cmd/consadm/consadm.c

	consadm.c revision 4bc0a2ef2b7ba50a7a717e7ddbf31472ad28e358
/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2005 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#pragma ident   "%Z%%M% %I% %E% SMI"

#include "utils.h"
#include <locale.h>
#include <poll.h>
#include <setjmp.h>
#include <signal.h>
#include <strings.h>
#include <stropts.h>
#include <syslog.h>
#include <sys/sysmsg_impl.h>
#include <sys/stat.h>
#include <sys/sysmacros.h>
#include <sys/systeminfo.h>
#include <sys/termios.h>
#include <sys/types.h>

#define CONSADM         "/usr/sbin/consadm"
#define CONSADMD        "/usr/sbin/consadmd"
#define CONSADMLOCK     "/tmp/CoNsAdM.lck"
#define CONSDAEMON      "consadmd"
#define MSGLOG          "/dev/msglog"
#define CONSOLE         "/dev/console"
#define WSCONS          "/dev/wscons"
#define CONSCONFIG      "/etc/consadm.conf"
#define SETCONSOLEPID       "/etc/consadm.pid"

#define CONFIG          0
#define UNCONFIG        1
#define COMMENT         '#'
#define NEWLINE         '\n'
#define SPACE           ' '
#define TAB         '   '

#define E_SUCCESS   0       /* Exit status for success */
#define E_ERROR     1       /* Exit status for error */
#define E_USAGE     2       /* Exit status for usage error */
#define E_NO_CARRIER    3       /* Exit status for no carrier */

/* useful data structures for lock function */
static struct flock fl;
#define LOCK_EX F_WRLCK

static char usage[] =
    "Usage: \n"
    "\tconsadm [ -p ] [ -a device ... ]\n"
    "\tconsadm [ -p ] [ -d device ... ]\n"
    "\tconsadm [ -p ]\n";

/* data structures ... */
static char conshdr[] =
    "#\n# consadm.conf\n#"
    "# Configuration parameters for console message redirection.\n"
    "# Do NOT edit this file by hand -- use consadm(1m) instead.\n"
    "#\n";
const char *pname;      /* program name */
static sigjmp_buf deadline;

/* command line arguments */
static int display;
static int persist;
static int addflag;
static int deleteflag;

/* function headers */
static void setaux(char *);
static void unsetaux(char *);
static void getconsole(void);
static boolean_t has_carrier(int fd);
static boolean_t modem_support(int fd);
static void setfallback(char *argv[]);
static void removefallback(void);
static void fallbackdaemon(void);
static void persistlist(void);
static int verifyarg(char *, int);
static int safeopen(char *);
static void catch_term(void);
static void catch_alarm(void);
static void catch_hup(void);
static void cleanup_on_exit(void);
static void addtolist(char *);
static void removefromlist(char *);
static int pathcmp(char *, char *);
static int lckfunc(int, int);
typedef void (*sig_handler_t)();
static int getlock(void);

/*
 * In main, return codes carry the following meaning:
 * 0 - successful
 * 1 - error during the command execution
 */

int
main(int argc, char *argv[])
{
    int index;
    struct  sigaction sa;
    int c;
    char    *p = strrchr(argv[0], '/');

    if (p == NULL)
        p = argv[0];
    else
        p++;

    pname = p;

    (void) setlocale(LC_ALL, "");
#if !defined(TEXT_DOMAIN)   /* Should be defined by cc -D */
#define TEXT_DOMAIN "SYS_TEST"  /* Use this only if it weren't */
#endif
    (void) textdomain(TEXT_DOMAIN);

    if (getuid() != 0)
        die(gettext("must be root to run this program\n"));

    /*
     * Handle normal termination signals that may be received.
     */
    sa.sa_handler = SIG_IGN;
    sa.sa_flags = 0;
    (void) sigemptyset(&sa.sa_mask);
    (void) sigaction(SIGHUP, &sa, NULL);
    (void) sigaction(SIGINT, &sa, NULL);
    (void) sigaction(SIGQUIT, &sa, NULL);
    (void) sigaction(SIGTERM, &sa, NULL);

