libnsl/dial/ulockf.c

/*
 * 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 2006 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*  Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
/*    All Rights Reserved   */

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

#include "mt.h"
#include "uucp.h"

static void stlock(char *);
static int  onelock(char *, char *, char *);

/*
 * make a lock file with given 'name'
 * If one already exists, send a signal 0 to the process--if
 * it fails, then unlink it and make a new one.
 *
 * input:
 *  name - name of the lock file to make
 *
 * return:
 *  0   -> success
 *  FAIL    -> failure
 */

static int
mklock(char *name)
{
    static  char pid[SIZEOFPID+2] = { '\0' }; /* +2 for '\n' and NULL */
    static char *tempfile;

    if (pid[0] == '\0') {
        tempfile = malloc(MAXNAMESIZE);
        if (tempfile == NULL)
            return (FAIL);
        (void) sprintf(pid, "%*ld\n", SIZEOFPID, (long)getpid());
        (void) snprintf(tempfile, MAXNAMESIZE, "%s/LTMP.%ld", X_LOCKDIR,
                            (long)getpid());
    }

    if (onelock(pid, tempfile, name) == -1) {
        (void) unlink(tempfile);
        if (cklock(name))
            return (FAIL);
        else {
            if (onelock(pid, tempfile, name)) {
            (void) unlink(tempfile);
            DEBUG(4, "ulockf failed in onelock()\n%s", "");
            return (FAIL);
            }
        }
    }
    stlock(name);
    return (0);
}

/*
 * check to see if the lock file exists and is still active
 * - use kill(pid, 0)
 *
 * return:
 *  0   -> success (lock file removed - no longer active
 *  FAIL    -> lock file still active
 */
static int
cklock(char *name)
{
    int ret;
    pid_t lpid = -1;
    char alpid[SIZEOFPID+2];    /* +2 for '\n' and NULL */
    int fd;

    fd = open(name, O_RDONLY);
    DEBUG(4, "ulockf name %s\n", name);
    if (fd == -1) {
        if (errno == ENOENT) {  /* file does not exist -- OK */
            return (0);
        }
        DEBUG(4, "Lock File--can't read (errno %d) --remove it!\n",
                                    errno);
        goto unlk;
    }
    ret = read(fd, (char *)alpid, SIZEOFPID + 1); /* +1 for '\n' */
    (void) close(fd);
    if (ret != (SIZEOFPID+1)) {

        DEBUG(4, "Lock File--bad format--remove it!\n%s", "");
        goto unlk;
    }
    lpid = (pid_t)strtol(alpid, NULL, 10);
    if ((ret = kill(lpid, 0)) == 0 || errno == EPERM) {
        DEBUG(4, "Lock File--process still active--not removed\n%s",
                                    "");
        return (FAIL);
    }
    /* process no longer active */
    DEBUG(4, "kill pid (%ld), ", (long)lpid);
    DEBUG(4, "returned %d", ret);
    DEBUG(4, "--ok to remove lock file (%s)\n", name);
unlk:

    if (unlink(name) != 0) {
        DEBUG(4, "ulockf failed in unlink()\n%s", "");
        return (FAIL);
    }
    return (0);
}

#define MAXLOCKS    10  /* maximum number of lock files */
static char *Lockfile[MAXLOCKS];
static int Nlocks = 0;

/*
 * put name in list of lock files
 * return:
 *  none
 */
static void
stlock(char *name)
{
    int i;
    char *p;

    for (i = 0; i < Nlocks; i++) {
        if (Lockfile[i] == NULL)
            break;
    }
    ASSERT(i < MAXLOCKS, "TOO MANY LOCKS", "", i);
    if (i >= Nlocks)
        i = Nlocks++;
    p = calloc((unsigned)strlen(name) + 1, sizeof (char));
    ASSERT(p != NULL, "CAN NOT ALLOCATE FOR", name, 0);
    (void) strcpy(p, name);
    Lockfile[i] = p;
}

