lib/sockets.c

/* sockets.c --- wrappers for Windows socket functions

   Copyright (C) 2008-2026 Free Software Foundation, Inc.

   This file is free software: you can redistribute it and/or modify
   it under the terms of the GNU Lesser General Public License as
   published by the Free Software Foundation; either version 2.1 of the
   License, or (at your option) any later version.

   This file is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public License
   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */

/* Written by Simon Josefsson */

#include <config.h>

/* Specification.  */
#include "sockets.h"

#if WINDOWS_SOCKETS

/* This includes winsock2.h on MinGW. */
# include <sys/socket.h>

# include "fd-hook.h"
# if GNULIB_MSVC_NOTHROW
#  include "msvc-nothrow.h"
# else
#  include <io.h>
# endif

/* Get set_winsock_errno, FD_TO_SOCKET etc. */
# include "w32sock.h"

static int
close_fd_maybe_socket (const struct fd_hook *remaining_list,
                       gl_close_fn primary,
                       int fd)
{
  /* Note about multithread-safety: There is a race condition where, between
     our calls to closesocket() and the primary close(), some other thread
     could make system calls that allocate precisely the same HANDLE value
     as sock; then the primary close() would call CloseHandle() on it.  */

  /* Test whether fd refers to a socket.  */
  SOCKET sock = FD_TO_SOCKET (fd);
  WSANETWORKEVENTS ev;
  ev.lNetworkEvents = 0xDEADBEEF;
  WSAEnumNetworkEvents (sock, NULL, &ev);
  if (ev.lNetworkEvents != 0xDEADBEEF)
    {
      /* fd refers to a socket.  */
      /* FIXME: other applications, like squid, use an undocumented
         _free_osfhnd free function.  But this is not enough: The 'osfile'
         flags for fd also needs to be cleared, but it is hard to access it.
         Instead, here we just close twice the file descriptor.  */
      if (closesocket (sock))
        {
          set_winsock_errno ();
          return -1;
        }
      else
        {
          /* This call frees the file descriptor and does a
             CloseHandle ((HANDLE) _get_osfhandle (fd)), which fails.  */
          _close (fd);
          return 0;
        }
    }
  else
    /* Some other type of file descriptor.  */
    return execute_close_hooks (remaining_list, primary, fd);
}

static int
ioctl_fd_maybe_socket (const struct fd_hook *remaining_list,
                       gl_ioctl_fn primary,
                       int fd, int request, void *arg)
{
  /* Test whether fd refers to a socket.  */
  SOCKET sock = FD_TO_SOCKET (fd);
  WSANETWORKEVENTS ev;
  ev.lNetworkEvents = 0xDEADBEEF;
  WSAEnumNetworkEvents (sock, NULL, &ev);
  if (ev.lNetworkEvents != 0xDEADBEEF)
    {
      /* fd refers to a socket.  */
      if (ioctlsocket (sock, request, arg) < 0)
        {
          set_winsock_errno ();
          return -1;
        }
      else
        return 0;
    }
  else
    /* Some other type of file descriptor.  */
    return execute_ioctl_hooks (remaining_list, primary, fd, request, arg);
}

static struct fd_hook fd_sockets_hook;

static int initialized_sockets_version /* = 0 */;

#endif /* WINDOWS_SOCKETS */

int
gl_sockets_startup (_GL_UNUSED int version)
{
#if WINDOWS_SOCKETS
  if (version > initialized_sockets_version)
    {
      WSADATA data;
      int err = WSAStartup (version, &data);
      if (err != 0)
        return 1;

      if (data.wVersion != version)
        {
          WSACleanup ();
          return 2;
        }

      if (initialized_sockets_version == 0)
        register_fd_hook (close_fd_maybe_socket, ioctl_fd_maybe_socket,
                          &fd_sockets_hook);

      initialized_sockets_version = version;
    }
#endif

  return 0;
}

int
gl_sockets_cleanup (void)
{
#if WINDOWS_SOCKETS
  initialized_sockets_version = 0;

  unregister_fd_hook (&fd_sockets_hook);

  int err = WSACleanup ();
  if (err != 0)
    return 1;
#endif

  return 0;
}