duplicated in all such forms and that any documentation,
 * advertising materials, and other materials related to such
 * distribution and use acknowledge that the software was developed
 * by Carnegie Mellon University.  The name of the
 * University may not be used to endorse or promote products derived
 * from this software without specific prior written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

#define RCSID	"$Id: tty.c,v 1.6 2001/03/12 22:59:01 paulus Exp $"

#include <stdio.h>
#include <ctype.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <signal.h>
#include <errno.h>
#include <fcntl.h>
#include <syslog.h>
#include <netdb.h>
#include <utmp.h>
#include <pwd.h>
#include <setjmp.h>
#include <sys/param.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#include "pppd.h"
#include "fsm.h"
#include "lcp.h"

void tty_process_extra_options __P((void));
void tty_check_options __P((void));
int  connect_tty __P((void));
void disconnect_tty __P((void));
void tty_close_fds __P((void));
void cleanup_tty __P((void));
void tty_do_send_config __P((int, u_int32_t, int, int));

static int setdevname __P((char *, char **, int));
static int setspeed __P((char *, char **, int));
static int setxonxoff __P((char **));
static int setescape __P((char **));
static void printescape __P((option_t *, void (*)(void *, char *,...),void *));
static void finish_tty __P((void));
static int start_charshunt __P((int, int));
static void stop_charshunt __P((void *, int));
static void charshunt_done __P((void *));
static void charshunt __P((int, int, char *));
static int record_write __P((FILE *, int code, u_char *buf, int nb,
			     struct timeval *));
static int open_socket __P((char *));
static void maybe_relock __P((void *, int));

static int pty_master;		/* fd for master side of pty */
static int pty_slave;		/* fd for slave side of pty */
static int real_ttyfd;		/* fd for actual serial port (not pty) */
static int ttyfd;		/* Serial port file descriptor */
static char speed_str[16];	/* Serial port speed as string */

mode_t tty_mode = (mode_t)-1;	/* Original access permissions to tty */
int baud_rate;			/* Actual bits/second for serial device */
char *callback_script;		/* script for doing callback */
int charshunt_pid;		/* Process ID for charshunt */
int locked;			/* lock() has succeeded */
struct stat devstat;		/* result of stat() on devnam */

/* option variables */
int	crtscts = 0;		/* Use hardware flow control */
bool	modem = 1;		/* Use modem control lines */
int	inspeed = 0;		/* Input/Output speed requested */
bool	lockflag = 0;		/* Create lock file to lock the serial dev */
char	*initializer = NULL;	/* Script to initialize physical link */
char	*connect_script = NULL;	/* Script to establish physical link */
char	*disconnect_script = NULL; /* Script to disestablish physical link */
char	*welcomer = NULL;	/* Script to run after phys link estab. */
char	*ptycommand = NULL;	/* Command to run on other side of pty */
bool	notty = 0;		/* Stdin/out is not a tty */
char	*record_file = NULL;	/* File to record chars sent/received */
int	max_data_rate;		/* max bytes/sec through charshunt */
bool	sync_serial = 0;	/* Device is synchronous serial device */
char	*pty_socket = NULL;	/* Socket to connect to pty */
int	using_pty = 0;		/* we're allocating a pty as the device */

extern uid_t uid;
extern int kill_link;

/* XXX */
extern int privopen;		/* don't lock, open device as root */

u_int32_t xmit_accm[8];		/* extended transmit ACCM */

/* option descriptors */
option_t tty_options[] = {
    /* device name must be first, or change connect_tty() below! */
    { "device name", o_wild, (void *) &setdevname,
      "Serial port device name",
      OPT_DEVNAM | OPT_PRIVFIX | OPT_NOARG  | OPT_A2STRVAL | OPT_STATIC,
      devnam},

    { "tty speed", o_wild, (void *) &setspeed,
      "Baud rate for serial port",
      OPT_PRIO | OPT_NOARG | OPT_A2STRVAL | OPT_STATIC, speed_str },

    { "lock", o_bool, &lockflag,
      "Lock serial device with UUCP-style lock file", OPT_PRIO | 1 },
    { "nolock", o_bool, &lockflag,
      "Don't lock serial device", OPT_PRIOSUB | OPT_PRIV },

    { "init", o_string, &initializer,
      "A program to initialize the device", OPT_PRIO | OPT_PRIVFIX },

    { "connect", o_string, &connect_script,
      "A program to set up a connection", OPT_PRIO | OPT_PRIVFIX },

    { "disconnect", o_string, &disconnect_script,
      "Program to disconnect serial device", OPT_PRIO | OPT_PRIVFIX },

