Tomato 1.24

[tomato.git] / release / src / router / busybox / loginutils / getty.c

/* vi: set sw=4 ts=4: */
/* agetty.c - another getty program for Linux. By W. Z. Venema 1989
 * Ported to Linux by Peter Orbaek <poe@daimi.aau.dk>
 * This program is freely distributable. The entire man-page used to
 * be here. Now read the real man-page agetty.8 instead.
 *
 * option added by Eric Rasmussen <ear@usfirst.org> - 12/28/95
 *
 * 1999-02-22 Arkadiusz Mickiewicz <misiek@misiek.eu.org>
 * - added Native Language Support
 *
 * 1999-05-05 Thorsten Kranzkowski <dl8bcu@gmx.net>
 * - enable hardware flow control before displaying /etc/issue
 *
 * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
 */

#include "libbb.h"
#include <syslog.h>

#if ENABLE_FEATURE_UTMP
#include <utmp.h> /* updwtmp() */
#endif

/*
 * Some heuristics to find out what environment we are in: if it is not
 * System V, assume it is SunOS 4.
 */
#ifdef LOGIN_PROCESS                    /* defined in System V utmp.h */
#include <sys/utsname.h>
#else /* if !sysV style, wtmp/utmp code is off */
#undef ENABLE_FEATURE_UTMP
#undef ENABLE_FEATURE_WTMP
#define ENABLE_FEATURE_UTMP 0
#define ENABLE_FEATURE_WTMP 0
#endif  /* LOGIN_PROCESS */

/*
 * Things you may want to modify.
 *
 * You may disagree with the default line-editing etc. characters defined
 * below. Note, however, that DEL cannot be used for interrupt generation
 * and for line editing at the same time.
 */

/* I doubt there are systems which still need this */
#undef HANDLE_ALLCAPS
#undef ANCIENT_BS_KILL_CHARS

#define _PATH_LOGIN "/bin/login"

/* If ISSUE is not defined, getty will never display the contents of the
 * /etc/issue file. You will not want to spit out large "issue" files at the
 * wrong baud rate.
 */
#define ISSUE "/etc/issue"              /* displayed before the login prompt */

/* Some shorthands for control characters. */
#define CTL(x)          ((x) ^ 0100)    /* Assumes ASCII dialect */
#define CR              CTL('M')        /* carriage return */
#define NL              CTL('J')        /* line feed */
#define BS              CTL('H')        /* back space */
#define DEL             CTL('?')        /* delete */

/* Defaults for line-editing etc. characters; you may want to change this. */
#define DEF_ERASE       DEL             /* default erase character */
#define DEF_INTR        CTL('C')        /* default interrupt character */
#define DEF_QUIT        CTL('\\')       /* default quit char */
#define DEF_KILL        CTL('U')        /* default kill char */
#define DEF_EOF         CTL('D')        /* default EOF char */
#define DEF_EOL         '\n'
#define DEF_SWITCH      0               /* default switch char */

/*
 * When multiple baud rates are specified on the command line, the first one
 * we will try is the first one specified.
 */
#define MAX_SPEED       10              /* max. nr. of baud rates */

/* Storage for command-line options. */
struct options {
        int flags;                      /* toggle switches, see below */
        unsigned timeout;               /* time-out period */
        const char *login;              /* login program */
        const char *tty;                /* name of tty */
        const char *initstring;         /* modem init string */
        const char *issue;              /* alternative issue file */
        int numspeed;                   /* number of baud rates to try */
        int speeds[MAX_SPEED];          /* baud rates to be tried */
};

/* Storage for things detected while the login name was read. */
struct chardata {
        unsigned char erase;    /* erase character */
        unsigned char kill;     /* kill character */
        unsigned char eol;      /* end-of-line character */
        unsigned char parity;   /* what parity did we see */
        /* (parity & 1): saw odd parity char with 7th bit set */
        /* (parity & 2): saw even parity char with 7th bit set */
        /* parity == 0: probably 7-bit, space parity? */
        /* parity == 1: probably 7-bit, odd parity? */
        /* parity == 2: probably 7-bit, even parity? */
        /* parity == 3: definitely 8 bit, no parity! */
        /* Hmm... with any value of "parity" 8 bit, no parity is possible */
#ifdef HANDLE_ALLCAPS
        unsigned char capslock; /* upper case without lower case */
#endif
};


