249 lines
7.3 KiB
C
249 lines
7.3 KiB
C
/****************************************************************************
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* net/utils/net_mask2pref.c
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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 "utils/utils.h"
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#if defined(CONFIG_NET_IPv4) || defined(CONFIG_NET_IPv6)
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/****************************************************************************
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* Private Data
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****************************************************************************/
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static const uint8_t g_nibblemap[16] =
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{
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0, 0, 0, 0, 0, 0, 0, 0, /* 0: No bits, 1-7: Should not happen */
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1, 1, 1, 1, /* 8: 1 bit, 9-b: Should not happen */
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2, 2, 3, 4 /* c: 2 bits, d: Should not happen, e: 3 bits, f: 4 bits */
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};
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/****************************************************************************
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* Private Functions
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****************************************************************************/
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/****************************************************************************
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* Name: net_msbits4
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*
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* Description:
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* Count the number of leading '1' bits in an 4-bit nibble
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*
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****************************************************************************/
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static inline uint8_t net_msbits4(uint8_t nibble)
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{
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/* Return the number of leading ones: 0-4) */
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return g_nibblemap[nibble];
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}
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/****************************************************************************
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* Name: net_msbits8
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*
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* Description:
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* Count the number of leading '1' bits in an 8-bit byte
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*
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****************************************************************************/
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static uint8_t net_msbits8(uint8_t byval)
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{
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uint8_t ones;
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/* Check the MS nibble */
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ones = net_msbits4(byval >> 4);
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if (ones == 4)
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{
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/* All ones, try the LS nibble */
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ones += net_msbits4(byval & 0x0f);
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}
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/* Return the number of leading ones (0-8) */
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return ones;
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}
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/****************************************************************************
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* Name: net_msbits16
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*
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* Description:
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* Count the number of leading '1' bits in a 16-bit half-workd
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*
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****************************************************************************/
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static inline uint8_t net_msbits16(uint16_t hword)
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{
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uint8_t ones;
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/* Look at the MS byte of the 16-bit value */
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ones = net_msbits8((uint8_t)(hword >> 8));
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if (ones == 8)
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{
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/* All '1's, try the LS byte */
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ones += net_msbits8((uint8_t)(hword & 0xff));
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}
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/* Return the number of leading ones (0-15) */
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return ones;
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}
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#endif /* CONFIG_NET_IPv4 || 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_ipv4_mask2pref
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*
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* Description:
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* Convert a 32-bit netmask to a prefix length. The NuttX IPv4
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* networking uses 32-bit network masks internally. This function
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* converts the IPv4 netmask to a prefix length.
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*
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* The prefix length is the number of MS '1' bits on in the netmask.
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* This, of course, assumes that all MS bits are '1' and all LS bits are
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* '0' with no intermixed 1's and 0's. This function searches from the MS
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* bit until the first '0' is found (this does not necessary mean that
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* there might not be additional '1' bits following the firs '0', but that
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* will be a malformed netmask.
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*
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* Input Parameters:
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* mask An IPv4 netmask in the form of in_addr_t
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*
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* Returned Value:
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* The prefix length, range 0-32 on success; This function will not
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* fail.
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*
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****************************************************************************/
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#ifdef CONFIG_NET_IPv4
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uint8_t net_ipv4_mask2pref(in_addr_t mask)
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{
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uint32_t hmask = NTOHL(mask);
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uint8_t ones = net_msbits16((uint16_t)(hmask >> 16));
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if (ones == 16)
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{
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ones += net_msbits16((uint16_t)(hmask & 0xffff));
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}
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return ones;
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}
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#endif /* CONFIG_NET_IPv4 */
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/****************************************************************************
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* Name: net_ipv6_mask2pref
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*
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* Description:
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* Convert a 128-bit netmask to a prefix length. The NuttX IPv6
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* networking uses 128-bit network masks internally. This function
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* converts the IPv6 netmask to a prefix length.
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*
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* The prefix length is the number of MS '1' bits on in the netmask.
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* This, of course, assumes that all MS bits are '1' and all LS bits are
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* '0' with no intermixed 1's and 0's. This function searches from the MS
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* bit until the first '0' is found (this does not necessary mean that
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* there might not be additional '1' bits following the firs '0', but that
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* will be a malformed netmask.
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*
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* Input Parameters:
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* mask Points to an IPv6 netmask in the form of uint16_t[8]
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*
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* Returned Value:
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* The prefix length, range 0-128 on success; This function will not
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* fail.
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*
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****************************************************************************/
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#ifdef CONFIG_NET_IPv6
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uint8_t net_ipv6_mask2pref(FAR const uint16_t *mask)
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{
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uint8_t preflen;
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int i;
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/* Count the leading all '1' 16-bit groups */
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for (i = 0, preflen = 0; i < 8 && mask[i] == 0xffff; i++, preflen += 16);
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/* Now i either, (1) indexes past the end of the mask, or (2) is the index
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* to the first half-word that is not equal to 0xffff.
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*/
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if (i < 8)
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{
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preflen += net_msbits16(NTOHS(mask[i]));
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}
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/* Return the prefix length */
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return preflen;
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}
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/****************************************************************************
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* Name: net_ipv6_common_pref
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*
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* Description:
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* Calculate the common prefix length of two IPv6 addresses.
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*
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* Input Parameters:
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* a1,a2 Points to IPv6 addresses in the form of uint16_t[8]
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*
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* Returned Value:
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* The common prefix length, range 0-128 on success; This function will
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* not fail.
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*
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****************************************************************************/
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uint8_t net_ipv6_common_pref(FAR const uint16_t *a1, FAR const uint16_t *a2)
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{
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uint8_t preflen;
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int i;
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/* Count the leading same 16-bit groups */
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for (i = 0, preflen = 0; i < 8 && a1[i] == a2[i]; i++, preflen += 16);
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/* Now i either, (1) indexes past the end of the mask, or (2) is the index
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* to the first half-word that is not equal between the addresses.
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*/
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if (i < 8)
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{
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preflen += net_msbits16(NTOHS(~(a1[i] ^ a2[i])));
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}
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/* Return the prefix length */
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return preflen;
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}
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#endif /* CONFIG_NET_IPv6 */
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