sysdeps/unix/sysv/linux/getsourcefilter.c

   1 /* Get 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 <assert.h>
  22 #include <errno.h>
  23 #include <stdlib.h>
  24 #include <string.h>
  25 #include <stdint.h>
  26 #include <netatalk/at.h>
  27 #include <netax25/ax25.h>
  28 #include <netinet/in.h>
  29 #include <netipx/ipx.h>
  30 #include <netpacket/packet.h>
  31 #include <netrose/rose.h>
  32 #include <sys/param.h>
  33 #include <sys/socket.h>
  34 #include "getsourcefilter.h"
  35
  36
  37 static const struct
  38 {
  39   int sol;
  40   int af;
  41   socklen_t size;
  42 }  sol_map[] =
  43   {
  44     /* Sort the array according to importance of the protocols.  Add
  45        more protocols when they become available.  */
  46     { SOL_IP, AF_INET, sizeof (struct sockaddr_in) },
  47     { SOL_IPV6, AF_INET6, sizeof (struct sockaddr_in6) },
  48     { SOL_AX25, AF_AX25, sizeof (struct sockaddr_ax25) },
  49     { SOL_IPX, AF_IPX, sizeof (struct sockaddr_ipx) },
  50     { SOL_ATALK, AF_APPLETALK, sizeof (struct sockaddr_at) },
  51     { SOL_ROSE, AF_ROSE, sizeof (struct sockaddr_rose) },
  52     { SOL_PACKET, AF_PACKET, sizeof (struct sockaddr_ll) }
  53   };
  54 #define NSOL_MAP (sizeof (sol_map) / sizeof (sol_map[0]))
  55
  56
  57 /* Try to determine the socket level value.  Ideally both side and
  58    family are set.  But sometimes only the size is correct and the
  59    family value might be bogus.  Loop over the array entries and look
  60    for a perfect match or the first match based on size.  */
  61 int
  62 __get_sol (int af, socklen_t len)
  63 {
  64   int first_size_sol = -1;
  65
  66   for (size_t cnt = 0; cnt < NSOL_MAP; ++cnt)
  67     {
  68       /* Just a test so that we make sure the special value used to
  69          signal the "we have so far no socket level value" is OK.  */
  70       assert (sol_map[cnt].sol != -1);
  71
  72       if (len == sol_map[cnt].size)
  73         {
  74           /* The size matches, which is a requirement.  If the family
  75              matches, too, we have a winner.  Otherwise we remember the
  76              socket level value for this protocol if it is the first
  77              match.  */
  78           if (af == sol_map[cnt].af)
  79             /* Bingo!  */
  80             return sol_map[cnt].sol;
  81
  82           if (first_size_sol == -1)
  83             first_size_sol = sol_map[cnt].sol;
  84       }
  85     }
  86
  87   return first_size_sol;
  88 }
  89
  90
  91 int
  92 getsourcefilter (int s, uint32_t interface, const struct sockaddr *group,
  93                  socklen_t grouplen, uint32_t *fmode, uint32_t *numsrc,
  94                  struct sockaddr_storage *slist)
  95 {
  96   /* We have to create an struct ip_msfilter object which we can pass
  97      to the kernel.  */
  98   socklen_t needed = GROUP_FILTER_SIZE (*numsrc);
  99   int use_alloca = __libc_use_alloca (needed);
 100
 101   struct group_filter *gf;
 102   if (use_alloca)
 103     gf = (struct group_filter *) alloca (needed);
 104   else
 105     {
 106       gf = (struct group_filter *) malloc (needed);
 107       if (gf == NULL)
 108         return -1;
 109     }
 110
 111   gf->gf_interface = interface;
 112   memcpy (&gf->gf_group, group, grouplen);
 113   gf->gf_numsrc = *numsrc;
 114
 115   /* We need to provide the appropriate socket level value.  */
 116   int result;
 117   int sol = __get_sol (group->sa_family, grouplen);
 118   if (sol == -1)
 119     {
 120       __set_errno (EINVAL);
 121       result = -1;
 122     }
 123   else
 124     {
 125       result = __getsockopt (s, sol, MCAST_MSFILTER, gf, &needed);
 126
 127       /* If successful, copy the results to the places the caller wants
 128          them in.  */
 129       if (result == 0)
 130         {
 131           *fmode = gf->gf_fmode;
 132           memcpy (slist, gf->gf_slist,
 133                   MIN (*numsrc, gf->gf_numsrc)
 134                   * sizeof (struct sockaddr_storage));
 135           *numsrc = gf->gf_numsrc;
 136         }
 137     }
 138
 139   if (! use_alloca)
 140     {
 141       int save_errno = errno;
 142       free (gf);
 143       __set_errno (save_errno);
 144     }
 145
 146   return result;
 147 }