/* Initial values for the above. */
static const struct chardata init_chardata = {
        DEF_ERASE,                              /* default erase character */
        DEF_KILL,                               /* default kill character */
        13,                                     /* default eol char */
        0,                                      /* space parity */
#ifdef HANDLE_ALLCAPS
        0,                                      /* no capslock */
#endif
};

static const char opt_string[] ALIGN1 = "I:LH:f:hil:mt:wn";
#define F_INITSTRING    (1 << 0)        /* -I initstring is set */
#define F_LOCAL         (1 << 1)        /* -L force local */
#define F_FAKEHOST      (1 << 2)        /* -H fake hostname */
#define F_CUSTISSUE     (1 << 3)        /* -f give alternative issue file */
#define F_RTSCTS        (1 << 4)        /* -h enable RTS/CTS flow control */
#define F_ISSUE         (1 << 5)        /* -i display /etc/issue */
#define F_LOGIN         (1 << 6)        /* -l non-default login program */
#define F_PARSE         (1 << 7)        /* -m process modem status messages */
#define F_TIMEOUT       (1 << 8)        /* -t time out */
#define F_WAITCRLF      (1 << 9)        /* -w wait for CR or LF */
#define F_NOPROMPT      (1 << 10)       /* -n don't ask for login name */


#define line_buf bb_common_bufsiz1

/* The following is used for understandable diagnostics. */
#ifdef DEBUGGING
static FILE *dbf;
#define DEBUGTERM "/dev/ttyp0"
#define debug(...) do { fprintf(dbf, __VA_ARGS__); fflush(dbf); } while (0)
#else
#define debug(...) ((void)0)
#endif


/* bcode - convert speed string to speed code; return <= 0 on failure */
static int bcode(const char *s)
{
        int value = bb_strtou(s, NULL, 10); /* yes, int is intended! */
        if (value < 0) /* bad terminating char, overflow, etc */
                return value;
        return tty_value_to_baud(value);
}

/* parse_speeds - parse alternate baud rates */
static void parse_speeds(struct options *op, char *arg)
{
        char *cp;

        /* NB: at least one iteration is always done */
        debug("entered parse_speeds\n");
        while ((cp = strsep(&arg, ",")) != NULL) {
                op->speeds[op->numspeed] = bcode(cp);
                if (op->speeds[op->numspeed] < 0)
                        bb_error_msg_and_die("bad speed: %s", cp);
                /* note: arg "0" turns into speed B0 */
                op->numspeed++;
                if (op->numspeed > MAX_SPEED)
                        bb_error_msg_and_die("too many alternate speeds");
        }
        debug("exiting parse_speeds\n");
}

/* parse_args - parse command-line arguments */
static void parse_args(char **argv, struct options *op, char **fakehost_p)
{
        char *ts;

        opt_complementary = "-2:t+"; /* at least 2 args; -t N */
        op->flags = getopt32(argv, opt_string,
                &(op->initstring), fakehost_p, &(op->issue),
                &(op->login), &op->timeout);
        argv += optind;
        if (op->flags & F_INITSTRING) {
                const char *p = op->initstring;
                char *q;

                op->initstring = q = xstrdup(p);
                /* copy optarg into op->initstring decoding \ddd
                   octal codes into chars */
                while (*p) {
                        if (*p == '\\') {
                                p++;
                                *q++ = bb_process_escape_sequence(&p);
                        } else {
                                *q++ = *p++;
                        }
                }
                *q = '\0';
        }
        op->flags ^= F_ISSUE;           /* invert flag "show /etc/issue" */
        debug("after getopt\n");

        /* we loosen up a bit and accept both "baudrate tty" and "tty baudrate" */
        op->tty = argv[0];      /* tty name */
        ts = argv[1];           /* baud rate(s) */
        if (isdigit(argv[0][0])) {
                /* a number first, assume it's a speed (BSD style) */
                op->tty = ts;   /* tty name is in argv[1] */
                ts = argv[0];   /* baud rate(s) */
        }
        parse_speeds(op, ts);