    /*
     * To make sure persistent state gets removed.
     */
    sa.sa_handler = cleanup_on_exit;
    sa.sa_flags = 0;
    (void) sigemptyset(&sa.sa_mask);
    (void) sigaction(SIGSEGV, &sa, NULL);
    (void) sigaction(SIGILL, &sa, NULL);
    (void) sigaction(SIGABRT, &sa, NULL);
    (void) sigaction(SIGBUS, &sa, NULL);

    if (strcmp(pname, CONSDAEMON) == 0) {
        fallbackdaemon();
        return (E_SUCCESS);
    }

    if (argc == 1)
        display++;
    else {
        while ((c = getopt(argc, argv, "adp")) != EOF)  {
            switch (c) {
            case 'a':
                addflag++;
                break;
            case 'd':
                deleteflag++;
                break;
            case 'p':
                persist++;
                break;
            default:
                (void) fprintf(stderr, gettext(usage));
                exit(E_USAGE);
                /*NOTREACHED*/
            }
        }
    }

    if (display) {
        getconsole();
        return (E_SUCCESS);
    }
    if (addflag && deleteflag) {
        (void) fprintf(stderr, gettext(usage));
        return (E_ERROR);
    }
    if (addflag) {
        if (optind == argc) {
            (void) fprintf(stderr, gettext(usage));
            return (E_ERROR);
        }
        /* separately check every device path specified */
        for (index = optind; index < argc; index++) {
            if (verifyarg(argv[index], addflag))
                return (E_ERROR);
        }

        for (index = optind; index < argc; index++) {
            setaux(argv[index]);
            if (persist)
                addtolist(argv[index]);
        }

        /*
         * start/restart daemon based on the auxilary
         * consoles at this time.
         */
        setfallback(argv);
        return (E_SUCCESS);
    } else if (deleteflag) {
        if (optind == argc) {
            (void) fprintf(stderr, gettext(usage));
            return (E_ERROR);
        }
        /* separately check every device path specified */
        for (index = optind; index < argc; index++) {
            if (verifyarg(argv[index], 0))
                return (E_ERROR);
        }

        for (index = optind; index < argc; index++) {
            unsetaux(argv[index]);
            if (persist && deleteflag)
                removefromlist(argv[index]);
        }

        /*
         * kill off daemon and restart with
         * new list of auxiliary consoles
         */
        setfallback(argv);
        return (E_SUCCESS);
    } else if (persist) {
        if (optind < argc) {
            (void) fprintf(stderr, gettext(usage));
            return (E_ERROR);
        }

        persistlist();
        return (E_SUCCESS);
    } else {
        (void) fprintf(stderr, gettext(usage));
        return (E_ERROR);
    }
} /* main */

/* for daemon to handle termination from user command */
static void
catch_term()
{
    exit(E_SUCCESS);
}

/* handle lack of carrier on open */
static void
catch_alarm()
{
    siglongjmp(deadline, 1);
}

/* caught a sighup */
static void
catch_hup()
{
    /*
     * ttymon sends sighup to consadmd because it has the serial
     * port open.  We catch the signal here, but process it
     * within fallbackdaemon().  We ignore the signal if the
     * errno returned was EINTR.
     */
}

/* Remove persistent state on receiving signal. */
static void
cleanup_on_exit()
{
    (void) unlink(CONSADMLOCK);
    exit(E_ERROR);
}

/*
 * send ioctl to /dev/sysmsg to route msgs of the device specified.
 */
static void
setaux(char *dev)
{
    int fd;

    if ((fd = safeopen(SYSMSG)) < 0)
        die(gettext("%s is missing or not a valid device\n"), SYSMSG);

    if (ioctl(fd, CIOCSETCONSOLE, dev) != 0) {
        /*
         * Let setting duplicate device be warning, consadm
         * must proceed to set persistence if requested.
         */
        if (errno == EBUSY)
            die(gettext("%s is already the default console\n"),
                dev);
        else if (errno != EEXIST)
            die(gettext("cannot get table entry"));
    }
    syslog(LOG_WARNING, "%s: Added auxiliary device %s", CONSADM, dev);

    (void) close(fd);
}

/*
 * Send ioctl to device specified and
 * Remove the entry from the list of auxiliary devices.
 */
static void
unsetaux(char *dev)
{
    int fd;

    if ((fd = safeopen(SYSMSG)) < 0)
        die(gettext("%s is missing or not a valid device\n"), SYSMSG);

    if (ioctl(fd, CIOCRMCONSOLE, dev) != 0) {
        if (errno == EBUSY)
            die(gettext("cannot unset the default console\n"));
    } else
        syslog(LOG_WARNING, "%s: Removed auxiliary device %s",
            CONSADM, dev);
    (void) close(fd);
}

static int
getlock(void)
{
    int lckfd;

