void
daemon_t::_grandchild(
pipe_t & c_pipe,
pipe_t & g_pipe
) {
try {
c_pipe.writer().close();
_init();
// Initialization finished successfully -- let parent know everything is ok.
g_pipe.writer().write( ok );
g_pipe.writer().close();
} catch ( std::exception const & ex ) {
g_pipe.writer().write( string_t( ex.what() ) + "\n" );
throw;
} catch ( ... ) {
g_pipe.writer().write( "Unknown exception occurred\n" );
throw;
}; // try
_body();
}; // _grandchild
void
daemon_t::_child(
pipe_t & c_pipe,
pipe_t & g_pipe
) {
try {
int error = -1;
c_pipe.reader().close();
g_pipe.reader().close();
// Reopen standard streams.
// Associate all the standard streams with `/dev/null'.
file_t null( * this );
null.open( "/dev/null", O_RDONLY, 0 );
error = dup2( null.fd(), STDIN_FILENO );
SYSERR( error < 0, "dup2", "Reopening stdin" );
null.close();
null.open( "/dev/null", O_WRONLY, 0 );
error = dup2( null.fd(), STDOUT_FILENO );
SYSERR( error < 0, "dup2", "Reopening stdout" );
error = dup2( null.fd(), STDERR_FILENO );
SYSERR( error < 0, "dup2", "Reopening stderr" );
null.close();
pid_t sid = 0;
ESYSCALL(
"creating session",
"setsid",
sid = setsid(),
sid > 0,
"session " << sid << " created"
);
// Ignore unused signals.
// We ignore signals in child so in grandchild these signals are fro the very beginning.
// If daemon need any of these signals, it will handle them explicitly.
thread_t::ignore_signal( SIGHUP );
thread_t::ignore_signal( SIGINT );
thread_t::ignore_signal( SIGQUIT );
thread_t::ignore_signal( SIGUSR1 );
thread_t::ignore_signal( SIGUSR2 );
thread_t::ignore_signal( SIGTERM );
thread_t::ignore_signal( SIGCHLD );
thread_t::ignore_signal( SIGTTIN );
thread_t::ignore_signal( SIGTTOU );
thread_t::ignore_signal( SIGWINCH );
pid_t pid = 0;
ESYSCALL(
"forking grandchild process",
"fork",
pid = fork(),
pid >= 0,
"grandchild process forked " << ( pid == 0 ? "(i am grandchild)" : "(i am child)" )
);
if ( pid == 0 ) {
_grandchild( c_pipe, g_pipe );
return; // TODO: or exit?
}; // if
g_pipe.writer().close();
ESYSCALL(
"anti-zombying grandchild",
"waitpid",
error = waitpid( pid, NULL, WNOHANG ),
error != -1,
"grandchild anti-zombied"
);
// We cannot just close pipe: on the parent end ir will be not clear if everything is ok
// or child silently died. So let us write `ok' to the pipe -- parent will know that we
// are really ok.
c_pipe.writer().write( ok );
} catch ( std::exception const & ex ) {
c_pipe.writer().write( string_t( ex.what() ) + "\n" );
} catch ( ... ) {
c_pipe.writer().write( "Unknown exception occurred\n" );
}; // try
c_pipe.writer().close();
}; // _child