Added lockfile mechanism to prevent multiple running instances.

1 files changed, 37 insertions, 1 deletions

diff --git a/usbmuxd/main.c b/usbmuxd/main.c
index ea332a4..88c31da 100644
--- a/usbmuxd/main.c
+++ b/usbmuxd/main.c
@@ -33,6 +33,7 @@ Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 #include <sys/socket.h>
 #include <sys/un.h>
 #include <sys/stat.h>
+#include <sys/fcntl.h>
 #include <getopt.h>
 #include <pwd.h>
 
@@ -42,6 +43,8 @@ Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 #include "client.h"
 
 static const char *socket_path = "/var/run/usbmuxd";
+static const char *lockfile = "/var/run/usbmuxd.lock";
+
 int should_exit;
 
 struct sigaction sa_old;
@@ -268,7 +271,9 @@ static void parse_opts(int argc, char **argv)
 int main(int argc, char *argv[])
 {
         int listenfd;
-        int res;
+        int res = 0;
+        FILE *lfd = NULL;
+        struct flock lock;
 
         parse_opts(argc, argv);
 
@@ -289,6 +294,22 @@ int main(int argc, char *argv[])
 
         set_signal_handlers();
 
+        lfd = fopen(lockfile, "r");
+        if (lfd) {
+                lock.l_type = 0;
+                lock.l_whence = SEEK_SET;
+                lock.l_start = 0;
+                lock.l_len = 0;
+                fcntl(fileno(lfd), F_GETLK, &lock);
+                fclose(lfd);
+                if (lock.l_type != F_UNLCK) {
+                        usbmuxd_log(LL_NOTICE,
+                                   "another instance is already running (pid %d). exiting.", lock.l_pid);
+                        res = -1;
+                        goto terminate;
+                }
+        }
+
         usbmuxd_log(LL_INFO, "Creating socket");
         listenfd = create_socket();
         if(listenfd < 0)
@@ -312,6 +333,20 @@ int main(int argc, char *argv[])
                 }
         }
 
+        // now open the lockfile and place the lock
+        lfd = fopen(lockfile, "w");
+        if (lfd) {
+                lock.l_type = F_WRLCK;
+                lock.l_whence = SEEK_SET;
+                lock.l_start = 0;
+                lock.l_len = 0;
+                if (fcntl(fileno(lfd), F_SETLK, &lock) == -1) {
+                        usbmuxd_log(LL_ERROR, "ERROR: lockfile locking failed!");
+                        log_disable_syslog();
+                        exit(EXIT_FAILURE);
+                }
+        }
+
         // drop elevated privileges
         if (drop_privileges && (getuid() == 0 || geteuid() == 0)) {
                 struct passwd *pw = getpwnam("nobody");
@@ -342,6 +377,7 @@ int main(int argc, char *argv[])
         usb_shutdown();
         device_shutdown();
         client_shutdown();
+terminate:
         usbmuxd_log(LL_NOTICE, "Shutdown complete");
 
         log_disable_syslog();