/**************************************************************************** * netutils/netlib/netlib_ipv6netmask2prefix.c * * Copyright (C) 2015 Gregory Nutt. All rights reserved. * Author: Gregory Nutt * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in * the documentation and/or other materials provided with the * distribution. * 3. Neither the name NuttX nor the names of its contributors may be * used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE * POSSIBILITY OF SUCH DAMAGE. * ****************************************************************************/ /**************************************************************************** * Included Files ****************************************************************************/ #include #include #include #include #ifdef CONFIG_NET_IPv6 /**************************************************************************** * Private Types ****************************************************************************/ /**************************************************************************** * Private Data ****************************************************************************/ static const uint8_t g_nibblemap[16] = { 0, 0, 0, 0, 0, 0, 0, 0, /* 0: No bits, 1-7: Should not happen */ 1, 1, 1, 1, /* 8: 1 bit, 9-b: Should not happen */ 2, 2, 3, 4 /* c: 2 bits, d: Should not happen, e: 3 bits, f: 4 bits */ }; /**************************************************************************** * Private Functions ****************************************************************************/ /**************************************************************************** * Name: netlib_msbits4 * * Description: * Count the number of leading '1' bits in an 4-bit nibble * ****************************************************************************/ static inline uint8_t netlib_msbits4(uint8_t nibble) { /* Return the number of leading zeroes: 0-4) */ return g_nibblemap[nibble]; } /**************************************************************************** * Name: netlib_msbits8 * * Description: * Count the number of leading '1' bits in an 8-bit byte * ****************************************************************************/ static uint8_t netlib_msbits8(uint8_t byval) { uint8_t ones; /* Check the MS nibble */ ones = netlib_msbits4(byval >> 4); if (ones == 4) { /* All ones, try the LS nibble */ ones += netlib_msbits4(byval & 0x0f); } /* Return the number of leading ones (0-8) */ return ones; } /**************************************************************************** * Name: netlib_msbits16 * * Description: * Count the number of leading '1' bits in a 16-bit half-workd * ****************************************************************************/ static inline uint8_t netlib_msbits16(uint16_t hword) { uint8_t ones; /* Look at the MS byte of the 16-bit value */ ones = netlib_msbits8((uint8_t)(hword >> 8)); if (ones == 8) { /* All '1's, try the LS byte */ ones += netlib_msbits8((uint8_t)(hword & 0xff)); } /* Return the number of leading ones (0-15) */ return ones; } /**************************************************************************** * Public Functions ****************************************************************************/ /**************************************************************************** * Name: netlib_ipv6netmask2prefix * * Description: * Convert a 128-bit netmask to a prefix length. The Nuttx IPv6 * networking uses 128-bit network masks internally. This function * converts the IPv6 netmask to a prefix length. * * The prefix length is the number of MS '1' bits on in the netmask. * This, of course, assumes that all MS bits are '1' and all LS bits are * '0' with no intermixed 1's and 0's. This function searches from the MS * bit until the first '0' is found (this does not necessary mean that * there might not be additional '1' bits following the firs '0', but that * will be a malformed netmask. * * Parameters: * mask Points to an IPv6 netmask in the form of uint16_t[8] * * Return: * The prefix length, range 0-128 on success; This function will not * fail. * ****************************************************************************/ uint8_t netlib_ipv6netmask2prefix(FAR const uint16_t *mask) { uint8_t preflen; int i; /* Count the leading all '1' 16-bit groups */ for (i = 0, preflen = 0; i < 8 && mask[i] == 0xffff; i++, preflen += 16); /* Now i either, (1) indexes past the end of the mask, or (2) is the index * to the first half-word that is not equal to 0xffff. */ if (i < 8) { preflen += netlib_msbits16(ntohs(mask[i])); } /* Return the prefix length */ return preflen; } #endif /* CONFIG_NET_IPv6 */