567 lines
13 KiB
C
567 lines
13 KiB
C
/* Functions for communicating with a remote tape drive.
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Copyright (C) 1988, 1992 Free Software Foundation, Inc.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
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/* The man page rmt(8) for /etc/rmt documents the remote mag tape
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protocol which rdump and rrestore use. Unfortunately, the man
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page is *WRONG*. The author of the routines I'm including originally
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wrote his code just based on the man page, and it didn't work, so he
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went to the rdump source to figure out why. The only thing he had to
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change was to check for the 'F' return code in addition to the 'E',
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and to separate the various arguments with \n instead of a space. I
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personally don't think that this is much of a problem, but I wanted to
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point it out. -- Arnold Robbins
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Originally written by Jeff Lee, modified some by Arnold Robbins.
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Redone as a library that can replace open, read, write, etc., by
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Fred Fish, with some additional work by Arnold Robbins.
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Modified to make all rmtXXX calls into macros for speed by Jay Fenlason.
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Use -DHAVE_NETDB_H for rexec code, courtesy of Dan Kegel, srs!dan. */
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#include <stdio.h>
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#include <sys/types.h>
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#include <signal.h>
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#ifdef HAVE_SYS_MTIO_H
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#include <sys/ioctl.h>
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#include <sys/mtio.h>
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#endif
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#ifdef HAVE_NETDB_H
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#include <netdb.h>
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#endif
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#include <errno.h>
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#include <setjmp.h>
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#include <sys/stat.h>
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#ifndef errno
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extern int errno;
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#endif
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#ifdef HAVE_UNISTD_H
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#include <unistd.h>
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#endif
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#ifdef STDC_HEADERS
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#include <string.h>
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#include <stdlib.h>
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#endif
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/* Maximum size of a fully qualified host name. */
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#define MAXHOSTLEN 257
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/* Size of buffers for reading and writing commands to rmt.
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(An arbitrary limit.) */
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#define CMDBUFSIZE 64
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#ifndef RETSIGTYPE
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#define RETSIGTYPE void
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#endif
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/* Maximum number of simultaneous remote tape connections.
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(Another arbitrary limit.) */
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#define MAXUNIT 4
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/* Return the parent's read side of remote tape connection FILDES. */
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#define READ(fildes) (from_rmt[fildes][0])
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/* Return the parent's write side of remote tape connection FILDES. */
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#define WRITE(fildes) (to_rmt[fildes][1])
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/* The pipes for receiving data from remote tape drives. */
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static int from_rmt[MAXUNIT][2] =
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{-1, -1, -1, -1, -1, -1, -1, -1};
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/* The pipes for sending data to remote tape drives. */
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static int to_rmt[MAXUNIT][2] =
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{-1, -1, -1, -1, -1, -1, -1, -1};
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/* Temporary variable used by macros in rmt.h. */
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char *__rmt_path;
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/* Close remote tape connection FILDES. */
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static void
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_rmt_shutdown (fildes)
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int fildes;
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{
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close (READ (fildes));
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close (WRITE (fildes));
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READ (fildes) = -1;
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WRITE (fildes) = -1;
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}
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/* Attempt to perform the remote tape command specified in BUF
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on remote tape connection FILDES.
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Return 0 if successful, -1 on error. */
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static int
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command (fildes, buf)
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int fildes;
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char *buf;
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{
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register int buflen;
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RETSIGTYPE (*pipe_handler) ();
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/* Save the current pipe handler and try to make the request. */
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pipe_handler = signal (SIGPIPE, SIG_IGN);
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buflen = strlen (buf);
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if (write (WRITE (fildes), buf, buflen) == buflen)
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{
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signal (SIGPIPE, pipe_handler);
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return 0;
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}
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/* Something went wrong. Close down and go home. */
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signal (SIGPIPE, pipe_handler);
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_rmt_shutdown (fildes);
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errno = EIO;
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return -1;
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}
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/* Read and return the status from remote tape connection FILDES.
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If an error occurred, return -1 and set errno. */
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static int
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status (fildes)
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int fildes;
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{
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int i;
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char c, *cp;
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char buffer[CMDBUFSIZE];
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/* Read the reply command line. */
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for (i = 0, cp = buffer; i < CMDBUFSIZE; i++, cp++)
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{
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if (read (READ (fildes), cp, 1) != 1)
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{
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_rmt_shutdown (fildes);
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errno = EIO;
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return -1;
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}
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if (*cp == '\n')
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{
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*cp = '\0';
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break;
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}
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}
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if (i == CMDBUFSIZE)
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{
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_rmt_shutdown (fildes);
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errno = EIO;
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return -1;
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}
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/* Check the return status. */
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for (cp = buffer; *cp; cp++)
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if (*cp != ' ')
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break;
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if (*cp == 'E' || *cp == 'F')
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{
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errno = atoi (cp + 1);
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/* Skip the error message line. */
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while (read (READ (fildes), &c, 1) == 1)
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if (c == '\n')
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break;
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if (*cp == 'F')
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_rmt_shutdown (fildes);
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return -1;
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}
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/* Check for mis-synced pipes. */
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if (*cp != 'A')
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{
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_rmt_shutdown (fildes);
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errno = EIO;
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return -1;
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}
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/* Got an `A' (success) response. */
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return atoi (cp + 1);
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}
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#ifdef HAVE_NETDB_H
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/* Execute /etc/rmt as user USER on remote system HOST using rexec.
