122 lines
4.1 KiB
C
122 lines
4.1 KiB
C
/****************************************************************************
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* net/utils/net_ipv6_pref2mask.c
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*
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* Copyright (C) 2015 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <gnutt@nuttx.org>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <nuttx/net/ip.h>
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#include "utils/utils.h"
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#ifdef CONFIG_NET_IPv6
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Function: net_ipv6_pref2mask
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*
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* Description:
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* Convert a IPv6 prefix length to a network mask. The prefix length
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* specifies the number of MS bits under mask (0-128)
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*
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* Parameters:
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* preflen - Determines the width of the netmask (in bits). Range 0-128
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* mask - The location to return the netmask.
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*
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* Returned Value:
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* None
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*
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****************************************************************************/
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void net_ipv6_pref2mask(uint8_t preflen, net_ipv6addr_t mask)
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{
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unsigned int bit;
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unsigned int i;
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/* Set the network mask. preflen is the number of MS bits under the mask.
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*
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* Eg. preflen = 38
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* NETMASK: ffff ffff fc00 0000 0000 0000 0000 0000
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* bit: 1 1..1
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* 1 1..3 3..4 4..6 6..7 8..9 9..1 1..2
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* 0..5 6..1 2..7 8..3 4..9 0..5 6..1 2..7
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* preflen: 1 1..1
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* 1 1..3 3..4 4..6 6..8 8..9 9..1 1..2
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* 1..6 7..2 3..8 9..4 5..0 1..6 7..2 3..8
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*/
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for (i = 0; i < 7; i++)
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{
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/* bit = {0, 16, 32, 48, 64, 80, 96, 112} */
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bit = i << 4;
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if (preflen > bit)
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{
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/* Eg. preflen = 38, bit = {0, 16, 32} */
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if (preflen > (bit + 16))
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{
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/* Eg. preflen = 38, bit = {0, 16} */
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mask[i] = 0xffff;
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}
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else
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{
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/* Eg. preflen = 38, bit = {32}
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* bit - preflen = 6
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* make = 0xffff << (16-6)
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* = 0xfc00
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*/
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mask[i] = 0xffff << (16 - (bit - preflen));
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}
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}
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else
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{
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/* Eg. preflen=38, bit= {48, 64, 80, 112} */
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mask[i] = 0x0000;
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}
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}
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}
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#endif /* CONFIG_NET_IPv6 */
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