src/unix/tty.c

/* Copyright Joyent, Inc. and other Node contributors. All rights reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to
 * deal in the Software without restriction, including without limitation the
 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
 * sell copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

#include "uv.h"
#include "internal.h"

#include <stdatomic.h>
#include <stdlib.h>
#include <assert.h>
#include <unistd.h>
#include <termios.h>
#include <errno.h>
#include <sys/ioctl.h>

#if defined(__MVS__) && !defined(IMAXBEL)
#define IMAXBEL 0
#endif

#if defined(__PASE__)
/* On IBM i PASE, for better compatibility with running interactive programs in
 * a 5250 environment, isatty() will return true for the stdin/stdout/stderr
 * streams created by QSH/QP2TERM.
 *
 * For more, see docs on PASE_STDIO_ISATTY in
 * https://www.ibm.com/support/knowledgecenter/ssw_ibm_i_74/apis/pase_environ.htm
 *
 * This behavior causes problems for Node as it expects that if isatty() returns
 * true that TTY ioctls will be supported by that fd (which is not an
 * unreasonable expectation) and when they don't it crashes with assertion
 * errors.
 *
 * Here, we create our own version of isatty() that uses ioctl() to identify
 * whether the fd is *really* a TTY or not.
 */
static int isreallyatty(int file) {
  int rc;

  rc = !ioctl(file, TXISATTY + 0x81, NULL);
  if (!rc && errno != EBADF)
      errno = ENOTTY;

  return rc;
}
#define isatty(fd) isreallyatty(fd)
#endif

static int orig_termios_fd = -1;
static struct termios orig_termios;
static _Atomic int termios_spinlock;

int uv__tcsetattr(int fd, int how, const struct termios *term) {
  int rc;

  do
    rc = tcsetattr(fd, how, term);
  while (rc == -1 && errno == EINTR);

  if (rc == -1)
    return UV__ERR(errno);

  return 0;
}

static int uv__tty_is_slave(const int fd) {
  int result;
#if defined(__linux__) || defined(__FreeBSD__)
  int dummy;

  result = ioctl(fd, TIOCGPTN, &dummy) != 0;
#elif defined(__APPLE__)
  char dummy[256];

  result = ioctl(fd, TIOCPTYGNAME, &dummy) != 0;
#elif defined(__NetBSD__)
  /*
   * NetBSD as an extension returns with ptsname(3) and ptsname_r(3) the slave
   * device name for both descriptors, the master one and slave one.
   *
   * Implement function to compare major device number with pts devices.
   *
   * The major numbers are machine-dependent, on NetBSD/amd64 they are
   * respectively:
   *  - master tty: ptc - major 6
   *  - slave tty:  pts - major 5
   */

  struct stat sb;
  /* Lookup device's major for the pts driver and cache it. */
  static devmajor_t pts = NODEVMAJOR;

  if (pts == NODEVMAJOR) {
    pts = getdevmajor("pts", S_IFCHR);
    if (pts == NODEVMAJOR)
      abort();
  }

  /* Lookup stat structure behind the file descriptor. */
  if (uv__fstat(fd, &sb) != 0)
    abort();

  /* Assert character device. */
  if (!S_ISCHR(sb.st_mode))
    abort();

  /* Assert valid major. */
  if (major(sb.st_rdev) == NODEVMAJOR)
    abort();

  result = (pts == major(sb.st_rdev));
#else
  /* Fallback to ptsname
   */
  result = ptsname(fd) == NULL;
#endif
  return result;
}

int uv_tty_init(uv_loop_t* loop, uv_tty_t* tty, int fd, int unused) {
  uv_handle_type type;
  int flags;
  int newfd;
  int r;
  int saved_flags;
  int mode;
  char path[256];
  (void)unused; /* deprecated parameter is no longer needed */

