From 285f7ad7d0aed48cd5cb13a2437e80d26fffc254 Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Wed, 3 Mar 2004 01:25:46 +0000
Subject: commit initial release

git-svn-id: file:///home/lennart/svn/public/pgets/trunk@3 768266df-afd4-0310-94a7-d396c829e022
---
 src/lock.c | 168 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 168 insertions(+)
 create mode 100644 src/lock.c

(limited to 'src/lock.c')

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;
+}
-- 
cgit