usr/src/usr.bin/tar/rtape_lib.c

/* Remote tape emulator subroutines.
   Copyright (C) 1988 Free Software Foundation

This file is part of GNU Tar.

GNU Tar 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 1, or (at your option)
any later version.

GNU Tar 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 GNU Tar; see the file COPYING.  If not, write to
the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */

/* JF: modified to make all rmtXXX calls into macros for speed */

#ifndef lint
static char *RCSid = "$Header: /usr/src/local/usr.lib/librmt/RCS/rmtlib.c,v 1.7 89/03/23 14:09:51 root Exp Locker: root $";
#endif

/*
 * $Log:        rmtlib.c,v $
 * Revision 1.7  89/03/23  14:09:51  root
 * Fix from haynes@ucscc.ucsc.edu for use w/compat. ADR.
 *
 * Revision 1.6  88/10/25  17:04:29  root
 * rexec code and a bug fix from srs!dan, miscellanious cleanup. ADR.
 *
 * Revision 1.5  88/10/25  16:30:17  root
 * Fix from jeff@gatech.edu for getting user@host:dev right. ADR.
 *
 * Revision 1.4  87/10/30  10:36:12  root
 * Made 4.2 syntax a compile time option. ADR.
 *
 * Revision 1.3  87/04/22  11:16:48  root
 * Two fixes from parmelee@wayback.cs.cornell.edu to correctly
 * do fd biasing and rmt protocol on 'S' command. ADR.
 *
 * Revision 1.2  86/10/09  16:38:53  root
 * Changed to reflect 4.3BSD rcp syntax. ADR.
 *
 * Revision 1.1  86/10/09  16:17:35  root
 * Initial revision
 *
 */

/*
 *      rmt --- remote tape emulator subroutines
 *
 *      Originally written by Jeff Lee, modified some by Arnold Robbins
 *
 *      WARNING:  The man page rmt(8) for /etc/rmt documents the remote mag
 *      tape protocol which rdump and rrestore use.  Unfortunately, the man
 *      page is *WRONG*.  The author of the routines I'm including originally
 *      wrote his code just based on the man page, and it didn't work, so he
 *      went to the rdump source to figure out why.  The only thing he had to
 *      change was to check for the 'F' return code in addition to the 'E',
 *      and to separate the various arguments with \n instead of a space.  I
 *      personally don't think that this is much of a problem, but I wanted to
 *      point it out.
 *      -- Arnold Robbins
 *
 *      Redone as a library that can replace open, read, write, etc, by
 *      Fred Fish, with some additional work by Arnold Robbins.
 */

/* Use -DUSE_REXEC for rexec code, courtesy of Dan Kegel, srs!dan */

#if defined(USG) && !defined(HAVE_MTIO)
#define NO_RMTIOCTL
#endif

#include <stdio.h>
#include <signal.h>
#include <sys/types.h>

#ifndef NO_RMTIOCTL
#include <sys/ioctl.h>
#include <sys/mtio.h>
#endif

#ifdef USE_REXEC
#include <netdb.h>
#endif

#include <errno.h>
#include <setjmp.h>
#include <sys/stat.h>

#define BUFMAGIC        64      /* a magic number for buffer sizes */

/*
 *      MAXUNIT --- Maximum number of remote tape file units
 */
#define MAXUNIT 4

/*
 *      READ --- Return the number of the read side file descriptor
 *      WRITE --- Return the number of the write side file descriptor
 */
#define READ(fd)        (Ctp[fd][0])
#define WRITE(fd)       (Ptc[fd][1])

static int Ctp[MAXUNIT][2] = { -1, -1, -1, -1, -1, -1, -1, -1 };
static int Ptc[MAXUNIT][2] = { -1, -1, -1, -1, -1, -1, -1, -1 };

extern int errno;

char *__rmt_path;

/*
 *      _rmt_panic --- close off a remote tape connection
 */

static void _rmt_panic(fildes)
int fildes;
{
        close(READ(fildes));
        close(WRITE(fildes));
        READ(fildes) = -1;
        WRITE(fildes) = -1;
}


