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apps/netutils/netlib: Add utilities to convert to/from prefix lengths from/to 128-bit network masks. Modify the NSH IPv6 ifconfig command to show the network mask in a more standard, human readable way.
This commit is contained in:
Gregory Nutt
188
netutils/netlib/netlib_ipv6netmask2prefix.c
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188
netutils/netlib/netlib_ipv6netmask2prefix.c
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/****************************************************************************
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* netutils/netlib/netlib_ipv6netmask2prefix.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 <stdint.h>
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#include <arpa/inet.h>
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#include <apps/netutils/netlib.h>
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#ifdef CONFIG_NET_IPv6
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/****************************************************************************
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* Private Types
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****************************************************************************/
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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: netlib_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 netlib_msbits4(uint8_t nibble)
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{
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/* Return the number of leading zeroes: 0-4) */
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return g_nibblemap[nibble];
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}
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/****************************************************************************
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* Name: netlib_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 netlib_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 = netlib_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 += netlib_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: netlib_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 netlib_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 = netlib_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 += netlib_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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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: netlib_ipv6netmask2prefix
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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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* 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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* Return:
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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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uint8_t netlib_ipv6netmask2prefix(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 += netlib_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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#endif /* CONFIG_NET_IPv6 */
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