/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*- */
/* dbus-sysdeps-unix.c Wrappers around UNIX system/libc features (internal to D-Bus implementation)
 * 
 * Copyright (C) 2002, 2003, 2006  Red Hat, Inc.
 * Copyright (C) 2003 CodeFactory AB
 *
 * Licensed under the Academic Free License version 2.1
 * 
 * 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
 *
 */

#define _GNU_SOURCE 

#include "dbus-internals.h"
#include "dbus-sysdeps.h"
#include "dbus-sysdeps-unix.h"
#include "dbus-threads.h"
#include "dbus-protocol.h"
#include "dbus-transport.h"
#include "dbus-string.h"
#include "dbus-userdb.h"
#include "dbus-list.h"
#include "dbus-credentials.h"

#include <sys/types.h>
#include <stdlib.h>
#include <string.h>
#include <signal.h>
#include <unistd.h>
#include <stdio.h>
#include <fcntl.h>
#include <sys/socket.h>
#include <dirent.h>
#include <sys/un.h>
#include <pwd.h>
#include <time.h>
#include <locale.h>
#include <sys/time.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <netinet/in.h>
#include <netdb.h>
#include <grp.h>

#ifdef HAVE_ERRNO_H
#include <errno.h>
#endif
#ifdef HAVE_WRITEV
#include <sys/uio.h>
#endif
#ifdef HAVE_POLL
#include <sys/poll.h>
#endif
#ifdef HAVE_BACKTRACE
#include <execinfo.h>
#endif
#ifdef HAVE_GETPEERUCRED
#include <ucred.h>
#endif

#ifdef HAVE_ADT
#include <bsm/adt.h>
#endif

#ifndef O_BINARY
#define O_BINARY 0
#endif

#ifndef AI_ADDRCONFIG
#define AI_ADDRCONFIG 0
#endif

#ifndef HAVE_SOCKLEN_T
#define socklen_t int
#endif

static dbus_bool_t
_dbus_open_socket (int              *fd_p,
                   int               domain,
                   int               type,
                   int               protocol,
                   DBusError        *error)
{
  *fd_p = socket (domain, type, protocol);
  if (*fd_p >= 0)
    {
      _dbus_verbose ("socket fd %d opened\n", *fd_p);
      return TRUE;
    }
  else
    {
      dbus_set_error(error,
                     _dbus_error_from_errno (errno),
                     "Failed to open socket: %s",
                     _dbus_strerror (errno));
      return FALSE;
    }
}

dbus_bool_t
_dbus_open_tcp_socket (int              *fd,
                       DBusError        *error)
{
  return _dbus_open_socket(fd, AF_INET, SOCK_STREAM, 0, error);
}

/**
 * Opens a UNIX domain socket (as in the socket() call).
 * Does not bind the socket.
 * @param fd return location for socket descriptor
 * @param error return location for an error
 * @returns #FALSE if error is set
 */
dbus_bool_t
_dbus_open_unix_socket (int              *fd,
                        DBusError        *error)
{
  return _dbus_open_socket(fd, PF_UNIX, SOCK_STREAM, 0, error);
}

/**
 * Closes a socket. Should not be used on non-socket
 * file descriptors or handles.
 *
 * @param fd the socket
 * @param error return location for an error
 * @returns #FALSE if error is set
 */
dbus_bool_t 
_dbus_close_socket (int               fd,
                    DBusError        *error)
{
  return _dbus_close (fd, error);
}

/**
 * Like _dbus_read(), but only works on sockets so is
 * available on Windows.
 *
 * @param fd the socket
 * @param buffer string to append data to
 * @param count max amount of data to read
 * @returns number of bytes appended to the string
 */
int
_dbus_read_socket (int               fd,
                   DBusString       *buffer,
                   int               count)
{
  return _dbus_read (fd, buffer, count);
}

/**
 * Like _dbus_write(), but only supports sockets
 * and is thus available on Windows.
 *
 * @param fd the file descriptor to write
 * @param buffer the buffer to write data from
 * @param start the first byte in the buffer to write
 * @param len the number of bytes to try to write
 * @returns the number of bytes written or -1 on error
 */
int
_dbus_write_socket (int               fd,
                    const DBusString *buffer,
                    int               start,
                    int               len)
{
  return _dbus_write (fd, buffer, start, len);
}

/**
 * write data to a pipe.
 *
 * @param pipe the pipe instance
 * @param buffer the buffer to write data from
 * @param start the first byte in the buffer to write
 * @param len the number of bytes to try to write
 * @param error error return
 * @returns the number of bytes written or -1 on error
 */
int
_dbus_pipe_write (DBusPipe         *pipe,
                  const DBusString *buffer,
                  int               start,
                  int               len,
                  DBusError        *error)
{
  int written;
  
  written = _dbus_write (pipe->fd_or_handle, buffer, start, len);
  if (written < 0)
    {
      dbus_set_error (error, DBUS_ERROR_FAILED,
                      "Writing to pipe: %s\n",
                      _dbus_strerror (errno));
    }
  return written;
}

/**
 * close a pipe.
 *
 * @param pipe the pipe instance
 * @param error return location for an error
 * @returns #FALSE if error is set
 */
int
_dbus_pipe_close  (DBusPipe         *pipe,
                   DBusError        *error)
{
  if (_dbus_close (pipe->fd_or_handle, error) < 0)
    {
      return -1;
    }
  else
    {
      _dbus_pipe_invalidate (pipe);
      return 0;
    }
}

/**
 * Like _dbus_write_two() but only works on sockets and is thus
 * available on Windows.
 * 
 * @param fd the file descriptor
 * @param buffer1 first buffer
 * @param start1 first byte to write in first buffer
 * @param len1 number of bytes to write from first buffer
 * @param buffer2 second buffer, or #NULL
 * @param start2 first byte to write in second buffer
 * @param len2 number of bytes to write in second buffer
 * @returns total bytes written from both buffers, or -1 on error
 */
int
_dbus_write_socket_two (int               fd,
                        const DBusString *buffer1,
                        int               start1,
                        int               len1,
                        const DBusString *buffer2,
                        int               start2,
                        int               len2)
{
  return _dbus_write_two (fd, buffer1, start1, len1,
                          buffer2, start2, len2);
}


/**
 * Thin wrapper around the read() system call that appends
 * the data it reads to the DBusString buffer. It appends
 * up to the given count, and returns the same value
 * and same errno as read(). The only exception is that
 * _dbus_read() handles EINTR for you. Also, _dbus_read() can
 * return ENOMEM, even though regular UNIX read doesn't.
 *
 * Unlike _dbus_read_socket(), _dbus_read() is not available
 * on Windows.
 * 
 * @param fd the file descriptor to read from
 * @param buffer the buffer to append data to
 * @param count the amount of data to read
 * @returns the number of bytes read or -1
 */
int
_dbus_read (int               fd,
            DBusString       *buffer,
            int               count)
{
  int bytes_read;
  int start;
  char *data;

  _dbus_assert (count >= 0);
  
  start = _dbus_string_get_length (buffer);

  if (!_dbus_string_lengthen (buffer, count))
    {
      errno = ENOMEM;
      return -1;
    }

  data = _dbus_string_get_data_len (buffer, start, count);

 again:
  
  bytes_read = read (fd, data, count);

  if (bytes_read < 0)
    {
      if (errno == EINTR)
        goto again;
      else
        {
          /* put length back (note that this doesn't actually realloc anything) */
          _dbus_string_set_length (buffer, start);
          return -1;
        }
    }
  else
    {
      /* put length back (doesn't actually realloc) */
      _dbus_string_set_length (buffer, start + bytes_read);

#if 0
      if (bytes_read > 0)
        _dbus_verbose_bytes_of_string (buffer, start, bytes_read);
#endif
      
      return bytes_read;
    }
}

/**
 * Thin wrapper around the write() system call that writes a part of a
 * DBusString and handles EINTR for you.
 * 
 * @param fd the file descriptor to write
 * @param buffer the buffer to write data from
 * @param start the first byte in the buffer to write
 * @param len the number of bytes to try to write
 * @returns the number of bytes written or -1 on error
 */
int
_dbus_write (int               fd,
             const DBusString *buffer,
             int               start,
             int               len)
{
  const char *data;
  int bytes_written;
  
  data = _dbus_string_get_const_data_len (buffer, start, len);
  
 again:

  bytes_written = write (fd, data, len);

  if (bytes_written < 0 && errno == EINTR)
    goto again;

#if 0
  if (bytes_written > 0)
    _dbus_verbose_bytes_of_string (buffer, start, bytes_written);
#endif
  
  return bytes_written;
}

/**
 * Like _dbus_write() but will use writev() if possible
 * to write both buffers in sequence. The return value
 * is the number of bytes written in the first buffer,
 * plus the number written in the second. If the first
 * buffer is written successfully and an error occurs
 * writing the second, the number of bytes in the first
 * is returned (i.e. the error is ignored), on systems that
 * don't have writev. Handles EINTR for you.
 * The second buffer may be #NULL.
 *
 * @param fd the file descriptor
 * @param buffer1 first buffer
 * @param start1 first byte to write in first buffer
 * @param len1 number of bytes to write from first buffer
 * @param buffer2 second buffer, or #NULL
 * @param start2 first byte to write in second buffer
 * @param len2 number of bytes to write in second buffer
 * @returns total bytes written from both buffers, or -1 on error
 */
int
_dbus_write_two (int               fd,
                 const DBusString *buffer1,
                 int               start1,
                 int               len1,
                 const DBusString *buffer2,
                 int               start2,
                 int               len2)
{
  _dbus_assert (buffer1 != NULL);
  _dbus_assert (start1 >= 0);
  _dbus_assert (start2 >= 0);
  _dbus_assert (len1 >= 0);
  _dbus_assert (len2 >= 0);
  
#ifdef HAVE_WRITEV
  {
    struct iovec vectors[2];
    const char *data1;
    const char *data2;
    int bytes_written;

    data1 = _dbus_string_get_const_data_len (buffer1, start1, len1);

    if (buffer2 != NULL)
      data2 = _dbus_string_get_const_data_len (buffer2, start2, len2);
    else
      {
        data2 = NULL;
        start2 = 0;
        len2 = 0;
      }
   
    vectors[0].iov_base = (char*) data1;
    vectors[0].iov_len = len1;
    vectors[1].iov_base = (char*) data2;
    vectors[1].iov_len = len2;

  again:
   
    bytes_written = writev (fd,
                            vectors,
                            data2 ? 2 : 1);

    if (bytes_written < 0 && errno == EINTR)
      goto again;
   
    return bytes_written;
  }
#else /* HAVE_WRITEV */
  {
    int ret1;
    
    ret1 = _dbus_write (fd, buffer1, start1, len1);
    if (ret1 == len1 && buffer2 != NULL)
      {
        ret2 = _dbus_write (fd, buffer2, start2, len2);
        if (ret2 < 0)
          ret2 = 0; /* we can't report an error as the first write was OK */
       
        return ret1 + ret2;
      }
    else
      return ret1;
  }
#endif /* !HAVE_WRITEV */   
}

#define _DBUS_MAX_SUN_PATH_LENGTH 99

/**
 * @def _DBUS_MAX_SUN_PATH_LENGTH
 *
 * Maximum length of the path to a UNIX domain socket,
 * sockaddr_un::sun_path member. POSIX requires that all systems
 * support at least 100 bytes here, including the nul termination.
 * We use 99 for the max value to allow for the nul.
 *
 * We could probably also do sizeof (addr.sun_path)
 * but this way we are the same on all platforms
 * which is probably a good idea.
 */

/**
 * Creates a socket and connects it to the UNIX domain socket at the
 * given path.  The connection fd is returned, and is set up as
 * nonblocking.
 * 
 * Uses abstract sockets instead of filesystem-linked sockets if
 * requested (it's possible only on Linux; see "man 7 unix" on Linux).
 * On non-Linux abstract socket usage always fails.
 *
 * @param path the path to UNIX domain socket
 * @param abstract #TRUE to use abstract namespace
 * @param error return location for error code
 * @returns connection file descriptor or -1 on error
 */
int
_dbus_connect_unix_socket (const char     *path,
                           dbus_bool_t     abstract,
                           DBusError      *error)
{
  int fd;
  size_t path_len;
  struct sockaddr_un addr;  