/*
 *      command --- attempt to perform a remote tape command
 */

static int command(fildes, buf)
int fildes;
char *buf;
{
        register int blen;
#ifdef SIGNAL_VOID
        void (*pstat)();
#else
        int (*pstat)();
#endif

/*
 *      save current pipe status and try to make the request
 */

        blen = strlen(buf);
        pstat = signal(SIGPIPE, SIG_IGN);
        if (write(WRITE(fildes), buf, blen) == blen)
        {
                signal(SIGPIPE, pstat);
                return(0);
        }

/*
 *      something went wrong. close down and go home
 */

        signal(SIGPIPE, pstat);
        _rmt_panic(fildes);

        errno = EIO;
        return(-1);
}


/*
 *      status --- retrieve the status from the pipe
 */

static int status(fildes)
int fildes;
{
        int i;
        char c, *cp;
        char buffer[BUFMAGIC];

/*
 *      read the reply command line
 */

        for (i = 0, cp = buffer; i < BUFMAGIC; i++, cp++)
        {
                if (read(READ(fildes), cp, 1) != 1)
                {
                        _rmt_panic(fildes);
                        errno = EIO;
                        return(-1);
                }
                if (*cp == '\n')
                {
                        *cp = 0;
                        break;
                }
        }

        if (i == BUFMAGIC)
        {
                _rmt_panic(fildes);
                errno = EIO;
                return(-1);
        }

/*
 *      check the return status
 */

        for (cp = buffer; *cp; cp++)
                if (*cp != ' ')
                        break;

        if (*cp == 'E' || *cp == 'F')
        {
                errno = atoi(cp + 1);
                while (read(READ(fildes), &c, 1) == 1)
                        if (c == '\n')
                                break;

                if (*cp == 'F')
                        _rmt_panic(fildes);

                return(-1);
        }

/*
 *      check for mis-synced pipes
 */

        if (*cp != 'A')
        {
                _rmt_panic(fildes);
                errno = EIO;
                return(-1);
        }

        return(atoi(cp + 1));
}

#ifdef USE_REXEC

/*
 * _rmt_rexec
 *
 * execute /etc/rmt on a remote system using rexec().
 * Return file descriptor of bidirectional socket for stdin and stdout
 * If username is NULL, or an empty string, uses current username.
 *
 * ADR: By default, this code is not used, since it requires that
 * the user have a .netrc file in his/her home directory, or that the
 * application designer be willing to have rexec prompt for login and
 * password info. This may be unacceptable, and .rhosts files for use
 * with rsh are much more common on BSD systems.
 */

static int
_rmt_rexec(host, user)
char *host;
char *user;             /* may be NULL */
{
        struct servent *rexecserv;
        int save_stdin = dup(fileno(stdin));
        int save_stdout = dup(fileno(stdout));
        int tape_fd;            /* Return value. */

        /*
         * When using cpio -o < filename, stdin is no longer the tty.
         * But the rexec subroutine reads the login and the passwd on stdin,
         * to allow remote execution of the command.
         * So, reopen stdin and stdout on /dev/tty before the rexec and
         * give them back their original value after.
         */
        if (freopen("/dev/tty", "r", stdin) == NULL)
                freopen("/dev/null", "r", stdin);
        if (freopen("/dev/tty", "w", stdout) == NULL)
                freopen("/dev/null", "w", stdout);

        rexecserv = getservbyname("exec", "tcp");
        if (NULL == rexecserv) {
                fprintf (stderr, "? exec/tcp: service not available.");
                exit (-1);
        }
        if ((user != NULL) && *user == '\0')
                user = (char *) NULL;
        tape_fd = rexec (&host, rexecserv->s_port, user, NULL,
                         "/etc/rmt", (int *)NULL);
        fclose(stdin);
        fdopen(save_stdin, "r");
        fclose(stdout);
        fdopen(save_stdout, "w");

        return tape_fd;
}
#endif /* USE_REXEC */

/*
 *      _rmt_open --- open a magtape device on system specified, as given user
 *
 *      file name has the form [user@]system:/dev/????
#ifdef COMPAT
 *      file name has the form system[.user]:/dev/????
#endif
 */