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Return a file descriptor of a bidirectional socket for stdin and stdout.
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If USER is NULL, or an empty string, use the current username.
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By default, this code is not used, since it requires that
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the user have a .netrc file in his/her home directory, or that the
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application designer be willing to have rexec prompt for login and
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password info. This may be unacceptable, and .rhosts files for use
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with rsh are much more common on BSD systems. */
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static int
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_rmt_rexec (host, user)
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char *host;
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char *user;
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{
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struct servent *rexecserv;
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int save_stdin = dup (fileno (stdin));
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int save_stdout = dup (fileno (stdout));
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int tape_fd; /* Return value. */
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/* When using cpio -o < filename, stdin is no longer the tty.
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But the rexec subroutine reads the login and the passwd on stdin,
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to allow remote execution of the command.
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So, reopen stdin and stdout on /dev/tty before the rexec and
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give them back their original value after. */
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if (freopen ("/dev/tty", "r", stdin) == NULL)
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freopen ("/dev/null", "r", stdin);
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if (freopen ("/dev/tty", "w", stdout) == NULL)
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freopen ("/dev/null", "w", stdout);
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rexecserv = getservbyname ("exec", "tcp");
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if (NULL == rexecserv)
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{
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fprintf (stderr, "exec/tcp: service not available");
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exit (1);
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}
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if (user != NULL && *user == '\0')
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user = NULL;
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tape_fd = rexec (&host, rexecserv->s_port, user, NULL,
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"/etc/rmt", (int *) NULL);
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fclose (stdin);
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fdopen (save_stdin, "r");
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fclose (stdout);
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fdopen (save_stdout, "w");
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return tape_fd;
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}
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#endif /* HAVE_NETDB_H */
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/* Open a magtape device on the system specified in PATH, as the given user.
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PATH has the form `[user@]system:/dev/????'.
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If COMPAT is defined, it can also have the form `system[.user]:/dev/????'.
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OFLAG is O_RDONLY, O_WRONLY, etc.
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MODE is ignored; 0666 is always used.
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If successful, return the remote tape pipe number plus BIAS.
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On error, return -1. */
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int
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__rmt_open (path, oflag, mode, bias)
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char *path;
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int oflag;
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int mode;
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int bias;
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{
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int i, rc;
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char buffer[CMDBUFSIZE]; /* Command buffer. */
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char system[MAXHOSTLEN]; /* The remote host name. */
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char device[CMDBUFSIZE]; /* The remote device name. */
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char login[CMDBUFSIZE]; /* The remote user name. */
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char *sys, *dev, *user; /* For copying into the above buffers. */
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sys = system;
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dev = device;
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user = login;
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/* Find an unused pair of file descriptors. */
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for (i = 0; i < MAXUNIT; i++)
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if (READ (i) == -1 && WRITE (i) == -1)
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break;
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if (i == MAXUNIT)
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{
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errno = EMFILE;
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return -1;
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}
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/* Pull apart the system and device, and optional user.
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Don't munge the original string. */
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while (*path != '@'
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#ifdef COMPAT
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&& *path != '.'
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#endif
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&& *path != ':')
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{
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*sys++ = *path++;
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}
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*sys = '\0';
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path++;
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if (*(path - 1) == '@')
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{
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/* Saw user part of user@host. Start over. */
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strcpy (user, system);
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sys = system;
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while (*path != ':')
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{
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*sys++ = *path++;
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}
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*sys = '\0';
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path++;
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}
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#ifdef COMPAT
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else if (*(path - 1) == '.')
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{
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while (*path != ':')
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{
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*user++ = *path++;
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}
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*user = '\0';
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path++;
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}
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#endif
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else
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*user = '\0';
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while (*path)
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{
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*dev++ = *path++;
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}
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*dev = '\0';
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#ifdef HAVE_NETDB_H
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/* Execute the remote command using rexec. */
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READ (i) = WRITE (i) = _rmt_rexec (system, login);
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if (READ (i) < 0)
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return -1;
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#else /* !HAVE_NETDB_H */
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/* Set up the pipes for the `rsh' command, and fork. */
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if (pipe (to_rmt[i]) == -1 || pipe (from_rmt[i]) == -1)
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return -1;
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rc = fork ();
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if (rc == -1)
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return -1;
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if (rc == 0)
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{
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/* Child. */
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close (0);
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dup (to_rmt[i][0]);
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close (to_rmt[i][0]);
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close (to_rmt[i][1]);
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close (1);
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dup (from_rmt[i][1]);
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close (from_rmt[i][0]);
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close (from_rmt[i][1]);
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setuid (getuid ());
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setgid (getgid ());
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if (*login)
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{
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execl ("/usr/bin/rsh", "rsh", "-l", login, system,
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"/etc/rmt", (char *) 0);
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}
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else
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{
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execl ("/usr/bin/rsh", "rsh", system,
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"/etc/rmt", (char *) 0);
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}
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/* Bad problems if we get here. */
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perror ("cannot execute remote shell");
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_exit (1);
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}
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/* Parent. */
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close (to_rmt[i][0]);
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close (from_rmt[i][1]);
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#endif /* !HAVE_NETDB_H */
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/* Attempt to open the tape device. */
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sprintf (buffer, "O%s\n%d\n", device, oflag);
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if (command (i, buffer) == -1 || status (i) == -1)
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return -1;
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return i + bias;
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}
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/* Close remote tape connection FILDES and shut down.