// TODO: if applet_name is set to "getty: TTY", bb_error_msg's get simpler!
// grep for "%s:"

        if (argv[2])
                xsetenv("TERM", argv[2]);

        debug("exiting parse_args\n");
}

/* open_tty - set up tty as standard { input, output, error } */
static void open_tty(const char *tty)
{
        /* Set up new standard input, unless we are given an already opened port. */
        if (NOT_LONE_DASH(tty)) {
//              struct stat st;
//              int cur_dir_fd;
//              int fd;

                /* Sanity checks... */
//              cur_dir_fd = xopen(".", O_DIRECTORY | O_NONBLOCK);
//              xchdir("/dev");
//              xstat(tty, &st);
//              if ((st.st_mode & S_IFMT) != S_IFCHR)
//                      bb_error_msg_and_die("%s: not a character device", tty);

                if (tty[0] != '/')
                        tty = xasprintf("/dev/%s", tty); /* will leak it */

                /* Open the tty as standard input. */
                debug("open(2)\n");
                close(0);
                /*fd =*/ xopen(tty, O_RDWR | O_NONBLOCK); /* uses fd 0 */

//              /* Restore current directory */
//              fchdir(cur_dir_fd);

                /* Open the tty as standard input, continued */
//              xmove_fd(fd, 0);
//              /* fd is >= cur_dir_fd, and cur_dir_fd gets closed too here: */
//              while (fd > 2)
//                      close(fd--);

                /* Set proper protections and ownership. */
                fchown(0, 0, 0);        /* 0:0 */
                fchmod(0, 0620);        /* crw--w---- */
        } else {
                /*
                 * Standard input should already be connected to an open port. Make
                 * sure it is open for read/write.
                 */
                if ((fcntl(0, F_GETFL) & O_RDWR) != O_RDWR)
                        bb_error_msg_and_die("stdin is not open for read/write");
        }
}

/* termios_init - initialize termios settings */
static void termios_init(struct termios *tp, int speed, struct options *op)
{
        speed_t ispeed, ospeed;
        /*
         * Initial termios settings: 8-bit characters, raw-mode, blocking i/o.
         * Special characters are set after we have read the login name; all
         * reads will be done in raw mode anyway. Errors will be dealt with
         * later on.
         */
#ifdef __linux__
        /* flush input and output queues, important for modems! */
        ioctl(0, TCFLSH, TCIOFLUSH); /* tcflush(0, TCIOFLUSH)? - same */
#endif
        ispeed = ospeed = speed;
        if (speed == B0) {
                /* Speed was specified as "0" on command line.
                 * Just leave it unchanged */
                ispeed = cfgetispeed(tp);
                ospeed = cfgetospeed(tp);
        }
        tp->c_cflag = CS8 | HUPCL | CREAD;
        if (op->flags & F_LOCAL)
                tp->c_cflag |= CLOCAL;
        cfsetispeed(tp, ispeed);
        cfsetospeed(tp, ospeed);

        tp->c_iflag = tp->c_lflag = tp->c_line = 0;
        tp->c_oflag = OPOST | ONLCR;
        tp->c_cc[VMIN] = 1;
        tp->c_cc[VTIME] = 0;

        /* Optionally enable hardware flow control */
#ifdef CRTSCTS
        if (op->flags & F_RTSCTS)
                tp->c_cflag |= CRTSCTS;
#endif

        tcsetattr_stdin_TCSANOW(tp);

        debug("term_io 2\n");
}

/* auto_baud - extract baud rate from modem status message */
static void auto_baud(char *buf, unsigned size_buf, struct termios *tp)
{
        int speed;
        int vmin;
        unsigned iflag;
        char *bp;
        int nread;

        /*
         * This works only if the modem produces its status code AFTER raising
         * the DCD line, and if the computer is fast enough to set the proper
         * baud rate before the message has gone by. We expect a message of the
         * following format:
         *
         * <junk><number><junk>
         *
         * The number is interpreted as the baud rate of the incoming call. If the
         * modem does not tell us the baud rate within one second, we will keep
         * using the current baud rate. It is advisable to enable BREAK
         * processing (comma-separated list of baud rates) if the processing of
         * modem status messages is enabled.
         */

