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/*
* Copyright 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 com.android.net.module.util;
import android.annotation.NonNull;
import android.annotation.Nullable;
import android.net.RouteInfo;
import java.net.Inet4Address;
import java.net.Inet6Address;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.Collection;
/**
* Collection of network common utilities.
* @hide
*/
public final class NetUtils {
/**
* Check if IP address type is consistent between two InetAddress.
* @return true if both are the same type. False otherwise.
*/
public static boolean addressTypeMatches(@NonNull InetAddress left,
@NonNull InetAddress right) {
return (((left instanceof Inet4Address) && (right instanceof Inet4Address))
|| ((left instanceof Inet6Address) && (right instanceof Inet6Address)));
}
/**
* Find the route from a Collection of routes that best matches a given address.
* May return null if no routes are applicable, or the best route is not a route of
* {@link RouteInfo.RTN_UNICAST} type.
*
* @param routes a Collection of RouteInfos to chose from
* @param dest the InetAddress your trying to get to
* @return the RouteInfo from the Collection that best fits the given address
*/
@Nullable
public static RouteInfo selectBestRoute(@Nullable Collection<RouteInfo> routes,
@Nullable InetAddress dest) {
if ((routes == null) || (dest == null)) return null;
RouteInfo bestRoute = null;
// pick a longest prefix match under same address type
for (RouteInfo route : routes) {
if (addressTypeMatches(route.getDestination().getAddress(), dest)) {
if ((bestRoute != null)
&& (bestRoute.getDestination().getPrefixLength()
>= route.getDestination().getPrefixLength())) {
continue;
}
if (route.matches(dest)) bestRoute = route;
}
}
if (bestRoute != null && bestRoute.getType() == RouteInfo.RTN_UNICAST) {
return bestRoute;
} else {
return null;
}
}
/**
* Get InetAddress masked with prefixLength. Will never return null.
* @param address the IP address to mask with
* @param prefixLength the prefixLength used to mask the IP
*/
public static InetAddress getNetworkPart(InetAddress address, int prefixLength) {
byte[] array = address.getAddress();
maskRawAddress(array, prefixLength);
InetAddress netPart = null;
try {
netPart = InetAddress.getByAddress(array);
} catch (UnknownHostException e) {
throw new RuntimeException("getNetworkPart error - " + e.toString());
}
return netPart;
}
/**
* Masks a raw IP address byte array with the specified prefix length.
*/
public static void maskRawAddress(byte[] array, int prefixLength) {
if (prefixLength < 0 || prefixLength > array.length * 8) {
throw new RuntimeException("IP address with " + array.length
+ " bytes has invalid prefix length " + prefixLength);
}
int offset = prefixLength / 8;
int remainder = prefixLength % 8;
byte mask = (byte) (0xFF << (8 - remainder));
if (offset < array.length) array[offset] = (byte) (array[offset] & mask);
offset++;
for (; offset < array.length; offset++) {
array[offset] = 0;
}
}
}
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