  _DBUS_ASSERT_ERROR_IS_CLEAR (error);

  _dbus_verbose ("connecting to unix socket %s abstract=%d\n",
                 path, abstract);
  
  
  if (!_dbus_open_unix_socket (&fd, error))
    {
      _DBUS_ASSERT_ERROR_IS_SET(error);
      return -1;
    }
  _DBUS_ASSERT_ERROR_IS_CLEAR(error);

  _DBUS_ZERO (addr);
  addr.sun_family = AF_UNIX;
  path_len = strlen (path);

  if (abstract)
    {
#ifdef HAVE_ABSTRACT_SOCKETS
      addr.sun_path[0] = '\0'; /* this is what says "use abstract" */
      path_len++; /* Account for the extra nul byte added to the start of sun_path */

      if (path_len > _DBUS_MAX_SUN_PATH_LENGTH)
        {
          dbus_set_error (error, DBUS_ERROR_BAD_ADDRESS,
                      "Abstract socket name too long\n");
          _dbus_close (fd, NULL);
          return -1;
	}
	
      strncpy (&addr.sun_path[1], path, path_len);
      /* _dbus_verbose_bytes (addr.sun_path, sizeof (addr.sun_path)); */
#else /* HAVE_ABSTRACT_SOCKETS */
      dbus_set_error (error, DBUS_ERROR_NOT_SUPPORTED,
                      "Operating system does not support abstract socket namespace\n");
      _dbus_close (fd, NULL);
      return -1;
#endif /* ! HAVE_ABSTRACT_SOCKETS */
    }
  else
    {
      if (path_len > _DBUS_MAX_SUN_PATH_LENGTH)
        {
          dbus_set_error (error, DBUS_ERROR_BAD_ADDRESS,
                      "Socket name too long\n");
          _dbus_close (fd, NULL);
          return -1;
	}

      strncpy (addr.sun_path, path, path_len);
    }
  
  if (connect (fd, (struct sockaddr*) &addr, _DBUS_STRUCT_OFFSET (struct sockaddr_un, sun_path) + path_len) < 0)
    {      
      dbus_set_error (error,
                      _dbus_error_from_errno (errno),
                      "Failed to connect to socket %s: %s",
                      path, _dbus_strerror (errno));

      _dbus_close (fd, NULL);
      fd = -1;
      
      return -1;
    }

  if (!_dbus_set_fd_nonblocking (fd, error))
    {
      _DBUS_ASSERT_ERROR_IS_SET (error);
      
      _dbus_close (fd, NULL);
      fd = -1;

      return -1;
    }

  return fd;
}

/**
 * Enables or disables the reception of credentials on the given socket during
 * the next message transmission.  This is only effective if the #LOCAL_CREDS
 * system feature exists, in which case the other side of the connection does
 * not have to do anything special to send the credentials.
 *
 * @param fd socket on which to change the #LOCAL_CREDS flag.
 * @param on whether to enable or disable the #LOCAL_CREDS flag.
 */
static dbus_bool_t
_dbus_set_local_creds (int fd, dbus_bool_t on)
{
  dbus_bool_t retval = TRUE;

#if defined(HAVE_CMSGCRED)
  /* NOOP just to make sure only one codepath is used 
   *      and to prefer CMSGCRED
   */
#elif defined(LOCAL_CREDS) 
  int val = on ? 1 : 0;
  if (setsockopt (fd, 0, LOCAL_CREDS, &val, sizeof (val)) < 0)
    {
      _dbus_verbose ("Unable to set LOCAL_CREDS socket option on fd %d\n", fd);
      retval = FALSE;
    }
  else
    _dbus_verbose ("LOCAL_CREDS %s for further messages on fd %d\n",
                   on ? "enabled" : "disabled", fd);
#endif

  return retval;
}

/**
 * Creates a socket and binds it to the given path,
 * then listens on the socket. The socket is
 * set to be nonblocking.
 *
 * Uses abstract sockets instead of filesystem-linked
 * sockets if requested (it's possible only on Linux;
 * see "man 7 unix" on Linux).
 * On non-Linux abstract socket usage always fails.
 *
 * @param path the socket name
 * @param abstract #TRUE to use abstract namespace
 * @param error return location for errors
 * @returns the listening file descriptor or -1 on error
 */
int
_dbus_listen_unix_socket (const char     *path,
                          dbus_bool_t     abstract,
                          DBusError      *error)
{
  int listen_fd;
  struct sockaddr_un addr;
  size_t path_len;

  _DBUS_ASSERT_ERROR_IS_CLEAR (error);

  _dbus_verbose ("listening on unix socket %s abstract=%d\n",
                 path, abstract);
  
  if (!_dbus_open_unix_socket (&listen_fd, error))
    {
      _DBUS_ASSERT_ERROR_IS_SET(error);
      return -1;
    }
  _DBUS_ASSERT_ERROR_IS_CLEAR(error);

  _DBUS_ZERO (addr);
  addr.sun_family = AF_UNIX;
  path_len = strlen (path);
  
  if (abstract)
    {
#ifdef HAVE_ABSTRACT_SOCKETS
      /* remember that abstract names aren't nul-terminated so we rely
       * on sun_path being filled in with zeroes above.
       */
      addr.sun_path[0] = '\0'; /* this is what says "use abstract" */
      path_len++; /* Account for the extra nul byte added to the start of sun_path */

      if (path_len > _DBUS_MAX_SUN_PATH_LENGTH)
        {
          dbus_set_error (error, DBUS_ERROR_BAD_ADDRESS,
                      "Abstract socket name too long\n");
          _dbus_close (listen_fd, NULL);
          return -1;
	}
      
      strncpy (&addr.sun_path[1], path, path_len);
      /* _dbus_verbose_bytes (addr.sun_path, sizeof (addr.sun_path)); */
#else /* HAVE_ABSTRACT_SOCKETS */
      dbus_set_error (error, DBUS_ERROR_NOT_SUPPORTED,
                      "Operating system does not support abstract socket namespace\n");
      _dbus_close (listen_fd, NULL);
      return -1;
#endif /* ! HAVE_ABSTRACT_SOCKETS */
    }
  else
    {
      /* Discussed security implications of this with Nalin,
       * and we couldn't think of where it would kick our ass, but
       * it still seems a bit sucky. It also has non-security suckage;
       * really we'd prefer to exit if the socket is already in use.
       * But there doesn't seem to be a good way to do this.
       *
       * Just to be extra careful, I threw in the stat() - clearly
       * the stat() can't *fix* any security issue, but it at least
       * avoids inadvertent/accidental data loss.
       */
      {
        struct stat sb;

        if (stat (path, &sb) == 0 &&
            S_ISSOCK (sb.st_mode))
          unlink (path);
      }

      if (path_len > _DBUS_MAX_SUN_PATH_LENGTH)
        {
          dbus_set_error (error, DBUS_ERROR_BAD_ADDRESS,
                      "Abstract socket name too long\n");
          _dbus_close (listen_fd, NULL);
          return -1;
	}
	
      strncpy (addr.sun_path, path, path_len);
    }
  
  if (bind (listen_fd, (struct sockaddr*) &addr, _DBUS_STRUCT_OFFSET (struct sockaddr_un, sun_path) + path_len) < 0)
    {
      dbus_set_error (error, _dbus_error_from_errno (errno),
                      "Failed to bind socket \"%s\": %s",
                      path, _dbus_strerror (errno));
      _dbus_close (listen_fd, NULL);
      return -1;
    }

  if (listen (listen_fd, 30 /* backlog */) < 0)
    {
      dbus_set_error (error, _dbus_error_from_errno (errno),
                      "Failed to listen on socket \"%s\": %s",
                      path, _dbus_strerror (errno));
      _dbus_close (listen_fd, NULL);
      return -1;
    }

  if (!_dbus_set_local_creds (listen_fd, TRUE))
    {
      dbus_set_error (error, _dbus_error_from_errno (errno),
                      "Failed to enable LOCAL_CREDS on socket \"%s\": %s",
                      path, _dbus_strerror (errno));
      close (listen_fd);
      return -1;
    }

  if (!_dbus_set_fd_nonblocking (listen_fd, error))
    {
      _DBUS_ASSERT_ERROR_IS_SET (error);
      _dbus_close (listen_fd, NULL);
      return -1;
    }
  
  /* Try opening up the permissions, but if we can't, just go ahead
   * and continue, maybe it will be good enough.
   */
  if (!abstract && chmod (path, 0777) < 0)
    _dbus_warn ("Could not set mode 0777 on socket %s\n",
                path);
  
  return listen_fd;
}

/**
 * Creates a socket and connects to a socket at the given host 
 * and port. The connection fd is returned, and is set up as
 * nonblocking.
 *
 * @param host the host name to connect to
 * @param port the port to connect to
 * @param family the address family to listen on, NULL for all
 * @param error return location for error code
 * @returns connection file descriptor or -1 on error
 */
int
_dbus_connect_tcp_socket (const char     *host,
                          const char     *port,
                          const char     *family,
                          DBusError      *error)
{
  int fd = -1, res;
  struct addrinfo hints;
  struct addrinfo *ai, *tmp;

  _DBUS_ASSERT_ERROR_IS_CLEAR (error);

  if (!_dbus_open_tcp_socket (&fd, error))
    {
      _DBUS_ASSERT_ERROR_IS_SET(error);
      return -1;
    }

  _DBUS_ASSERT_ERROR_IS_CLEAR(error);

  _DBUS_ZERO (hints);

  if (!family)
    hints.ai_family = AF_UNSPEC;
  else if (!strcmp(family, "ipv4"))
    hints.ai_family = AF_INET;
  else if (!strcmp(family, "ipv6"))
    hints.ai_family = AF_INET6;
  else
    {
      dbus_set_error (error,
                      _dbus_error_from_errno (errno),
                      "Unknown address family %s", family);
      return -1;
    }
  hints.ai_protocol = IPPROTO_TCP;
  hints.ai_socktype = SOCK_STREAM;
  hints.ai_flags = AI_ADDRCONFIG;

  if ((res = getaddrinfo(host, port, &hints, &ai)) != 0)
    {
      dbus_set_error (error,
                      _dbus_error_from_errno (errno),
                      "Failed to lookup host/port: \"%s:%s\": %s (%d)",
                      host, port, gai_strerror(res), res);
      _dbus_close (fd, NULL);
      return -1;
    }

  tmp = ai;
  while (tmp)
    {
      if (!_dbus_open_socket (&fd, tmp->ai_family, SOCK_STREAM, 0, error))
        {
          freeaddrinfo(ai);
          _DBUS_ASSERT_ERROR_IS_SET(error);
          return -1;
        }
      _DBUS_ASSERT_ERROR_IS_CLEAR(error);

      if (connect (fd, (struct sockaddr*) tmp->ai_addr, tmp->ai_addrlen) < 0)
        {
          _dbus_close(fd, NULL);
          fd = -1;
          tmp = tmp->ai_next;
          continue;
        }

      break;
    }
  freeaddrinfo(ai);

  if (fd == -1)
    {
      dbus_set_error (error,
                      _dbus_error_from_errno (errno),
                      "Failed to connect to socket \"%s:%s\" %s",
                      host, port, _dbus_strerror(errno));
      return -1;
    }


  if (!_dbus_set_fd_nonblocking (fd, error))
    {
      _dbus_close (fd, NULL);
      fd = -1;

      return -1;
    }

  return fd;
}

/**
 * Creates a socket and binds it to the given path, then listens on
 * the socket. The socket is set to be nonblocking.  In case of port=0
 * a random free port is used and returned in the port parameter.
 * If inaddr_any is specified, the hostname is ignored.
 *
 * @param host the host name to listen on
 * @param port the port to listen on, if zero a free port will be used
 * @param family the address family to listen on, NULL for all
 * @param retport string to return the actual port listened on
 * @param fds_p location to store returned file descriptors
 * @param error return location for errors
 * @returns the number of listening file descriptors or -1 on error
 */
int
_dbus_listen_tcp_socket (const char     *host,
                         const char     *port,
                         const char     *family,
                         DBusString     *retport,
                         int           **fds_p,
                         DBusError      *error)
{
  int nlisten_fd = 0, *listen_fd = NULL, res, i;
  struct addrinfo hints;
  struct addrinfo *ai, *tmp;

