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/* $Id$
*
* This file is part of pgets.
*
* pgets 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 2 of the License, or (at your
* option) any later version.
*
* pgets 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 pgets; if not, write to the Free Software Foundation,
* Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
*/
#define _GNU_SOURCE
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include <unistd.h>
#include <sys/stat.h>
#include <stdio.h>
#include <limits.h>
#include <fcntl.h>
#include <errno.h>
#include <signal.h>
#include <stdlib.h>
#include <string.h>
#include <inttypes.h>
#include <pwd.h>
#include <libdaemon/dlog.h>
#include "lock.h"
#include "util.h"
#ifndef LOCKDIR
#define LOCKDIR "/var/lock"
#endif
static const char *lockfile(const char *dev) {
static char lockfile[PATH_MAX];
snprintf(lockfile, sizeof(lockfile), LOCKDIR"/LCK..%s", basename((char*) dev));
return lockfile;
}
static const char *tempfile(const char *path) {
static char t[PATH_MAX];
snprintf(t, sizeof(t), "%s.tmp.%lu", path, (unsigned long) getpid());
return t;
}
int device_lock(const char *dev, const char *appname) {
struct stat st;
int fd;
const char *path, *temp;
char buf[100];
char uidbuf[32];
uid_t uid;
if (stat(LOCKDIR, &st) != 0 || !S_ISDIR(st.st_mode)) {
fprintf(stderr, "Failed to lock device, directory "LOCKDIR" not existent.\n");
return -1;
}
path = lockfile(dev);
temp = tempfile(path);
for (;;) {
mode_t u;
struct passwd* pw;
char *username;
if ((fd = open(path, O_RDONLY)) < 0) {
if (errno != ENOENT) {
fprintf(stderr, "Failed to open lock file: %s\n", strerror(errno));
return -1;
}
}
if (fd >= 0) {
ssize_t n;
n = loop_read(fd, buf, sizeof(buf) - 1);
close(fd);
if (n < 0) {
close(fd);
fprintf(stderr, "Failed to read from lock file: %s\n", strerror(errno));
return -1;
}
if (n > 0) {
pid_t pid;
if (n == 4)
pid = (pid_t) *((uint32_t*) buf);
else {
unsigned long v;
buf[n] = 0;
sscanf(buf, "%lu", &v);
pid = (pid_t) v;
}
if (pid > 0) {
if (kill(pid, 0) < 0 && errno == ESRCH) {
fprintf(stderr, "Lockfile is stale. Overriding it.\n");
/* Yes, here is a race condition */
unlink(path);
} else
return 1;
}
}
}
u = umask(0033);
fd = open(temp, O_WRONLY | O_CREAT | O_EXCL, 0666);
umask(u);
if (fd < 0) {
fprintf(stderr, "Failed to create temporary lock file: %s\n", strerror(errno));
return -1;
}
uid = getuid();
if ((pw = getpwuid(uid)))
username = pw->pw_name;
else
snprintf(username = uidbuf, sizeof(uidbuf), "%lu", (unsigned long) uid);
snprintf(buf, sizeof(buf), "%10lu %s %.20s\n", (unsigned long) getpid(), appname, username);
if (loop_write(fd, buf, strlen(buf)) < 0) {
fprintf(stderr, "Failed to write to temporary lock file: %s\n", strerror(errno));
close(fd);
return -1;
}
close(fd);
if (link(temp, path) < 0) {
if (errno == EEXIST)
continue;
fprintf(stderr, "Failed to link temporary lock file: %s\n", strerror(errno));
}
unlink(temp);
return 0;
}
}
int device_unlock(const char *dev) {
if (unlink(lockfile(dev)) < 0) {
fprintf(stderr, "Failed to remove lock file: %s\n", strerror(errno));
return -1;
}
return 0;
}
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