    if ((lckfd = open(CONSADMLOCK, O_CREAT | O_EXCL | O_WRONLY,
        S_IRUSR | S_IWUSR)) < 0) {
        if (errno == EEXIST)
            die(gettext("currently busy, try again later.\n"));
        else
            die(gettext("cannot open %s"), CONSADMLOCK);
    }
    if (lckfunc(lckfd, LOCK_EX) == -1) {
        (void) close(lckfd);
        (void) unlink(CONSADMLOCK);
        die(gettext("fcntl operation failed"));
    }
    return (lckfd);
}

static void
addtolist(char *dev)
{
    int lckfd, fd;
    FILE    *fp, *nfp;
    char    newfile[MAXPATHLEN];
    char    buf[MAXPATHLEN];
    int len;
    boolean_t   found = B_FALSE;

    /* update file of devices configured to get console msgs. */

    lckfd = getlock();

    /* Open new file */
    (void) snprintf(newfile, sizeof (newfile), "%s%d",
        CONSCONFIG, (int)getpid());
    if (((fd = creat(newfile, 0644)) < 0) ||
        ((nfp = fdopen(fd, "w")) == NULL)) {
        (void) close(lckfd);
        (void) unlink(CONSADMLOCK);
        die(gettext("could not create new %s file"), CONSCONFIG);
    }

    /* Add header to new file */
    (void) fprintf(nfp, "%s", conshdr);

    /* Check that the file doesn't already exist */
    if ((fp = fopen(CONSCONFIG, "r")) != NULL) {
        while (fgets(buf, MAXPATHLEN, fp) != NULL) {
            if (buf[0] == COMMENT || buf[0] == NEWLINE ||
                buf[0] == SPACE || buf[0] == TAB)
                continue;
            len = strlen(buf);
            buf[len - 1] = NULL; /* Clear carriage return */
            if (pathcmp(dev, buf) == 0) {
                /* they match so use name passed in. */
                (void) fprintf(nfp, "%s\n", dev);
                found = B_TRUE;
            } else
                (void) fprintf(nfp, "%s\n", buf);
        }
    }
    /* User specified persistent settings */
    if (found == B_FALSE)
        (void) fprintf(nfp, "%s\n", dev);

    (void) fclose(fp);
    (void) fclose(nfp);
    (void) rename(newfile, CONSCONFIG);
    (void) close(lckfd);
    (void) unlink(CONSADMLOCK);
}

/* The list in CONSCONFIG gives the persistence capability in the proto */
static void
removefromlist(char *dev)
{
    int lckfd;
    FILE    *fp, *nfp;
    char    newfile[MAXPATHLEN + 1];
    char    len;
    char    value[MAXPATHLEN + 1];
    boolean_t   newcontents = B_FALSE;

    /* update file of devices configured to get console msgs. */

    lckfd = getlock();

    if ((fp = fopen(CONSCONFIG, "r")) == NULL) {
        (void) close(lckfd);
        (void) unlink(CONSADMLOCK);
        return;
    }

    /* Open new file */
    (void) snprintf(newfile, sizeof (newfile), "%s%d",
        CONSCONFIG, (int)getpid());
    if ((nfp = fopen(newfile, "w")) == NULL) {
        (void) close(lckfd);
        (void) unlink(CONSADMLOCK);
        die(gettext("cannot create new %s file"), CONSCONFIG);
    }

    /* Add header to new file */
    (void) fprintf(nfp, "%s", conshdr);

    /*
     * Check whether the path duplicates what is already in the
     * file.
     */
    while (fgets(value, MAXPATHLEN, fp) != NULL) {
        /* skip comments */
        if (value[0] == COMMENT || value[0] == NEWLINE ||
            value[0] == SPACE || value[0] == TAB)
            continue;
        len = strlen(value);
        value[len - 1] = NULL; /* Clear carriage return */
        if (pathcmp(dev, value) == 0) {
            /* they match so don't write it */
            continue;
        }
        (void) fprintf(nfp, "%s\n", value);
        newcontents = B_TRUE;
    }
    (void) fclose(fp);
    (void) fclose(nfp);
    /* Remove the file if there aren't any auxiliary consoles */
    if (newcontents)
        (void) rename(newfile, CONSCONFIG);
    else {
        (void) unlink(CONSCONFIG);
        (void) unlink(newfile);
    }
    (void) close(lckfd);
    (void) unlink(CONSADMLOCK);
}

static int
pathcmp(char *adev, char *bdev)
{
    struct stat st1;
    struct stat st2;

    if (strcmp(adev, bdev) == 0)
        return (0);

