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openpty: improve implementation and handling of platforms without it
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
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Christian Brauner
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Jul 6, 2020
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,76 +1,136 @@ | ||
| /* | ||
| * openpty: glibc implementation | ||
| * | ||
| * Copyright (C) 1998, 1999, 2004 Free Software Foundation, Inc. | ||
| * | ||
| * Authors: | ||
| * Zack Weinberg <zack@rabi.phys.columbia.edu>, 1998. | ||
| * | ||
| * This library is free software; you can redistribute it and/or | ||
| * modify it under the terms of the GNU Lesser General Public | ||
| * License as published by the Free Software Foundation; either | ||
| * version 2.1 of the License, or (at your option) any later version. | ||
| * This library 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 | ||
| * Lesser General Public License for more details. | ||
| * You should have received a copy of the GNU Lesser General Public | ||
| * License along with this library; if not, write to the Free Software | ||
| * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | ||
| */ | ||
|
|
||
| #define _XOPEN_SOURCE /* See feature_test_macros(7) */ | ||
| /* SPDX-License-Identifier: LGPL-2.1+ */ | ||
|
|
||
| #define _GNU_SOURCE | ||
| #include <errno.h> | ||
| #include <fcntl.h> | ||
| #include <limits.h> | ||
| #include <stdlib.h> | ||
| #include <string.h> | ||
| #include <sys/ioctl.h> | ||
| #include <sys/types.h> | ||
| #include <termios.h> | ||
| #include <unistd.h> | ||
| #include <sys/types.h> | ||
| #include <sys/ioctl.h> | ||
|
|
||
| #define _PATH_DEVPTMX "/dev/ptmx" | ||
| #ifdef HAVE_PTY_H | ||
| #include <pty.h> | ||
| #endif | ||
|
|
||
| int openpty (int *aptx, int *apty, char *name, struct termios *termp, | ||
| struct winsize *winp) | ||
| static int pts_name(int fd, char **pts, size_t buf_len) | ||
| { | ||
| char buf[PATH_MAX]; | ||
| int ptx, pty; | ||
| int rv; | ||
| char *buf = *pts; | ||
|
|
||
| for (;;) { | ||
| char *new_buf; | ||
|
|
||
| if (buf_len) { | ||
| rv = ptsname_r(fd, buf, buf_len); | ||
|
|
||
| if (rv != 0 || memchr(buf, '\0', buf_len)) | ||
| /* We either got an error, or we succeeded and the | ||
| returned name fit in the buffer. */ | ||
| break; | ||
|
|
||
| /* Try again with a longer buffer. */ | ||
| buf_len += buf_len; /* Double it */ | ||
| } else | ||
| /* No initial buffer; start out by mallocing one. */ | ||
| buf_len = 128; /* First time guess. */ | ||
|
|
||
| if (buf != *pts) | ||
| /* We've already malloced another buffer at least once. */ | ||
| new_buf = realloc(buf, buf_len); | ||
| else | ||
| new_buf = malloc(buf_len); | ||
| if (!new_buf) { | ||
| rv = -1; | ||
| break; | ||
| } | ||
| buf = new_buf; | ||
| } | ||
|
|
||
| if (rv == 0) | ||
| *pts = buf; /* Return buffer to the user. */ | ||
| else if (buf != *pts) | ||
| free(buf); /* Free what we malloced when returning an error. */ | ||
|
|
||
| return rv; | ||
| } | ||
|
|
||
| int __unlockpt(int fd) | ||
| { | ||
| #ifdef TIOCSPTLCK | ||
| int unlock = 0; | ||
|
|
||
| if (ioctl(fd, TIOCSPTLCK, &unlock)) { | ||
| if (errno != EINVAL) | ||
| return -1; | ||
| } | ||
| #endif | ||
| return 0; | ||
| } | ||
|
|
||
| int openpty(int *ptx, int *pty, char *name, const struct termios *termp, | ||
| const struct winsize *winp) | ||
| { | ||
| char _buf[PATH_MAX]; | ||
| char *buf = _buf; | ||
| int ptx_fd, ret = -1, pty_fd = -1; | ||
|
|
||
| *buf = '\0'; | ||
|
|
||
| ptx_fd = open("/dev/ptmx", O_RDWR | O_NOCTTY); | ||
| if (ptx_fd == -1) | ||
| return -1; | ||
|
|
||
| if (__unlockpt(ptx_fd)) | ||
| goto on_error; | ||
|
|
||
| #ifdef TIOCGPTPEER | ||
| /* Try to allocate pty_fd solely based on ptx_fd first. */ | ||
| pty_fd = ioctl(ptx_fd, TIOCGPTPEER, O_RDWR | O_NOCTTY); | ||
| #endif | ||
| if (pty_fd == -1) { | ||
| /* Fallback to path-based pty_fd allocation in case kernel doesn't | ||
| * support TIOCGPTPEER. | ||
| */ | ||
| if (pts_name(ptx_fd, &buf, sizeof(_buf))) | ||
| goto on_error; | ||
|
|
||
| ptx = open(_PATH_DEVPTMX, O_RDWR); | ||
| if (ptx == -1) | ||
| return -1; | ||
| pty_fd = open(buf, O_RDWR | O_NOCTTY); | ||
| if (pty_fd == -1) | ||
| goto on_error; | ||
| } | ||
|
|
||
| if (grantpt(ptx)) | ||
| goto fail; | ||
| if (termp) | ||
| tcsetattr(pty_fd, TCSAFLUSH, termp); | ||
| #ifdef TIOCSWINSZ | ||
| if (winp) | ||
| ioctl(pty_fd, TIOCSWINSZ, winp); | ||
| #endif | ||
|
|
||
| if (unlockpt(ptx)) | ||
| goto fail; | ||
| *ptx = ptx_fd; | ||
| *pty = pty_fd; | ||
| if (name != NULL) { | ||
| if (*buf == '\0') | ||
| if (pts_name(ptx_fd, &buf, sizeof(_buf))) | ||
| goto on_error; | ||
|
|
||
| if (ptyname_r(ptx, buf, sizeof buf)) | ||
| goto fail; | ||
| strcpy(name, buf); | ||
| } | ||
|
|
||
| pty = open(buf, O_RDWR | O_NOCTTY); | ||
| if (pty == -1) | ||
| goto fail; | ||
| ret = 0; | ||
|
|
||
| /* XXX Should we ignore errors here? */ | ||
| if (termp) | ||
| tcsetattr(pty, TCSAFLUSH, termp); | ||
| if (winp) | ||
| ioctl(pty, TIOCSWINSZ, winp); | ||
| on_error: | ||
| if (ret == -1) { | ||
| close(ptx_fd); | ||
|
|
||
| *aptx = ptx; | ||
| *apty = pty; | ||
| if (name != NULL) | ||
| strcpy(name, buf); | ||
| if (pty_fd != -1) | ||
| close(pty_fd); | ||
| } | ||
|
|
||
| return 0; | ||
| if (buf != _buf) | ||
| free(buf); | ||
|
|
||
| fail: | ||
| close(ptx); | ||
| return -1; | ||
| return ret; | ||
| } |
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