  /* File descriptors that refer to files cannot be monitored with epoll.
   * That restriction also applies to character devices like /dev/random
   * (but obviously not /dev/tty.)
   */
  type = uv_guess_handle(fd);
  if (type == UV_FILE || type == UV_UNKNOWN_HANDLE)
    return UV_EINVAL;

  flags = 0;
  newfd = -1;

  /* Save the fd flags in case we need to restore them due to an error. */
  do
    saved_flags = fcntl(fd, F_GETFL);
  while (saved_flags == -1 && errno == EINTR);

  if (saved_flags == -1)
    return UV__ERR(errno);
  mode = saved_flags & O_ACCMODE;

  /* Reopen the file descriptor when it refers to a tty. This lets us put the
   * tty in non-blocking mode without affecting other processes that share it
   * with us.
   *
   * Example: `node | cat` - if we put our fd 0 in non-blocking mode, it also
   * affects fd 1 of `cat` because both file descriptors refer to the same
   * struct file in the kernel. When we reopen our fd 0, it points to a
   * different struct file, hence changing its properties doesn't affect
   * other processes.
   */
  if (type == UV_TTY) {
    /* Reopening a pty in master mode won't work either because the reopened
     * pty will be in slave mode (*BSD) or reopening will allocate a new
     * master/slave pair (Linux). Therefore check if the fd points to a
     * slave device.
     */
    if (uv__tty_is_slave(fd) && ttyname_r(fd, path, sizeof(path)) == 0)
      r = uv__open_cloexec(path, mode | O_NOCTTY);
    else
      r = -1;

    if (r < 0) {
      /* fallback to using blocking writes */
      if (mode != O_RDONLY)
        flags |= UV_HANDLE_BLOCKING_WRITES;
      goto skip;
    }

    newfd = r;

    r = uv__dup2_cloexec(newfd, fd);
    if (r < 0 && r != UV_EINVAL) {
      /* EINVAL means newfd == fd which could conceivably happen if another
       * thread called close(fd) between our calls to isatty() and open().
       * That's a rather unlikely event but let's handle it anyway.
       */
      uv__close(newfd);
      return r;
    }

    fd = newfd;
  }

skip:
  uv__stream_init(loop, (uv_stream_t*) tty, UV_TTY);

  /* If anything fails beyond this point we need to remove the handle from
   * the handle queue, since it was added by uv__handle_init in uv_stream_init.
   */

  if (!(flags & UV_HANDLE_BLOCKING_WRITES))
    uv__nonblock(fd, 1);

#if defined(__APPLE__)
  r = uv__stream_try_select((uv_stream_t*) tty, &fd);
  if (r) {
    int rc = r;
    if (newfd != -1)
      uv__close(newfd);
    uv__queue_remove(&tty->handle_queue);
    do
      r = fcntl(fd, F_SETFL, saved_flags);
    while (r == -1 && errno == EINTR);
    return rc;
  }
#endif

  if (mode != O_WRONLY)
    flags |= UV_HANDLE_READABLE;
  if (mode != O_RDONLY)
    flags |= UV_HANDLE_WRITABLE;

  uv__stream_open((uv_stream_t*) tty, fd, flags);
  tty->mode = UV_TTY_MODE_NORMAL;

  return 0;
}

static void uv__tty_make_raw(struct termios* tio) {
  assert(tio != NULL);

#if defined __sun || defined __MVS__
  /*
   * This implementation of cfmakeraw for Solaris and derivatives is taken from
   * http://www.perkin.org.uk/posts/solaris-portability-cfmakeraw.html.
   */
  tio->c_iflag &= ~(IMAXBEL | IGNBRK | BRKINT | PARMRK | ISTRIP | INLCR |
                    IGNCR | ICRNL | IXON);
  tio->c_oflag &= ~OPOST;
  tio->c_lflag &= ~(ECHO | ECHONL | ICANON | ISIG | IEXTEN);
  tio->c_cflag &= ~(CSIZE | PARENB);
  tio->c_cflag |= CS8;

