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/* wydawca - automatic release submission daemon
   Copyright (C) 2007, 2009-2013 Sergey Poznyakoff

   Wydawca is free software; you can redistribute it and/or modify it
   under the terms of the GNU General Public License as published by the
   Free Software Foundation; either version 3 of the License, or (at your
   option) any later version.

   Wydawca is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License along
   with wydawca. If not, see <http://www.gnu.org/licenses/>. */

#include "wydawca.h"

int enable_locking = 1;
char *lockdir;
time_t lock_expire_time = 5 * 60;
time_t lock_timeout = 60;

#define LOCKFILE_MODE        0644

static int
stat_check(const char *file, int fd, int links)
{
	struct stat fn_stat;
	struct stat fd_stat;
	int err = 0;
	int localfd = -1;

	if (fd == -1) {
		localfd = open(file, O_RDONLY);

		if (localfd == -1)
			return errno;
		fd = localfd;
	}

	/* We should always be able to stat a valid fd, so this
	   is an error condition. */
	if (lstat(file, &fn_stat) || fstat(fd, &fd_stat))
		err = errno;
	else {
		/* If the link and stat don't report the same info, or the
		   file is a symlink, fail the locking. */
#define CHK(X) if(X) err = EINVAL

		CHK(!S_ISREG(fn_stat.st_mode));
		CHK(!S_ISREG(fd_stat.st_mode));
		CHK(fn_stat.st_nlink != links);
		CHK(fn_stat.st_dev != fd_stat.st_dev);
		CHK(fn_stat.st_ino != fd_stat.st_ino);
		CHK(fn_stat.st_mode != fd_stat.st_mode);
		CHK(fn_stat.st_nlink != fd_stat.st_nlink);
		CHK(fn_stat.st_uid != fd_stat.st_uid);
		CHK(fn_stat.st_gid != fd_stat.st_gid);
		CHK(fn_stat.st_rdev != fd_stat.st_rdev);

#undef CHK
	}
	if (localfd != -1)
		close(localfd);

	return err;
}

int
_lock_internal(const char *file, const char *fname)
{
	int err = 0;
	int fd;
	FILE *fp;

	fd = open(fname, O_WRONLY | O_CREAT | O_EXCL, LOCKFILE_MODE);
	if (fd == -1) {
		if (errno == EEXIST)
			return LOCK_RETRY;
		else {
			wy_log(LOG_ERR, _("cannot create lock file %s: %s"),
			       fname, strerror(errno));
			return LOCK_FAILURE;
		}
	}
	close(fd);

	/* Try to link to the lockfile. */
	if (link(fname, file) == -1) {
		unlink(fname);
		if (errno == EEXIST)
			return LOCK_RETRY;
		else {
			wy_log(LOG_ERR, _("cannot create lock file %s: %s"),
			       file, strerror(errno));
			return LOCK_FAILURE;
		}
	}

	if ((fd = open(file, O_RDWR)) == -1) {
		unlink(fname);
		wy_log(LOG_ERR, _("cannot open lock file %s: %s"),
		       fname, strerror(errno));
		return LOCK_FAILURE;
	}

	err = stat_check(fname, fd, 2);
	if (err) {
		unlink(fname);
		wy_log(LOG_ERR, _("lock file check failed: %s"),
		       strerror(errno));
		return (err == EINVAL) ? LOCK_INVALID : LOCK_FAILURE;
	}

	unlink(fname);

	fp = fdopen(fd, "w");
	fprintf(fp, "%lu", (unsigned long)getpid());
	fclose(fp);

	return 0;
}

static void
expire_stale_lock(const char *file)
{
	int stale = 0;
	char buf[80];
	int fd;
	int len;

	fd = open(file, O_RDONLY);
	if (fd == -1)
		return;

	len = read(fd, buf, sizeof(buf) - 1);
	if (len > 0) {
		pid_t pid;

		buf[len] = 0;
		pid = strtoul(buf, NULL, 10);
		if (pid > 0) {
			/* Process is gone so we try to remove the lock. */
			if (kill(pid, 0) == -1)
				stale = 1;
		} else
			stale = 1;	/* Corrupted file, remove the lock. */
	}

	if (!stale && lock_expire_time > 0) {
		struct stat stbuf;
		fstat(fd, &stbuf);
		/* The lock has expired. */
		if ((time(NULL) - stbuf.st_mtime) > lock_expire_time)
			stale = 1;
	}

	close(fd);
	if (stale)
		unlink(file);
}

static char *
host_name()
{
	static char *hostbuf = NULL;
	size_t size = 0;
	int rc;

	if (hostbuf)
		return hostbuf;

	do {
		if (!hostbuf) {
			size = 256;
			hostbuf = grecs_malloc(size);
		} else {
			size_t ns = size * 2;
			if (size < ns)
				grecs_alloc_die();
			size = ns;
			hostbuf = grecs_realloc(hostbuf, size);
		}
	}
	while ((rc = gethostname(hostbuf, size)) == -1 &&
	       (errno == EINVAL
#ifdef ENAMETOOLONG
		|| errno == ENAMETOOLONG
#endif
	       ));
	if (rc) {
		wy_log(LOG_ERR, _("cannot get hostname: %s"), strerror(rc));
		exit(EX_SOFTWARE);
	}
	return hostbuf;
}

int
wydawca_lock(const char *lockname)
{
	char *tempname = NULL;
	size_t size = 0;
	int rc;

	if (!enable_locking)
		return 0;
	expire_stale_lock(lockname);

	/* build the NFS hitching-post to the lock file */
	grecs_asprintf(&tempname, &size, "%s.%lu.%lu.%s",
		       lockname,
		       (unsigned long)getpid(),
		       (unsigned long)time(NULL), host_name());
	if (!tempname)
		return LOCK_FAILURE;
	if (lock_timeout) {
		time_t start = time(NULL);

		do {
			rc = _lock_internal(lockname, tempname);
			if (rc == LOCK_RETRY)
				sleep(1);
			else
				break;
		}
		while (time(NULL) - start < lock_timeout);
	} else
		rc = _lock_internal(lockname, tempname);

	free(tempname);
	return rc;
}

void
wydawca_unlock(const char *lockfile)
{
	if (enable_locking)
		unlink(lockfile);
}

static char *
fix_tagname(const char *tag)
{
	char *tagname = grecs_strdup(tag);
	char *p;

	for (p = tagname; *p; p++)
		if (!isalnum(*p) && *p != '_' && *p != '-')
			*p = '_';
	return tagname;
}

char *
wydawca_lockname(const char *tag)
{
	char *lockname = NULL;
	size_t size = 0;
	char *tagname = fix_tagname(tag);
	grecs_asprintf(&lockname, &size, "%s/LCK.%s", lockdir, tagname);
	if (!lockname)
		grecs_alloc_die();
	free(tagname);
	return lockname;
}

void
wydawca_lock_init()
{
	if (enable_locking) {
		if (!lockdir)
			lockdir = grecs_strdup(LOCALSTATEDIR "/lock/" PACKAGE);
		if (create_hierarchy(lockdir, 0))
			exit(EX_OSFILE);
	}
}

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