  *fds_p = NULL;
  _DBUS_ASSERT_ERROR_IS_CLEAR (error);

  _DBUS_ZERO (hints);

  if (!family)
    hints.ai_family = AF_UNSPEC;
  else if (!strcmp(family, "ipv4"))
    hints.ai_family = AF_INET;
  else if (!strcmp(family, "ipv6"))
    hints.ai_family = AF_INET6;
  else
    {
      dbus_set_error (error,
                      _dbus_error_from_errno (errno),
                      "Unknown address family %s", family);
      return -1;
    }

  hints.ai_protocol = IPPROTO_TCP;
  hints.ai_socktype = SOCK_STREAM;
  hints.ai_flags = AI_ADDRCONFIG | AI_PASSIVE;

 redo_lookup_with_port:
  if ((res = getaddrinfo(host, port, &hints, &ai)) != 0 || !ai)
    {
      dbus_set_error (error,
                      _dbus_error_from_errno (errno),
                      "Failed to lookup host/port: \"%s:%s\": %s (%d)",
                      host ? host : "*", port, gai_strerror(res), res);
      return -1;
    }

  tmp = ai;
  while (tmp)
    {
      int fd = -1, *newlisten_fd;
      if (!_dbus_open_socket (&fd, tmp->ai_family, SOCK_STREAM, 0, error))
        {
          _DBUS_ASSERT_ERROR_IS_SET(error);
          goto failed;
        }
      _DBUS_ASSERT_ERROR_IS_CLEAR(error);

      if (bind (fd, (struct sockaddr*) tmp->ai_addr, tmp->ai_addrlen) < 0)
        {
          _dbus_close(fd, NULL);
          if (errno == EADDRINUSE)
            {
              /* Depending on kernel policy, it may or may not
                 be neccessary to bind to both IPv4 & 6 addresses
                 so ignore EADDRINUSE here */
              tmp = tmp->ai_next;
              continue;
            }
          dbus_set_error (error, _dbus_error_from_errno (errno),
                          "Failed to bind socket \"%s:%s\": %s",
                          host ? host : "*", port, _dbus_strerror (errno));
          goto failed;
        }

      if (listen (fd, 30 /* backlog */) < 0)
        {
          _dbus_close (fd, NULL);
          dbus_set_error (error, _dbus_error_from_errno (errno),
                          "Failed to listen on socket \"%s:%s\": %s",
                          host ? host : "*", port, _dbus_strerror (errno));
          goto failed;
        }

      newlisten_fd = dbus_realloc(listen_fd, sizeof(int)*(nlisten_fd+1));
      if (!newlisten_fd)
        {
          _dbus_close (fd, NULL);
          dbus_set_error (error, _dbus_error_from_errno (errno),
                          "Failed to allocate file handle array: %s",
                          _dbus_strerror (errno));
          goto failed;
        }
      listen_fd = newlisten_fd;
      listen_fd[nlisten_fd] = fd;
      nlisten_fd++;

      if (!_dbus_string_get_length(retport))
        {
          /* If the user didn't specify a port, or used 0, then
             the kernel chooses a port. After the first address
             is bound to, we need to force all remaining addresses
             to use the same port */
          if (!port || !strcmp(port, "0"))
            {
              struct sockaddr_storage addr;
              socklen_t addrlen;
              char portbuf[50];

              addrlen = sizeof(addr);
              getsockname(fd, (struct sockaddr*) &addr, &addrlen);

              if ((res = getnameinfo((struct sockaddr*)&addr, addrlen, NULL, 0,
                                     portbuf, sizeof(portbuf),
                                     NI_NUMERICHOST)) != 0)
                {
                  dbus_set_error (error, _dbus_error_from_errno (errno),
                                  "Failed to resolve port \"%s:%s\": %s (%s)",
                                  host ? host : "*", port, gai_strerror(res), res);
                  goto failed;
                }
              if (!_dbus_string_append(retport, portbuf))
                {
                  dbus_set_error (error, DBUS_ERROR_NO_MEMORY, NULL);
                  goto failed;
                }

              /* Release current address list & redo lookup */
              port = _dbus_string_get_const_data(retport);
              freeaddrinfo(ai);
              goto redo_lookup_with_port;
            }
          else
            {
              if (!_dbus_string_append(retport, port))
                {
                    dbus_set_error (error, DBUS_ERROR_NO_MEMORY, NULL);
                    goto failed;
                }
            }
        }

      tmp = tmp->ai_next;
    }
  freeaddrinfo(ai);
  ai = NULL;

  if (!nlisten_fd)
    {
      errno = EADDRINUSE;
      dbus_set_error (error, _dbus_error_from_errno (errno),
                      "Failed to bind socket \"%s:%s\": %s",
                      host ? host : "*", port, _dbus_strerror (errno));
      return -1;
    }

  for (i = 0 ; i < nlisten_fd ; i++)
    {
      if (!_dbus_set_fd_nonblocking (listen_fd[i], error))
        {
          goto failed;
        }
    }

  *fds_p = listen_fd;

  return nlisten_fd;

 failed:
  if (ai)
    freeaddrinfo(ai);
  for (i = 0 ; i < nlisten_fd ; i++)
    _dbus_close(listen_fd[i], NULL);
  dbus_free(listen_fd);
  return -1;
}

static dbus_bool_t
write_credentials_byte (int             server_fd,
                        DBusError      *error)
{
  int bytes_written;
  char buf[1] = { '\0' };
#if defined(HAVE_CMSGCRED) 
  struct {
	  struct cmsghdr hdr;
	  struct cmsgcred cred;
  } cmsg;
  struct iovec iov;
  struct msghdr msg;
  iov.iov_base = buf;
  iov.iov_len = 1;

  memset (&msg, 0, sizeof (msg));
  msg.msg_iov = &iov;
  msg.msg_iovlen = 1;

  msg.msg_control = &cmsg;
  msg.msg_controllen = sizeof (cmsg);
  memset (&cmsg, 0, sizeof (cmsg));
  cmsg.hdr.cmsg_len = sizeof (cmsg);
  cmsg.hdr.cmsg_level = SOL_SOCKET;
  cmsg.hdr.cmsg_type = SCM_CREDS;
#endif

  _DBUS_ASSERT_ERROR_IS_CLEAR (error);
  
 again:

#if defined(HAVE_CMSGCRED) 
  bytes_written = sendmsg (server_fd, &msg, 0);
#else
  bytes_written = write (server_fd, buf, 1);
#endif

  if (bytes_written < 0 && errno == EINTR)
    goto again;

  if (bytes_written < 0)
    {
      dbus_set_error (error, _dbus_error_from_errno (errno),
                      "Failed to write credentials byte: %s",
                     _dbus_strerror (errno));
      return FALSE;
    }
  else if (bytes_written == 0)
    {
      dbus_set_error (error, DBUS_ERROR_IO_ERROR,
                      "wrote zero bytes writing credentials byte");
      return FALSE;
    }
  else
    {
      _dbus_assert (bytes_written == 1);
      _dbus_verbose ("wrote credentials byte\n");
      return TRUE;
    }
}

/**
 * Reads a single byte which must be nul (an error occurs otherwise),
 * and reads unix credentials if available. Clears the credentials
 * object, then adds pid/uid if available, so any previous credentials
 * stored in the object are lost.
 *
 * Return value indicates whether a byte was read, not whether
 * we got valid credentials. On some systems, such as Linux,
 * reading/writing the byte isn't actually required, but we do it
 * anyway just to avoid multiple codepaths.
 * 
 * Fails if no byte is available, so you must select() first.
 *
 * The point of the byte is that on some systems we have to
 * use sendmsg()/recvmsg() to transmit credentials.
 *
 * @param client_fd the client file descriptor
 * @param credentials object to add client credentials to
 * @param error location to store error code
 * @returns #TRUE on success
 */
dbus_bool_t
_dbus_read_credentials_socket  (int              client_fd,
                                DBusCredentials *credentials,
                                DBusError       *error)
{
  struct msghdr msg;
  struct iovec iov;
  char buf;
  dbus_uid_t uid_read;
  dbus_pid_t pid_read;
  int bytes_read;
  
  uid_read = DBUS_UID_UNSET;
  pid_read = DBUS_PID_UNSET;
  
#ifdef HAVE_CMSGCRED 
  struct {
    struct cmsghdr hdr;
    struct cmsgcred cred;
  } cmsg;

#elif defined(LOCAL_CREDS)
  struct {
    struct cmsghdr hdr;
    struct sockcred cred;
  } cmsg;
#endif

  _DBUS_ASSERT_ERROR_IS_CLEAR (error);
  
  /* The POSIX spec certainly doesn't promise this, but
   * we need these assertions to fail as soon as we're wrong about
   * it so we can do the porting fixups
   */
  _dbus_assert (sizeof (pid_t) <= sizeof (dbus_pid_t));
  _dbus_assert (sizeof (uid_t) <= sizeof (dbus_uid_t));
  _dbus_assert (sizeof (gid_t) <= sizeof (dbus_gid_t));

  _dbus_credentials_clear (credentials);

  /* Systems supporting LOCAL_CREDS are configured to have this feature
   * enabled (if it does not conflict with HAVE_CMSGCRED) prior accepting
   * the connection.  Therefore, the received message must carry the
   * credentials information without doing anything special.
   */

  iov.iov_base = &buf;
  iov.iov_len = 1;

  memset (&msg, 0, sizeof (msg));
  msg.msg_iov = &iov;
  msg.msg_iovlen = 1;

#if defined(HAVE_CMSGCRED) || defined(LOCAL_CREDS)
  memset (&cmsg, 0, sizeof (cmsg));
  msg.msg_control = &cmsg;
  msg.msg_controllen = sizeof (cmsg);
#endif

 again:
  bytes_read = recvmsg (client_fd, &msg, 0);

  if (bytes_read < 0)
    {
      if (errno == EINTR)
	goto again;

      /* EAGAIN or EWOULDBLOCK would be unexpected here since we would
       * normally only call read_credentials if the socket was ready
       * for reading
       */
      
      dbus_set_error (error, _dbus_error_from_errno (errno),
                      "Failed to read credentials byte: %s",
                      _dbus_strerror (errno));
      return FALSE;
    }
  else if (bytes_read == 0)
    {
      /* this should not happen unless we are using recvmsg wrong,
       * so is essentially here for paranoia
       */
      dbus_set_error (error, DBUS_ERROR_FAILED,
                      "Failed to read credentials byte (zero-length read)");
      return FALSE;
    }
  else if (buf != '\0')
    {
      dbus_set_error (error, DBUS_ERROR_FAILED,
                      "Credentials byte was not nul");
      return FALSE;
    }

#if defined(HAVE_CMSGCRED) || defined(LOCAL_CREDS)
  if (cmsg.hdr.cmsg_len < sizeof (cmsg) || cmsg.hdr.cmsg_type != SCM_CREDS)
    {
      dbus_set_error (error, DBUS_ERROR_FAILED,
                      "Message from recvmsg() was not SCM_CREDS");
      return FALSE;
    }
#endif

  _dbus_verbose ("read credentials byte\n");