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Return 0 if successful, -1 on error. */
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int
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__rmt_close (fildes)
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int fildes;
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{
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int rc;
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if (command (fildes, "C\n") == -1)
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return -1;
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rc = status (fildes);
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_rmt_shutdown (fildes);
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return rc;
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}
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/* Read up to NBYTE bytes into BUF from remote tape connection FILDES.
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Return the number of bytes read on success, -1 on error. */
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int
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__rmt_read (fildes, buf, nbyte)
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int fildes;
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char *buf;
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unsigned int nbyte;
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{
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int rc, i;
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char buffer[CMDBUFSIZE];
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sprintf (buffer, "R%d\n", nbyte);
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if (command (fildes, buffer) == -1 || (rc = status (fildes)) == -1)
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return -1;
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for (i = 0; i < rc; i += nbyte, buf += nbyte)
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{
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nbyte = read (READ (fildes), buf, rc - i);
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if (nbyte <= 0)
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{
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_rmt_shutdown (fildes);
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errno = EIO;
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return -1;
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}
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}
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return rc;
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}
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/* Write NBYTE bytes from BUF to remote tape connection FILDES.
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Return the number of bytes written on success, -1 on error. */
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int
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__rmt_write (fildes, buf, nbyte)
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int fildes;
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char *buf;
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unsigned int nbyte;
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{
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char buffer[CMDBUFSIZE];
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RETSIGTYPE (*pipe_handler) ();
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sprintf (buffer, "W%d\n", nbyte);
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if (command (fildes, buffer) == -1)
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return -1;
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pipe_handler = signal (SIGPIPE, SIG_IGN);
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if (write (WRITE (fildes), buf, nbyte) == nbyte)
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{
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signal (SIGPIPE, pipe_handler);
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return status (fildes);
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}
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/* Write error. */
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signal (SIGPIPE, pipe_handler);
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_rmt_shutdown (fildes);
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errno = EIO;
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return -1;
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}
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/* Perform an imitation lseek operation on remote tape connection FILDES.
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Return the new file offset if successful, -1 if on error. */
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long
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__rmt_lseek (fildes, offset, whence)
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int fildes;
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long offset;
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int whence;
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{
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char buffer[CMDBUFSIZE];
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sprintf (buffer, "L%ld\n%d\n", offset, whence);
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if (command (fildes, buffer) == -1)
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return -1;
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return status (fildes);
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}
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/* Perform a raw tape operation on remote tape connection FILDES.
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Return the results of the ioctl, or -1 on error. */
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#ifdef MTIOCTOP
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int
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__rmt_ioctl (fildes, op, arg)
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int fildes, op;
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char *arg;
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{
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char c;
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int rc, cnt;
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char buffer[CMDBUFSIZE];
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switch (op)
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{
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default:
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errno = EINVAL;
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return -1;
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case MTIOCTOP:
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/* MTIOCTOP is the easy one. Nothing is transfered in binary. */
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sprintf (buffer, "I%d\n%d\n", ((struct mtop *) arg)->mt_op,
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((struct mtop *) arg)->mt_count);
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if (command (fildes, buffer) == -1)
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return -1;
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return status (fildes); /* Return the count. */
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case MTIOCGET:
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/* Grab the status and read it directly into the structure.
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This assumes that the status buffer is not padded
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and that 2 shorts fit in a long without any word
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alignment problems; i.e., the whole struct is contiguous.
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NOTE - this is probably NOT a good assumption. */
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if (command (fildes, "S") == -1 || (rc = status (fildes)) == -1)
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return -1;
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for (; rc > 0; rc -= cnt, arg += cnt)
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{
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cnt = read (READ (fildes), arg, rc);
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if (cnt <= 0)
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{
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_rmt_shutdown (fildes);
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errno = EIO;
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return -1;
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}
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}
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/* Check for byte position. mt_type is a small integer field
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(normally) so we will check its magnitude. If it is larger than
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256, we will assume that the bytes are swapped and go through
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and reverse all the bytes. */
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if (((struct mtget *) arg)->mt_type < 256)
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return 0;
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for (cnt = 0; cnt < rc; cnt += 2)
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{
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c = arg[cnt];
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arg[cnt] = arg[cnt + 1];
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arg[cnt + 1] = c;
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}
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return 0;
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}
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}
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#endif
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