    { "welcome", o_string, &welcomer,
      "Script to welcome client", OPT_PRIO | OPT_PRIVFIX },

    { "pty", o_string, &ptycommand,
      "Script to run on pseudo-tty master side",
      OPT_PRIO | OPT_PRIVFIX | OPT_DEVNAM },

    { "notty", o_bool, &notty,
      "Input/output is not a tty", OPT_DEVNAM | 1 },

    { "socket", o_string, &pty_socket,
      "Send and receive over socket, arg is host:port",
      OPT_PRIO | OPT_DEVNAM },

    { "record", o_string, &record_file,
      "Record characters sent/received to file", OPT_PRIO },

    { "crtscts", o_int, &crtscts,
      "Set hardware (RTS/CTS) flow control",
      OPT_PRIO | OPT_NOARG | OPT_VAL(1) },
    { "cdtrcts", o_int, &crtscts,
      "Set alternate hardware (DTR/CTS) flow control",
      OPT_PRIOSUB | OPT_NOARG | OPT_VAL(2) },
    { "nocrtscts", o_int, &crtscts,
      "Disable hardware flow control",
      OPT_PRIOSUB | OPT_NOARG | OPT_VAL(-1) },
    { "-crtscts", o_int, &crtscts,
      "Disable hardware flow control",
      OPT_PRIOSUB | OPT_ALIAS | OPT_NOARG | OPT_VAL(-1) },
    { "nocdtrcts", o_int, &crtscts,
      "Disable hardware flow control",
      OPT_PRIOSUB | OPT_ALIAS | OPT_NOARG | OPT_VAL(-1) },
    { "xonxoff", o_special_noarg, (void *)setxonxoff,
      "Set software (XON/XOFF) flow control", OPT_PRIOSUB },

    { "modem", o_bool, &modem,
      "Use modem control lines", OPT_PRIO | 1 },
    { "local", o_bool, &modem,
      "Don't use modem control lines", OPT_PRIOSUB | 0 },

    { "sync", o_bool, &sync_serial,
      "Use synchronous HDLC serial encoding", 1 },

    { "datarate", o_int, &max_data_rate,
      "Maximum data rate in bytes/sec (with pty, notty or record option)",
      OPT_PRIO },

    { "escape", o_special, (void *)setescape,
      "List of character codes to escape on transmission",
      OPT_A2PRINTER, (void *)printescape },

    { NULL }
};


struct channel tty_channel = {
	tty_options,
	&tty_process_extra_options,
	&tty_check_options,
	&connect_tty,
	&disconnect_tty,
	&tty_establish_ppp,
	&tty_disestablish_ppp,
	&tty_do_send_config,
	&tty_recv_config,
	&cleanup_tty,
	&tty_close_fds
};

/*
 * setspeed - Set the serial port baud rate.
 * If doit is 0, the call is to check whether this option is
 * potentially a speed value.
 */
static int
setspeed(arg, argv, doit)
    char *arg;
    char **argv;
    int doit;
{
	char *ptr;
	int spd;

	spd = strtol(arg, &ptr, 0);
	if (ptr == arg || *ptr != 0 || spd == 0)
		return 0;
	if (doit) {
		inspeed = spd;
		slprintf(speed_str, sizeof(speed_str), "%d", spd);
	}
	return 1;
}


/*
 * setdevname - Set the device name.
 * If doit is 0, the call is to check whether this option is
 * potentially a device name.
 */
static int
setdevname(cp, argv, doit)
    char *cp;
    char **argv;
    int doit;
{
	struct stat statbuf;
	char dev[MAXPATHLEN];

	if (*cp == 0)
		return 0;

	if (strncmp("/dev/", cp, 5) != 0) {
		strlcpy(dev, "/dev/", sizeof(dev));
		strlcat(dev, cp, sizeof(dev));
		cp = dev;
	}

	/*
	 * Check if there is a character device by this name.
	 */
	if (stat(cp, &statbuf) < 0) {
		if (!doit)
			return errno != ENOENT;
		option_error("Couldn't stat %s: %m", cp);
		return 0;
	}
	if (!S_ISCHR(statbuf.st_mode)) {
		if (doit)
			option_error("%s is not a character device", cp);
		return 0;
	}

	if (doit) {
		strlcpy(devnam, cp, sizeof(devnam));
		devstat = statbuf;
		default_device = 0;
	}
  
	return 1;
}

static int
setxonxoff(argv)
    char **argv;
{
	lcp_wantoptions[0].asyncmap |= 0x000A0000;	/* escape ^S and ^Q */
	lcp_wantoptions[0].neg_asyncmap = 1;

