109 lines
3.4 KiB
C
109 lines
3.4 KiB
C
/****************************************************************************
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* net/utils/net_ipv6_pref2mask.c
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*
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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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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* Name: 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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* Input Parameters:
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* mask - The location to return the netmask.
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* preflen - Determines the width of the netmask (in bits). Range 0-128
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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(net_ipv6addr_t mask, uint8_t preflen)
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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 < 8; 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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* preflen - bit = 6
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* mask = 0xffff << (16-6)
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* = 0xfc00
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*/
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mask[i] = HTONS(0xffff << (16 - (preflen - bit)));
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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, 96, 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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