/*
 * remove the named lock. If named lock is NULL,
 *  then remove all locks currently in list.
 * return:
 *  none
 */
static void
rmlock(char *name)
{
    int i;

    for (i = 0; i < Nlocks; i++) {
        if (Lockfile[i] == NULL)
            continue;
        if (name == NULL || EQUALS(name, Lockfile[i])) {
            (void) unlink(Lockfile[i]);
            free(Lockfile[i]);
            Lockfile[i] = NULL;
        }
    }
}

/*
 * makes a lock on behalf of pid.
 * input:
 *  pid - process id
 *  tempfile - name of a temporary in the same file system
 *  name - lock file name (full path name)
 * return:
 *  -1 - failed
 *  0  - lock made successfully
 */
static int
onelock(char *pid, char *tempfile, char *name)
{
    int fd;
    char    cb[100];

    fd = creat(tempfile, (mode_t)0444);
    if (fd < 0) {
        (void) snprintf(cb, sizeof (cb),
                    "%s %s %d", tempfile, name, errno);
        logent("ULOCKC", cb);
        if ((errno == EMFILE) || (errno == ENFILE))
            (void) unlink(tempfile);
        return (-1);
    }
    /* +1 for '\n' */
    if (write(fd, pid, SIZEOFPID+1) != (SIZEOFPID+1)) {
        (void) snprintf(cb, sizeof (cb),
                    "%s %s %d", tempfile, name, errno);
        logent("ULOCKW", cb);
        (void) unlink(tempfile);
        return (-1);
    }
    (void) chmod(tempfile, (mode_t)0444);
    (void) chown(tempfile, UUCPUID, UUCPGID);
    (void) close(fd);
    if (link(tempfile, name) < 0) {
        DEBUG(4, "%s: ", strerror(errno));
        DEBUG(4, "link(%s, ", tempfile);
        DEBUG(4, "%s)\n", name);
        if (unlink(tempfile) <  0) {
            (void) snprintf(cb, sizeof (cb),
                    "ULK err %s %d", tempfile,  errno);
            logent("ULOCKLNK", cb);
        }
        return (-1);
    }
    if (unlink(tempfile) < 0) {
        (void) snprintf(cb, sizeof (cb), "%s %d", tempfile, errno);
        logent("ULOCKF", cb);
    }
    return (0);
}

/*
 * fd_mklock(fd) - lock the device indicated by fd is possible
 *
 * return -
 *  SUCCESS - this process now has the fd locked
 *  FAIL - this process was not able to lock the fd
 */

static int
fd_mklock(int fd)
{
    int tries = 0;
    struct stat64 _st_buf;
    char lockname[BUFSIZ];

    if (fstat64(fd, &_st_buf) != 0)
        return (FAIL);

    (void) snprintf(lockname, sizeof (lockname),
        "%s.%3.3lu.%3.3lu.%3.3lu", L_LOCK,
        (unsigned long)major(_st_buf.st_dev),
        (unsigned long)major(_st_buf.st_rdev),
        (unsigned long)minor(_st_buf.st_rdev));

    if (mklock(lockname) == FAIL)
        return (FAIL);

    while (lockf(fd, F_TLOCK, 0L) != 0) {
        DEBUG(7, "fd_mklock: lockf returns %d\n", errno);
        if ((++tries >= MAX_LOCKTRY) || (errno != EAGAIN)) {
            rmlock(lockname);
            logent("fd_mklock", "lockf failed");
            return (FAIL);
        }
        (void) sleep(2);
    }
    DEBUG(7, "fd_mklock: ok\n%s", "");
    return (SUCCESS);
}

/*
 * remove the locks associated with the device file descriptor
 *
 * return -
 *  SUCCESS - both BNU lock file and advisory locks removed
 *  FAIL -
 */

static void
fd_rmlock(int fd)
{
    struct stat64 _st_buf;
    char lockname[BUFSIZ];

    if (fstat64(fd, &_st_buf) == 0) {
        (void) snprintf(lockname, sizeof (lockname),
            "%s.%3.3lu.%3.3lu.%3.3lu", L_LOCK,
            (unsigned long)major(_st_buf.st_dev),
            (unsigned long)major(_st_buf.st_rdev),
            (unsigned long)minor(_st_buf.st_rdev));
        rmlock(lockname);
    }
    (void) lockf(fd, F_ULOCK, 0L);
}