  {
#ifdef SO_PEERCRED
    struct ucred cr;   
    int cr_len = sizeof (cr);
    
    if (getsockopt (client_fd, SOL_SOCKET, SO_PEERCRED, &cr, &cr_len) == 0 &&
	cr_len == sizeof (cr))
      {
	pid_read = cr.pid;
	uid_read = cr.uid;
      }
    else
      {
	_dbus_verbose ("Failed to getsockopt() credentials, returned len %d/%d: %s\n",
		       cr_len, (int) sizeof (cr), _dbus_strerror (errno));
      }
#elif defined(HAVE_CMSGCRED)
    pid_read = cmsg.cred.cmcred_pid;
    uid_read = cmsg.cred.cmcred_euid;
#elif defined(LOCAL_CREDS)
    pid_read = DBUS_PID_UNSET;
    uid_read = cmsg.cred.sc_uid;
    /* Since we have already got the credentials from this socket, we can
     * disable its LOCAL_CREDS flag if it was ever set. */
    _dbus_set_local_creds (client_fd, FALSE);
#elif defined(HAVE_GETPEEREID)
    uid_t euid;
    gid_t egid;
    if (getpeereid (client_fd, &euid, &egid) == 0)
      {
        uid_read = euid;
      }
    else
      {
        _dbus_verbose ("Failed to getpeereid() credentials: %s\n", _dbus_strerror (errno));
      }
#elif defined(HAVE_GETPEERUCRED)
    ucred_t * ucred = NULL;
    if (getpeerucred (client_fd, &ucred) == 0)
      {
        pid_read = ucred_getpid (ucred);
        uid_read = ucred_geteuid (ucred);
#ifdef HAVE_ADT
        /* generate audit session data based on socket ucred */
        adt_session_data_t *adth = NULL;
        adt_export_data_t *data = NULL;
        size_t size = 0;
        if (adt_start_session (&adth, NULL, 0) || (adth == NULL))
          {
            _dbus_verbose ("Failed to adt_start_session(): %s\n", _dbus_strerror (errno));
          }
        else 
          {
            if (adt_set_from_ucred (adth, ucred, ADT_NEW)) 
              {
                _dbus_verbose ("Failed to adt_set_from_ucred(): %s\n", _dbus_strerror (errno));
              }
            else
              {
                size = adt_export_session_data (adth, &data);
                if (size <= 0)
                  {
                    _dbus_verbose ("Failed to adt_export_session_data(): %s\n", _dbus_strerror (errno));
                  }
                else
                  {
                    _dbus_credentials_add_adt_audit_data (credentials, data, size);
                    free (data);
                  }
              }
            (void) adt_end_session (adth);
          }
#endif /* HAVE_ADT */
      }
    else
      {
        _dbus_verbose ("Failed to getpeerucred() credentials: %s\n", _dbus_strerror (errno));
      }
    if (ucred != NULL)
      ucred_free (ucred);
#else /* !SO_PEERCRED && !HAVE_CMSGCRED && !HAVE_GETPEEREID && !HAVE_GETPEERUCRED */
    _dbus_verbose ("Socket credentials not supported on this OS\n");
#endif
  }

  _dbus_verbose ("Credentials:"
                 "  pid "DBUS_PID_FORMAT
                 "  uid "DBUS_UID_FORMAT
                 "\n",
		 pid_read,
		 uid_read);

  if (pid_read != DBUS_PID_UNSET)
    {
      if (!_dbus_credentials_add_unix_pid (credentials, pid_read))
        {
          _DBUS_SET_OOM (error);
          return FALSE;
        }
    }

  if (uid_read != DBUS_UID_UNSET)
    {
      if (!_dbus_credentials_add_unix_uid (credentials, uid_read))
        {
          _DBUS_SET_OOM (error);
          return FALSE;
        }
    }
  
  return TRUE;
}

/**
 * Sends a single nul byte with our UNIX credentials as ancillary
 * data.  Returns #TRUE if the data was successfully written.  On
 * systems that don't support sending credentials, just writes a byte,
 * doesn't send any credentials.  On some systems, such as Linux,
 * reading/writing the byte isn't actually required, but we do it
 * anyway just to avoid multiple codepaths.
 *
 * Fails if no byte can be written, so you must select() first.
 *
 * The point of the byte is that on some systems we have to
 * use sendmsg()/recvmsg() to transmit credentials.
 *
 * @param server_fd file descriptor for connection to server
 * @param error return location for error code
 * @returns #TRUE if the byte was sent
 */
dbus_bool_t
_dbus_send_credentials_socket  (int              server_fd,
                                DBusError       *error)
{
  _DBUS_ASSERT_ERROR_IS_CLEAR (error);
  
  if (write_credentials_byte (server_fd, error))
    return TRUE;
  else
    return FALSE;
}

/**
 * Accepts a connection on a listening socket.
 * Handles EINTR for you.
 *
 * @param listen_fd the listen file descriptor
 * @returns the connection fd of the client, or -1 on error
 */
int
_dbus_accept  (int listen_fd)
{
  int client_fd;
  struct sockaddr addr;
  socklen_t addrlen;

  addrlen = sizeof (addr);
  
 retry:
  client_fd = accept (listen_fd, &addr, &addrlen);
  
  if (client_fd < 0)
    {
      if (errno == EINTR)
        goto retry;
    }

  _dbus_verbose ("client fd %d accepted\n", client_fd);
  
  return client_fd;
}

/**
 * Checks to make sure the given directory is 
 * private to the user 
 *
 * @param dir the name of the directory
 * @param error error return
 * @returns #FALSE on failure
 **/
dbus_bool_t
_dbus_check_dir_is_private_to_user (DBusString *dir, DBusError *error)
{
  const char *directory;
  struct stat sb;
	
  _DBUS_ASSERT_ERROR_IS_CLEAR (error);
    
  directory = _dbus_string_get_const_data (dir);
	
  if (stat (directory, &sb) < 0)
    {
      dbus_set_error (error, _dbus_error_from_errno (errno),
                      "%s", _dbus_strerror (errno));
   
      return FALSE;
    }
    
  if ((S_IROTH & sb.st_mode) || (S_IWOTH & sb.st_mode) ||
      (S_IRGRP & sb.st_mode) || (S_IWGRP & sb.st_mode))
    {
      dbus_set_error (error, DBUS_ERROR_FAILED,
                     "%s directory is not private to the user", directory);
      return FALSE;
    }
    
  return TRUE;
}

static dbus_bool_t
fill_user_info_from_passwd (struct passwd *p,
                            DBusUserInfo  *info,
                            DBusError     *error)
{
  _dbus_assert (p->pw_name != NULL);
  _dbus_assert (p->pw_dir != NULL);
  
  info->uid = p->pw_uid;
  info->primary_gid = p->pw_gid;
  info->username = _dbus_strdup (p->pw_name);
  info->homedir = _dbus_strdup (p->pw_dir);
  
  if (info->username == NULL ||
      info->homedir == NULL)
    {
      dbus_set_error (error, DBUS_ERROR_NO_MEMORY, NULL);
      return FALSE;
    }

  return TRUE;
}

static dbus_bool_t
fill_user_info (DBusUserInfo       *info,
                dbus_uid_t          uid,
                const DBusString   *username,
                DBusError          *error)
{
  const char *username_c;
  
  /* exactly one of username/uid provided */
  _dbus_assert (username != NULL || uid != DBUS_UID_UNSET);
  _dbus_assert (username == NULL || uid == DBUS_UID_UNSET);

  info->uid = DBUS_UID_UNSET;
  info->primary_gid = DBUS_GID_UNSET;
  info->group_ids = NULL;
  info->n_group_ids = 0;
  info->username = NULL;
  info->homedir = NULL;
  
  if (username != NULL)
    username_c = _dbus_string_get_const_data (username);
  else
    username_c = NULL;

  /* For now assuming that the getpwnam() and getpwuid() flavors
   * are always symmetrical, if not we have to add more configure
   * checks
   */
  
#if defined (HAVE_POSIX_GETPWNAM_R) || defined (HAVE_NONPOSIX_GETPWNAM_R)
  {
    struct passwd *p;
    int result;
    size_t buflen;
    char *buf;
    struct passwd p_str;

    /* retrieve maximum needed size for buf */
    buflen = sysconf (_SC_GETPW_R_SIZE_MAX);

    /* sysconf actually returns a long, but everything else expects size_t,
     * so just recast here.
     * https://bugs.freedesktop.org/show_bug.cgi?id=17061
     */
    if ((long) buflen <= 0)
      buflen = 1024;

    result = -1;
    while (1)
      {
        buf = dbus_malloc (buflen);
        if (buf == NULL)
          {
            dbus_set_error (error, DBUS_ERROR_NO_MEMORY, NULL);
            return FALSE;
          }

        p = NULL;
#ifdef HAVE_POSIX_GETPWNAM_R
        if (uid != DBUS_UID_UNSET)
          result = getpwuid_r (uid, &p_str, buf, buflen,
                               &p);
        else
          result = getpwnam_r (username_c, &p_str, buf, buflen,
                               &p);
#else
        if (uid != DBUS_UID_UNSET)
          p = getpwuid_r (uid, &p_str, buf, buflen);
        else
          p = getpwnam_r (username_c, &p_str, buf, buflen);
        result = 0;
#endif /* !HAVE_POSIX_GETPWNAM_R */
        //Try a bigger buffer if ERANGE was returned
        if (result == ERANGE && buflen < 512 * 1024)
          {
            dbus_free (buf);
            buflen *= 2;
          }
        else
          {
            break;
          }
      }
    if (result == 0 && p == &p_str)
      {
        if (!fill_user_info_from_passwd (p, info, error))
          {
            dbus_free (buf);
            return FALSE;
          }
        dbus_free (buf);
      }
    else
      {
        dbus_set_error (error, _dbus_error_from_errno (errno),
                        "User \"%s\" unknown or no memory to allocate password entry\n",
                        username_c ? username_c : "???");
        _dbus_verbose ("User %s unknown\n", username_c ? username_c : "???");
        dbus_free (buf);
        return FALSE;
      }
  }
#else /* ! HAVE_GETPWNAM_R */
  {
    /* I guess we're screwed on thread safety here */
    struct passwd *p;

    if (uid != DBUS_UID_UNSET)
      p = getpwuid (uid);
    else
      p = getpwnam (username_c);

    if (p != NULL)
      {
        if (!fill_user_info_from_passwd (p, info, error))
          {
            return FALSE;
          }
      }
    else
      {
        dbus_set_error (error, _dbus_error_from_errno (errno),
                        "User \"%s\" unknown or no memory to allocate password entry\n",
                        username_c ? username_c : "???");
        _dbus_verbose ("User %s unknown\n", username_c ? username_c : "???");
        return FALSE;
      }
  }
#endif  /* ! HAVE_GETPWNAM_R */

  /* Fill this in so we can use it to get groups */
  username_c = info->username;
  
#ifdef HAVE_GETGROUPLIST
  {
    gid_t *buf;
    int buf_count;
    int i;
    
    buf_count = 17;
    buf = dbus_new (gid_t, buf_count);
    if (buf == NULL)
      {
        dbus_set_error (error, DBUS_ERROR_NO_MEMORY, NULL);
        goto failed;
      }
    
    if (getgrouplist (username_c,
                      info->primary_gid,
                      buf, &buf_count) < 0)
      {
        gid_t *new = dbus_realloc (buf, buf_count * sizeof (buf[0]));
        if (new == NULL)
          {
            dbus_set_error (error, DBUS_ERROR_NO_MEMORY, NULL);
            dbus_free (buf);
            goto failed;
          }
        
        buf = new;

        errno = 0;
        if (getgrouplist (username_c, info->primary_gid, buf, &buf_count) < 0)
          {
            dbus_set_error (error,
                            _dbus_error_from_errno (errno),
                            "Failed to get groups for username \"%s\" primary GID "
                            DBUS_GID_FORMAT ": %s\n",
                            username_c, info->primary_gid,
                            _dbus_strerror (errno));
            dbus_free (buf);
            goto failed;
          }
      }

    info->group_ids = dbus_new (dbus_gid_t, buf_count);
    if (info->group_ids == NULL)
      {
        dbus_set_error (error, DBUS_ERROR_NO_MEMORY, NULL);
        dbus_free (buf);
        goto failed;
      }
    
    for (i = 0; i < buf_count; ++i)
      info->group_ids[i] = buf[i];

    info->n_group_ids = buf_count;
    
    dbus_free (buf);
  }
#else  /* HAVE_GETGROUPLIST */
  {
    /* We just get the one group ID */
    info->group_ids = dbus_new (dbus_gid_t, 1);
    if (info->group_ids == NULL)
      {
        dbus_set_error (error, DBUS_ERROR_NO_MEMORY, NULL);
        goto failed;
      }

    info->n_group_ids = 1;