    if (stat(adev, &st1) != 0 || !S_ISCHR(st1.st_mode))
        die(gettext("invalid device %s\n"), adev);

    if (stat(bdev, &st2) != 0 || !S_ISCHR(st2.st_mode))
        die(gettext("invalid device %s\n"), bdev);

    if (st1.st_rdev == st2.st_rdev)
        return (0);

    return (1);
}

/*
 * Display configured consoles.
 */
static void
getconsole(void)
{
    int fd;
    int bufsize = 0;        /* size of device cache */
    char    *infop, *ptr, *p;   /* info structure for ioctl's */

    if ((fd = safeopen(SYSMSG)) < 0)
        die(gettext("%s is missing or not a valid device\n"), SYSMSG);

    if ((bufsize = ioctl(fd, CIOCGETCONSOLE, NULL)) < 0)
        die(gettext("cannot get table entry\n"));
    if (bufsize == 0)
        return;

    if ((infop = calloc(bufsize, sizeof (char))) == NULL)
        die(gettext("cannot allocate buffer"));

    if (ioctl(fd, CIOCGETCONSOLE, infop) < 0)
        die(gettext("cannot get table entry\n"));

    ptr = infop;
    while (ptr != NULL) {
        p = strchr(ptr, ' ');
        if (p == NULL) {
            (void) printf("%s\n", ptr);
            break;
        }
        *p++ = '\0';
        (void) printf("%s\n", ptr);
        ptr = p;
    }
    (void) close(fd);
}

/*
 * It is supposed that if the device supports TIOCMGET then it
 * might be a serial device.
 */
static boolean_t
modem_support(int fd)
{
    int modem_state;

    if (ioctl(fd, TIOCMGET, &modem_state) == 0)
        return (B_TRUE);
    else
        return (B_FALSE);
}

static boolean_t
has_carrier(int fd)
{
    int modem_state;

    if (ioctl(fd, TIOCMGET, &modem_state) == 0)
        return ((modem_state & TIOCM_CAR) != 0);
    else {
        return (B_FALSE);
    }
}

static void
setfallback(char *argv[])
{
    pid_t   pid;
    FILE    *fp;
    char    *cmd = CONSADMD;
    int lckfd, fd;

    lckfd = getlock();

    /*
     * kill off any existing daemon
     * remove /etc/consadm.pid
     */
    removefallback();

    /* kick off a daemon */
    if ((pid = fork()) == (pid_t)0) {
        /* always fallback to /dev/console */
        argv[0] = cmd;
        argv[1] = NULL;
        (void) close(0);
        (void) close(1);
        (void) close(2);
        (void) close(lckfd);
        if ((fd = open(MSGLOG, O_RDWR)) < 0)
            die(gettext("cannot open %s"), MSGLOG);
        (void) dup2(fd, 1);
        (void) dup2(fd, 2);
        (void) execv(cmd, argv);
        exit(E_SUCCESS);
    } else if (pid == -1)
        die(gettext("%s not started"), CONSADMD);

    if ((fp = fopen(SETCONSOLEPID, "w")) == NULL)
        die(gettext("cannot open %s"), SETCONSOLEPID);
    /* write daemon pid to file */
    (void) fprintf(fp, "%d\n", (int)pid);
    (void) fclose(fp);
    (void) close(lckfd);
    (void) unlink(CONSADMLOCK);
}

/*
 * Remove the daemon that would have implemented the automatic
 * fallback in event of carrier loss on the serial console.
 */
static void
removefallback(void)
{
    FILE    *fp;
    int pid;

    if ((fp = fopen(SETCONSOLEPID, "r+")) == NULL)
        /* file doesn't exist, so no work to do */
        return;

    if (fscanf(fp, "%d\n", &pid) <= 0) {
        (void) fclose(fp);
        (void) unlink(SETCONSOLEPID);
        return;
    }

    /*
     * Don't shoot ourselves in the foot by killing init,
     * sched, pageout, or fsflush.
     */
    if (pid == 0 || pid == 1 || pid == 2 || pid == 3) {
        (void) unlink(SETCONSOLEPID);
        return;
    }
    /*
     * kill off the existing daemon listed in
     * /etc/consadm.pid
     */
    (void) kill((pid_t)pid, SIGTERM);