#define MAXHOSTLEN      257     /* BSD allows very long host names... */

int __rmt_open (path, oflag, mode, bias)
char *path;
int oflag;
int mode;
int bias;
{
        int i, rc;
        char buffer[BUFMAGIC];
        char system[MAXHOSTLEN];
        char device[BUFMAGIC];
        char login[BUFMAGIC];
        char *sys, *dev, *user;

        sys = system;
        dev = device;
        user = login;

/*
 *      first, find an open pair of file descriptors
 */

        for (i = 0; i < MAXUNIT; i++)
                if (READ(i) == -1 && WRITE(i) == -1)
                        break;

        if (i == MAXUNIT)
        {
                errno = EMFILE;
                return(-1);
        }

/*
 *      pull apart system and device, and optional user
 *      don't munge original string
 *      if COMPAT is defined, also handle old (4.2) style person.site notation.
 */

        while (*path != '@'
#ifdef COMPAT
                        && *path != '.'
#endif
                        && *path != ':') {
                *sys++ = *path++;
        }
        *sys = '\0';
        path++;

        if (*(path - 1) == '@')
        {
                (void) strcpy (user, system);   /* saw user part of user@host */
                sys = system;                   /* start over */
                while (*path != ':') {
                        *sys++ = *path++;
                }
                *sys = '\0';
                path++;
        }
#ifdef COMPAT
        else if (*(path - 1) == '.')
        {
                while (*path != ':') {
                        *user++ = *path++;
                }
                *user = '\0';
                path++;
        }
#endif
        else
                *user = '\0';

        while (*path) {
                *dev++ = *path++;
        }
        *dev = '\0';

#ifdef USE_REXEC
/*
 *      Execute the remote command using rexec
 */
        READ(i) = WRITE(i) = _rmt_rexec(system, login);
        if (READ(i) < 0)
                return -1;
#else
/*
 *      setup the pipes for the 'rsh' command and fork
 */

        if (pipe(Ptc[i]) == -1 || pipe(Ctp[i]) == -1)
                return(-1);

        if ((rc = fork()) == -1)
                return(-1);

        if (rc == 0)
        {
                close(0);
                dup(Ptc[i][0]);
                close(Ptc[i][0]); close(Ptc[i][1]);
                close(1);
                dup(Ctp[i][1]);
                close(Ctp[i][0]); close(Ctp[i][1]);
                (void) setuid (getuid ());
                (void) setgid (getgid ());
                if (*login)
                {
                        execl("/usr/ucb/rsh", "rsh", system, "-l", login,
                                "/etc/rmt", (char *) 0);
                        execl("/usr/bin/remsh", "remsh", system, "-l", login,
                                "/etc/rmt", (char *) 0);
                        execl("/usr/bin/rsh", "rsh", system, "-l", login,
                                "/etc/rmt", (char *) 0);
                        execl("/usr/bsd/rsh", "rsh", system, "-l", login,
                                "/etc/rmt", (char *)0);
                        execl("/usr/bin/nsh", "nsh", system, "-l", login,
                                "/etc/rmt", (char *)0);
                }
                else
                {
                        execl("/usr/ucb/rsh", "rsh", system,
                                "/etc/rmt", (char *) 0);
                        execl("/usr/bin/remsh", "remsh", system,
                                "/etc/rmt", (char *) 0);
                        execl("/usr/bin/rsh", "rsh", system,
                                "/etc/rmt", (char *) 0);
                        execl("/usr/bsd/rsh", "rsh", system,
                                "/etc/rmt", (char *) 0);
                        execl("/usr/bin/nsh", "nsh", system,
                                "/etc/rmt", (char *)0);
                }

/*
 *      bad problems if we get here
 */

                perror("remote shell exec");
                exit(1);
        }

        close(Ptc[i][0]); close(Ctp[i][1]);
#endif

/*
 *      now attempt to open the tape device
 */

        sprintf(buffer, "O%s\n%d\n", device, oflag);
        if (command(i, buffer) == -1 || status(i) == -1)
                return(-1);

        return(i+bias);
}


/*
 *      _rmt_close --- close a remote magtape unit and shut down
 */

 int __rmt_close(fildes)
int fildes;
{
        int rc;

        if (command(fildes, "C\n") != -1)
        {
                rc = status(fildes);

