forked from osmocom/wireshark
93 lines
2.5 KiB
C
93 lines
2.5 KiB
C
/* addr_and_mask.c
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* Routines to fetch IPv4 and IPv6 addresses from a tvbuff and then mask
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* out bits other than those covered by a prefix length
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*
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* Wireshark - Network traffic analyzer
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* By Gerald Combs <gerald@wireshark.org>
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* Copyright 1998 Gerald Combs
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#include "config.h"
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#include <stdlib.h>
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#include <string.h>
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#include "tvbuff.h"
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#include "ipv6-utils.h"
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#include "addr_and_mask.h"
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guint32
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ip_get_subnet_mask(const guint32 mask_length)
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{
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static const guint32 masks[33] = {
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0x00000000,
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0x80000000, 0xc0000000, 0xe0000000, 0xf0000000,
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0xf8000000, 0xfc000000, 0xfe000000, 0xff000000,
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0xff800000, 0xffc00000, 0xffe00000, 0xfff00000,
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0xfff80000, 0xfffc0000, 0xfffe0000, 0xffff0000,
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0xffff8000, 0xffffc000, 0xffffe000, 0xfffff000,
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0xfffff800, 0xfffffc00, 0xfffffe00, 0xffffff00,
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0xffffff80, 0xffffffc0, 0xffffffe0, 0xfffffff0,
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0xfffffff8, 0xfffffffc, 0xfffffffe, 0xffffffff,
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};
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g_assert(mask_length <= 32);
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return masks[mask_length];
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}
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/*
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* These routines return the length of the address in bytes on success
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* and -1 if the prefix length is too long.
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*/
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int
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ipv4_addr_and_mask(tvbuff_t *tvb, int offset, guint8 *addr, guint32 prefix_len)
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{
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guint32 addr_len;
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if (prefix_len > 32)
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return -1;
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addr_len = (prefix_len + 7) / 8;
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memset(addr, 0, 4);
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tvb_memcpy(tvb, addr, offset, addr_len);
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if (prefix_len % 8)
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addr[addr_len - 1] &= ((0xff00 >> (prefix_len % 8)) & 0xff);
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return addr_len;
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}
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int
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ipv6_addr_and_mask(tvbuff_t *tvb, int offset, struct e_in6_addr *addr,
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guint32 prefix_len)
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{
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guint32 addr_len;
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if (prefix_len > 128)
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return -1;
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addr_len = (prefix_len + 7) / 8;
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memset(addr->bytes, 0, 16);
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tvb_memcpy(tvb, addr->bytes, offset, addr_len);
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if (prefix_len % 8) {
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addr->bytes[addr_len - 1] &=
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((0xff00 >> (prefix_len % 8)) & 0xff);
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}
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return addr_len;
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}
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