    (void) fclose(fp);
    (void) unlink(SETCONSOLEPID);
}

/*
 * Assume we always fall back to /dev/console.
 * parameter passed in will always be the auxiliary device.
 * The daemon will not start after the last device has been removed.
 */
static void
fallbackdaemon(void)
{
    int fd, sysmfd, ret = 0;
    char    **devpaths;
    pollfd_t    *fds;
    nfds_t  nfds = 0;
    int index;
    int pollagain;
    struct  sigaction sa;
    int bufsize = 0;        /* length of device cache paths */
    int cachesize = 0;      /* size of device cache */
    char    *infop, *ptr, *p;   /* info structure for ioctl's */

    /*
     * catch SIGTERM cause it might be coming from user via consadm
     */
    sa.sa_handler = catch_term;
    sa.sa_flags = 0;
    (void) sigemptyset(&sa.sa_mask);
    (void) sigaction(SIGTERM, &sa, NULL);

    /*
     * catch SIGHUP cause it might be coming from a disconnect
     */
    sa.sa_handler = catch_hup;
    sa.sa_flags = 0;
    (void) sigemptyset(&sa.sa_mask);
    (void) sigaction(SIGHUP, &sa, NULL);

    if ((sysmfd = safeopen(SYSMSG)) < 0)
        die(gettext("%s is missing or not a valid device\n"), SYSMSG);

    if ((bufsize = ioctl(sysmfd, CIOCGETCONSOLE, NULL)) < 0)
        die(gettext("cannot get table entry\n"));
    if (bufsize == 0)
        return;

    if ((infop = calloc(bufsize, sizeof (char))) == NULL)
        die(gettext("cannot allocate buffer"));

    if (ioctl(sysmfd, CIOCGETCONSOLE, infop) < 0)
        die(gettext("cannot get table entry\n"));

    ptr = infop;
    while (ptr != NULL) {
        p = strchr(ptr, ' ');
        if (p == NULL) {
            cachesize++;
            break;
        }
        p++;
        cachesize++;
        ptr = p;
    }

    if ((fds = calloc(cachesize, sizeof (struct pollfd))) == NULL)
        die(gettext("cannot allocate buffer"));

    if ((devpaths = calloc(cachesize, sizeof (char *))) == NULL)
        die(gettext("cannot allocate buffer"));

    ptr = infop;
    while (ptr != NULL) {
        p = strchr(ptr, ' ');
        if (p == NULL) {
            if ((fd = safeopen(ptr)) < 0) {
                warn(gettext("cannot open %s, continuing"),
                    ptr);
                break;
            }
            if (!has_carrier(fd)) {
                (void) close(fd);
                warn(gettext(
            "no carrier on %s, device will not be monitored.\n"),
                    ptr);
                break;
            } else {
                fds[nfds].fd = fd;
                fds[nfds].events = 0;

                if ((devpaths[nfds] =
                    malloc(strlen(ptr) + 1)) == NULL)
                    die(gettext("cannot allocate buffer"));

                (void) strcpy(devpaths[nfds], ptr);
                nfds++;
                if (nfds >= cachesize)
                    break;
            }
            break;
        }
        *p++ = '\0';

        if ((fd = safeopen(ptr)) < 0) {
            warn(gettext("cannot open %s, continuing"), ptr);
            ptr = p;
            continue;
        }
        if (!has_carrier(fd)) {
            (void) close(fd);
            warn(gettext(
            "no carrier on %s, device will not be monitored.\n"),
                ptr);
            ptr = p;
            continue;
        } else {
            fds[nfds].fd = fd;
            fds[nfds].events = 0;

            if ((devpaths[nfds] = malloc(strlen(ptr) + 1)) == NULL)
                die(gettext("cannot allocate buffer"));

            (void) strcpy(devpaths[nfds], ptr);
            nfds++;
            if (nfds >= cachesize)
                break;
        }
        ptr = p;
    }
    (void) close(sysmfd);

    /* no point polling if no devices with carrier */
    if (nfds == 0)
        return;

