1 /*
2  * Copyright (C) 2019 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.net.module.util;
18 
19 import android.net.MacAddress;
20 import android.text.TextUtils;
21 
22 import java.net.NetworkInterface;
23 import java.net.SocketException;
24 
25 
26 /**
27  * Encapsulate the interface parameters common to IpClient/IpServer components.
28  *
29  * Basically all java.net.NetworkInterface methods throw Exceptions. IpClient
30  * and IpServer (sub)components need most or all of this information at some
31  * point during their lifecycles, so pass only this simplified object around
32  * which can be created once when IpClient/IpServer are told to start.
33  *
34  * @hide
35  */
36 public class InterfaceParams {
37     public final String name;
38     public final int index;
39     public final boolean hasMacAddress;
40     public final MacAddress macAddr;
41     public final int defaultMtu;
42 
43     // TODO: move the below to NetworkStackConstants when this class is moved to the NetworkStack.
44     private static final int ETHER_MTU = 1500;
45     private static final int IPV6_MIN_MTU = 1280;
46 
47 
48     /**
49      * Return InterfaceParams corresponding with an interface name
50      * @param name the interface name
51      */
getByName(String name)52     public static InterfaceParams getByName(String name) {
53         final NetworkInterface netif = getNetworkInterfaceByName(name);
54         if (netif == null) return null;
55 
56         // Not all interfaces have MAC addresses, e.g. rmnet_data0.
57         final MacAddress macAddr = getMacAddress(netif);
58 
59         try {
60             return new InterfaceParams(name, netif.getIndex(), macAddr, netif.getMTU());
61         } catch (IllegalArgumentException | SocketException e) {
62             return null;
63         }
64     }
65 
InterfaceParams(String name, int index, MacAddress macAddr)66     public InterfaceParams(String name, int index, MacAddress macAddr) {
67         this(name, index, macAddr, ETHER_MTU);
68     }
69 
InterfaceParams(String name, int index, MacAddress macAddr, int defaultMtu)70     public InterfaceParams(String name, int index, MacAddress macAddr, int defaultMtu) {
71         if (TextUtils.isEmpty(name)) {
72             throw new IllegalArgumentException("impossible interface name");
73         }
74 
75         if (index <= 0) throw new IllegalArgumentException("invalid interface index");
76 
77         this.name = name;
78         this.index = index;
79         this.hasMacAddress = (macAddr != null);
80         this.macAddr = hasMacAddress ? macAddr : MacAddress.fromBytes(new byte[] {
81                 0x02, 0x00, 0x00, 0x00, 0x00, 0x00 });
82         this.defaultMtu = (defaultMtu > IPV6_MIN_MTU) ? defaultMtu : IPV6_MIN_MTU;
83     }
84 
85     @Override
toString()86     public String toString() {
87         return String.format("%s/%d/%s/%d", name, index, macAddr, defaultMtu);
88     }
89 
getNetworkInterfaceByName(String name)90     private static NetworkInterface getNetworkInterfaceByName(String name) {
91         try {
92             return NetworkInterface.getByName(name);
93         } catch (NullPointerException | SocketException e) {
94             return null;
95         }
96     }
97 
getMacAddress(NetworkInterface netif)98     private static MacAddress getMacAddress(NetworkInterface netif) {
99         try {
100             return MacAddress.fromBytes(netif.getHardwareAddress());
101         } catch (IllegalArgumentException | NullPointerException | SocketException e) {
102             return null;
103         }
104     }
105 }
106