mutter/src/wayland/meta-xwayland.c

/*
 * X Wayland Support
 *
 * Copyright (C) 2013 Intel Corporation
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 *
 * This program 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
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
 * 02111-1307, USA.
 */

#include "meta-xwayland-private.h"

#include <glib.h>

#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/socket.h>
#include <sys/un.h>

static char *
create_lockfile (int display, int *display_out)
{
  char *filename;
  int size;
  char pid[11];
  int fd;

  do
    {
      char *end;
      pid_t other;

      filename = g_strdup_printf ("/tmp/.X%d-lock", display);
      fd = open (filename, O_WRONLY | O_CLOEXEC | O_CREAT | O_EXCL, 0444);

      if (fd < 0 && errno == EEXIST)
        {
          fd = open (filename, O_CLOEXEC, O_RDONLY);
          if (fd < 0 || read (fd, pid, 11) != 11)
            {
              const char *msg = strerror (errno);
              g_warning ("can't read lock file %s: %s", filename, msg);
              g_free (filename);

              /* ignore error and try the next display number */
              display++;
              continue;
          }
          close (fd);

          other = strtol (pid, &end, 0);
          if (end != pid + 10)
            {
              g_warning ("can't parse lock file %s", filename);
              g_free (filename);

              /* ignore error and try the next display number */
              display++;
              continue;
          }

          if (kill (other, 0) < 0 && errno == ESRCH)
            {
              g_warning ("unlinking stale lock file %s", filename);
              if (unlink (filename) < 0)
                {
                  const char *msg = strerror (errno);
                  g_warning ("failed to unlink stale lock file: %s", msg);
                  display++;
                }
              g_free (filename);
              continue;
          }

          g_free (filename);
          display++;
          continue;
        }
      else if (fd < 0)
        {
          const char *msg = strerror (errno);
          g_warning ("failed to create lock file %s: %s", filename , msg);
          g_free (filename);
          return NULL;
        }

      break;
    }
  while (1);

  /* Subtle detail: we use the pid of the wayland compositor, not the xserver
   * in the lock file. */
  size = snprintf (pid, 11, "%10d\n", getpid ());
  if (size != 11 || write (fd, pid, 11) != 11)
    {
      unlink (filename);
      close (fd);
      g_warning ("failed to write pid to lock file %s", filename);
      g_free (filename);
      return NULL;
    }

  close (fd);

  *display_out = display;
  return filename;
}

static int
bind_to_abstract_socket (int display)
{
  struct sockaddr_un addr;
  socklen_t size, name_size;
  int fd;

  fd = socket (PF_LOCAL, SOCK_STREAM | SOCK_CLOEXEC, 0);
  if (fd < 0)
    return -1;

  addr.sun_family = AF_LOCAL;
  name_size = snprintf (addr.sun_path, sizeof addr.sun_path,
                        "%c/tmp/.X11-unix/X%d", 0, display);
  size = offsetof (struct sockaddr_un, sun_path) + name_size;
  if (bind (fd, (struct sockaddr *) &addr, size) < 0)
    {
      g_warning ("failed to bind to @%s: %s\n",
                 addr.sun_path + 1, strerror (errno));
      close (fd);
      return -1;
    }

  if (listen (fd, 1) < 0)
    {
      close (fd);
      return -1;
    }

  return fd;
}

static int
bind_to_unix_socket (int display)
{
  struct sockaddr_un addr;
  socklen_t size, name_size;
  int fd;

  fd = socket (PF_LOCAL, SOCK_STREAM | SOCK_CLOEXEC, 0);
  if (fd < 0)
    return -1;

  addr.sun_family = AF_LOCAL;
  name_size = snprintf (addr.sun_path, sizeof addr.sun_path,
                        "/tmp/.X11-unix/X%d", display) + 1;
  size = offsetof (struct sockaddr_un, sun_path) + name_size;
  unlink (addr.sun_path);
  if (bind (fd, (struct sockaddr *) &addr, size) < 0)
    {
      char *msg = strerror (errno);
      g_warning ("failed to bind to %s (%s)\n", addr.sun_path, msg);
      close (fd);
      return -1;
    }

  if (listen (fd, 1) < 0) {
      unlink (addr.sun_path);
      close (fd);
      return -1;
  }

  return fd;
}

gboolean
meta_xwayland_start (MetaWaylandCompositor *compositor)
{
  int display = 0;
  char *lockfile = NULL;
  int sp[2];
  pid_t pid;

  do
    {
      lockfile = create_lockfile (display, &display);
      if (!lockfile)
        {
         g_warning ("Failed to create an X lock file");
         return FALSE;
        }

      compositor->xwayland_abstract_fd = bind_to_abstract_socket (display);
      if (compositor->xwayland_abstract_fd < 0)
        {
          unlink (lockfile);

          if (errno == EADDRINUSE)
            {
              display++;
              continue;
            }
          else
            return FALSE;
        }

      compositor->xwayland_unix_fd = bind_to_unix_socket (display);
      if (compositor->xwayland_abstract_fd < 0)
        {
          unlink (lockfile);
          close (compositor->xwayland_abstract_fd);
          return FALSE;
        }

      break;
    }
  while (1);

  compositor->xwayland_display_index = display;
  compositor->xwayland_lockfile = lockfile;

  /* We want xwayland to be a wayland client so we make a socketpair to setup a
   * wayland protocol connection. */
  if (socketpair (AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0, sp) < 0)
    {
      g_warning ("socketpair failed\n");
      unlink (lockfile);
      return 1;
    }

  switch ((pid = fork()))
    {
    case 0:
        {
          char *fd_string;
          char *display_name;
          /* Make sure the client end of the socket pair doesn't get closed
           * when we exec xwayland. */
          int flags = fcntl (sp[1], F_GETFD);
          if (flags != -1)
            fcntl (sp[1], F_SETFD, flags & ~FD_CLOEXEC);

          fd_string = g_strdup_printf ("%d", sp[1]);
          setenv ("WAYLAND_SOCKET", fd_string, 1);
          g_free (fd_string);

          display_name = g_strdup_printf (":%d",
                                          compositor->xwayland_display_index);

          if (execl (XWAYLAND_PATH,
                     XWAYLAND_PATH,
                     display_name,
                     "-wayland",
                     "-rootless",
                     "-retro",
                     "-noreset",
                     /* FIXME: does it make sense to log to the filesystem by
                      * default? */
                     "-logfile", "/tmp/xwayland.log",
                     "-nolisten", "all",
                     NULL) < 0)
            {
              char *msg = strerror (errno);
              g_warning ("xwayland exec failed: %s", msg);
            }
          exit (-1);
          return FALSE;
        }
    default:
      g_message ("forked X server, pid %d\n", pid);

      close (sp[1]);
      compositor->xwayland_client =
        wl_client_create (compositor->wayland_display, sp[0]);

      compositor->xwayland_pid = pid;
      break;

    case -1:
      g_error ("Failed to fork for xwayland server");
      return FALSE;
    }

  return TRUE;
}

void
meta_xwayland_stop (MetaWaylandCompositor *compositor)
{
  char path[256];

  snprintf (path, sizeof path, "/tmp/.X%d-lock",
            compositor->xwayland_display_index);
  unlink (path);
  snprintf (path, sizeof path, "/tmp/.X11-unix/X%d",
            compositor->xwayland_display_index);
  unlink (path);

  unlink (compositor->xwayland_lockfile);
}