/**
Acquire the lock for the socket
Returns the name of the lock file if successful or
NULL if unable to obtain lock.
The returned string must be free()d after unlink()ing the file to release
the lock
*/
static bool acquire_socket_lock(const std::string &sock_name, std::string *out_lockfile_name)
{
bool success = false;
std::string lockfile;
lockfile.reserve(sock_name.size() + strlen(LOCKPOSTFIX));
lockfile = sock_name;
lockfile.append(LOCKPOSTFIX);
if (acquire_lock_file(lockfile, LOCKTIMEOUT, 1))
{
out_lockfile_name->swap(lockfile);
success = true;
}
return success;
}
/**
Acquire the lock for the socket
Returns the name of the lock file if successful or
NULL if unable to obtain lock.
The returned string must be free()d after unlink()ing the file to release
the lock
*/
static char *acquire_socket_lock( const char *sock_name )
{
size_t len = strlen( sock_name );
char *lockfile = (char *)malloc( len + strlen( LOCKPOSTFIX ) + 1 );
if( lockfile == NULL )
{
wperror( L"acquire_socket_lock" );
exit( EXIT_FAILURE );
}
strcpy( lockfile, sock_name );
strcpy( lockfile + len, LOCKPOSTFIX );
if ( !acquire_lock_file( lockfile, LOCKTIMEOUT, 1 ) )
{
free( lockfile );
lockfile = NULL;
}
return lockfile;
}
long become_daemon(const char *run_as_user,
const char *work_dir,
const char *lock_file,
int *fd_lock_file)
{
pid_t pid;
int fd;
*fd_lock_file = DAEMON_BAD_FD_LOCK_FILE;
// Switch to specified user
if (run_as_user) {
struct passwd *pw_info = getpwnam(run_as_user);
if (pw_info) {
if (setuid(pw_info->pw_uid) == -1) {
syslog_error("setuid failed for %s, code=%d (%s)",
run_as_user, errno, strerror(errno));
return DAEMON_FAILURE;
}
}
else {
syslog_error("getpwnam failed for %s", run_as_user);
return DAEMON_FAILURE;
}
}
// Step 1 : Create a child process
pid = fork();
switch (pid) {
case -1 :
syslog_error("fork(1) failed, code=%d (%s)", errno, strerror(errno));
return DAEMON_FAILURE;
case 0 :
break; // Child falls through
default :
exit(EXIT_SUCCESS); // Parent terminates OK
}
// Step 2 : Become leader of new session
if (setsid() == -1) {
syslog_error("setsid failed, code=%d (%s)", errno, strerror(errno));
return DAEMON_FAILURE;
}
// Step 3 : Ensure no controlling terminal
pid = fork();
switch (pid) {
case -1 :
syslog_error("fork(2) failed, code=%d (%s)", errno, strerror(errno));
return DAEMON_FAILURE;
case 0 :
break; // Grand-child falls through
default :
exit(EXIT_SUCCESS); // Child terminates OK
}
// This process (grand-child) will be the actual daemon
// Step 4 : Clear file mode creation mask
umask(0);
// Step 5 : Change current working directory
if (chdir(work_dir) == -1) {
syslog_error("chdir to '%s' failed, code=%d (%s)",
work_dir, errno, strerror(errno));
return DAEMON_FAILURE;
}
// Step 6: Close standard file descriptors
close(STDIN_FILENO);
close(STDOUT_FILENO);
close(STDERR_FILENO);
// Step 7 : Redirect standard file descriptors to /dev/null
fd = open("/dev/null", O_RDWR);
if (fd != STDIN_FILENO) {
syslog_error("Redirect STDIN failed, code=%d (%s)",
errno, strerror(errno));
return DAEMON_FAILURE;
}
if (dup2(STDIN_FILENO, STDOUT_FILENO) != STDOUT_FILENO) {
syslog_error("Redirect STDOUT failed, code=%d (%s)",
errno, strerror(errno));
return DAEMON_FAILURE;
}
if (dup2(STDIN_FILENO, STDERR_FILENO) != STDERR_FILENO) {
syslog_error("Redirect STDERR failed, code=%d (%s)",
errno, strerror(errno));
return DAEMON_FAILURE;
}
// Create lock file to prevent more than one instance
// of the daemon is being executed
if (lock_file) {
if (acquire_lock_file(lock_file,
fd_lock_file) != DAEMON_SUCCESS) {
return DAEMON_FAILURE;
}
}
return DAEMON_SUCCESS;
}