    (info->group_ids)[0] = info->primary_gid;
  }
#endif /* HAVE_GETGROUPLIST */

  _DBUS_ASSERT_ERROR_IS_CLEAR (error);
  
  return TRUE;
  
 failed:
  _DBUS_ASSERT_ERROR_IS_SET (error);
  return FALSE;
}

/**
 * Gets user info for the given username.
 *
 * @param info user info object to initialize
 * @param username the username
 * @param error error return
 * @returns #TRUE on success
 */
dbus_bool_t
_dbus_user_info_fill (DBusUserInfo     *info,
                      const DBusString *username,
                      DBusError        *error)
{
  return fill_user_info (info, DBUS_UID_UNSET,
                         username, error);
}

/**
 * Gets user info for the given user ID.
 *
 * @param info user info object to initialize
 * @param uid the user ID
 * @param error error return
 * @returns #TRUE on success
 */
dbus_bool_t
_dbus_user_info_fill_uid (DBusUserInfo *info,
                          dbus_uid_t    uid,
                          DBusError    *error)
{
  return fill_user_info (info, uid,
                         NULL, error);
}

/**
 * Adds the credentials of the current process to the
 * passed-in credentials object.
 *
 * @param credentials credentials to add to
 * @returns #FALSE if no memory; does not properly roll back on failure, so only some credentials may have been added
 */
dbus_bool_t
_dbus_credentials_add_from_current_process (DBusCredentials *credentials)
{
  /* The POSIX spec certainly doesn't promise this, but
   * we need these assertions to fail as soon as we're wrong about
   * it so we can do the porting fixups
   */
  _dbus_assert (sizeof (pid_t) <= sizeof (dbus_pid_t));
  _dbus_assert (sizeof (uid_t) <= sizeof (dbus_uid_t));
  _dbus_assert (sizeof (gid_t) <= sizeof (dbus_gid_t));

  if (!_dbus_credentials_add_unix_pid(credentials, _dbus_getpid()))
    return FALSE;
  if (!_dbus_credentials_add_unix_uid(credentials, _dbus_geteuid()))
    return FALSE;

  return TRUE;
}

/**
 * Append to the string the identity we would like to have when we
 * authenticate, on UNIX this is the current process UID and on
 * Windows something else, probably a Windows SID string.  No escaping
 * is required, that is done in dbus-auth.c. The username here
 * need not be anything human-readable, it can be the machine-readable
 * form i.e. a user id.
 * 
 * @param str the string to append to
 * @returns #FALSE on no memory
 */
dbus_bool_t
_dbus_append_user_from_current_process (DBusString *str)
{
  return _dbus_string_append_uint (str,
                                   _dbus_geteuid ());
}

/**
 * Gets our process ID
 * @returns process ID
 */
dbus_pid_t
_dbus_getpid (void)
{
  return getpid ();
}

/** Gets our UID
 * @returns process UID
 */
dbus_uid_t
_dbus_getuid (void)
{
  return getuid ();
}

/** Gets our effective UID
 * @returns process effective UID
 */
dbus_uid_t
_dbus_geteuid (void)
{
  return geteuid ();
}

/**
 * The only reason this is separate from _dbus_getpid() is to allow it
 * on Windows for logging but not for other purposes.
 * 
 * @returns process ID to put in log messages
 */
unsigned long
_dbus_pid_for_log (void)
{
  return getpid ();
}

/**
 * Gets a UID from a UID string.
 *
 * @param uid_str the UID in string form
 * @param uid UID to fill in
 * @returns #TRUE if successfully filled in UID
 */
dbus_bool_t
_dbus_parse_uid (const DBusString      *uid_str,
                 dbus_uid_t            *uid)
{
  int end;
  long val;
  
  if (_dbus_string_get_length (uid_str) == 0)
    {
      _dbus_verbose ("UID string was zero length\n");
      return FALSE;
    }

  val = -1;
  end = 0;
  if (!_dbus_string_parse_int (uid_str, 0, &val,
                               &end))
    {
      _dbus_verbose ("could not parse string as a UID\n");
      return FALSE;
    }
  
  if (end != _dbus_string_get_length (uid_str))
    {
      _dbus_verbose ("string contained trailing stuff after UID\n");
      return FALSE;
    }

  *uid = val;

  return TRUE;
}


_DBUS_DEFINE_GLOBAL_LOCK (atomic);

#if DBUS_USE_ATOMIC_INT_486_COND
/* Taken from CVS version 1.7 of glibc's sysdeps/i386/i486/atomicity.h */
/* Since the asm stuff here is gcc-specific we go ahead and use "inline" also */
static inline dbus_int32_t
atomic_exchange_and_add (DBusAtomic            *atomic,
                         volatile dbus_int32_t  val)
{
  register dbus_int32_t result;

  __asm__ __volatile__ ("lock; xaddl %0,%1"
                        : "=r" (result), "=m" (atomic->value)
			: "0" (val), "m" (atomic->value));
  return result;
}
#endif

/**
 * Atomically increments an integer
 *
 * @param atomic pointer to the integer to increment
 * @returns the value before incrementing
 *
 * @todo implement arch-specific faster atomic ops
 */
dbus_int32_t
_dbus_atomic_inc (DBusAtomic *atomic)
{
#if DBUS_USE_ATOMIC_INT_486_COND
  return atomic_exchange_and_add (atomic, 1);
#else
  dbus_int32_t res;
  _DBUS_LOCK (atomic);
  res = atomic->value;
  atomic->value += 1;
  _DBUS_UNLOCK (atomic);
  return res;
#endif
}

/**
 * Atomically decrement an integer
 *
 * @param atomic pointer to the integer to decrement
 * @returns the value before decrementing
 *
 * @todo implement arch-specific faster atomic ops
 */
dbus_int32_t
_dbus_atomic_dec (DBusAtomic *atomic)
{
#if DBUS_USE_ATOMIC_INT_486_COND
  return atomic_exchange_and_add (atomic, -1);
#else
  dbus_int32_t res;
  
  _DBUS_LOCK (atomic);
  res = atomic->value;
  atomic->value -= 1;
  _DBUS_UNLOCK (atomic);
  return res;
#endif
}

#ifdef DBUS_BUILD_TESTS
/** Gets our GID
 * @returns process GID
 */
dbus_gid_t
_dbus_getgid (void)
{
  return getgid ();
}
#endif

/**
 * Wrapper for poll().
 *
 * @param fds the file descriptors to poll
 * @param n_fds number of descriptors in the array
 * @param timeout_milliseconds timeout or -1 for infinite
 * @returns numbers of fds with revents, or <0 on error
 */
int
_dbus_poll (DBusPollFD *fds,
            int         n_fds,
            int         timeout_milliseconds)
{
#if defined(HAVE_POLL) && !defined(BROKEN_POLL)
  /* This big thing is a constant expression and should get optimized
   * out of existence. So it's more robust than a configure check at
   * no cost.
   */
  if (_DBUS_POLLIN == POLLIN &&
      _DBUS_POLLPRI == POLLPRI &&
      _DBUS_POLLOUT == POLLOUT &&
      _DBUS_POLLERR == POLLERR &&
      _DBUS_POLLHUP == POLLHUP &&
      _DBUS_POLLNVAL == POLLNVAL &&
      sizeof (DBusPollFD) == sizeof (struct pollfd) &&
      _DBUS_STRUCT_OFFSET (DBusPollFD, fd) ==
      _DBUS_STRUCT_OFFSET (struct pollfd, fd) &&
      _DBUS_STRUCT_OFFSET (DBusPollFD, events) ==
      _DBUS_STRUCT_OFFSET (struct pollfd, events) &&
      _DBUS_STRUCT_OFFSET (DBusPollFD, revents) ==
      _DBUS_STRUCT_OFFSET (struct pollfd, revents))
    {
      return poll ((struct pollfd*) fds,
                   n_fds, 
                   timeout_milliseconds);
    }
  else
    {
      /* We have to convert the DBusPollFD to an array of
       * struct pollfd, poll, and convert back.
       */
      _dbus_warn ("didn't implement poll() properly for this system yet\n");
      return -1;
    }
#else /* ! HAVE_POLL */

  fd_set read_set, write_set, err_set;
  int max_fd = 0;
  int i;
  struct timeval tv;
  int ready;
  
  FD_ZERO (&read_set);
  FD_ZERO (&write_set);
  FD_ZERO (&err_set);

  for (i = 0; i < n_fds; i++)
    {
      DBusPollFD *fdp = &fds[i];

      if (fdp->events & _DBUS_POLLIN)
	FD_SET (fdp->fd, &read_set);

      if (fdp->events & _DBUS_POLLOUT)
	FD_SET (fdp->fd, &write_set);

      FD_SET (fdp->fd, &err_set);

      max_fd = MAX (max_fd, fdp->fd);
    }
    
  tv.tv_sec = timeout_milliseconds / 1000;
  tv.tv_usec = (timeout_milliseconds % 1000) * 1000;

  ready = select (max_fd + 1, &read_set, &write_set, &err_set,
                  timeout_milliseconds < 0 ? NULL : &tv);

  if (ready > 0)
    {
      for (i = 0; i < n_fds; i++)
	{
	  DBusPollFD *fdp = &fds[i];

	  fdp->revents = 0;

	  if (FD_ISSET (fdp->fd, &read_set))
	    fdp->revents |= _DBUS_POLLIN;

	  if (FD_ISSET (fdp->fd, &write_set))
	    fdp->revents |= _DBUS_POLLOUT;

	  if (FD_ISSET (fdp->fd, &err_set))
	    fdp->revents |= _DBUS_POLLERR;
	}
    }

  return ready;
#endif
}

/**
 * Get current time, as in gettimeofday().
 *
 * @param tv_sec return location for number of seconds
 * @param tv_usec return location for number of microseconds (thousandths)
 */
void
_dbus_get_current_time (long *tv_sec,
                        long *tv_usec)
{
  struct timeval t;

  gettimeofday (&t, NULL);

  if (tv_sec)
    *tv_sec = t.tv_sec;
  if (tv_usec)
    *tv_usec = t.tv_usec;
}

/**
 * Appends the contents of the given file to the string,
 * returning error code. At the moment, won't open a file
 * more than a megabyte in size.
 *
 * @param str the string to append to
 * @param filename filename to load
 * @param error place to set an error
 * @returns #FALSE if error was set
 */
dbus_bool_t
_dbus_file_get_contents (DBusString       *str,
                         const DBusString *filename,
                         DBusError        *error)
{
  int fd;
  struct stat sb;
  int orig_len;
  int total;
  const char *filename_c;

  _DBUS_ASSERT_ERROR_IS_CLEAR (error);
  
  filename_c = _dbus_string_get_const_data (filename);
  
  /* O_BINARY useful on Cygwin */
  fd = open (filename_c, O_RDONLY | O_BINARY);
  if (fd < 0)
    {
      dbus_set_error (error, _dbus_error_from_errno (errno),
                      "Failed to open \"%s\": %s",
                      filename_c,
                      _dbus_strerror (errno));
      return FALSE;
    }

  _dbus_verbose ("file fd %d opened\n", fd);
  
  if (fstat (fd, &sb) < 0)
    {
      dbus_set_error (error, _dbus_error_from_errno (errno),
                      "Failed to stat \"%s\": %s",
                      filename_c,
                      _dbus_strerror (errno));

      _dbus_verbose ("fstat() failed: %s",
                     _dbus_strerror (errno));
      
