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/* addr_and_mask.c
* Routines to fetch IPv4 and IPv6 addresses from a tvbuff and then mask
* out bits other than those covered by a prefix length
*
* Wireshark - Network traffic analyzer
* By Gerald Combs <gerald@wireshark.org>
* Copyright 1998 Gerald Combs
*
* SPDX-License-Identifier: GPL-2.0-or-later
*/
#include "config.h"
#include <stdlib.h>
#include <string.h>
#include "tvbuff.h"
#include "ipv6.h"
#include "addr_and_mask.h"
#include <wsutil/ws_assert.h>
guint32
ip_get_subnet_mask(const guint32 mask_length)
{
static const guint32 masks[33] = {
0x00000000,
0x80000000, 0xc0000000, 0xe0000000, 0xf0000000,
0xf8000000, 0xfc000000, 0xfe000000, 0xff000000,
0xff800000, 0xffc00000, 0xffe00000, 0xfff00000,
0xfff80000, 0xfffc0000, 0xfffe0000, 0xffff0000,
0xffff8000, 0xffffc000, 0xffffe000, 0xfffff000,
0xfffff800, 0xfffffc00, 0xfffffe00, 0xffffff00,
0xffffff80, 0xffffffc0, 0xffffffe0, 0xfffffff0,
0xfffffff8, 0xfffffffc, 0xfffffffe, 0xffffffff,
};
ws_assert(mask_length <= 32);
return masks[mask_length];
}
/*
* These routines return the length of the address in bytes on success
* and -1 if the prefix length is too long.
*/
int
tvb_get_ipv4_addr_with_prefix_len(tvbuff_t *tvb, int offset, ws_in4_addr *addr,
guint32 prefix_len)
{
guint8 addr_len;
if (prefix_len > 32)
return -1;
addr_len = (prefix_len + 7) / 8;
*addr = 0;
tvb_memcpy(tvb, addr, offset, addr_len);
if (prefix_len % 8)
((guint8*)addr)[addr_len - 1] &= ((0xff00 >> (prefix_len % 8)) & 0xff);
return addr_len;
}
int
tvb_get_ipv6_addr_with_prefix_len(tvbuff_t *tvb, int offset, ws_in6_addr *addr,
guint32 prefix_len)
{
guint32 addr_len;
if (prefix_len > 128)
return -1;
addr_len = (prefix_len + 7) / 8;
memset(addr->bytes, 0, 16);
tvb_memcpy(tvb, addr->bytes, offset, addr_len);
if (prefix_len % 8) {
addr->bytes[addr_len - 1] &=
((0xff00 >> (prefix_len % 8)) & 0xff);
}
return addr_len;
}
/*
* Editor modelines - https://www.wireshark.org/tools/modelines.html
*
* Local variables:
* c-basic-offset: 8
* tab-width: 8
* indent-tabs-mode: t
* End:
*
* vi: set shiftwidth=8 tabstop=8 noexpandtab:
* :indentSize=8:tabSize=8:noTabs=false:
*/
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