Fix daemonization and lockfile madness

1 files changed, 140 insertions, 61 deletions

diff --git a/usbmuxd/main.c b/usbmuxd/main.c
index be7451f..6b3c881 100644
--- a/usbmuxd/main.c
+++ b/usbmuxd/main.c
@@ -33,7 +33,8 @@ 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 <sys/types.h>
+#include <fcntl.h>
 #include <getopt.h>
 #include <pwd.h>
 #include <grp.h>
@@ -44,7 +45,7 @@ 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";
+static const char *lockfile = "/var/run/usbmuxd.pid";
 
 int should_exit;
 
@@ -55,6 +56,9 @@ static const char *drop_user = "usbmux";
 static int opt_udev = 0;
 static int opt_exit = 0;
 static int exit_signal = 0;
+static int daemon_pipe;
+
+static int report_to_parent = 0;
 
 int create_socket(void) {
         struct sockaddr_un bind_addr;
@@ -191,25 +195,47 @@ int main_loop(int listenfd)
 /**
  * make this program run detached from the current console
  */
-static int daemonize()
+static int daemonize(void)
 {
         pid_t pid;
         pid_t sid;
+        int pfd[2];
+        int res;
 
         // already a daemon
         if (getppid() == 1)
                 return 0;
 
+        if((res = pipe(pfd)) < 0) {
+                usbmuxd_log(LL_FATAL, "pipe() failed.");
+                return res;
+        }
+
         pid = fork();
         if (pid < 0) {
-                exit(EXIT_FAILURE);
+                usbmuxd_log(LL_FATAL, "fork() failed.");
+                return pid;
         }
 
         if (pid > 0) {
                 // exit parent process
-                exit(EXIT_SUCCESS);
+                int status;
+                close(pfd[1]);
+
+                if((res = read(pfd[0],&status,sizeof(int))) != sizeof(int)) {
+                        fprintf(stderr, "usbmuxd: ERROR: Failed to get init status from child, check syslog for messages.\n");
+                        exit(1);
+                }
+                if(status != 0)
+                        fprintf(stderr, "usbmuxd: ERROR: Child process exited with error %d, check syslog for messages.\n", status);
+                exit(status);
         }
         // At this point we are executing as the child process
+        // but we need to do one more fork
+
+        daemon_pipe = pfd[1];
+        close(pfd[0]);
+        report_to_parent = 1;
 
         // Change the file mode mask
         umask(0);
@@ -217,23 +243,57 @@ static int daemonize()
         // Create a new SID for the child process
         sid = setsid();
         if (sid < 0) {
+                usbmuxd_log(LL_FATAL, "setsid() failed.");
                 return -1;
         }
+
+        pid = fork();
+        if (pid < 0) {
+                usbmuxd_log(LL_FATAL, "fork() failed (second).");
+                return pid;
+        }
+
+        if (pid > 0) {
+                // exit parent process
+                close(daemon_pipe);
+                exit(0);
+        }
+
         // Change the current working directory.
         if ((chdir("/")) < 0) {
+                usbmuxd_log(LL_FATAL, "chdir() failed");
                 return -2;
         }
         // Redirect standard files to /dev/null
         if (!freopen("/dev/null", "r", stdin)) {
-                usbmuxd_log(LL_ERROR, "ERROR: redirection of stdin failed.");
+                usbmuxd_log(LL_FATAL, "Redirection of stdin failed.");
+                return -3;
         }
         if (!freopen("/dev/null", "w", stdout)) {
-                usbmuxd_log(LL_ERROR, "ERROR: redirection of stdout failed.");
+                usbmuxd_log(LL_FATAL, "Redirection of stdout failed.");
+                return -3;
+        }
+
+        return 0;
+}
+
+static int notify_parent(int status)
+{
+        int res;
+
+        report_to_parent = 0;
+        if ((res = write(daemon_pipe, &status, sizeof(int))) != sizeof(int)) {
+                usbmuxd_log(LL_FATAL, "Could not notify parent!");
+                if(res >= 0)
+                        return -2;
+                else
+                        return res;
         }
+        close(daemon_pipe);
         if (!freopen("/dev/null", "w", stderr)) {
-                usbmuxd_log(LL_ERROR, "ERROR: redirection of stderr failed.");
+                usbmuxd_log(LL_FATAL, "Redirection of stderr failed.");
+                return -1;
         }
-
         return 0;
 }
 
@@ -310,8 +370,9 @@ int main(int argc, char *argv[])
 {
         int listenfd;
         int res = 0;
-        FILE *lfd = NULL;
+        int lfd;
         struct flock lock;
+        char pids[10];
 
         parse_opts(argc, argv);
 