      _dbus_close (fd, NULL);
      
      return FALSE;
    }

  if (sb.st_size > _DBUS_ONE_MEGABYTE)
    {
      dbus_set_error (error, DBUS_ERROR_FAILED,
                      "File size %lu of \"%s\" is too large.",
                      (unsigned long) sb.st_size, filename_c);
      _dbus_close (fd, NULL);
      return FALSE;
    }
  
  total = 0;
  orig_len = _dbus_string_get_length (str);
  if (sb.st_size > 0 && S_ISREG (sb.st_mode))
    {
      int bytes_read;

      while (total < (int) sb.st_size)
        {
          bytes_read = _dbus_read (fd, str,
                                   sb.st_size - total);
          if (bytes_read <= 0)
            {
              dbus_set_error (error, _dbus_error_from_errno (errno),
                              "Error reading \"%s\": %s",
                              filename_c,
                              _dbus_strerror (errno));

              _dbus_verbose ("read() failed: %s",
                             _dbus_strerror (errno));
              
              _dbus_close (fd, NULL);
              _dbus_string_set_length (str, orig_len);
              return FALSE;
            }
          else
            total += bytes_read;
        }

      _dbus_close (fd, NULL);
      return TRUE;
    }
  else if (sb.st_size != 0)
    {
      _dbus_verbose ("Can only open regular files at the moment.\n");
      dbus_set_error (error, DBUS_ERROR_FAILED,
                      "\"%s\" is not a regular file",
                      filename_c);
      _dbus_close (fd, NULL);
      return FALSE;
    }
  else
    {
      _dbus_close (fd, NULL);
      return TRUE;
    }
}

/**
 * Writes a string out to a file. If the file exists,
 * it will be atomically overwritten by the new data.
 *
 * @param str the string to write out
 * @param filename the file to save string to
 * @param error error to be filled in on failure
 * @returns #FALSE on failure
 */
dbus_bool_t
_dbus_string_save_to_file (const DBusString *str,
                           const DBusString *filename,
                           DBusError        *error)
{
  int fd;
  int bytes_to_write;
  const char *filename_c;
  DBusString tmp_filename;
  const char *tmp_filename_c;
  int total;
  dbus_bool_t need_unlink;
  dbus_bool_t retval;

  _DBUS_ASSERT_ERROR_IS_CLEAR (error);
  
  fd = -1;
  retval = FALSE;
  need_unlink = FALSE;
  
  if (!_dbus_string_init (&tmp_filename))
    {
      dbus_set_error (error, DBUS_ERROR_NO_MEMORY, NULL);
      return FALSE;
    }

  if (!_dbus_string_copy (filename, 0, &tmp_filename, 0))
    {
      dbus_set_error (error, DBUS_ERROR_NO_MEMORY, NULL);
      _dbus_string_free (&tmp_filename);
      return FALSE;
    }
  
  if (!_dbus_string_append (&tmp_filename, "."))
    {
      dbus_set_error (error, DBUS_ERROR_NO_MEMORY, NULL);
      _dbus_string_free (&tmp_filename);
      return FALSE;
    }

#define N_TMP_FILENAME_RANDOM_BYTES 8
  if (!_dbus_generate_random_ascii (&tmp_filename, N_TMP_FILENAME_RANDOM_BYTES))
    {
      dbus_set_error (error, DBUS_ERROR_NO_MEMORY, NULL);
      _dbus_string_free (&tmp_filename);
      return FALSE;
    }
    
  filename_c = _dbus_string_get_const_data (filename);
  tmp_filename_c = _dbus_string_get_const_data (&tmp_filename);

  fd = open (tmp_filename_c, O_WRONLY | O_BINARY | O_EXCL | O_CREAT,
             0600);
  if (fd < 0)
    {
      dbus_set_error (error, _dbus_error_from_errno (errno),
                      "Could not create %s: %s", tmp_filename_c,
                      _dbus_strerror (errno));
      goto out;
    }

  _dbus_verbose ("tmp file fd %d opened\n", fd);
  
  need_unlink = TRUE;
  
  total = 0;
  bytes_to_write = _dbus_string_get_length (str);

  while (total < bytes_to_write)
    {
      int bytes_written;

      bytes_written = _dbus_write (fd, str, total,
                                   bytes_to_write - total);

      if (bytes_written <= 0)
        {
          dbus_set_error (error, _dbus_error_from_errno (errno),
                          "Could not write to %s: %s", tmp_filename_c,
                          _dbus_strerror (errno));
          
          goto out;
        }

      total += bytes_written;
    }

  if (fsync(fd))
    {
      dbus_set_error (error, _dbus_error_from_errno (errno),
                      "Could not synchronize file %s: %s",
                      tmp_filename_c, _dbus_strerror (errno));

      goto out;
  }

  if (!_dbus_close (fd, NULL))
    {
      dbus_set_error (error, _dbus_error_from_errno (errno),
                      "Could not close file %s: %s",
                      tmp_filename_c, _dbus_strerror (errno));

      goto out;
    }

  fd = -1;
  
  if (rename (tmp_filename_c, filename_c) < 0)
    {
      dbus_set_error (error, _dbus_error_from_errno (errno),
                      "Could not rename %s to %s: %s",
                      tmp_filename_c, filename_c,
                      _dbus_strerror (errno));

      goto out;
    }

  need_unlink = FALSE;
  
  retval = TRUE;
  
 out:
  /* close first, then unlink, to prevent ".nfs34234235" garbage
   * files
   */

  if (fd >= 0)
    _dbus_close (fd, NULL);
        
  if (need_unlink && unlink (tmp_filename_c) < 0)
    _dbus_verbose ("Failed to unlink temp file %s: %s\n",
                   tmp_filename_c, _dbus_strerror (errno));

  _dbus_string_free (&tmp_filename);

  if (!retval)
    _DBUS_ASSERT_ERROR_IS_SET (error);
  
  return retval;
}

/** Makes the file readable by every user in the system.
 *
 * @param filename the filename
 * @param error error location
 * @returns #TRUE if the file's permissions could be changed.
 */
dbus_bool_t
_dbus_make_file_world_readable(const DBusString *filename,
                               DBusError *error)
{
  const char *filename_c;

  _DBUS_ASSERT_ERROR_IS_CLEAR (error);

  filename_c = _dbus_string_get_const_data (filename);
  if (chmod (filename_c, 0644) == -1)
    {
      dbus_set_error (error,
                      DBUS_ERROR_FAILED,
                      "Could not change permissions of file %s: %s\n",
                      filename_c,
                      _dbus_strerror (errno));
      return FALSE;
    }
  return TRUE;
}

/** Creates the given file, failing if the file already exists.
 *
 * @param filename the filename
 * @param error error location
 * @returns #TRUE if we created the file and it didn't exist
 */
dbus_bool_t
_dbus_create_file_exclusively (const DBusString *filename,
                               DBusError        *error)
{
  int fd;
  const char *filename_c;

  _DBUS_ASSERT_ERROR_IS_CLEAR (error);
  
  filename_c = _dbus_string_get_const_data (filename);
  
  fd = open (filename_c, O_WRONLY | O_BINARY | O_EXCL | O_CREAT,
             0600);
  if (fd < 0)
    {
      dbus_set_error (error,
                      DBUS_ERROR_FAILED,
                      "Could not create file %s: %s\n",
                      filename_c,
                      _dbus_strerror (errno));
      return FALSE;
    }

  _dbus_verbose ("exclusive file fd %d opened\n", fd);
  
  if (!_dbus_close (fd, NULL))
    {
      dbus_set_error (error,
                      DBUS_ERROR_FAILED,
                      "Could not close file %s: %s\n",
                      filename_c,
                      _dbus_strerror (errno));
      return FALSE;
    }
  
  return TRUE;
}

/**
 * Deletes the given file.
 *
 * @param filename the filename
 * @param error error location
 * 
 * @returns #TRUE if unlink() succeeded
 */
dbus_bool_t
_dbus_delete_file (const DBusString *filename,
                   DBusError        *error)
{
  const char *filename_c;

  _DBUS_ASSERT_ERROR_IS_CLEAR (error);
  
  filename_c = _dbus_string_get_const_data (filename);

  if (unlink (filename_c) < 0)
    {
      dbus_set_error (error, DBUS_ERROR_FAILED,
                      "Failed to delete file %s: %s\n",
                      filename_c, _dbus_strerror (errno));
      return FALSE;
    }
  else
    return TRUE;
}

/**
 * Creates a directory; succeeds if the directory
 * is created or already existed.
 *
 * @param filename directory filename
 * @param error initialized error object
 * @returns #TRUE on success
 */
dbus_bool_t
_dbus_create_directory (const DBusString *filename,
                        DBusError        *error)
{
  const char *filename_c;

  _DBUS_ASSERT_ERROR_IS_CLEAR (error);
  
  filename_c = _dbus_string_get_const_data (filename);

  if (mkdir (filename_c, 0700) < 0)
    {
      if (errno == EEXIST)
        return TRUE;
      
      dbus_set_error (error, DBUS_ERROR_FAILED,
                      "Failed to create directory %s: %s\n",
                      filename_c, _dbus_strerror (errno));
      return FALSE;
    }
  else
    return TRUE;
}

/**
 * Appends the given filename to the given directory.
 *
 * @todo it might be cute to collapse multiple '/' such as "foo//"
 * concat "//bar"
 *
 * @param dir the directory name
 * @param next_component the filename
 * @returns #TRUE on success
 */
dbus_bool_t
_dbus_concat_dir_and_file (DBusString       *dir,
                           const DBusString *next_component)
{
  dbus_bool_t dir_ends_in_slash;
  dbus_bool_t file_starts_with_slash;

  if (_dbus_string_get_length (dir) == 0 ||
      _dbus_string_get_length (next_component) == 0)
    return TRUE;
  
  dir_ends_in_slash = '/' == _dbus_string_get_byte (dir,
                                                    _dbus_string_get_length (dir) - 1);

  file_starts_with_slash = '/' == _dbus_string_get_byte (next_component, 0);

  if (dir_ends_in_slash && file_starts_with_slash)
    {
      _dbus_string_shorten (dir, 1);
    }
  else if (!(dir_ends_in_slash || file_starts_with_slash))
    {
      if (!_dbus_string_append_byte (dir, '/'))
        return FALSE;
    }

  return _dbus_string_copy (next_component, 0, dir,
                            _dbus_string_get_length (dir));
}

/** nanoseconds in a second */
#define NANOSECONDS_PER_SECOND       1000000000
/** microseconds in a second */
#define MICROSECONDS_PER_SECOND      1000000
/** milliseconds in a second */
#define MILLISECONDS_PER_SECOND      1000
/** nanoseconds in a millisecond */
#define NANOSECONDS_PER_MILLISECOND  1000000
/** microseconds in a millisecond */
#define MICROSECONDS_PER_MILLISECOND 1000

/**
 * Sleeps the given number of milliseconds.
 * @param milliseconds number of milliseconds
 */
void
_dbus_sleep_milliseconds (int milliseconds)
{
#ifdef HAVE_NANOSLEEP
  struct timespec req;
  struct timespec rem;

  req.tv_sec = milliseconds / MILLISECONDS_PER_SECOND;
  req.tv_nsec = (milliseconds % MILLISECONDS_PER_SECOND) * NANOSECONDS_PER_MILLISECOND;
  rem.tv_sec = 0;
  rem.tv_nsec = 0;

  while (nanosleep (&req, &rem) < 0 && errno == EINTR)
    req = rem;
#elif defined (HAVE_USLEEP)
  usleep (milliseconds * MICROSECONDS_PER_MILLISECOND);
#else /* ! HAVE_USLEEP */
  sleep (MAX (milliseconds / 1000, 1));
#endif
}

static dbus_bool_t
_dbus_generate_pseudorandom_bytes (DBusString *str,
                                   int         n_bytes)
{
  int old_len;
  char *p;
  
  old_len = _dbus_string_get_length (str);

  if (!_dbus_string_lengthen (str, n_bytes))
    return FALSE;

  p = _dbus_string_get_data_len (str, old_len, n_bytes);