	crtscts = -2;
	return 1;
}

/*
 * setescape - add chars to the set we escape on transmission.
 */
static int
setescape(argv)
    char **argv;
{
    int n, ret;
    char *p, *endp;

    p = *argv;
    ret = 1;
    while (*p) {
	n = strtol(p, &endp, 16);
	if (p == endp) {
	    option_error("escape parameter contains invalid hex number '%s'",
			 p);
	    return 0;
	}
	p = endp;
	if (n < 0 || n == 0x5E || n > 0xFF) {
	    option_error("can't escape character 0x%x", n);
	    ret = 0;
	} else
	    xmit_accm[n >> 5] |= 1 << (n & 0x1F);
	while (*p == ',' || *p == ' ')
	    ++p;
    }
    lcp_allowoptions[0].asyncmap = xmit_accm[0];
    return ret;
}

static void
printescape(opt, printer, arg)
    option_t *opt;
    void (*printer) __P((void *, char *, ...));
    void *arg;
{
	int n;
	int first = 1;

	for (n = 0; n < 256; ++n) {
		if (n == 0x7d)
			n += 2;		/* skip 7d, 7e */
		if (xmit_accm[n >> 5] & (1 << (n & 0x1f))) {
			if (!first)
				printer(arg, ",");
			else
				first = 0;
			printer(arg, "%x", n);
		}
	}
	if (first)
		printer(arg, "oops # nothing escaped");
}

/*
 * tty_init - do various tty-related initializations.
 */
void tty_init()
{
    add_notifier(&pidchange, maybe_relock, 0);
    the_channel = &tty_channel;
    xmit_accm[3] = 0x60000000;
}

/*
 * tty_process_extra_options - work out which tty device we are using
 * and read its options file.
 */
void tty_process_extra_options()
{
	using_pty = notty || ptycommand != NULL || pty_socket != NULL;
	if (using_pty)
		return;
	if (default_device) {
		char *p;
		if (!isatty(0) || (p = ttyname(0)) == NULL) {
			option_error("no device specified and stdin is not a tty");
			exit(EXIT_OPTION_ERROR);
		}
		strlcpy(devnam, p, sizeof(devnam));
		if (stat(devnam, &devstat) < 0)
			fatal("Couldn't stat default device %s: %m", devnam);
	}


	/*
	 * Parse the tty options file.
	 * The per-tty options file should not change
	 * ptycommand, pty_socket, notty or devnam.
	 * options_for_tty doesn't override options set on the command line,
	 * except for some privileged options.
	 */
	if (!options_for_tty())
		exit(EXIT_OPTION_ERROR);
}

/*
 * tty_check_options - do consistency checks on the options we were given.
 */
void
tty_check_options()
{
	struct stat statbuf;
	int fdflags;

	if (demand && connect_script == 0) {
		option_error("connect script is required for demand-dialling\n");
		exit(EXIT_OPTION_ERROR);
	}
	/* default holdoff to 0 if no connect script has been given */
	if (connect_script == 0 && !holdoff_specified)
		holdoff = 0;

	if (using_pty) {
		if (!default_device) {
			option_error("%s option precludes specifying device name",
				     notty? "notty": "pty");
			exit(EXIT_OPTION_ERROR);
		}
		if (ptycommand != NULL && notty) {
			option_error("pty option is incompatible with notty option");
			exit(EXIT_OPTION_ERROR);
		}
		if (pty_socket != NULL && (ptycommand != NULL || notty)) {
			option_error("socket option is incompatible with pty and notty");
			exit(EXIT_OPTION_ERROR);
		}
		default_device = notty;
		lockflag = 0;
		modem = 0;
		if (notty && log_to_fd <= 1)
			log_to_fd = -1;
	} else {
		/*
		 * If the user has specified a device which is the same as
		 * the one on stdin, pretend they didn't specify any.
		 * If the device is already open read/write on stdin,
		 * we assume we don't need to lock it, and we can open it
		 * as root.
		 */
		if (fstat(0, &statbuf) >= 0 && S_ISCHR(statbuf.st_mode)
		    && statbuf.st_rdev == devstat.st_rdev) {
			default_device = 1;
			fdflags = fcntl(0, F_GETFL);
			if (fdflags != -1 && (fdflags & O_ACCMODE) == O_RDWR)
				privopen = 1;
		}
	}
	if (default_device)
		nodetach = 1;

	/*
	 * Don't send log messages to the serial port, it tends to
	 * confuse the peer. :-)
	 */
	if (log_to_fd >= 0 && fstat(log_to_fd, &statbuf) >= 0
	    && S_ISCHR(statbuf.st_mode) && statbuf.st_rdev == devstat.st_rdev)
		log_to_fd = -1;
}

