lib/accept4.c

   1 /* Accept a connection on a socket, with specific opening flags.
   2    Copyright (C) 2009-2017 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 <http://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 #include "msvc-nothrow.h"
  26
  27 #ifndef SOCK_CLOEXEC
  28 # define SOCK_CLOEXEC 0
  29 #endif
  30
  31 int
  32 accept4 (int sockfd, struct sockaddr *addr, socklen_t *addrlen, int flags)
  33 {
  34   int fd;
  35
  36 #if HAVE_ACCEPT4
  37 # undef accept4
  38   /* Try the system call first, if it exists.  (We may be running with a glibc
  39      that has the function but with an older kernel that lacks it.)  */
  40   {
  41     /* Cache the information whether the system call really exists.  */
  42     static int have_accept4_really; /* 0 = unknown, 1 = yes, -1 = no */
  43     if (have_accept4_really >= 0)
  44       {
  45         int result = accept4 (sockfd, addr, addrlen, flags);
  46         if (!(result < 0 && errno == ENOSYS))
  47           {
  48             have_accept4_really = 1;
  49             return result;
  50           }
  51         have_accept4_really = -1;
  52       }
  53   }
  54 #endif
  55
  56   /* Check the supported flags.  */
  57   if ((flags & ~(SOCK_CLOEXEC | O_TEXT | O_BINARY)) != 0)
  58     {
  59       errno = EINVAL;
  60       return -1;
  61     }
  62
  63   fd = accept (sockfd, addr, addrlen);
  64   if (fd < 0)
  65     return -1;
  66
  67 #if SOCK_CLOEXEC
  68 # if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__
  69 /* Native Windows API.  */
  70   if (flags & SOCK_CLOEXEC)
  71     {
  72       HANDLE curr_process = GetCurrentProcess ();
  73       HANDLE old_handle = (HANDLE) _get_osfhandle (fd);
  74       HANDLE new_handle;
  75       int nfd;
  76
  77       if (!DuplicateHandle (curr_process,           /* SourceProcessHandle */
  78                             old_handle,             /* SourceHandle */
  79                             curr_process,           /* TargetProcessHandle */
  80                             (PHANDLE) &new_handle,  /* TargetHandle */
  81                             (DWORD) 0,              /* DesiredAccess */
  82                             FALSE,                  /* InheritHandle */
  83                             DUPLICATE_SAME_ACCESS)) /* Options */
  84         {
  85           close (fd);
  86           errno = EBADF; /* arbitrary */
  87           return -1;
  88         }
  89
  90       /* Closing fd before allocating the new fd ensures that the new fd will
  91          have the minimum possible value.  */
  92       close (fd);
  93       nfd = _open_osfhandle ((intptr_t) new_handle,
  94                              O_NOINHERIT | (flags & (O_TEXT | O_BINARY)));
  95       if (nfd < 0)
  96         {
  97           CloseHandle (new_handle);
  98           return -1;
  99         }
 100       return nfd;
 101     }
 102 # else
 103 /* Unix API.  */
 104   if (flags & SOCK_CLOEXEC)
 105     {
 106       int fcntl_flags;
 107
 108       if ((fcntl_flags = fcntl (fd, F_GETFD, 0)) < 0
 109           || fcntl (fd, F_SETFD, fcntl_flags | FD_CLOEXEC) == -1)
 110         {
 111           int saved_errno = errno;
 112           close (fd);
 113           errno = saved_errno;
 114           return -1;
 115         }
 116     }
 117 # endif
 118 #endif
 119
 120 #if O_BINARY
 121   if (flags & O_BINARY)
 122     set_binary_mode (fd, O_BINARY);
 123   else if (flags & O_TEXT)
 124     set_binary_mode (fd, O_TEXT);
 125 #endif
 126
 127   return fd;
 128 }