diff options
Diffstat (limited to 'src/lock.c')
| -rw-r--r-- | src/lock.c | 168 |
1 files changed, 168 insertions, 0 deletions
diff --git a/src/lock.c b/src/lock.c new file mode 100644 index 0000000..91878d4 --- /dev/null +++ b/src/lock.c @@ -0,0 +1,168 @@ +/* $Id$ + * + * 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; +} |