1package eu.siacs.conversations.utils;
 2
 3import android.annotation.TargetApi;
 4import android.content.Context;
 5import android.net.ConnectivityManager;
 6import android.net.LinkProperties;
 7import android.net.Network;
 8import android.net.RouteInfo;
 9import android.os.Build;
10
11import java.net.Inet4Address;
12import java.net.InetAddress;
13import java.util.ArrayList;
14import java.util.List;
15
16import de.measite.minidns.dnsserverlookup.AbstractDNSServerLookupMechanism;
17import de.measite.minidns.dnsserverlookup.AndroidUsingExec;
18
19public class AndroidUsingLinkProperties extends AbstractDNSServerLookupMechanism {
20
21    private final Context context;
22
23    protected AndroidUsingLinkProperties(Context context) {
24        super(AndroidUsingLinkProperties.class.getSimpleName(), AndroidUsingExec.PRIORITY - 1);
25        this.context = context;
26    }
27
28    @Override
29    public boolean isAvailable() {
30        return Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP;
31    }
32
33    @Override
34    @TargetApi(21)
35    public String[] getDnsServerAddresses() {
36        ConnectivityManager connectivityManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
37        Network[] networks = connectivityManager == null ? null : connectivityManager.getAllNetworks();
38        if (networks == null) {
39            return new String[0];
40        }
41        List<String> servers = new ArrayList<>();
42        for(Network network : networks) {
43            LinkProperties linkProperties = connectivityManager.getLinkProperties(network);
44            if (linkProperties != null) {
45                if (hasDefaultRoute(linkProperties)) {
46                    servers.addAll(0, getIPv4First(linkProperties.getDnsServers()));
47                } else {
48                    servers.addAll(getIPv4First(linkProperties.getDnsServers()));
49                }
50            }
51        }
52        return servers.toArray(new String[servers.size()]);
53    }
54
55    private static List<String> getIPv4First(List<InetAddress> in) {
56        List<String> out = new ArrayList<>();
57        for(InetAddress addr : in) {
58            if (addr instanceof Inet4Address) {
59                out.add(0, addr.getHostAddress());
60            } else {
61                out.add(addr.getHostAddress());
62            }
63        }
64        return out;
65    }
66
67    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
68    private static boolean hasDefaultRoute(LinkProperties linkProperties) {
69        for(RouteInfo route: linkProperties.getRoutes()) {
70            if (route.isDefaultRoute()) {
71                return true;
72            }
73        }
74        return false;
75    }
76}