+/*!
+ * Get lock on db lock file
+ *
+ * @args cmd (r) lock command:
+ * LOCK_FREE: close lockfd
+ * LOCK_UNLOCK: unlock lockm keep lockfd open
+ * LOCK_EXCL: F_WRLCK on lockfd
+ * LOCK_SHRD: F_RDLCK on lockfd
+ * @args dbpath (r) path to lockfile, only used on first call,
+ * later the stored fd is used
+ * @returns LOCK_FREE/LOCK_UNLOCK return 0 on success, -1 on error
+ * LOCK_EXCL/LOCK_SHRD return LOCK_EXCL or LOCK_SHRD respectively on
+ * success, 0 if the lock couldn't be acquired, -1 on other errors
+ */
+int get_lock(int cmd, const char *dbpath)
+{
+ static int lockfd = -1;
+ int ret;
+ char lockpath[PATH_MAX];
+ struct stat st;
+
+ switch (cmd) {
+ case LOCK_FREE:
+ if (lockfd == -1)
+ return -1;
+ close(lockfd);
+ lockfd = -1;
+ return 0;
+
+ case LOCK_UNLOCK:
+ if (lockfd == -1)
+ return -1;
+ return unlock(lockfd, 0, SEEK_SET, 0);
+
+ case LOCK_EXCL:
+ case LOCK_SHRD:
+ if (lockfd == -1) {
+ if ( (strlen(dbpath) + strlen(LOCKFILENAME+1)) > (PATH_MAX - 1) ) {
+ LOG(log_error, logtype_cnid, ".AppleDB pathname too long");
+ return -1;
+ }
+ strncpy(lockpath, dbpath, PATH_MAX - 1);
+ strcat(lockpath, "/");
+ strcat(lockpath, LOCKFILENAME);
+
+ if ((lockfd = open(lockpath, O_RDWR | O_CREAT, 0644)) < 0) {
+ LOG(log_error, logtype_cnid, "Error opening lockfile: %s", strerror(errno));
+ return -1;
+ }
+
+ if ((stat(dbpath, &st)) != 0) {
+ LOG(log_error, logtype_cnid, "Error statting lockfile: %s", strerror(errno));
+ return -1;
+ }
+
+ if ((chown(lockpath, st.st_uid, st.st_gid)) != 0) {
+ LOG(log_error, logtype_cnid, "Error inheriting lockfile permissions: %s",
+ strerror(errno));
+ return -1;
+ }
+ }
+
+ if (cmd == LOCK_EXCL)
+ ret = write_lock(lockfd, 0, SEEK_SET, 0);
+ else
+ ret = read_lock(lockfd, 0, SEEK_SET, 0);
+
+ if (ret != 0) {
+ if (cmd == LOCK_SHRD)
+ LOG(log_error, logtype_cnid, "Volume CNID db is locked, try again...");
+ return 0;
+ }
+
+ LOG(log_debug, logtype_cnid, "get_lock: got %s lock",
+ cmd == LOCK_EXCL ? "LOCK_EXCL" : "LOCK_SHRD");
+ return cmd;
+
+ default:
+ return -1;
+ } /* switch(cmd) */
+
+ /* deadc0de, never get here */
+ return -1;
+}
+