| /* |
| * Copyright (C) 2018 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.server.connectivity.tethering; |
| |
| import android.annotation.Nullable; |
| import android.net.LinkProperties; |
| import android.net.NetworkCapabilities; |
| import android.net.RouteInfo; |
| import android.net.util.InterfaceSet; |
| |
| import java.net.InetAddress; |
| import java.net.UnknownHostException; |
| |
| /** |
| * @hide |
| */ |
| public final class TetheringInterfaceUtils { |
| private static final InetAddress IN6ADDR_ANY = getByAddress( |
| new byte[] {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}); |
| private static final InetAddress INADDR_ANY = getByAddress(new byte[] {0, 0, 0, 0}); |
| |
| /** |
| * Get upstream interfaces for tethering based on default routes for IPv4/IPv6. |
| * @return null if there is no usable interface, or a set of at least one interface otherwise. |
| */ |
| public static @Nullable InterfaceSet getTetheringInterfaces(UpstreamNetworkState ns) { |
| if (ns == null) { |
| return null; |
| } |
| |
| final LinkProperties lp = ns.linkProperties; |
| final String if4 = getInterfaceForDestination(lp, INADDR_ANY); |
| final String if6 = getIPv6Interface(ns); |
| |
| return (if4 == null && if6 == null) ? null : new InterfaceSet(if4, if6); |
| } |
| |
| /** |
| * Get the upstream interface for IPv6 tethering. |
| * @return null if there is no usable interface, or the interface name otherwise. |
| */ |
| public static @Nullable String getIPv6Interface(UpstreamNetworkState ns) { |
| // Broadly speaking: |
| // |
| // [1] does the upstream have an IPv6 default route? |
| // |
| // and |
| // |
| // [2] does the upstream have one or more global IPv6 /64s |
| // dedicated to this device? |
| // |
| // In lieu of Prefix Delegation and other evaluation of whether a |
| // prefix may or may not be dedicated to this device, for now just |
| // check whether the upstream is TRANSPORT_CELLULAR. This works |
| // because "[t]he 3GPP network allocates each default bearer a unique |
| // /64 prefix", per RFC 6459, Section 5.2. |
| final boolean canTether = |
| (ns != null) && (ns.network != null) |
| && (ns.linkProperties != null) && (ns.networkCapabilities != null) |
| // At least one upstream DNS server: |
| && ns.linkProperties.hasIpv6DnsServer() |
| // Minimal amount of IPv6 provisioning: |
| && ns.linkProperties.hasGlobalIpv6Address() |
| // Temporary approximation of "dedicated prefix": |
| && ns.networkCapabilities.hasTransport(NetworkCapabilities.TRANSPORT_CELLULAR); |
| |
| return canTether |
| ? getInterfaceForDestination(ns.linkProperties, IN6ADDR_ANY) |
| : null; |
| } |
| |
| private static String getInterfaceForDestination(LinkProperties lp, InetAddress dst) { |
| final RouteInfo ri = (lp != null) |
| ? RouteInfo.selectBestRoute(lp.getAllRoutes(), dst) |
| : null; |
| return (ri != null) ? ri.getInterface() : null; |
| } |
| |
| private static InetAddress getByAddress(final byte[] addr) { |
| try { |
| return InetAddress.getByAddress(null, addr); |
| } catch (UnknownHostException e) { |
| throw new AssertionError("illegal address length" + addr.length); |
| } |
| } |
| } |