pipe.c

   1 /*  -*- c-file-style: "linux" -*-
   2  *
   3  * Copyright (C) 1996-2000 by Andrew Tridgell
   4  * Copyright (C) Paul Mackerras 1996
   5  * Copyright (C) 2001, 2002 by Martin Pool <mbp@samba.org>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  20  */
  21
  22 #include "rsync.h"
  23
  24 extern int am_sender;
  25 extern int am_server;
  26 extern int blocking_io;
  27 extern int orig_umask;
  28 extern int filesfrom_fd;
  29
  30 /**
  31  * Create a child connected to use on stdin/stdout.
  32  *
  33  * This is derived from CVS code
  34  *
  35  * Note that in the child STDIN is set to blocking and STDOUT
  36  * is set to non-blocking. This is necessary as rsh relies on stdin being blocking
  37  *  and ssh relies on stdout being non-blocking
  38  *
  39  * If blocking_io is set then use blocking io on both fds. That can be
  40  * used to cope with badly broken rsh implementations like the one on
  41  * Solaris.
  42  **/
  43 pid_t piped_child(char **command, int *f_in, int *f_out)
  44 {
  45         pid_t pid;
  46         int to_child_pipe[2];
  47         int from_child_pipe[2];
  48
  49         if (verbose >= 2) {
  50                 print_child_argv(command);
  51         }
  52
  53         if (fd_pair(to_child_pipe) < 0 || fd_pair(from_child_pipe) < 0) {
  54                 rsyserr(FERROR, errno, "pipe");
  55                 exit_cleanup(RERR_IPC);
  56         }
  57
  58         pid = do_fork();
  59         if (pid == -1) {
  60                 rsyserr(FERROR, errno, "fork");
  61                 exit_cleanup(RERR_IPC);
  62         }
  63
  64         if (pid == 0) {
  65                 if (dup2(to_child_pipe[0], STDIN_FILENO) < 0 ||
  66                     close(to_child_pipe[1]) < 0 ||
  67                     close(from_child_pipe[0]) < 0 ||
  68                     dup2(from_child_pipe[1], STDOUT_FILENO) < 0) {
  69                         rsyserr(FERROR, errno, "Failed to dup/close");
  70                         exit_cleanup(RERR_IPC);
  71                 }
  72                 if (to_child_pipe[0] != STDIN_FILENO)
  73                         close(to_child_pipe[0]);
  74                 if (from_child_pipe[1] != STDOUT_FILENO)
  75                         close(from_child_pipe[1]);
  76                 umask(orig_umask);
  77                 set_blocking(STDIN_FILENO);
  78                 if (blocking_io > 0)
  79                         set_blocking(STDOUT_FILENO);
  80                 execvp(command[0], command);
  81                 rsyserr(FERROR, errno, "Failed to exec %s",
  82                         safe_fname(command[0]));
  83                 exit_cleanup(RERR_IPC);
  84         }
  85
  86         if (close(from_child_pipe[1]) < 0 || close(to_child_pipe[0]) < 0) {
  87                 rsyserr(FERROR, errno, "Failed to close");
  88                 exit_cleanup(RERR_IPC);
  89         }
  90
  91         *f_in = from_child_pipe[0];
  92         *f_out = to_child_pipe[1];
  93
  94         return pid;
  95 }
  96
  97 /* This function forks a child which calls child_main().  First,
  98  * however, it has to establish communication paths to and from the
  99  * newborn child.  It creates two socket pairs -- one for writing to
 100  * the child (from the parent) and one for reading from the child
 101  * (writing to the parent).  Since that's four socket ends, each
 102  * process has to close the two ends it doesn't need.  The remaining
 103  * two socket ends are retained for reading and writing.  In the
 104  * child, the STDIN and STDOUT file descriptors refer to these
 105  * sockets.  In the parent, the function arguments f_in and f_out are
 106  * set to refer to these sockets. */
 107 pid_t local_child(int argc, char **argv, int *f_in, int *f_out,
 108                   int (*child_main)(int, char*[]))
 109 {
 110         pid_t pid;
 111         int to_child_pipe[2];
 112         int from_child_pipe[2];
 113
 114         if (fd_pair(to_child_pipe) < 0 ||
 115             fd_pair(from_child_pipe) < 0) {
 116                 rsyserr(FERROR, errno, "pipe");
 117                 exit_cleanup(RERR_IPC);
 118         }
 119
 120         pid = do_fork();
 121         if (pid == -1) {
 122                 rsyserr(FERROR, errno, "fork");
 123                 exit_cleanup(RERR_IPC);
 124         }
 125
 126         if (pid == 0) {
 127                 am_sender = !am_sender;
 128                 am_server = 1;
 129
 130                 if (!am_sender)
 131                         filesfrom_fd = -1;
 132
 133                 if (dup2(to_child_pipe[0], STDIN_FILENO) < 0 ||
 134                     close(to_child_pipe[1]) < 0 ||
 135                     close(from_child_pipe[0]) < 0 ||
 136                     dup2(from_child_pipe[1], STDOUT_FILENO) < 0) {
 137                         rsyserr(FERROR, errno, "Failed to dup/close");
 138                         exit_cleanup(RERR_IPC);
 139                 }
 140                 if (to_child_pipe[0] != STDIN_FILENO)
 141                         close(to_child_pipe[0]);
 142                 if (from_child_pipe[1] != STDOUT_FILENO)
 143                         close(from_child_pipe[1]);
 144                 child_main(argc, argv);
 145         }
 146
 147         if (!am_sender)
 148                 filesfrom_fd = -1;
 149
 150         if (close(from_child_pipe[1]) < 0 ||
 151             close(to_child_pipe[0]) < 0) {
 152                 rsyserr(FERROR, errno, "Failed to close");
 153                 exit_cleanup(RERR_IPC);
 154         }
 155
 156         *f_in = from_child_pipe[0];
 157         *f_out = to_child_pipe[1];
 158
 159         return pid;
 160 }