pipe.c

   1 /*
   2  * Routines used to setup various kinds of inter-process pipes.
   3  *
   4  * Copyright (C) 1996-2000 Andrew Tridgell
   5  * Copyright (C) 1996 Paul Mackerras
   6  * Copyright (C) 2001, 2002 Martin Pool <mbp@samba.org>
   7  * Copyright (C) 2004-2020 Wayne Davison
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License as published by
  11  * the Free Software Foundation; either version 3 of the License, or
  12  * (at your option) any later version.
  13  *
  14  * This program is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17  * GNU General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU General Public License along
  20  * with this program; if not, visit the http://fsf.org website.
  21  */
  22
  23 #include "rsync.h"
  24
  25 extern int am_sender;
  26 extern int am_server;
  27 extern int blocking_io;
  28 extern int filesfrom_fd;
  29 extern int munge_symlinks;
  30 extern char *logfile_name;
  31 extern int remote_option_cnt;
  32 extern const char **remote_options;
  33 extern struct chmod_mode_struct *chmod_modes;
  34
  35 /**
  36  * Create a child connected to us via its stdin/stdout.
  37  *
  38  * This is derived from CVS code
  39  *
  40  * Note that in the child STDIN is set to blocking and STDOUT
  41  * is set to non-blocking. This is necessary as rsh relies on stdin being blocking
  42  *  and ssh relies on stdout being non-blocking
  43  *
  44  * If blocking_io is set then use blocking io on both fds. That can be
  45  * used to cope with badly broken rsh implementations like the one on
  46  * Solaris.
  47  **/
  48 pid_t piped_child(char **command, int *f_in, int *f_out)
  49 {
  50         pid_t pid;
  51         int to_child_pipe[2];
  52         int from_child_pipe[2];
  53
  54         if (DEBUG_GTE(CMD, 1))
  55                 print_child_argv("opening connection using:", command);
  56
  57         if (fd_pair(to_child_pipe) < 0 || fd_pair(from_child_pipe) < 0) {
  58                 rsyserr(FERROR, errno, "pipe");
  59                 exit_cleanup(RERR_IPC);
  60         }
  61
  62         pid = do_fork();
  63         if (pid == -1) {
  64                 rsyserr(FERROR, errno, "fork");
  65                 exit_cleanup(RERR_IPC);
  66         }
  67
  68         if (pid == 0) {
  69                 if (dup2(to_child_pipe[0], STDIN_FILENO) < 0
  70                  || close(to_child_pipe[1]) < 0
  71                  || close(from_child_pipe[0]) < 0
  72                  || dup2(from_child_pipe[1], STDOUT_FILENO) < 0) {
  73                         rsyserr(FERROR, errno, "Failed to dup/close");
  74                         exit_cleanup(RERR_IPC);
  75                 }
  76                 if (to_child_pipe[0] != STDIN_FILENO)
  77                         close(to_child_pipe[0]);
  78                 if (from_child_pipe[1] != STDOUT_FILENO)
  79                         close(from_child_pipe[1]);
  80                 set_blocking(STDIN_FILENO);
  81                 if (blocking_io > 0)
  82                         set_blocking(STDOUT_FILENO);
  83                 execvp(command[0], command);
  84                 rsyserr(FERROR, errno, "Failed to exec %s", command[0]);
  85                 exit_cleanup(RERR_IPC);
  86         }
  87
  88         if (close(from_child_pipe[1]) < 0 || close(to_child_pipe[0]) < 0) {
  89                 rsyserr(FERROR, errno, "Failed to close");
  90                 exit_cleanup(RERR_IPC);
  91         }
  92
  93         *f_in = from_child_pipe[0];
  94         *f_out = to_child_pipe[1];
  95
  96         return pid;
  97 }
  98
  99 /* This function forks a child which calls child_main().  First,
 100  * however, it has to establish communication paths to and from the
 101  * newborn child.  It creates two socket pairs -- one for writing to
 102  * the child (from the parent) and one for reading from the child
 103  * (writing to the parent).  Since that's four socket ends, each
 104  * process has to close the two ends it doesn't need.  The remaining
 105  * two socket ends are retained for reading and writing.  In the
 106  * child, the STDIN and STDOUT file descriptors refer to these
 107  * sockets.  In the parent, the function arguments f_in and f_out are
 108  * set to refer to these sockets. */
 109 pid_t local_child(int argc, char **argv, int *f_in, int *f_out,
 110                   int (*child_main)(int, char*[]))
 111 {
 112         pid_t pid;
 113         int to_child_pipe[2];
 114         int from_child_pipe[2];
 115
 116         /* The parent process is always the sender for a local rsync. */
 117         assert(am_sender);
 118
 119         if (fd_pair(to_child_pipe) < 0 || fd_pair(from_child_pipe) < 0) {
 120                 rsyserr(FERROR, errno, "pipe");
 121                 exit_cleanup(RERR_IPC);
 122         }
 123
 124         pid = do_fork();
 125         if (pid == -1) {
 126                 rsyserr(FERROR, errno, "fork");
 127                 exit_cleanup(RERR_IPC);
 128         }
 129
 130         if (pid == 0) {
 131                 am_sender = 0;
 132                 am_server = 1;
 133                 filesfrom_fd = -1;
 134                 munge_symlinks = 0; /* Each side needs its own option. */
 135                 chmod_modes = NULL; /* Let the sending side handle this. */
 136
 137                 /* Let the client side handle this. */
 138                 if (logfile_name) {
 139                         logfile_name = NULL;
 140                         logfile_close();
 141                 }
 142
 143                 if (remote_option_cnt) {
 144                         int rc = remote_option_cnt + 1;
 145                         const char **rv = remote_options;
 146                         if (!parse_arguments(&rc, &rv)) {
 147                                 option_error();
 148                                 exit_cleanup(RERR_SYNTAX);
 149                         }
 150                 }
 151
 152                 if (dup2(to_child_pipe[0], STDIN_FILENO) < 0
 153                  || close(to_child_pipe[1]) < 0
 154                  || close(from_child_pipe[0]) < 0
 155                  || dup2(from_child_pipe[1], STDOUT_FILENO) < 0) {
 156                         rsyserr(FERROR, errno, "Failed to dup/close");
 157                         exit_cleanup(RERR_IPC);
 158                 }
 159                 if (to_child_pipe[0] != STDIN_FILENO)
 160                         close(to_child_pipe[0]);
 161                 if (from_child_pipe[1] != STDOUT_FILENO)
 162                         close(from_child_pipe[1]);
 163 #ifdef ICONV_CONST
 164                 setup_iconv();
 165 #endif
 166                 child_main(argc, argv);
 167         }
 168
 169         if (close(from_child_pipe[1]) < 0 || close(to_child_pipe[0]) < 0) {
 170                 rsyserr(FERROR, errno, "Failed to close");
 171                 exit_cleanup(RERR_IPC);
 172         }
 173
 174         *f_in = from_child_pipe[0];
 175         *f_out = to_child_pipe[1];
 176
 177         return pid;
 178 }