        /*
         * Use 7-bit characters, don't block if input queue is empty. Errors will
         * be dealt with later on.
         */
        iflag = tp->c_iflag;
        tp->c_iflag |= ISTRIP;          /* enable 8th-bit stripping */
        vmin = tp->c_cc[VMIN];
        tp->c_cc[VMIN] = 0;             /* don't block if queue empty */
        tcsetattr_stdin_TCSANOW(tp);

        /*
         * Wait for a while, then read everything the modem has said so far and
         * try to extract the speed of the dial-in call.
         */
        sleep(1);
        nread = safe_read(STDIN_FILENO, buf, size_buf - 1);
        if (nread > 0) {
                buf[nread] = '\0';
                for (bp = buf; bp < buf + nread; bp++) {
                        if (isdigit(*bp)) {
                                speed = bcode(bp);
                                if (speed > 0) {
                                        tp->c_cflag &= ~CBAUD;
                                        tp->c_cflag |= speed;
                                }
                                break;
                        }
                }
        }

        /* Restore terminal settings. Errors will be dealt with later on. */
        tp->c_iflag = iflag;
        tp->c_cc[VMIN] = vmin;
        tcsetattr_stdin_TCSANOW(tp);
}

/* do_prompt - show login prompt, optionally preceded by /etc/issue contents */
static void do_prompt(struct options *op)
{
#ifdef ISSUE
        print_login_issue(op->issue, op->tty);
#endif
        print_login_prompt();
}

#ifdef HANDLE_ALLCAPS
/* all_is_upcase - string contains upper case without lower case */
/* returns 1 if true, 0 if false */
static int all_is_upcase(const char *s)
{
        while (*s)
                if (islower(*s++))
                        return 0;
        return 1;
}
#endif

/* get_logname - get user name, establish parity, speed, erase, kill, eol;
 * return NULL on BREAK, logname on success */
static char *get_logname(char *logname, unsigned size_logname,
                struct options *op, struct chardata *cp)
{
        char *bp;
        char c;                         /* input character, full eight bits */
        char ascval;                    /* low 7 bits of input character */
        int bits;                       /* # of "1" bits per character */
        int mask;                       /* mask with 1 bit up */
        static const char erase[][3] = {/* backspace-space-backspace */
                "\010\040\010",                 /* space parity */
                "\010\040\010",                 /* odd parity */
                "\210\240\210",                 /* even parity */
                "\010\040\010",                 /* 8 bit no parity */
        };

        /* NB: *cp is pre-initialized with init_chardata */

        /* Flush pending input (esp. after parsing or switching the baud rate). */
        sleep(1);
        ioctl(0, TCFLSH, TCIFLUSH); /* tcflush(0, TCIOFLUSH)? - same */

        /* Prompt for and read a login name. */
        logname[0] = '\0';
        while (!logname[0]) {
                /* Write issue file and prompt, with "parity" bit == 0. */
                do_prompt(op);

                /* Read name, watch for break, parity, erase, kill, end-of-line. */
                bp = logname;
                cp->eol = '\0';
                while (cp->eol == '\0') {

                        /* Do not report trivial EINTR/EIO errors. */
                        if (read(STDIN_FILENO, &c, 1) < 1) {
                                if (errno == EINTR || errno == EIO)
                                        exit(EXIT_SUCCESS);
                                bb_perror_msg_and_die("%s: read", op->tty);
                        }

                        /* BREAK. If we have speeds to try,
                         * return NULL (will switch speeds and return here) */
                        if (c == '\0' && op->numspeed > 1)
                                return NULL;

                        /* Do parity bit handling. */
                        if (!(op->flags & F_LOCAL) && (c & 0x80)) {       /* "parity" bit on? */
                                bits = 1;
                                mask = 1;
                                while (mask & 0x7f) {
                                        if (mask & c)
                                                bits++; /* count "1" bits */
                                        mask <<= 1;
                                }
                                /* ... |= 2 - even, 1 - odd */
                                cp->parity |= 2 - (bits & 1);
                        }

