lib/accept4.c

   1 /* Accept a connection on a socket, with specific opening flags.
   2    Copyright (C) 2009-2019 Free Software Foundation, Inc.
   3
   4    This program is free software; you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation; either version 2, or (at your option)
   7    any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License along
  15    with this program; if not, see <https://www.gnu.org/licenses/>.  */
  16
  17 #include <config.h>
  18
  19 /* Specification.  */
  20 #include <sys/socket.h>
  21
  22 #include <errno.h>
  23 #include <fcntl.h>
  24 #include "binary-io.h"
  25 #if GNULIB_MSVC_NOTHROW
  26 # include "msvc-nothrow.h"
  27 #else
  28 # include <io.h>
  29 #endif
  30
  31 #ifndef SOCK_CLOEXEC
  32 # define SOCK_CLOEXEC 0
  33 #endif
  34
  35 int
  36 accept4 (int sockfd, struct sockaddr *addr, socklen_t *addrlen, int flags)
  37 {
  38   int fd;
  39
  40 #if HAVE_ACCEPT4
  41 # undef accept4
  42   /* Try the system call first, if it exists.  (We may be running with a glibc
  43      that has the function but with an older kernel that lacks it.)  */
  44   {
  45     /* Cache the information whether the system call really exists.  */
  46     static int have_accept4_really; /* 0 = unknown, 1 = yes, -1 = no */
  47     if (have_accept4_really >= 0)
  48       {
  49         int result = accept4 (sockfd, addr, addrlen, flags);
  50         if (!(result < 0 && errno == ENOSYS))
  51           {
  52             have_accept4_really = 1;
  53             return result;
  54           }
  55         have_accept4_really = -1;
  56       }
  57   }
  58 #endif
  59
  60   /* Check the supported flags.  */
  61   if ((flags & ~(SOCK_CLOEXEC | O_TEXT | O_BINARY)) != 0)
  62     {
  63       errno = EINVAL;
  64       return -1;
  65     }
  66
  67   fd = accept (sockfd, addr, addrlen);
  68   if (fd < 0)
  69     return -1;
  70
  71 #if SOCK_CLOEXEC
  72 # if defined _WIN32 && ! defined __CYGWIN__
  73 /* Native Windows API.  */
  74   if (flags & SOCK_CLOEXEC)
  75     {
  76       HANDLE curr_process = GetCurrentProcess ();
  77       HANDLE old_handle = (HANDLE) _get_osfhandle (fd);
  78       HANDLE new_handle;
  79       int nfd;
  80
  81       if (!DuplicateHandle (curr_process,           /* SourceProcessHandle */
  82                             old_handle,             /* SourceHandle */
  83                             curr_process,           /* TargetProcessHandle */
  84                             (PHANDLE) &new_handle,  /* TargetHandle */
  85                             (DWORD) 0,              /* DesiredAccess */
  86                             FALSE,                  /* InheritHandle */
  87                             DUPLICATE_SAME_ACCESS)) /* Options */
  88         {
  89           close (fd);
  90           errno = EBADF; /* arbitrary */
  91           return -1;
  92         }
  93
  94       /* Closing fd before allocating the new fd ensures that the new fd will
  95          have the minimum possible value.  */
  96       close (fd);
  97       nfd = _open_osfhandle ((intptr_t) new_handle,
  98                              O_NOINHERIT | (flags & (O_TEXT | O_BINARY)));
  99       if (nfd < 0)
 100         {
 101           CloseHandle (new_handle);
 102           return -1;
 103         }
 104       return nfd;
 105     }
 106 # else
 107 /* Unix API.  */
 108   if (flags & SOCK_CLOEXEC)
 109     {
 110       int fcntl_flags;
 111
 112       if ((fcntl_flags = fcntl (fd, F_GETFD, 0)) < 0
 113           || fcntl (fd, F_SETFD, fcntl_flags | FD_CLOEXEC) == -1)
 114         {
 115           int saved_errno = errno;
 116           close (fd);
 117           errno = saved_errno;
 118           return -1;
 119         }
 120     }
 121 # endif
 122 #endif
 123
 124 #if O_BINARY
 125   if (flags & O_BINARY)
 126     set_binary_mode (fd, O_BINARY);
 127   else if (flags & O_TEXT)
 128     set_binary_mode (fd, O_TEXT);
 129 #endif
 130
 131   return fd;
 132 }