  _dbus_generate_pseudorandom_bytes_buffer (p, n_bytes);

  return TRUE;
}

/**
 * Generates the given number of random bytes,
 * using the best mechanism we can come up with.
 *
 * @param str the string
 * @param n_bytes the number of random bytes to append to string
 * @returns #TRUE on success, #FALSE if no memory
 */
dbus_bool_t
_dbus_generate_random_bytes (DBusString *str,
                             int         n_bytes)
{
  int old_len;
  int fd;

  /* FALSE return means "no memory", if it could
   * mean something else then we'd need to return
   * a DBusError. So we always fall back to pseudorandom
   * if the I/O fails.
   */
  
  old_len = _dbus_string_get_length (str);
  fd = -1;

  /* note, urandom on linux will fall back to pseudorandom */
  fd = open ("/dev/urandom", O_RDONLY);
  if (fd < 0)
    return _dbus_generate_pseudorandom_bytes (str, n_bytes);

  _dbus_verbose ("/dev/urandom fd %d opened\n", fd);
  
  if (_dbus_read (fd, str, n_bytes) != n_bytes)
    {
      _dbus_close (fd, NULL);
      _dbus_string_set_length (str, old_len);
      return _dbus_generate_pseudorandom_bytes (str, n_bytes);
    }

  _dbus_verbose ("Read %d bytes from /dev/urandom\n",
                 n_bytes);
  
  _dbus_close (fd, NULL);
  
  return TRUE;
}

/**
 * Exit the process, returning the given value.
 *
 * @param code the exit code
 */
void
_dbus_exit (int code)
{
  _exit (code);
}

/**
 * A wrapper around strerror() because some platforms
 * may be lame and not have strerror(). Also, never
 * returns NULL.
 *
 * @param error_number errno.
 * @returns error description.
 */
const char*
_dbus_strerror (int error_number)
{
  const char *msg;
  
  msg = strerror (error_number);
  if (msg == NULL)
    msg = "unknown";

  return msg;
}

/**
 * signal (SIGPIPE, SIG_IGN);
 */
void
_dbus_disable_sigpipe (void)
{
  signal (SIGPIPE, SIG_IGN);
}

/**
 * Sets the file descriptor to be close
 * on exec. Should be called for all file
 * descriptors in D-Bus code.
 *
 * @param fd the file descriptor
 */
void
_dbus_fd_set_close_on_exec (int fd)
{
  int val;
  
  val = fcntl (fd, F_GETFD, 0);
  
  if (val < 0)
    return;

  val |= FD_CLOEXEC;
  
  fcntl (fd, F_SETFD, val);
}

/**
 * Closes a file descriptor.
 *
 * @param fd the file descriptor
 * @param error error object
 * @returns #FALSE if error set
 */
dbus_bool_t
_dbus_close (int        fd,
             DBusError *error)
{
  _DBUS_ASSERT_ERROR_IS_CLEAR (error);
  
 again:
  if (close (fd) < 0)
    {
      if (errno == EINTR)
        goto again;

      dbus_set_error (error, _dbus_error_from_errno (errno),
                      "Could not close fd %d", fd);
      return FALSE;
    }

  return TRUE;
}

/**
 * Sets a file descriptor to be nonblocking.
 *
 * @param fd the file descriptor.
 * @param error address of error location.
 * @returns #TRUE on success.
 */
dbus_bool_t
_dbus_set_fd_nonblocking (int             fd,
                          DBusError      *error)
{
  int val;

  _DBUS_ASSERT_ERROR_IS_CLEAR (error);
  
  val = fcntl (fd, F_GETFL, 0);
  if (val < 0)
    {
      dbus_set_error (error, _dbus_error_from_errno (errno),
                      "Failed to get flags from file descriptor %d: %s",
                      fd, _dbus_strerror (errno));
      _dbus_verbose ("Failed to get flags for fd %d: %s\n", fd,
                     _dbus_strerror (errno));
      return FALSE;
    }

  if (fcntl (fd, F_SETFL, val | O_NONBLOCK) < 0)
    {
      dbus_set_error (error, _dbus_error_from_errno (errno),
                      "Failed to set nonblocking flag of file descriptor %d: %s",
                      fd, _dbus_strerror (errno));
      _dbus_verbose ("Failed to set fd %d nonblocking: %s\n",
                     fd, _dbus_strerror (errno));

      return FALSE;
    }

  return TRUE;
}

/**
 * On GNU libc systems, print a crude backtrace to stderr.  On other
 * systems, print "no backtrace support" and block for possible gdb
 * attachment if an appropriate environment variable is set.
 */
void
_dbus_print_backtrace (void)
{  
#if defined (HAVE_BACKTRACE) && defined (DBUS_BUILT_R_DYNAMIC)
  void *bt[500];
  int bt_size;
  int i;
  char **syms;
  
  bt_size = backtrace (bt, 500);

  syms = backtrace_symbols (bt, bt_size);
  
  i = 0;
  while (i < bt_size)
    {
      /* don't use dbus_warn since it can _dbus_abort() */
      fprintf (stderr, "  %s\n", syms[i]);
      ++i;
    }
  fflush (stderr);

  free (syms);
#elif defined (HAVE_BACKTRACE) && ! defined (DBUS_BUILT_R_DYNAMIC)
  fprintf (stderr, "  D-Bus not built with -rdynamic so unable to print a backtrace\n");
#else
  fprintf (stderr, "  D-Bus not compiled with backtrace support so unable to print a backtrace\n");
#endif
}

/**
 * Creates a full-duplex pipe (as in socketpair()).
 * Sets both ends of the pipe nonblocking.
 *
 * @todo libdbus only uses this for the debug-pipe server, so in
 * principle it could be in dbus-sysdeps-util.c, except that
 * dbus-sysdeps-util.c isn't in libdbus when tests are enabled and the
 * debug-pipe server is used.
 * 
 * @param fd1 return location for one end
 * @param fd2 return location for the other end
 * @param blocking #TRUE if pipe should be blocking
 * @param error error return
 * @returns #FALSE on failure (if error is set)
 */
dbus_bool_t
_dbus_full_duplex_pipe (int        *fd1,
                        int        *fd2,
                        dbus_bool_t blocking,
                        DBusError  *error)
{
#ifdef HAVE_SOCKETPAIR
  int fds[2];

  _DBUS_ASSERT_ERROR_IS_CLEAR (error);
  
  if (socketpair (AF_UNIX, SOCK_STREAM, 0, fds) < 0)
    {
      dbus_set_error (error, _dbus_error_from_errno (errno),
                      "Could not create full-duplex pipe");
      return FALSE;
    }

  if (!blocking &&
      (!_dbus_set_fd_nonblocking (fds[0], NULL) ||
       !_dbus_set_fd_nonblocking (fds[1], NULL)))
    {
      dbus_set_error (error, _dbus_error_from_errno (errno),
                      "Could not set full-duplex pipe nonblocking");
      
      _dbus_close (fds[0], NULL);
      _dbus_close (fds[1], NULL);
      
      return FALSE;
    }
  
  *fd1 = fds[0];
  *fd2 = fds[1];

  _dbus_verbose ("full-duplex pipe %d <-> %d\n",
                 *fd1, *fd2);
  
  return TRUE;  
#else
  _dbus_warn ("_dbus_full_duplex_pipe() not implemented on this OS\n");
  dbus_set_error (error, DBUS_ERROR_FAILED,
                  "_dbus_full_duplex_pipe() not implemented on this OS");
  return FALSE;
#endif
}


/**
 * Measure the length of the given format string and arguments,
 * not including the terminating nul.
 *
 * @param format a printf-style format string
 * @param args arguments for the format string
 * @returns length of the given format string and args
 */
int
_dbus_printf_string_upper_bound (const char *format,
                                 va_list     args)
{
  char c;
  return vsnprintf (&c, 1, format, args);
}

/**
 * Gets the temporary files directory by inspecting the environment variables 
 * TMPDIR, TMP, and TEMP in that order. If none of those are set "/tmp" is returned
 *
 * @returns location of temp directory
 */
const char*
_dbus_get_tmpdir(void)
{
  static const char* tmpdir = NULL;

  if (tmpdir == NULL)
    {
      /* TMPDIR is what glibc uses, then
       * glibc falls back to the P_tmpdir macro which
       * just expands to "/tmp"
       */
      if (tmpdir == NULL)
        tmpdir = getenv("TMPDIR");

      /* These two env variables are probably
       * broken, but maybe some OS uses them?
       */
      if (tmpdir == NULL)
        tmpdir = getenv("TMP");
      if (tmpdir == NULL)
        tmpdir = getenv("TEMP");

      /* And this is the sane fallback. */
      if (tmpdir == NULL)
        tmpdir = "/tmp";
    }
  
  _dbus_assert(tmpdir != NULL);
  
  return tmpdir;
}

/**
 * Determines the address of the session bus by querying a
 * platform-specific method.
 *
 * If successful, returns #TRUE and appends the address to @p
 * address. If a failure happens, returns #FALSE and
 * sets an error in @p error.
 *
 * @param address a DBusString where the address can be stored
 * @param error a DBusError to store the error in case of failure
 * @returns #TRUE on success, #FALSE if an error happened
 */
dbus_bool_t
_dbus_get_autolaunch_address (DBusString *address,
                              DBusError  *error)
{
  static char *argv[6];
  int address_pipe[2] = { -1, -1 };
  int errors_pipe[2] = { -1, -1 };
  pid_t pid;
  int ret;
  int status;
  int orig_len;
  int i;
  DBusString uuid;
  dbus_bool_t retval;
  
  _DBUS_ASSERT_ERROR_IS_CLEAR (error);
  retval = FALSE;

  if (!_dbus_string_init (&uuid))
    {
      _DBUS_SET_OOM (error);
      return FALSE;
    }
  
  if (!_dbus_get_local_machine_uuid_encoded (&uuid))
    {
      _DBUS_SET_OOM (error);
      goto out;
    }
  
  i = 0;
  argv[i] = "dbus-launch";
  ++i;
  argv[i] = "--autolaunch";
  ++i;
  argv[i] = _dbus_string_get_data (&uuid);
  ++i;
  argv[i] = "--binary-syntax";
  ++i;
  argv[i] = "--close-stderr";
  ++i;
  argv[i] = NULL;
  ++i;

  _dbus_assert (i == _DBUS_N_ELEMENTS (argv));
  
  orig_len = _dbus_string_get_length (address);
  
#define READ_END        0
#define WRITE_END       1
  if (pipe (address_pipe) < 0)
    {
      dbus_set_error (error, _dbus_error_from_errno (errno),
                      "Failed to create a pipe: %s",
                      _dbus_strerror (errno));
      _dbus_verbose ("Failed to create a pipe to call dbus-launch: %s\n",
                     _dbus_strerror (errno));
      goto out;
    }
  if (pipe (errors_pipe) < 0)
    {
      dbus_set_error (error, _dbus_error_from_errno (errno),
                      "Failed to create a pipe: %s",
                      _dbus_strerror (errno));
      _dbus_verbose ("Failed to create a pipe to call dbus-launch: %s\n",
                     _dbus_strerror (errno));
      goto out;
    }

  pid = fork ();
  if (pid < 0)
    {
      dbus_set_error (error, _dbus_error_from_errno (errno),
                      "Failed to fork(): %s",
                      _dbus_strerror (errno));
      _dbus_verbose ("Failed to fork() to call dbus-launch: %s\n",
                     _dbus_strerror (errno));
      goto out;
    }

  if (pid == 0)
    {
      /* child process */
      int maxfds;
      int fd;

      fd = open ("/dev/null", O_RDWR);
      if (fd == -1)
        /* huh?! can't open /dev/null? */
        _exit (1);

      _dbus_verbose ("/dev/null fd %d opened\n", fd);
      