                _rmt_panic(fildes);
                return(rc);
        }

        return(-1);
}


/*
 *      _rmt_read --- read a buffer from a remote tape
 */

int __rmt_read(fildes, buf, nbyte)
int fildes;
char *buf;
unsigned int nbyte;
{
        int rc, i;
        char buffer[BUFMAGIC];

        sprintf(buffer, "R%d\n", nbyte);
        if (command(fildes, buffer) == -1 || (rc = status(fildes)) == -1)
                return(-1);

        for (i = 0; i < rc; i += nbyte, buf += nbyte)
        {
                nbyte = read(READ(fildes), buf, rc);
                if (nbyte <= 0)
                {
                        _rmt_panic(fildes);
                        errno = EIO;
                        return(-1);
                }
        }

        return(rc);
}


/*
 *      _rmt_write --- write a buffer to the remote tape
 */

int __rmt_write(fildes, buf, nbyte)
int fildes;
char *buf;
unsigned int nbyte;
{
        char buffer[BUFMAGIC];
#ifdef SIGNAL_VOID
        void (*pstat)();
#else
        int (*pstat)();
#endif

        sprintf(buffer, "W%d\n", nbyte);
        if (command(fildes, buffer) == -1)
                return(-1);

        pstat = signal(SIGPIPE, SIG_IGN);
        if (write(WRITE(fildes), buf, nbyte) == nbyte)
        {
                signal (SIGPIPE, pstat);
                return(status(fildes));
        }

        signal (SIGPIPE, pstat);
        _rmt_panic(fildes);
        errno = EIO;
        return(-1);
}


/*
 *      _rmt_lseek --- perform an imitation lseek operation remotely
 */

long __rmt_lseek(fildes, offset, whence)
int fildes;
long offset;
int whence;
{
        char buffer[BUFMAGIC];

        sprintf(buffer, "L%d\n%d\n", offset, whence);
        if (command(fildes, buffer) == -1)
                return(-1);

        return(status(fildes));
}


/*
 *      _rmt_ioctl --- perform raw tape operations remotely
 */

#ifndef NO_RMTIOCTL
__rmt_ioctl(fildes, op, arg)
int fildes, op;
char *arg;
{
        char c;
        int rc, cnt;
        char buffer[BUFMAGIC];

/*
 *      MTIOCOP is the easy one. nothing is transfered in binary
 */

        if (op == MTIOCTOP)
        {
                sprintf(buffer, "I%d\n%d\n", ((struct mtop *) arg)->mt_op,
                        ((struct mtop *) arg)->mt_count);
                if (command(fildes, buffer) == -1)
                        return(-1);
                return(status(fildes));
        }

/*
 *      we can only handle 2 ops, if not the other one, punt
 */

        if (op != MTIOCGET)
        {
                errno = EINVAL;
                return(-1);
        }

/*
 *      grab the status and read it directly into the structure
 *      this assumes that the status buffer is (hopefully) not
 *      padded and that 2 shorts fit in a long without any word
 *      alignment problems, ie - the whole struct is contiguous
 *      NOTE - this is probably NOT a good assumption.
 */

        if (command(fildes, "S") == -1 || (rc = status(fildes)) == -1)
                return(-1);

        for (; rc > 0; rc -= cnt, arg += cnt)
        {
                cnt = read(READ(fildes), arg, rc);
                if (cnt <= 0)
                {
                        _rmt_panic(fildes);
                        errno = EIO;
                        return(-1);
                }
        }

/*
 *      now we check for byte position. mt_type is a small integer field
 *      (normally) so we will check its magnitude. if it is larger than
 *      256, we will assume that the bytes are swapped and go through
 *      and reverse all the bytes
 */

        if (((struct mtget *) arg)->mt_type < 256)
                return(0);

        for (cnt = 0; cnt < rc; cnt += 2)
        {
                c = arg[cnt];
                arg[cnt] = arg[cnt+1];
                arg[cnt+1] = c;
        }

        return(0);
  }
#endif /* NO_RMTIOCTL */