/*
 * connect_tty - get the serial port ready to start doing PPP.
 * That is, open the serial port, set its speed and mode, and run
 * the connector and/or welcomer.
 */
int connect_tty()
{
	char *connector;
	int fdflags;
	struct stat statbuf;
	char numbuf[16];

	/*
	 * Get a pty master/slave pair if the pty, notty, socket,
	 * or record options were specified.
	 */
	error("connect_tty");
	strlcpy(ppp_devnam, devnam, sizeof(ppp_devnam));
	pty_master = -1;
	pty_slave = -1;
	real_ttyfd = -1;
	if (using_pty || record_file != NULL) {
		if (!get_pty(&pty_master, &pty_slave, ppp_devnam, uid)) {
			error("Couldn't allocate pseudo-tty");
			status = EXIT_FATAL_ERROR;
			return -1;
		}
		set_up_tty(pty_slave, 1);
	}

	/*
	 * Lock the device if we've been asked to.
	 */
	status = EXIT_LOCK_FAILED;
	if (lockflag && !privopen) {
		if (lock(devnam) < 0)
			return -1;
		locked = 1;
	}

	/*
	 * Open the serial device and set it up to be the ppp interface.
	 * First we open it in non-blocking mode so we can set the
	 * various termios flags appropriately.  If we aren't dialling
	 * out and we want to use the modem lines, we reopen it later
	 * in order to wait for the carrier detect signal from the modem.
	 */
	hungup = 0;
	kill_link = 0;
	connector = doing_callback? callback_script: connect_script;
	if (devnam[0] != 0) {
		for (;;) {
			/* If the user specified the device name, become the
			   user before opening it. */
			int err, prio;

			prio = privopen? OPRIO_ROOT: tty_options[0].priority;
			if (prio < OPRIO_ROOT)
				seteuid(uid);
			error("devname=%s",devnam);
			ttyfd = open(devnam, O_NONBLOCK | O_RDWR, 0);
			err = errno;
			if (prio < OPRIO_ROOT)
				seteuid(0);
			if (ttyfd >= 0)
				break;
			errno = err;
			if (err != EINTR) {
				error("Failed to open %s: %m", devnam);
				status = EXIT_OPEN_FAILED;
			}
			if (!persist || err != EINTR)
				return -1;
		}
		real_ttyfd = ttyfd;
		if ((fdflags = fcntl(ttyfd, F_GETFL)) == -1
		    || fcntl(ttyfd, F_SETFL, fdflags & ~O_NONBLOCK) < 0)
			warn("Couldn't reset non-blocking mode on device: %m");

		/*
		 * Do the equivalent of `mesg n' to stop broadcast messages.
		 */
		if (fstat(ttyfd, &statbuf) < 0
		    || fchmod(ttyfd, statbuf.st_mode & ~(S_IWGRP | S_IWOTH)) < 0) {
			warn("Couldn't restrict write permissions to %s: %m", devnam);
		} else
			tty_mode = statbuf.st_mode;

		/*
		 * Set line speed, flow control, etc.
		 * If we have a non-null connection or initializer script,
		 * on most systems we set CLOCAL for now so that we can talk
		 * to the modem before carrier comes up.  But this has the
		 * side effect that we might miss it if CD drops before we
		 * get to clear CLOCAL below.  On systems where we can talk
		 * successfully to the modem with CLOCAL clear and CD down,
		 * we could clear CLOCAL at this point.
		 */
		set_up_tty(ttyfd, ((connector != NULL && connector[0] != 0)
				   || initializer != NULL));
	}

	/*
	 * If the pty, socket, notty and/or record option was specified,
	 * start up the character shunt now.
	 */
	status = EXIT_PTYCMD_FAILED;
	if (ptycommand != NULL) {
		if (record_file != NULL) {
			int ipipe[2], opipe[2], ok;

			if (pipe(ipipe) < 0 || pipe(opipe) < 0)
				fatal("Couldn't create pipes for record option: %m");
			ok = device_script(ptycommand, opipe[0], ipipe[1], 1) == 0
				&& start_charshunt(ipipe[0], opipe[1]);
			close(ipipe[0]);
			close(ipipe[1]);
			close(opipe[0]);
			close(opipe[1]);
			if (!ok)
				return -1;
		} else {
			if (device_script(ptycommand, pty_master, pty_master, 1) < 0)
				return -1;
			ttyfd = pty_slave;
			close(pty_master);
			pty_master = -1;
		}
	} else if (pty_socket != NULL) {
		int fd = open_socket(pty_socket);
		if (fd < 0)
			return -1;