epan/addr_and_mask.c

   1 /* addr_and_mask.c
   2  * Routines to fetch IPv4 and IPv6 addresses from a tvbuff and then mask
   3  * out bits other than those covered by a prefix length
   4  *
   5  * $Id$
   6  *
   7  * Wireshark - Network traffic analyzer
   8  * By Gerald Combs <gerald@wireshark.org>
   9  * Copyright 1998 Gerald Combs
  10  *
  11  * This program is free software; you can redistribute it and/or
  12  * modify it under the terms of the GNU General Public License
  13  * as published by the Free Software Foundation; either version 2
  14  * of the License, or (at your option) any later version.
  15  *
  16  * This program is distributed in the hope that it will be useful,
  17  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19  * GNU General Public License for more details.
  20  *
  21  * You should have received a copy of the GNU General Public License
  22  * along with this program; if not, write to the Free Software
  23  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  24  */
  25
  26 #include "config.h"
  27
  28 #include <stdlib.h>
  29 #include <string.h>
  30
  31 #include "tvbuff.h"
  32 #include "ipv6-utils.h"
  33 #include "addr_and_mask.h"
  34
  35 guint32
  36 ip_get_subnet_mask(const guint32 mask_length)
  37 {
  38         static guint32 masks[33] = {
  39                 0x00000000,
  40                 0x80000000, 0xc0000000, 0xe0000000, 0xf0000000,
  41                 0xf8000000, 0xfc000000, 0xfe000000, 0xff000000,
  42                 0xff800000, 0xffc00000, 0xffe00000, 0xfff00000,
  43                 0xfff80000, 0xfffc0000, 0xfffe0000, 0xffff0000,
  44                 0xffff8000, 0xffffc000, 0xffffe000, 0xfffff000,
  45                 0xfffff800, 0xfffffc00, 0xfffffe00, 0xffffff00,
  46                 0xffffff80, 0xffffffc0, 0xffffffe0, 0xfffffff0,
  47                 0xfffffff8, 0xfffffffc, 0xfffffffe, 0xffffffff,
  48         };
  49
  50         g_assert(mask_length <= 32);
  51
  52         return masks[mask_length];
  53 }
  54
  55 /*
  56  * These routines return the length of the address in bytes on success
  57  * and -1 if the prefix length is too long.
  58  */
  59
  60 int
  61 ipv4_addr_and_mask(tvbuff_t *tvb, int offset, guint8 *addr, guint32 prefix_len)
  62 {
  63         guint32 addr_len;
  64
  65         if (prefix_len > 32)
  66                 return -1;
  67
  68         addr_len = (prefix_len + 7) / 8;
  69         memset(addr, 0, 4);
  70         tvb_memcpy(tvb, addr, offset, addr_len);
  71         if (prefix_len % 8)
  72                 addr[addr_len - 1] &= ((0xff00 >> (prefix_len % 8)) & 0xff);
  73         return addr_len;
  74 }
  75
  76 int
  77 ipv6_addr_and_mask(tvbuff_t *tvb, int offset, struct e_in6_addr *addr,
  78     guint32 prefix_len)
  79 {
  80         guint32 addr_len;
  81
  82         if (prefix_len > 128)
  83                 return -1;
  84
  85         addr_len = (prefix_len + 7) / 8;
  86         memset(addr->bytes, 0, 16);
  87         tvb_memcpy(tvb, addr->bytes, offset, addr_len);
  88         if (prefix_len % 8) {
  89                 addr->bytes[addr_len - 1] &=
  90                     ((0xff00 >> (prefix_len % 8)) & 0xff);
  91         }
  92
  93         return addr_len;
  94 }