pipe.c

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/*  -*- c-file-style: "linux" -*-
 *
 * Copyright (C) 1996-2000 by Andrew Tridgell
 * Copyright (C) Paul Mackerras 1996
 * Copyright (C) 2001, 2002 by Martin Pool <mbp@samba.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include "rsync.h"

extern int am_sender;
extern int am_server;
extern int blocking_io;
extern int filesfrom_fd;
extern mode_t orig_umask;
extern struct chmod_mode_struct *chmod_modes;

/**
 * Create a child connected to us via its stdin/stdout.
 *
 * This is derived from CVS code
 *
 * Note that in the child STDIN is set to blocking and STDOUT
 * is set to non-blocking. This is necessary as rsh relies on stdin being blocking
 *  and ssh relies on stdout being non-blocking
 *
 * If blocking_io is set then use blocking io on both fds. That can be
 * used to cope with badly broken rsh implementations like the one on
 * Solaris.
 **/
pid_t piped_child(char **command, int *f_in, int *f_out)
{
        pid_t pid;
        int to_child_pipe[2];
        int from_child_pipe[2];

        if (verbose >= 2) {
                print_child_argv(command);
        }

        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) {
                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]);
                umask(orig_umask);
                set_blocking(STDIN_FILENO);
                if (blocking_io > 0)
                        set_blocking(STDOUT_FILENO);
                execvp(command[0], command);
                rsyserr(FERROR, errno, "Failed to exec %s", command[0]);
                exit_cleanup(RERR_IPC);
        }

        if (close(from_child_pipe[1]) < 0 || close(to_child_pipe[0]) < 0) {
                rsyserr(FERROR, errno, "Failed to close");
                exit_cleanup(RERR_IPC);
        }

        *f_in = from_child_pipe[0];
        *f_out = to_child_pipe[1];

        return pid;
}

/* 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
 * two socket ends are retained for reading and writing.  In the
 * child, the STDIN and STDOUT file descriptors refer to these
 * 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;
                chmod_modes = NULL; /* Let the sending side handle this. */

                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]);
                child_main(argc, argv);
        }

        if (close(from_child_pipe[1]) < 0 ||
            close(to_child_pipe[0]) < 0) {
                rsyserr(FERROR, errno, "Failed to close");
                exit_cleanup(RERR_IPC);
        }

        *f_in = from_child_pipe[0];
        *f_out = to_child_pipe[1];

        return pid;
}

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