  /*
   * By default, most software expects a pending read to block until at
   * least one byte becomes available.  As per termio(7I), this requires
   * setting the MIN and TIME parameters appropriately.
   *
   * As a somewhat unfortunate artifact of history, the MIN and TIME slots
   * in the control character array overlap with the EOF and EOL slots used
   * for canonical mode processing.  Because the EOF character needs to be
   * the ASCII EOT value (aka Control-D), it has the byte value 4.  When
   * switching to raw mode, this is interpreted as a MIN value of 4; i.e.,
   * reads will block until at least four bytes have been input.
   *
   * Other platforms with a distinct MIN slot like Linux and FreeBSD appear
   * to default to a MIN value of 1, so we'll force that value here:
   */
  tio->c_cc[VMIN] = 1;
  tio->c_cc[VTIME] = 0;
#else
  cfmakeraw(tio);
#endif /* #ifdef __sun */
}

int uv_tty_set_mode(uv_tty_t* tty, uv_tty_mode_t mode) {
  struct termios tmp;
  int expected;
  int fd;
  int rc;

  if (tty->mode == (int) mode)
    return 0;

  fd = uv__stream_fd(tty);
  if (tty->mode == UV_TTY_MODE_NORMAL && mode != UV_TTY_MODE_NORMAL) {
    do
      rc = tcgetattr(fd, &tty->orig_termios);
    while (rc == -1 && errno == EINTR);

    if (rc == -1)
      return UV__ERR(errno);

    /* This is used for uv_tty_reset_mode() */
    do
      expected = 0;
    while (!atomic_compare_exchange_strong(&termios_spinlock, &expected, 1));

    if (orig_termios_fd == -1) {
      orig_termios = tty->orig_termios;
      orig_termios_fd = fd;
    }

    atomic_store(&termios_spinlock, 0);
  }

  tmp = tty->orig_termios;
  switch (mode) {
    case UV_TTY_MODE_NORMAL:
      break;
    case UV_TTY_MODE_RAW:
      tmp.c_iflag &= ~(BRKINT | ICRNL | INPCK | ISTRIP | IXON);
      tmp.c_oflag |= (ONLCR);
      tmp.c_cflag |= (CS8);
      tmp.c_lflag &= ~(ECHO | ICANON | IEXTEN | ISIG);
      tmp.c_cc[VMIN] = 1;
      tmp.c_cc[VTIME] = 0;
      break;
    case UV_TTY_MODE_IO:
      uv__tty_make_raw(&tmp);
      break;
  }

  /* Apply changes after draining */
  rc = uv__tcsetattr(fd, TCSADRAIN, &tmp);
  if (rc == 0)
    tty->mode = mode;

  return rc;
}


void uv__tty_close(uv_tty_t* handle) {
  int expected;
  int fd;

  fd = handle->io_watcher.fd;
  if (fd == -1)
    goto done;

  /* This is used for uv_tty_reset_mode() */
  do
    expected = 0;
  while (!atomic_compare_exchange_strong(&termios_spinlock, &expected, 1));

  if (fd == orig_termios_fd) {
    /* XXX(bnoordhuis) the tcsetattr is probably wrong when there are still
     * other uv_tty_t handles active that refer to the same tty/pty but it's
     * hard to recognize that particular situation without maintaining some
     * kind of process-global data structure, and that still won't work in a
     * multi-process setup.
     */
    uv__tcsetattr(fd, TCSANOW, &orig_termios);
    orig_termios_fd = -1;
  }

  atomic_store(&termios_spinlock, 0);

done:
  uv__stream_close((uv_stream_t*) handle);
}


int uv_tty_get_winsize(uv_tty_t* tty, int* width, int* height) {
  struct winsize ws;
  int err;

  do
    err = ioctl(uv__stream_fd(tty), TIOCGWINSZ, &ws);
  while (err == -1 && errno == EINTR);

  if (err == -1)
    return UV__ERR(errno);

