1/* Open a pseudoterminal.
2 Copyright (C) 2018-2022 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
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, see
17 <https://www.gnu.org/licenses/>. */
18
19#include <support/tty.h>
20#include <support/check.h>
21#include <support/support.h>
22
23#include <errno.h>
24#include <stdlib.h>
25#include <string.h>
26
27#include <fcntl.h>
28#include <termios.h>
29#include <sys/ioctl.h>
30#include <unistd.h>
31
32/* As ptsname, but allocates space for an appropriately-sized string
33 using malloc. */
34static char *
35xptsname (int fd)
36{
37 int rv;
38 size_t buf_len = 128;
39 char *buf = xmalloc (buf_len);
40 for (;;)
41 {
42 rv = ptsname_r (fd, buf, buf_len);
43 if (rv)
44 FAIL_EXIT1 ("ptsname_r: %s", strerror (errno));
45
46 if (memchr (buf, '\0', buf_len))
47 return buf; /* ptsname succeeded and the buffer was not truncated */
48
49 buf_len *= 2;
50 buf = xrealloc (buf, buf_len);
51 }
52}
53
54void
55support_openpty (int *a_outer, int *a_inner, char **a_name,
56 const struct termios *termp,
57 const struct winsize *winp)
58{
59 int outer = -1, inner = -1;
60 char *namebuf = 0;
61
62 outer = posix_openpt (O_RDWR | O_NOCTTY);
63 if (outer == -1)
64 FAIL_EXIT1 ("posix_openpt: %s", strerror (errno));
65
66 if (grantpt (outer))
67 FAIL_EXIT1 ("grantpt: %s", strerror (errno));
68
69 if (unlockpt (outer))
70 FAIL_EXIT1 ("unlockpt: %s", strerror (errno));
71
72
73#ifdef TIOCGPTPEER
74 inner = ioctl (outer, TIOCGPTPEER, O_RDWR | O_NOCTTY);
75#endif
76 if (inner == -1)
77 {
78 /* The kernel might not support TIOCGPTPEER, fall back to open
79 by name. */
80 namebuf = xptsname (outer);
81 inner = open (namebuf, O_RDWR | O_NOCTTY);
82 if (inner == -1)
83 FAIL_EXIT1 ("%s: %s", namebuf, strerror (errno));
84 }
85
86 if (termp)
87 {
88 if (tcsetattr (inner, TCSAFLUSH, termp))
89 FAIL_EXIT1 ("tcsetattr: %s", strerror (errno));
90 }
91#ifdef TIOCSWINSZ
92 if (winp)
93 {
94 if (ioctl (inner, TIOCSWINSZ, winp))
95 FAIL_EXIT1 ("TIOCSWINSZ: %s", strerror (errno));
96 }
97#endif
98
99 if (a_name)
100 {
101 if (!namebuf)
102 namebuf = xptsname (outer);
103 *a_name = namebuf;
104 }
105 else
106 free (namebuf);
107 *a_outer = outer;
108 *a_inner = inner;
109}
110