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
7 * Wireshark - Network traffic analyzer
8 * By Gerald Combs <gerald@wireshark.org>
9 * Copyright 1998 Gerald Combs
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.
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.
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.
32 #include "addr_and_mask.h"
35 ip_get_subnet_mask(const guint32 mask_length)
37 static guint32 masks[33] = {
39 0x80000000, 0xc0000000, 0xe0000000, 0xf0000000,
40 0xf8000000, 0xfc000000, 0xfe000000, 0xff000000,
41 0xff800000, 0xffc00000, 0xffe00000, 0xfff00000,
42 0xfff80000, 0xfffc0000, 0xfffe0000, 0xffff0000,
43 0xffff8000, 0xffffc000, 0xffffe000, 0xfffff000,
44 0xfffff800, 0xfffffc00, 0xfffffe00, 0xffffff00,
45 0xffffff80, 0xffffffc0, 0xffffffe0, 0xfffffff0,
46 0xfffffff8, 0xfffffffc, 0xfffffffe, 0xffffffff,
49 g_assert(mask_length <= 32);
51 return masks[mask_length];
55 * These routines return the length of the address in bytes on success
56 * and -1 if the prefix length is too long.
60 ipv4_addr_and_mask(tvbuff_t *tvb, int offset, guint8 *addr, guint32 prefix_len)
67 addr_len = (prefix_len + 7) / 8;
69 tvb_memcpy(tvb, addr, offset, addr_len);
71 addr[addr_len - 1] &= ((0xff00 >> (prefix_len % 8)) & 0xff);
76 ipv6_addr_and_mask(tvbuff_t *tvb, int offset, struct e_in6_addr *addr,
84 addr_len = (prefix_len + 7) / 8;
85 memset(addr->bytes, 0, 16);
86 tvb_memcpy(tvb, addr->bytes, offset, addr_len);
88 addr->bytes[addr_len - 1] &=
89 ((0xff00 >> (prefix_len % 8)) & 0xff);