[lxc-devel] [lxc/master] openpty: improve implementation and handling of platforms without it
brauner on Github
lxc-bot at linuxcontainers.org
Mon Jul 6 08:55:30 UTC 2020
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From 8977888f3e3fd115c1f822a8d32d5238f3a2ab2d Mon Sep 17 00:00:00 2001
From: Christian Brauner <christian.brauner at ubuntu.com>
Date: Mon, 6 Jul 2020 10:54:46 +0200
Subject: [PATCH] openpty: improve implementation and handling of platforms
without it
Signed-off-by: Christian Brauner <christian.brauner at ubuntu.com>
---
configure.ac | 6 +-
src/include/openpty.c | 171 ++++++++++++++++++++++++++++--------------
src/include/openpty.h | 28 +------
src/lxc/Makefile.am | 14 +++-
src/lxc/conf.c | 2 +-
src/lxc/terminal.c | 2 +-
6 files changed, 135 insertions(+), 88 deletions(-)
diff --git a/configure.ac b/configure.ac
index 61db4f2c1f..f74d29a726 100644
--- a/configure.ac
+++ b/configure.ac
@@ -663,7 +663,7 @@ fi
AC_CHECK_LIB(pthread, main)
AC_CHECK_FUNCS(statvfs)
AC_CHECK_LIB(util, openpty)
-AC_CHECK_FUNCS([openpty hasmntopt setmntent endmntent utmpxname])
+AC_CHECK_FUNCS([hasmntopt setmntent endmntent utmpxname])
AC_CHECK_FUNCS([getgrgid_r],
AM_CONDITIONAL(HAVE_GETGRGID_R, true)
AC_DEFINE(HAVE_GETGRGID_R,1,[Have getgrgid_r]),
@@ -684,6 +684,10 @@ AC_CHECK_FUNCS([keyctl],
AM_CONDITIONAL(HAVE_KEYCTL, true)
AC_DEFINE(HAVE_KEYCTL,1,[Have keyctl]),
AM_CONDITIONAL(HAVE_KEYCTL, false))
+AC_CHECK_FUNCS([openpty],
+ AM_CONDITIONAL(HAVE_OPENPTY, true)
+ AC_DEFINE(HAVE_OPENPTY,1,[Have openpty]),
+ AM_CONDITIONAL(HAVE_OPENPTY, false))
AC_CHECK_FUNCS([prlimit],
AM_CONDITIONAL(HAVE_PRLIMIT, true)
AC_DEFINE(HAVE_PRLIMIT,1,[Have prlimit]),
diff --git a/src/include/openpty.c b/src/include/openpty.c
index 5a1bdbadb2..67badb4fb1 100644
--- a/src/include/openpty.c
+++ b/src/include/openpty.c
@@ -1,76 +1,135 @@
- /*
- * openpty: glibc implementation
- *
- * Copyright (C) 1998, 1999, 2004 Free Software Foundation, Inc.
- *
- * Authors:
- * Zack Weinberg <zack at 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/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;
}
diff --git a/src/include/openpty.h b/src/include/openpty.h
index 3b67739ad7..8d4699f9a0 100644
--- a/src/include/openpty.h
+++ b/src/include/openpty.h
@@ -1,25 +1,4 @@
-/*
- * openpty: glibc implementation
- *
- * Copyright (C) 1998, 1999, 2004 Free Software Foundation, Inc.
- *
- * Authors:
- * Zack Weinberg <zack at 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
- */
+/* SPDX-License-Identifier: LGPL-2.1+ */
#ifndef _OPENPTY_H
#define _OPENPTY_H
@@ -32,8 +11,7 @@
* attributes according to @__termp and @__winp and return handles for both
* ends in @__aptx and @__apts.
*/
-extern int openpty (int *__aptx, int *__apts, char *__name,
- const struct termios *__termp,
- const struct winsize *__winp);
+extern int openpty(int *ptx, int *pty, char *name, const struct termios *termp,
+ const struct winsize *winp);
#endif
diff --git a/src/lxc/Makefile.am b/src/lxc/Makefile.am
index d1e23647e0..473bca5c1d 100644
--- a/src/lxc/Makefile.am
+++ b/src/lxc/Makefile.am
@@ -54,8 +54,11 @@ noinst_HEADERS = api_extensions.h \
if IS_BIONIC
noinst_HEADERS += ../include/fexecve.h \
- ../include/lxcmntent.h \
- ../include/openpty.h
+ ../include/lxcmntent.h
+endif
+
+if !HAVE_OPENPTY
+noinst_HEADERS += ../include/openpty.h
endif
if !HAVE_PRLIMIT
@@ -156,8 +159,11 @@ liblxc_la_SOURCES = af_unix.c af_unix.h \
if IS_BIONIC
liblxc_la_SOURCES += ../include/fexecve.c ../include/fexecve.h \
- ../include/lxcmntent.c ../include/lxcmntent.h \
- ../include/openpty.c ../include/openpty.h
+ ../include/lxcmntent.c ../include/lxcmntent.h
+endif
+
+if !HAVE_OPENPTY
+liblxc_la_SOURCES += ../include/openpty.c ../include/openpty.h
endif
if !HAVE_GETGRGID_R
diff --git a/src/lxc/conf.c b/src/lxc/conf.c
index e009006429..b26bbfa326 100644
--- a/src/lxc/conf.c
+++ b/src/lxc/conf.c
@@ -69,7 +69,7 @@
#include <sys/statvfs.h>
#endif
-#if HAVE_PTY_H
+#if HAVE_OPENPTY
#include <pty.h>
#else
#include <../include/openpty.h>
diff --git a/src/lxc/terminal.c b/src/lxc/terminal.c
index d76a313f5e..7d70218974 100644
--- a/src/lxc/terminal.c
+++ b/src/lxc/terminal.c
@@ -29,7 +29,7 @@
#include "terminal.h"
#include "utils.h"
-#if HAVE_PTY_H
+#if HAVE_OPENPTY
#include <pty.h>
#else
#include <../include/openpty.h>
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