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