login/openpty.c

   1 /* Copyright (C) 1998, 1999 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Zack Weinberg <zack@rabi.phys.columbia.edu>, 1998.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <errno.h>
  21 #include <fcntl.h>
  22 #include <limits.h>
  23 #include <pty.h>
  24 #include <stdlib.h>
  25 #include <string.h>
  26 #include <termios.h>
  27 #include <unistd.h>
  28 #include <sys/types.h>
  29
  30
  31 /* Return the result of ptsname_r in the buffer pointed to by PTS,
  32    which should be of length BUF_LEN.  If it is too long to fit in
  33    this buffer, a sufficiently long buffer is allocated using malloc,
  34    and returned in PTS.  0 is returned upon success, -1 otherwise.  */
  35 static int
  36 pts_name (int fd, char **pts, size_t buf_len)
  37 {
  38   int rv;
  39   char *buf = *pts;
  40
  41   for (;;)
  42     {
  43       char *new_buf;
  44
  45       if (buf_len)
  46         {
  47           rv = ptsname_r (fd, buf, buf_len);
  48
  49           if (rv != 0 || memchr (buf, '\0', buf_len))
  50             /* We either got an error, or we succeeded and the
  51                returned name fit in the buffer.  */
  52             break;
  53
  54           /* Try again with a longer buffer.  */
  55           buf_len += buf_len;   /* Double it */
  56         }
  57       else
  58         /* No initial buffer; start out by mallocing one.  */
  59         buf_len = 128;          /* First time guess.  */
  60
  61       if (buf != *pts)
  62         /* We've already malloced another buffer at least once.  */
  63         new_buf = realloc (buf, buf_len);
  64       else
  65         new_buf = malloc (buf_len);
  66       if (! new_buf)
  67         {
  68           rv = -1;
  69           __set_errno (ENOMEM);
  70           break;
  71         }
  72       buf = new_buf;
  73     }
  74
  75   if (rv == 0)
  76     *pts = buf;         /* Return buffer to the user.  */
  77   else if (buf != *pts)
  78     free (buf);         /* Free what we malloced when returning an error.  */
  79
  80   return rv;
  81 }
  82
  83 /* Create pseudo tty master slave pair and set terminal attributes
  84    according to TERMP and WINP.  Return handles for both ends in
  85    AMASTER and ASLAVE, and return the name of the slave end in NAME.  */
  86 int
  87 openpty (int *amaster, int *aslave, char *name, struct termios *termp,
  88          struct winsize *winp)
  89 {
  90 #ifdef PATH_MAX
  91   char _buf[PATH_MAX];
  92 #else
  93   char _buf[512];
  94 #endif
  95   char *buf = _buf;
  96   int master, slave;
  97
  98   master = getpt ();
  99   if (master == -1)
 100     return -1;
 101
 102   if (grantpt (master))
 103     goto fail;
 104
 105   if (unlockpt (master))
 106     goto fail;
 107
 108   if (pts_name (master, &buf, sizeof (_buf)))
 109     goto fail;
 110
 111   slave = open (buf, O_RDWR | O_NOCTTY);
 112   if (slave == -1)
 113     {
 114       if (buf != _buf)
 115         free (buf);
 116
 117       goto fail;
 118     }
 119
 120   /* XXX Should we ignore errors here?  */
 121   if(termp)
 122     tcsetattr (slave, TCSAFLUSH, termp);
 123   if (winp)
 124     ioctl (slave, TIOCSWINSZ, winp);
 125
 126   *amaster = master;
 127   *aslave = slave;
 128   if (name != NULL)
 129     strcpy (name, buf);
 130
 131   if (buf != _buf)
 132     free (buf);
 133   return 0;
 134
 135  fail:
 136   close (master);
 137   return -1;
 138 }