                        /* Do erase, kill and end-of-line processing. */
                        ascval = c & 0x7f;
                        switch (ascval) {
                        case CR:
                        case NL:
                                *bp = '\0';             /* terminate logname */
                                cp->eol = ascval;       /* set end-of-line char */
                                break;
                        case BS:
                        case DEL:
#ifdef ANCIENT_BS_KILL_CHARS
                        case '#':
#endif
                                cp->erase = ascval;     /* set erase character */
                                if (bp > logname) {
                                        full_write(STDOUT_FILENO, erase[cp->parity], 3);
                                        bp--;
                                }
                                break;
                        case CTL('U'):
#ifdef ANCIENT_BS_KILL_CHARS
                        case '@':
#endif
                                cp->kill = ascval;      /* set kill character */
                                while (bp > logname) {
                                        full_write(STDOUT_FILENO, erase[cp->parity], 3);
                                        bp--;
                                }
                                break;
                        case CTL('D'):
                                exit(EXIT_SUCCESS);
                        default:
                                if (!isprint(ascval)) {
                                        /* ignore garbage characters */
                                } else if ((int)(bp - logname) >= size_logname - 1) {
                                        bb_error_msg_and_die("%s: input overrun", op->tty);
                                } else {
                                        full_write(STDOUT_FILENO, &c, 1); /* echo the character */
                                        *bp++ = ascval; /* and store it */
                                }
                                break;
                        }
                }
        }
        /* Handle names with upper case and no lower case. */

#ifdef HANDLE_ALLCAPS
        cp->capslock = all_is_upcase(logname);
        if (cp->capslock) {
                for (bp = logname; *bp; bp++)
                        if (isupper(*bp))
                                *bp = tolower(*bp);     /* map name to lower case */
        }
#endif
        return logname;
}

/* termios_final - set the final tty mode bits */
static void termios_final(struct options *op, struct termios *tp, struct chardata *cp)
{
        /* General terminal-independent stuff. */
        tp->c_iflag |= IXON | IXOFF;    /* 2-way flow control */
        tp->c_lflag |= ICANON | ISIG | ECHO | ECHOE | ECHOK | ECHOKE;
        /* no longer| ECHOCTL | ECHOPRT */
        tp->c_oflag |= OPOST;
        /* tp->c_cflag = 0; */
        tp->c_cc[VINTR] = DEF_INTR;     /* default interrupt */
        tp->c_cc[VQUIT] = DEF_QUIT;     /* default quit */
        tp->c_cc[VEOF] = DEF_EOF;       /* default EOF character */
        tp->c_cc[VEOL] = DEF_EOL;
        tp->c_cc[VSWTC] = DEF_SWITCH;   /* default switch character */

        /* Account for special characters seen in input. */
        if (cp->eol == CR) {
                tp->c_iflag |= ICRNL;   /* map CR in input to NL */
                tp->c_oflag |= ONLCR;   /* map NL in output to CR-NL */
        }
        tp->c_cc[VERASE] = cp->erase;   /* set erase character */
        tp->c_cc[VKILL] = cp->kill;     /* set kill character */

        /* Account for the presence or absence of parity bits in input. */
        switch (cp->parity) {
        case 0:                                 /* space (always 0) parity */
// I bet most people go here - they use only 7-bit chars in usernames....
                break;
        case 1:                                 /* odd parity */
                tp->c_cflag |= PARODD;
                /* FALLTHROUGH */
        case 2:                                 /* even parity */
                tp->c_cflag |= PARENB;
                tp->c_iflag |= INPCK | ISTRIP;
                /* FALLTHROUGH */
        case (1 | 2):                           /* no parity bit */
                tp->c_cflag &= ~CSIZE;
                tp->c_cflag |= CS7;
// FIXME: wtf? case 3: we saw both even and odd 8-bit bytes -
// it's probably some umlauts etc, but definitely NOT 7-bit!!!
// Entire parity detection madness here just begs for deletion...
                break;
        }