@@ -333,60 +394,77 @@ 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) {
-                        if (opt_exit) {
-                                if (lock.l_pid && !kill(lock.l_pid, 0)) {
-                                        usbmuxd_log(LL_NOTICE, "sending signal %d to instance with pid %d", exit_signal, lock.l_pid);
-                                        if (kill(lock.l_pid, exit_signal) < 0) {
-                                                usbmuxd_log(LL_FATAL, "Error: could not deliver signal %d to pid %d", exit_signal, lock.l_pid);
-                                        }
-                                        res = 0;
-                                        goto terminate;
-                                } else {
-                                        usbmuxd_log(LL_ERROR, "Could not determine pid of the other running instance!");
+        res = lfd = open(lockfile, O_WRONLY|O_CREAT, 0644);
+        if(res == -1) {
+                usbmuxd_log(LL_FATAL, "Could not open lockfile");
+                goto terminate;
+        }
+        lock.l_type = F_WRLCK;
+        lock.l_whence = SEEK_SET;
+        lock.l_start = 0;
+        lock.l_len = 0;
+        fcntl(lfd, F_GETLK, &lock);
+        close(lfd);
+        if (lock.l_type != F_UNLCK) {
+                if (opt_exit) {
+                        if (lock.l_pid && !kill(lock.l_pid, 0)) {
+                                usbmuxd_log(LL_NOTICE, "Sending signal %d to instance with pid %d", exit_signal, lock.l_pid);
+                                res = 0;
+                                if (kill(lock.l_pid, exit_signal) < 0) {
+                                        usbmuxd_log(LL_FATAL, "Could not deliver signal %d to pid %d", exit_signal, lock.l_pid);
                                         res = -1;
-                                        goto terminate;
                                 }
+                                goto terminate;
                         } else {
-                                if (!opt_udev) {
-                                        usbmuxd_log(LL_ERROR, "Another instance is already running (pid %d). exiting.", lock.l_pid);
-                                        res = -1;
-                                } else {
-                                        usbmuxd_log(LL_NOTICE, "Another instance is already running (pid %d). exiting.", lock.l_pid);
-                                        res = 0;
-                                }
+                                usbmuxd_log(LL_ERROR, "Could not determine pid of the other running instance!");
+                                res = -1;
                                 goto terminate;
                         }
+                } else {
+                        if (!opt_udev) {
+                                usbmuxd_log(LL_ERROR, "Another instance is already running (pid %d). exiting.", lock.l_pid);
+                                res = -1;
+                        } else {
+                                usbmuxd_log(LL_NOTICE, "Another instance is already running (pid %d). exiting.", lock.l_pid);
+                                res = 0;
+                        }
+                        goto terminate;
                 }
         }
+        unlink(lockfile);
 
         if (opt_exit) {
                 usbmuxd_log(LL_NOTICE, "No running instance found, none killed. exiting.");
                 goto terminate;
         }
 
-        // 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 ((res = fcntl(fileno(lfd), F_SETLK, &lock)) < 0) {
-                        usbmuxd_log(LL_FATAL, "Lockfile locking failed!");
+        if (!foreground) {
+                if ((res = daemonize()) < 0) {
+                        fprintf(stderr, "usbmuxd: FATAL: Could not daemonize!\n");
+                        usbmuxd_log(LL_FATAL, "Could not daemonize!");
                         goto terminate;
                 }
-        } else {
-                usbmuxd_log(LL_FATAL, "Lockfile open failed!");
-                res = -1;
+        }
+
+        // now open the lockfile and place the lock
+        res = lfd = open(lockfile, O_WRONLY|O_CREAT|O_TRUNC|O_EXCL, 0644);
+        if(res < 0) {
+                usbmuxd_log(LL_FATAL, "Could not open lockfile");
+                goto terminate;
+        }
+        lock.l_type = F_WRLCK;
+        lock.l_whence = SEEK_SET;
+        lock.l_start = 0;
+        lock.l_len = 0;
+        if ((res = fcntl(lfd, F_SETLK, &lock)) < 0) {
+                usbmuxd_log(LL_FATAL, "Lockfile locking failed!");
+                goto terminate;
+        }
+        sprintf(pids, "%d", getpid());
+        if ((res = write(lfd, pids, strlen(pids))) != strlen(pids)) {
+                usbmuxd_log(LL_FATAL, "Could not write pidfile!");
+                if(res >= 0)
+                        res = -2;
                 goto terminate;
         }
 
@@ -400,7 +478,7 @@ int main(int argc, char *argv[])
                 struct passwd *pw = getpwnam(drop_user);
                 if (!pw) {
                         usbmuxd_log(LL_FATAL, "Dropping privileges failed, check if user '%s' exists!", drop_user);
-                        res = 1;
+                        res = -1;
                         goto terminate;
                 }
 
@@ -420,12 +498,12 @@ int main(int argc, char *argv[])
                 // security check
                 if (setuid(0) != -1) {
                         usbmuxd_log(LL_FATAL, "Failed to drop privileges properly!");
-                        res = 1;
+                        res = -1;
                         goto terminate;
                 }
                 if (getuid() != pw->pw_uid || getgid() != pw->pw_gid) {
                         usbmuxd_log(LL_FATAL, "Failed to drop privileges properly!");
-                        res = 1;
+                        res = -1;
                         goto terminate;
                 }
                 usbmuxd_log(LL_NOTICE, "Successfully dropped privileges to '%s'", drop_user);
@@ -441,13 +519,9 @@ int main(int argc, char *argv[])
 
         usbmuxd_log(LL_NOTICE, "Initialization complete");
 
-        if (!foreground) {
-                if ((res = daemonize()) < 0) {
-                        fprintf(stderr, "usbmuxd: FATAL: Could not daemonize!\n");
-                        usbmuxd_log(LL_FATAL, "Could not daemonize!");
+        if (report_to_parent)
+                if((res = notify_parent(0)) < 0)
                         goto terminate;
-                }
-        }
 
         res = main_loop(listenfd);
         if(res < 0)
@@ -463,7 +537,12 @@ int main(int argc, char *argv[])
 terminate:
         log_disable_syslog();
 
-        if(res < 0)
-                return -res;
-        return 0;
+        if (res < 0)
+                res = -res;
+        else
+                res = 0;
+        if (report_to_parent)
+                notify_parent(res);
+
+        return res;
 }