Remi NGUYEN VAN | 25a7e4f | 2018-03-09 14:07:18 +0900 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2018 The Android Open Source Project |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | package com.android.server.connectivity.tethering; |
| 18 | |
| 19 | import android.annotation.Nullable; |
| 20 | import android.net.LinkProperties; |
| 21 | import android.net.NetworkCapabilities; |
| 22 | import android.net.NetworkState; |
| 23 | import android.net.RouteInfo; |
| 24 | import android.net.util.InterfaceSet; |
| 25 | |
| 26 | import java.net.Inet4Address; |
| 27 | import java.net.Inet6Address; |
| 28 | import java.net.InetAddress; |
| 29 | |
| 30 | /** |
| 31 | * @hide |
| 32 | */ |
| 33 | public final class TetheringInterfaceUtils { |
| 34 | /** |
| 35 | * Get upstream interfaces for tethering based on default routes for IPv4/IPv6. |
| 36 | * @return null if there is no usable interface, or a set of at least one interface otherwise. |
| 37 | */ |
| 38 | public static @Nullable InterfaceSet getTetheringInterfaces(NetworkState ns) { |
| 39 | if (ns == null) { |
| 40 | return null; |
| 41 | } |
| 42 | |
| 43 | final LinkProperties lp = ns.linkProperties; |
| 44 | final String if4 = getInterfaceForDestination(lp, Inet4Address.ANY); |
| 45 | final String if6 = getIPv6Interface(ns); |
| 46 | |
| 47 | return (if4 == null && if6 == null) ? null : new InterfaceSet(if4, if6); |
| 48 | } |
| 49 | |
| 50 | /** |
| 51 | * Get the upstream interface for IPv6 tethering. |
| 52 | * @return null if there is no usable interface, or the interface name otherwise. |
| 53 | */ |
| 54 | public static @Nullable String getIPv6Interface(NetworkState ns) { |
| 55 | // Broadly speaking: |
| 56 | // |
| 57 | // [1] does the upstream have an IPv6 default route? |
| 58 | // |
| 59 | // and |
| 60 | // |
| 61 | // [2] does the upstream have one or more global IPv6 /64s |
| 62 | // dedicated to this device? |
| 63 | // |
| 64 | // In lieu of Prefix Delegation and other evaluation of whether a |
| 65 | // prefix may or may not be dedicated to this device, for now just |
| 66 | // check whether the upstream is TRANSPORT_CELLULAR. This works |
| 67 | // because "[t]he 3GPP network allocates each default bearer a unique |
| 68 | // /64 prefix", per RFC 6459, Section 5.2. |
| 69 | final boolean canTether = |
paulhu | d9736de | 2019-03-08 16:35:20 +0800 | [diff] [blame] | 70 | (ns != null) && (ns.network != null) |
| 71 | && (ns.linkProperties != null) && (ns.networkCapabilities != null) |
Remi NGUYEN VAN | 25a7e4f | 2018-03-09 14:07:18 +0900 | [diff] [blame] | 72 | // At least one upstream DNS server: |
paulhu | d9736de | 2019-03-08 16:35:20 +0800 | [diff] [blame] | 73 | && ns.linkProperties.hasIpv6DnsServer() |
Remi NGUYEN VAN | 25a7e4f | 2018-03-09 14:07:18 +0900 | [diff] [blame] | 74 | // Minimal amount of IPv6 provisioning: |
paulhu | d9736de | 2019-03-08 16:35:20 +0800 | [diff] [blame] | 75 | && ns.linkProperties.hasGlobalIpv6Address() |
Remi NGUYEN VAN | 25a7e4f | 2018-03-09 14:07:18 +0900 | [diff] [blame] | 76 | // Temporary approximation of "dedicated prefix": |
paulhu | d9736de | 2019-03-08 16:35:20 +0800 | [diff] [blame] | 77 | && ns.networkCapabilities.hasTransport(NetworkCapabilities.TRANSPORT_CELLULAR); |
Remi NGUYEN VAN | 25a7e4f | 2018-03-09 14:07:18 +0900 | [diff] [blame] | 78 | |
| 79 | return canTether |
| 80 | ? getInterfaceForDestination(ns.linkProperties, Inet6Address.ANY) |
| 81 | : null; |
| 82 | } |
| 83 | |
| 84 | private static String getInterfaceForDestination(LinkProperties lp, InetAddress dst) { |
| 85 | final RouteInfo ri = (lp != null) |
| 86 | ? RouteInfo.selectBestRoute(lp.getAllRoutes(), dst) |
| 87 | : null; |
| 88 | return (ri != null) ? ri.getInterface() : null; |
| 89 | } |
| 90 | } |