        /* Account for upper case without lower case. */
#ifdef HANDLE_ALLCAPS
        if (cp->capslock) {
                tp->c_iflag |= IUCLC;
                tp->c_lflag |= XCASE;
                tp->c_oflag |= OLCUC;
        }
#endif
        /* Optionally enable hardware flow control */
#ifdef CRTSCTS
        if (op->flags & F_RTSCTS)
                tp->c_cflag |= CRTSCTS;
#endif

        /* Finally, make the new settings effective */
        /* It's tcsetattr_stdin_TCSANOW() + error check */
        ioctl_or_perror_and_die(0, TCSETS, tp, "%s: TCSETS", op->tty);
}

#if ENABLE_FEATURE_UTMP
static void touch(const char *filename)
{
        if (access(filename, R_OK | W_OK) == -1)
                close(open(filename, O_WRONLY | O_CREAT, 0664));
}

/* update_utmp - update our utmp entry */
static void update_utmp(const char *line, char *fakehost)
{
        struct utmp ut;
        struct utmp *utp;
        int mypid = getpid();

        /* In case we won't find an entry below... */
        memset(&ut, 0, sizeof(ut));
        safe_strncpy(ut.ut_id, line + 3, sizeof(ut.ut_id));

        /*
         * The utmp file holds miscellaneous information about things started by
         * /sbin/init and other system-related events. Our purpose is to update
         * the utmp entry for the current process, in particular the process type
         * and the tty line we are listening to. Return successfully only if the
         * utmp file can be opened for update, and if we are able to find our
         * entry in the utmp file.
         */
        touch(_PATH_UTMP);

        utmpname(_PATH_UTMP);
        setutent();
        while ((utp = getutent()) != NULL) {
                if (utp->ut_type == INIT_PROCESS && utp->ut_pid == mypid) {
                        memcpy(&ut, utp, sizeof(ut));
                        break;
                }
        }

        strcpy(ut.ut_user, "LOGIN");
        safe_strncpy(ut.ut_line, line, sizeof(ut.ut_line));
        if (fakehost)
                safe_strncpy(ut.ut_host, fakehost, sizeof(ut.ut_host));
        ut.ut_tv.tv_sec = time(NULL);
        ut.ut_type = LOGIN_PROCESS;
        ut.ut_pid = mypid;

        pututline(&ut);
        endutent();

#if ENABLE_FEATURE_WTMP
        touch(bb_path_wtmp_file);
        updwtmp(bb_path_wtmp_file, &ut);
#endif
}
#endif /* CONFIG_FEATURE_UTMP */

int getty_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int getty_main(int argc UNUSED_PARAM, char **argv)
{
        int n;
        char *fakehost = NULL;          /* Fake hostname for ut_host */
        char *logname;                  /* login name, given to /bin/login */
        /* Merging these into "struct local" may _seem_ to reduce
         * parameter passing, but today's gcc will inline
         * statics which are called once anyway, so don't do that */
        struct chardata chardata;       /* set by get_logname() */
        struct termios termios;         /* terminal mode bits */
        struct options options;

        chardata = init_chardata;

        memset(&options, 0, sizeof(options));
        options.login = _PATH_LOGIN;    /* default login program */
        options.tty = "tty1";           /* default tty line */
        options.initstring = "";        /* modem init string */
#ifdef ISSUE
        options.issue = ISSUE;          /* default issue file */
#endif

        /* Parse command-line arguments. */
        parse_args(argv, &options, &fakehost);

        logmode = LOGMODE_NONE;

        /* Create new session, lose controlling tty, if any */
        /* docs/ctty.htm says:
         * "This is allowed only when the current process
         *  is not a process group leader" - is this a problem? */
        setsid();
        /* close stdio, and stray descriptors, just in case */
        n = xopen(bb_dev_null, O_RDWR);
        /* dup2(n, 0); - no, we need to handle "getty - 9600" too */
        xdup2(n, 1);
        xdup2(n, 2);
        while (n > 2)
                close(n--);

        /* Logging. We want special flavor of error_msg_and_die */
        die_sleep = 10;
        msg_eol = "\r\n";
        /* most likely will internally use fd #3 in CLOEXEC mode: */
        openlog(applet_name, LOG_PID, LOG_AUTH);
        logmode = LOGMODE_BOTH;