      /* set-up stdXXX */
      close (address_pipe[READ_END]);
      close (errors_pipe[READ_END]);
      close (0);                /* close stdin */
      close (1);                /* close stdout */
      close (2);                /* close stderr */

      if (dup2 (fd, 0) == -1)
        _exit (1);
      if (dup2 (address_pipe[WRITE_END], 1) == -1)
        _exit (1);
      if (dup2 (errors_pipe[WRITE_END], 2) == -1)
        _exit (1);

      maxfds = sysconf (_SC_OPEN_MAX);
      /* Pick something reasonable if for some reason sysconf
       * says unlimited.
       */
      if (maxfds < 0)
        maxfds = 1024;
      /* close all inherited fds */
      for (i = 3; i < maxfds; i++)
        close (i);

      execv (DBUS_BINDIR "/dbus-launch", argv);

      /* failed, try searching PATH */
      execvp ("dbus-launch", argv);

      /* still nothing, we failed */
      _exit (1);
    }

  /* parent process */
  close (address_pipe[WRITE_END]);
  close (errors_pipe[WRITE_END]);
  address_pipe[WRITE_END] = -1;
  errors_pipe[WRITE_END] = -1;

  ret = 0;
  do 
    {
      ret = _dbus_read (address_pipe[READ_END], address, 1024);
    }
  while (ret > 0);

  /* reap the child process to avoid it lingering as zombie */
  do
    {
      ret = waitpid (pid, &status, 0);
    }
  while (ret == -1 && errno == EINTR);

  /* We succeeded if the process exited with status 0 and
     anything was read */
  if (!WIFEXITED (status) || WEXITSTATUS (status) != 0 ||
      _dbus_string_get_length (address) == orig_len)
    {
      /* The process ended with error */
      DBusString error_message;
      _dbus_string_init (&error_message);
      ret = 0;
      do
	{
	  ret = _dbus_read (errors_pipe[READ_END], &error_message, 1024);
	}
      while (ret > 0);

      _dbus_string_set_length (address, orig_len);
      if (_dbus_string_get_length (&error_message) > 0)
	dbus_set_error (error, DBUS_ERROR_SPAWN_EXEC_FAILED,
			"dbus-launch failed to autolaunch D-Bus session: %s",
			_dbus_string_get_data (&error_message));
      else
	dbus_set_error (error, DBUS_ERROR_SPAWN_EXEC_FAILED,
			"Failed to execute dbus-launch to autolaunch D-Bus session");
      goto out;
    }

  retval = TRUE;
  
 out:
  if (retval)
    _DBUS_ASSERT_ERROR_IS_CLEAR (error);
  else
    _DBUS_ASSERT_ERROR_IS_SET (error);

  if (address_pipe[0] != -1)
    close (address_pipe[0]);
  if (address_pipe[1] != -1)
    close (address_pipe[1]);
  if (errors_pipe[0] != -1)
    close (errors_pipe[0]);
  if (errors_pipe[1] != -1)
    close (errors_pipe[1]);

  _dbus_string_free (&uuid);
  return retval;
}

/**
 * Reads the uuid of the machine we're running on from
 * the dbus configuration. Optionally try to create it
 * (only root can do this usually).
 *
 * On UNIX, reads a file that gets created by dbus-uuidgen
 * in a post-install script. On Windows, if there's a standard
 * machine uuid we could just use that, but I can't find one
 * with the right properties (the hardware profile guid can change
 * without rebooting I believe). If there's no standard one
 * we might want to use the registry instead of a file for
 * this, and I'm not sure how we'd ensure the uuid gets created.
 *
 * @param machine_id guid to init with the machine's uuid
 * @param create_if_not_found try to create the uuid if it doesn't exist
 * @param error the error return
 * @returns #FALSE if the error is set
 */
dbus_bool_t
_dbus_read_local_machine_uuid (DBusGUID   *machine_id,
                               dbus_bool_t create_if_not_found,
                               DBusError  *error)
{
  DBusString filename;
  _dbus_string_init_const (&filename, DBUS_MACHINE_UUID_FILE);
  return _dbus_read_uuid_file (&filename, machine_id, create_if_not_found, error);
}

#define DBUS_UNIX_STANDARD_SESSION_SERVICEDIR "/dbus-1/services"
#define DBUS_UNIX_STANDARD_SYSTEM_SERVICEDIR "/dbus-1/system-services"


/**
 * Returns the standard directories for a session bus to look for service 
 * activation files 
 *
 * On UNIX this should be the standard xdg freedesktop.org data directories:
 *
 * XDG_DATA_HOME=${XDG_DATA_HOME-$HOME/.local/share}
 * XDG_DATA_DIRS=${XDG_DATA_DIRS-/usr/local/share:/usr/share}
 *
 * and
 *
 * DBUS_DATADIR
 *
 * @param dirs the directory list we are returning
 * @returns #FALSE on OOM 
 */

dbus_bool_t 
_dbus_get_standard_session_servicedirs (DBusList **dirs)
{
  const char *xdg_data_home;
  const char *xdg_data_dirs;
  DBusString servicedir_path;

  if (!_dbus_string_init (&servicedir_path))
    return FALSE;

  xdg_data_home = _dbus_getenv ("XDG_DATA_HOME");
  xdg_data_dirs = _dbus_getenv ("XDG_DATA_DIRS");

  if (xdg_data_dirs != NULL)
    {
      if (!_dbus_string_append (&servicedir_path, xdg_data_dirs))
        goto oom;

      if (!_dbus_string_append (&servicedir_path, ":"))
        goto oom;
    }
  else
    {
      if (!_dbus_string_append (&servicedir_path, "/usr/local/share:/usr/share:"))
        goto oom;
    }

  /* 
   * add configured datadir to defaults
   * this may be the same as an xdg dir
   * however the config parser should take 
   * care of duplicates 
   */
  if (!_dbus_string_append (&servicedir_path, DBUS_DATADIR":"))
        goto oom;

  if (xdg_data_home != NULL)
    {
      if (!_dbus_string_append (&servicedir_path, xdg_data_home))
        goto oom;
    }
  else
    {
      const DBusString *homedir;
      DBusString local_share;

      if (!_dbus_homedir_from_current_process (&homedir))
        goto oom;
       
      if (!_dbus_string_append (&servicedir_path, _dbus_string_get_const_data (homedir)))
        goto oom;

      _dbus_string_init_const (&local_share, "/.local/share");
      if (!_dbus_concat_dir_and_file (&servicedir_path, &local_share))
        goto oom;
    }

  if (!_dbus_split_paths_and_append (&servicedir_path, 
                                     DBUS_UNIX_STANDARD_SESSION_SERVICEDIR, 
                                     dirs))
    goto oom;

  _dbus_string_free (&servicedir_path);  
  return TRUE;

 oom:
  _dbus_string_free (&servicedir_path);
  return FALSE;
}


/**
 * Returns the standard directories for a system bus to look for service 
 * activation files 
 *
 * On UNIX this should be the standard xdg freedesktop.org data directories:
 *
 * XDG_DATA_DIRS=${XDG_DATA_DIRS-/usr/local/share:/usr/share}
 *
 * and
 *
 * DBUS_DATADIR
 *
 * On Windows there is no system bus and this function can return nothing.
 *
 * @param dirs the directory list we are returning
 * @returns #FALSE on OOM 
 */

dbus_bool_t 
_dbus_get_standard_system_servicedirs (DBusList **dirs)
{
  const char *xdg_data_dirs;
  DBusString servicedir_path;

  if (!_dbus_string_init (&servicedir_path))
    return FALSE;

  xdg_data_dirs = _dbus_getenv ("XDG_DATA_DIRS");

  if (xdg_data_dirs != NULL)
    {
      if (!_dbus_string_append (&servicedir_path, xdg_data_dirs))
        goto oom;

      if (!_dbus_string_append (&servicedir_path, ":"))
        goto oom;
    }
  else
    {
      if (!_dbus_string_append (&servicedir_path, "/usr/local/share:/usr/share:"))
        goto oom;
    }

  /* 
   * add configured datadir to defaults
   * this may be the same as an xdg dir
   * however the config parser should take 
   * care of duplicates 
   */
  if (!_dbus_string_append (&servicedir_path, DBUS_DATADIR":"))
        goto oom;

  if (!_dbus_split_paths_and_append (&servicedir_path, 
                                     DBUS_UNIX_STANDARD_SYSTEM_SERVICEDIR, 
                                     dirs))
    goto oom;

  _dbus_string_free (&servicedir_path);  
  return TRUE;

 oom:
  _dbus_string_free (&servicedir_path);
  return FALSE;
}

/**
 * Append the absolute path of the system.conf file
 * (there is no system bus on Windows so this can just
 * return FALSE and print a warning or something)
 * 
 * @param str the string to append to
 * @returns #FALSE if no memory
 */
dbus_bool_t
_dbus_append_system_config_file (DBusString *str)
{
  return _dbus_string_append (str, DBUS_SYSTEM_CONFIG_FILE);
}

/**
 * Append the absolute path of the session.conf file.
 * 
 * @param str the string to append to
 * @returns #FALSE if no memory
 */
dbus_bool_t
_dbus_append_session_config_file (DBusString *str)
{
  return _dbus_string_append (str, DBUS_SESSION_CONFIG_FILE);
}

/**
 * Called when the bus daemon is signaled to reload its configuration; any
 * caches should be nuked. Of course any caches that need explicit reload
 * are probably broken, but c'est la vie.
 *
 * 
 */
void
_dbus_flush_caches (void)
{
  _dbus_user_database_flush_system ();
}

/**
 * Appends the directory in which a keyring for the given credentials
 * should be stored.  The credentials should have either a Windows or
 * UNIX user in them.  The directory should be an absolute path.
 *
 * On UNIX the directory is ~/.dbus-keyrings while on Windows it should probably
 * be something else, since the dotfile convention is not normal on Windows.
 * 
 * @param directory string to append directory to
 * @param credentials credentials the directory should be for
 *  
 * @returns #FALSE on no memory
 */
dbus_bool_t
_dbus_append_keyring_directory_for_credentials (DBusString      *directory,
                                                DBusCredentials *credentials)
{
  DBusString homedir;
  DBusString dotdir;
  dbus_uid_t uid;
  
  _dbus_assert (credentials != NULL);
  _dbus_assert (!_dbus_credentials_are_anonymous (credentials));
  
  if (!_dbus_string_init (&homedir))
    return FALSE;

  uid = _dbus_credentials_get_unix_uid (credentials);
  _dbus_assert (uid != DBUS_UID_UNSET);

  if (!_dbus_homedir_from_uid (uid, &homedir))
    goto failed;
  
#ifdef DBUS_BUILD_TESTS
  {
    const char *override;
    
    override = _dbus_getenv ("DBUS_TEST_HOMEDIR");
    if (override != NULL && *override != '\0')
      {
        _dbus_string_set_length (&homedir, 0);
        if (!_dbus_string_append (&homedir, override))
          goto failed;

        _dbus_verbose ("Using fake homedir for testing: %s\n",
                       _dbus_string_get_const_data (&homedir));
      }
    else
      {
        static dbus_bool_t already_warned = FALSE;
        if (!already_warned)
          {
            _dbus_warn ("Using your real home directory for testing, set DBUS_TEST_HOMEDIR to avoid\n");
            already_warned = TRUE;
          }
      }
  }
#endif

  _dbus_string_init_const (&dotdir, ".dbus-keyrings");
  if (!_dbus_concat_dir_and_file (&homedir,
                                  &dotdir))
    goto failed;
  
  if (!_dbus_string_copy (&homedir, 0,
                          directory, _dbus_string_get_length (directory))) {
    goto failed;
  }

  _dbus_string_free (&homedir);
  return TRUE;
  
 failed: 
  _dbus_string_free (&homedir);
  return FALSE;
}


/**
 * See if errno is EAGAIN or EWOULDBLOCK (this has to be done differently
 * for Winsock so is abstracted)
 *
 * @returns #TRUE if errno == EAGAIN or errno == EWOULDBLOCK
 */
dbus_bool_t
_dbus_get_is_errno_eagain_or_ewouldblock (void)
{
  return errno == EAGAIN || errno == EWOULDBLOCK;
}

/* tests in dbus-sysdeps-util.c */