    for (;;) {
        /* daemon sleeps waiting for a hangup on the console */
        ret = poll(fds, nfds, INFTIM);
        if (ret == -1) {
            /* Check if ttymon is trying to get rid of us */
            if (errno == EINTR)
                continue;
            warn(gettext("cannot poll device"));
            return;
        } else if (ret == 0) {
            warn(gettext("timeout (%d milleseconds) occured\n"),
                INFTIM);
            return;
        } else {
            /* Go through poll list looking for events. */
            for (index = 0; index < nfds; index++) {
                /* expected result */
                if ((fds[index].revents & POLLHUP) ==
                    POLLHUP) {
                    /*
                     * unsetaux console.  Take out of list
                     * of current auxiliary consoles.
                     */
                    unsetaux((char *)devpaths[index]);
                    warn(gettext(
                    "lost carrier, unsetting console %s\n"),
                        devpaths[index]);
                    syslog(LOG_WARNING,
                "%s: lost carrier, unsetting auxiliary device %s",
                        CONSADM, devpaths[index]);
                    free(devpaths[index]);
                    devpaths[index] = NULL;
                    (void) close(fds[index].fd);
                    fds[index].fd = -1;
                    fds[index].revents = 0;
                    continue;
                }
                if ((fds[index].revents & POLLERR) ==
                    POLLERR) {
                    warn(gettext("poll error\n"));
                    continue;
                } else if (fds[index].revents != 0) {
                    warn(gettext(
                        "unexpected poll result 0x%x\n"),
                        fds[index].revents);
                    continue;
                }
            }
            /* check whether any left to poll */
            pollagain = B_FALSE;
            for (index = 0; index < nfds; index++)
                if (fds[index].fd != -1)
                    pollagain = B_TRUE;
            if (pollagain == B_TRUE)
                continue;
            else
                return;
        }
    }
}

static void
persistlist(void)
{
    FILE    *fp;
    char    value[MAXPATHLEN + 1];
    int lckfd;

    lckfd = getlock();

    if ((fp = fopen(CONSCONFIG, "r")) != NULL) {
        while (fgets(value, MAXPATHLEN, fp) != NULL) {
            /* skip comments */
            if (value[0] == COMMENT ||
                value[0] == NEWLINE ||
                value[0] == SPACE || value[0] == TAB)
                continue;
            (void) fprintf(stdout, "%s", value);
        }
        (void) fclose(fp);
    }
    (void) close(lckfd);
    (void) unlink(CONSADMLOCK);
}

static int
verifyarg(char *dev, int flag)
{
    struct stat st;
    int fd;
    int ret = 0;

    if (dev == NULL) {
        warn(gettext("specify device(s)\n"));
        ret = 1;
        goto err_exit;
    }

    if (dev[0] != '/') {
        warn(gettext("device name must begin with a '/'\n"));
        ret = 1;
        goto err_exit;
    }

    if ((pathcmp(dev, SYSMSG) == 0) ||
        (pathcmp(dev, WSCONS) == 0) ||
        (pathcmp(dev, CONSOLE) == 0)) {
        /* they match */
        warn(gettext("invalid device %s\n"), dev);
        ret = 1;
        goto err_exit;
    }

    if (stat(dev, &st) || ! S_ISCHR(st.st_mode)) {
        warn(gettext("invalid device %s\n"), dev);
        ret = 1;
        goto err_exit;
    }

    /* Delete operation doesn't require this checking */
    if ((fd = safeopen(dev)) < 0) {
        if (flag) {
            warn(gettext("invalid device %s\n"), dev);
            ret = 1;
        }
        goto err_exit;
    }
    if (!modem_support(fd)) {
        warn(gettext("invalid device %s\n"), dev);
        (void) close(fd);
        ret = 1;
        goto err_exit;
    }

    /* Only verify carrier if it's an add operation */
    if (flag) {
        if (!has_carrier(fd)) {
            warn(gettext("failure, no carrier on %s\n"), dev);
            ret = 1;
            goto err_exit;
        }
    }
err_exit:
    return (ret);
}

/*
 * Open the pseudo device, but be prepared to catch sigalarm if we block
 * cause there isn't any carrier present.
 */
static int
safeopen(char *devp)
{
    int fd;
    struct  sigaction sigact;

    sigact.sa_flags = SA_RESETHAND | SA_NODEFER;
    sigact.sa_handler = catch_alarm;
    (void) sigemptyset(&sigact.sa_mask);
    (void) sigaction(SIGALRM, &sigact, NULL);
    if (sigsetjmp(deadline, 1) != 0)
        return (-1);
    (void) alarm(5);
    /* The sysmsg driver sets NONBLOCK and NDELAY, but what the hell */
    if ((fd = open(devp, O_RDWR | O_NOCTTY | O_NONBLOCK | O_NDELAY)) < 0)
        return (-1);
    (void) alarm(0);
    sigact.sa_flags = 0;
    sigact.sa_handler = SIG_DFL;
    (void) sigemptyset(&sigact.sa_mask);
    (void) sigaction(SIGALRM, &sigact, NULL);
    return (fd);
}

static int
lckfunc(int fd, int flag)
{
    fl.l_type = flag;
    return (fcntl(fd, F_SETLKW, &fl));
}