#ifdef DEBUGGING
        dbf = xfopen_for_write(DEBUGTERM);
        for (n = 1; argv[n]; n++) {
                debug(argv[n]);
                debug("\n");
        }
#endif

        /* Open the tty as standard input, if it is not "-" */
        /* If it's not "-" and not taken yet, it will become our ctty */
        debug("calling open_tty\n");
        open_tty(options.tty);
        ndelay_off(0);
        debug("duping\n");
        xdup2(0, 1);
        xdup2(0, 2);

        /*
         * The following ioctl will fail if stdin is not a tty, but also when
         * there is noise on the modem control lines. In the latter case, the
         * common course of action is (1) fix your cables (2) give the modem more
         * time to properly reset after hanging up. SunOS users can achieve (2)
         * by patching the SunOS kernel variable "zsadtrlow" to a larger value;
         * 5 seconds seems to be a good value.
         */
        /* tcgetattr() + error check */
        ioctl_or_perror_and_die(0, TCGETS, &termios, "%s: TCGETS", options.tty);

#ifdef __linux__
// FIXME: do we need this? Otherwise "-" case seems to be broken...
        // /* Forcibly make fd 0 our controlling tty, even if another session
        //  * has it as a ctty. (Another session loses ctty). */
        // ioctl(0, TIOCSCTTY, (void*)1);
        /* Make ourself a foreground process group within our session */
        tcsetpgrp(0, getpid());
#endif

#if ENABLE_FEATURE_UTMP
        /* Update the utmp file. This tty is ours now! */
        update_utmp(options.tty, fakehost);
#endif

        /* Initialize the termios settings (raw mode, eight-bit, blocking i/o). */
        debug("calling termios_init\n");
        termios_init(&termios, options.speeds[0], &options);

        /* Write the modem init string and DON'T flush the buffers */
        if (options.flags & F_INITSTRING) {
                debug("writing init string\n");
                /* todo: use xwrite_str? */
                full_write(STDOUT_FILENO, options.initstring, strlen(options.initstring));
        }

        /* Optionally detect the baud rate from the modem status message */
        debug("before autobaud\n");
        if (options.flags & F_PARSE)
                auto_baud(line_buf, sizeof(line_buf), &termios);

        /* Set the optional timer */
        alarm(options.timeout); /* if 0, alarm is not set */

        /* Optionally wait for CR or LF before writing /etc/issue */
        if (options.flags & F_WAITCRLF) {
                char ch;

                debug("waiting for cr-lf\n");
                while (safe_read(STDIN_FILENO, &ch, 1) == 1) {
                        debug("read %x\n", (unsigned char)ch);
                        ch &= 0x7f;                     /* strip "parity bit" */
                        if (ch == '\n' || ch == '\r')
                                break;
                }
        }

        logname = NULL;
        if (!(options.flags & F_NOPROMPT)) {
                /* NB:termios_init already set line speed
                 * to options.speeds[0] */
                int baud_index = 0;

                while (1) {
                        /* Read the login name. */
                        debug("reading login name\n");
                        logname = get_logname(line_buf, sizeof(line_buf),
                                        &options, &chardata);
                        if (logname)
                                break;
                        /* we are here only if options.numspeed > 1 */
                        baud_index = (baud_index + 1) % options.numspeed;
                        cfsetispeed(&termios, options.speeds[baud_index]);
                        cfsetospeed(&termios, options.speeds[baud_index]);
                        tcsetattr_stdin_TCSANOW(&termios);
                }
        }

        /* Disable timer. */
        alarm(0);

        /* Finalize the termios settings. */
        termios_final(&options, &termios, &chardata);

        /* Now the newline character should be properly written. */
        full_write(STDOUT_FILENO, "\n", 1);

        /* Let the login program take care of password validation. */
        /* We use PATH because we trust that root doesn't set "bad" PATH,
         * and getty is not suid-root applet. */
        /* With -n, logname == NULL, and login will ask for username instead */
        BB_EXECLP(options.login, options.login, "--", logname, NULL);
        bb_error_msg_and_die("%s: can't exec %s", options.tty, options.login);
}