xref: /illumos-gate/usr/src/lib/libnsl/dial/ulockf.c (revision 1da57d55)

/*
 * 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  	*/

#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 success (lock file removed - no longer active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);
}