  *width = ws.ws_col;
  *height = ws.ws_row;

  return 0;
}


uv_handle_type uv_guess_handle(uv_file file) {
  struct sockaddr_storage ss;
  struct stat s;
  socklen_t len;
  int type;

  if (file < 0)
    return UV_UNKNOWN_HANDLE;

  if (isatty(file))
    return UV_TTY;

  if (uv__fstat(file, &s)) {
#if defined(__PASE__)
    /* On ibmi receiving RST from TCP instead of FIN immediately puts fd into
     * an error state. fstat will return EINVAL, getsockname will also return
     * EINVAL, even if sockaddr_storage is valid. (If file does not refer to a
     * socket, ENOTSOCK is returned instead.)
     * In such cases, we will permit the user to open the connection as uv_tcp
     * still, so that the user can get immediately notified of the error in
     * their read callback and close this fd.
     */
    len = sizeof(ss);
    if (getsockname(file, (struct sockaddr*) &ss, &len)) {
      if (errno == EINVAL)
        return UV_TCP;
    }
#endif
    return UV_UNKNOWN_HANDLE;
  }

  if (S_ISREG(s.st_mode))
    return UV_FILE;

  if (S_ISCHR(s.st_mode))
    return UV_FILE;  /* XXX UV_NAMED_PIPE? */

  if (S_ISFIFO(s.st_mode))
    return UV_NAMED_PIPE;

  if (!S_ISSOCK(s.st_mode))
    return UV_UNKNOWN_HANDLE;

  len = sizeof(ss);
  if (getsockname(file, (struct sockaddr*) &ss, &len)) {
#if defined(_AIX)
    /* On aix receiving RST from TCP instead of FIN immediately puts fd into
     * an error state. In such case getsockname will return EINVAL, even if
     * sockaddr_storage is valid.
     * In such cases, we will permit the user to open the connection as uv_tcp
     * still, so that the user can get immediately notified of the error in
     * their read callback and close this fd.
     */
    if (errno == EINVAL) {
      return UV_TCP;
    }
#endif
    return UV_UNKNOWN_HANDLE;
  }

  len = sizeof(type);
  if (getsockopt(file, SOL_SOCKET, SO_TYPE, &type, &len))
    return UV_UNKNOWN_HANDLE;

  if (type == SOCK_DGRAM)
    if (ss.ss_family == AF_INET || ss.ss_family == AF_INET6)
      return UV_UDP;

  if (type == SOCK_STREAM) {
#if defined(_AIX) || defined(__DragonFly__)
    /* on AIX/DragonFly the getsockname call returns an empty sa structure
     * for sockets of type AF_UNIX.  For all other types it will
     * return a properly filled in structure.
     */
    if (len == 0)
      return UV_NAMED_PIPE;
#endif /* defined(_AIX) || defined(__DragonFly__) */

    if (ss.ss_family == AF_INET || ss.ss_family == AF_INET6)
      return UV_TCP;
    if (ss.ss_family == AF_UNIX)
      return UV_NAMED_PIPE;
  }

  return UV_UNKNOWN_HANDLE;
}


/* This function is async signal-safe, meaning that it's safe to call from
 * inside a signal handler _unless_ execution was inside uv_tty_set_mode()'s
 * critical section when the signal was raised.
 */
int uv_tty_reset_mode(void) {
  int saved_errno;
  int err;

  saved_errno = errno;

  if (atomic_exchange(&termios_spinlock, 1))
    return UV_EBUSY;  /* In uv_tty_set_mode() or uv__tty_close(). */

  err = 0;
  if (orig_termios_fd != -1)
    err = uv__tcsetattr(orig_termios_fd, TCSANOW, &orig_termios);

  atomic_store(&termios_spinlock, 0);
  errno = saved_errno;

  return err;
}

void uv_tty_set_vterm_state(uv_tty_vtermstate_t state) {
}

int uv_tty_get_vterm_state(uv_tty_vtermstate_t* state) {
  return UV_ENOTSUP;
}