sysdeps/unix/sysv/linux/getipv4sourcefilter.c

   1 /* Get IPv4 source filter.  Linux version.
   2    Copyright (C) 2004-2018 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@redhat.com>, 2004.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 #include <alloca.h>
  21 #include <errno.h>
  22 #include <stdlib.h>
  23 #include <string.h>
  24 #include <stdint.h>
  25 #include <netinet/in.h>
  26 #include <sys/param.h>
  27 #include <sys/socket.h>
  28
  29
  30 int
  31 getipv4sourcefilter (int s, struct in_addr interface, struct in_addr group,
  32                      uint32_t *fmode, uint32_t *numsrc, struct in_addr *slist)
  33 {
  34   /* We have to create an struct ip_msfilter object which we can pass
  35      to the kernel.  */
  36   socklen_t needed = IP_MSFILTER_SIZE (*numsrc);
  37   int use_alloca = __libc_use_alloca (needed);
  38
  39   struct ip_msfilter *imsf;
  40   if (use_alloca)
  41     imsf = (struct ip_msfilter *) alloca (needed);
  42   else
  43     {
  44       imsf = (struct ip_msfilter *) malloc (needed);
  45       if (imsf == NULL)
  46         return -1;
  47     }
  48
  49   imsf->imsf_multiaddr = group;
  50   imsf->imsf_interface = interface;
  51   imsf->imsf_numsrc = *numsrc;
  52
  53   int result = __getsockopt (s, SOL_IP, IP_MSFILTER, imsf, &needed);
  54
  55   /* If successful, copy the results to the places the caller wants
  56      them in.  */
  57   if (result == 0)
  58     {
  59       *fmode = imsf->imsf_fmode;
  60       memcpy (slist, imsf->imsf_slist,
  61               MIN (*numsrc, imsf->imsf_numsrc) * sizeof (struct in_addr));
  62       *numsrc = imsf->imsf_numsrc;
  63     }
  64
  65   if (! use_alloca)
  66     {
  67       int save_errno = errno;
  68       free (imsf);
  69       __set_errno (save_errno);
  70     }
  71
  72   return result;
  73 }