/*
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* Copyright (C) 2019 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* 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,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package android.net.shared;
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import java.net.Inet4Address;
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import java.net.InetAddress;
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import java.net.UnknownHostException;
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/**
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* Collection of utilities to work with IPv4 addresses.
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* @hide
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*/
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public class Inet4AddressUtils {
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/**
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* Convert a IPv4 address from an integer to an InetAddress (0x04030201 -> 1.2.3.4)
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*
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* <p>This method uses the higher-order int bytes as the lower-order IPv4 address bytes,
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* which is an unusual convention. Consider {@link #intToInet4AddressHTH(int)} instead.
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* @param hostAddress an int coding for an IPv4 address, where higher-order int byte is
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* lower-order IPv4 address byte
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*/
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public static Inet4Address intToInet4AddressHTL(int hostAddress) {
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return intToInet4AddressHTH(Integer.reverseBytes(hostAddress));
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}
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/**
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* Convert a IPv4 address from an integer to an InetAddress (0x01020304 -> 1.2.3.4)
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* @param hostAddress an int coding for an IPv4 address
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*/
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public static Inet4Address intToInet4AddressHTH(int hostAddress) {
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byte[] addressBytes = { (byte) (0xff & (hostAddress >> 24)),
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(byte) (0xff & (hostAddress >> 16)),
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(byte) (0xff & (hostAddress >> 8)),
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(byte) (0xff & hostAddress) };
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try {
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return (Inet4Address) InetAddress.getByAddress(addressBytes);
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} catch (UnknownHostException e) {
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throw new AssertionError();
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}
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}
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/**
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* Convert an IPv4 address from an InetAddress to an integer (1.2.3.4 -> 0x01020304)
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*
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* <p>This conversion can help order IP addresses: considering the ordering
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* 192.0.2.1 < 192.0.2.2 < ..., resulting ints will follow that ordering if read as unsigned
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* integers with {@link Integer#toUnsignedLong}.
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* @param inetAddr is an InetAddress corresponding to the IPv4 address
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* @return the IP address as integer
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*/
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public static int inet4AddressToIntHTH(Inet4Address inetAddr)
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throws IllegalArgumentException {
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byte [] addr = inetAddr.getAddress();
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return ((addr[0] & 0xff) << 24) | ((addr[1] & 0xff) << 16)
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| ((addr[2] & 0xff) << 8) | (addr[3] & 0xff);
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}
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/**
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* Convert a IPv4 address from an InetAddress to an integer (1.2.3.4 -> 0x04030201)
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*
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* <p>This method stores the higher-order IPv4 address bytes in the lower-order int bytes,
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* which is an unusual convention. Consider {@link #inet4AddressToIntHTH(Inet4Address)} instead.
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* @param inetAddr is an InetAddress corresponding to the IPv4 address
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* @return the IP address as integer
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*/
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public static int inet4AddressToIntHTL(Inet4Address inetAddr) {
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return Integer.reverseBytes(inet4AddressToIntHTH(inetAddr));
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}
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/**
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* Convert a network prefix length to an IPv4 netmask integer (prefixLength 17 -> 0xffff8000)
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* @return the IPv4 netmask as an integer
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*/
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public static int prefixLengthToV4NetmaskIntHTH(int prefixLength)
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throws IllegalArgumentException {
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if (prefixLength < 0 || prefixLength > 32) {
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throw new IllegalArgumentException("Invalid prefix length (0 <= prefix <= 32)");
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}
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// (int)a << b is equivalent to a << (b & 0x1f): can't shift by 32 (-1 << 32 == -1)
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return prefixLength == 0 ? 0 : 0xffffffff << (32 - prefixLength);
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}
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/**
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* Convert a network prefix length to an IPv4 netmask integer (prefixLength 17 -> 0x0080ffff).
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*
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* <p>This method stores the higher-order IPv4 address bytes in the lower-order int bytes,
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* which is an unusual convention. Consider {@link #prefixLengthToV4NetmaskIntHTH(int)} instead.
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* @return the IPv4 netmask as an integer
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*/
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public static int prefixLengthToV4NetmaskIntHTL(int prefixLength)
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throws IllegalArgumentException {
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return Integer.reverseBytes(prefixLengthToV4NetmaskIntHTH(prefixLength));
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}
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/**
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* Convert an IPv4 netmask to a prefix length, checking that the netmask is contiguous.
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* @param netmask as a {@code Inet4Address}.
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* @return the network prefix length
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* @throws IllegalArgumentException the specified netmask was not contiguous.
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* @hide
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*/
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public static int netmaskToPrefixLength(Inet4Address netmask) {
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// inetAddressToInt returns an int in *network* byte order.
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int i = inet4AddressToIntHTH(netmask);
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int prefixLength = Integer.bitCount(i);
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int trailingZeros = Integer.numberOfTrailingZeros(i);
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if (trailingZeros != 32 - prefixLength) {
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throw new IllegalArgumentException("Non-contiguous netmask: " + Integer.toHexString(i));
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}
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return prefixLength;
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}
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/**
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* Returns the implicit netmask of an IPv4 address, as was the custom before 1993.
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*/
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public static int getImplicitNetmask(Inet4Address address) {
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int firstByte = address.getAddress()[0] & 0xff; // Convert to an unsigned value.
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if (firstByte < 128) {
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return 8;
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} else if (firstByte < 192) {
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return 16;
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} else if (firstByte < 224) {
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return 24;
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} else {
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return 32; // Will likely not end well for other reasons.
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}
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}
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/**
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* Get the broadcast address for a given prefix.
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*
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* <p>For example 192.168.0.1/24 -> 192.168.0.255
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*/
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public static Inet4Address getBroadcastAddress(Inet4Address addr, int prefixLength)
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throws IllegalArgumentException {
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final int intBroadcastAddr = inet4AddressToIntHTH(addr)
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return intToInet4AddressHTH(intBroadcastAddr);
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}
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/**
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* Get a prefix mask as Inet4Address for a given prefix length.
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*
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* <p>For example 20 -> 255.255.240.0
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*/
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public static Inet4Address getPrefixMaskAsInet4Address(int prefixLength)
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throws IllegalArgumentException {
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return intToInet4AddressHTH(prefixLengthToV4NetmaskIntHTH(prefixLength));
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}
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}
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