Function local_child

pipe.c:109–178

This function forks a child which calls child_main(). First, * however, it has to establish communication paths to and from the * newborn child. It creates two socket pairs -- one for writing to * the child (from the parent) and one for reading from the child * (writing to the parent). Since that's four socket ends, each * process has to close the two ends it doesn't need. The remaining

 * sockets.  In the parent, the function arguments f_in and f_out are
 * set to refer to these sockets. */
pid_t local_child(int argc, char **argv, int *f_in, int *f_out,
		  int (*child_main)(int, char*[]))
{
	pid_t pid;
	int to_child_pipe[2];
	int from_child_pipe[2];

	/* The parent process is always the sender for a local rsync. */
	assert(am_sender);

	if (fd_pair(to_child_pipe) < 0 || fd_pair(from_child_pipe) < 0) {
		rsyserr(FERROR, errno, "pipe");
		exit_cleanup(RERR_IPC);
	}

	pid = do_fork();
	if (pid == -1) {
		rsyserr(FERROR, errno, "fork");
		exit_cleanup(RERR_IPC);
	}

	if (pid == 0) {
		am_sender = 0;
		am_server = 1;
		filesfrom_fd = -1;
		munge_symlinks = 0; /* Each side needs its own option. */
		chmod_modes = NULL; /* Let the sending side handle this. */

		/* Let the client side handle this. */
		if (logfile_name) {
			logfile_name = NULL;
			logfile_close();
		}

		if (remote_option_cnt) {
			int rc = remote_option_cnt + 1;
			const char **rv = remote_options;
			if (!parse_arguments(&rc, &rv)) {
				option_error();
				exit_cleanup(RERR_SYNTAX);
			}
		}

		if (dup2(to_child_pipe[0], STDIN_FILENO) < 0
		 || close(to_child_pipe[1]) < 0
		 || close(from_child_pipe[0]) < 0
		 || dup2(from_child_pipe[1], STDOUT_FILENO) < 0) {
			rsyserr(FERROR, errno, "Failed to dup/close");
			exit_cleanup(RERR_IPC);
		}
		if (to_child_pipe[0] != STDIN_FILENO)
			close(to_child_pipe[0]);
		if (from_child_pipe[1] != STDOUT_FILENO)
			close(from_child_pipe[1]);
#ifdef ICONV_CONST
		setup_iconv();
#endif
		child_main(argc, argv);