ui: support DNS SRV lookup & show resolved inetendpoint

Signed-off-by: panxuesen <[email protected]>

gradle/libs.versions.toml

@@ -21,6 +21,7 @@ jsr305 = "com.google.code.findbugs:jsr305:3.0.2"
 junit = "junit:junit:4.13.2"
 kotlinx-coroutines-android = "org.jetbrains.kotlinx:kotlinx-coroutines-android:1.7.0"
 zxing-android-embedded = "com.journeyapps:zxing-android-embedded:4.3.0"
+dnsjava = "dnsjava:dnsjava:3.4.2"
 
 [plugins]
 android-application = { id = "com.android.application", version.ref = "agp" }

tunnel/build.gradle.kts

@@ -67,6 +67,7 @@ android {
 dependencies {
     implementation(libs.androidx.annotation)
     implementation(libs.androidx.collection)
+    implementation(libs.dnsjava)
     compileOnly(libs.jsr305)
     testImplementation(libs.junit)
 }

tunnel/src/main/java/com/wireguard/config/InetEndpoint.java

@@ -7,6 +7,16 @@
 
 import com.wireguard.util.NonNullForAll;
 
+import org.xbill.DNS.DClass;
+import org.xbill.DNS.ExtendedResolver;
+import org.xbill.DNS.Lookup;
+import org.xbill.DNS.Record;
+import org.xbill.DNS.Resolver;
+import org.xbill.DNS.SRVRecord;
+import org.xbill.DNS.SimpleResolver;
+import org.xbill.DNS.TextParseException;
+import org.xbill.DNS.Type;
+
 import java.net.Inet4Address;
 import java.net.InetAddress;
 import java.net.URI;
@@ -15,6 +25,7 @@
 import java.time.Duration;
 import java.time.Instant;
 import java.util.Optional;
+import java.util.concurrent.TimeUnit;
 import java.util.regex.Pattern;
 
 import androidx.annotation.Nullable;
@@ -46,6 +57,11 @@ private InetEndpoint(final String host, final boolean isResolved, final int port
     public static InetEndpoint parse(final String endpoint) throws ParseException {
         if (FORBIDDEN_CHARACTERS.matcher(endpoint).find())
             throw new ParseException(InetEndpoint.class, endpoint, "Forbidden characters");
+        if (endpoint.contains("_")) {
+            // SRV records
+            final String host = endpoint.split(":")[0];
+            return new InetEndpoint(host, false, 0);
+        }
         final URI uri;
         try {
             uri = new URI("wg://" + endpoint);
@@ -92,21 +108,60 @@ public Optional<InetEndpoint> getResolved() {
             return Optional.of(this);
         synchronized (lock) {
             //TODO(zx2c4): Implement a real timeout mechanism using DNS TTL
-            if (Duration.between(lastResolution, Instant.now()).toMinutes() > 1) {
-                try {
-                    // Prefer v4 endpoints over v6 to work around DNS64 and IPv6 NAT issues.
-                    final InetAddress[] candidates = InetAddress.getAllByName(host);
-                    InetAddress address = candidates[0];
-                    for (final InetAddress candidate : candidates) {
-                        if (candidate instanceof Inet4Address) {
-                            address = candidate;
-                            break;
+            final long ttlTimeout = Duration.between(lastResolution, Instant.now()).toSeconds();
+            if (ttlTimeout > 60) {
+                resolved = null;
+                final String[] target = {host};
+                final int[] targetPort = {port};
+                if (host.contains("_")) {
+                    // SRV records
+                    try {
+                        final Lookup lookup = new Lookup(host, Type.SRV, DClass.IN);
+                        final Resolver resolver1 = new SimpleResolver("223.5.5.5");
+                        final Resolver resolver2 = new SimpleResolver("223.6.6.6");
+                        final Resolver[] resolvers = {resolver1, resolver2};
+                        final Resolver extendedResolver = new ExtendedResolver(resolvers);
+                        lookup.setResolver(extendedResolver);
+                        lookup.setCache(null);
+                        final Record[] records = lookup.run();
+                        if (lookup.getResult() == Lookup.SUCCESSFUL) {
+                            for (final Record record : records) {
+                                final SRVRecord srv = (SRVRecord) record;
+                                try {
+                                    target[0] = srv.getTarget().toString(true);
+                                    targetPort[0] = srv.getPort();
+                                    InetAddresses.parse(target[0]);
+                                    // Parsing ths host as a numeric address worked, so we don't need to do DNS lookups.
+                                    resolved = new InetEndpoint(target[0], true, targetPort[0]);
+                                } catch (final ParseException ignored) {
+                                    // Failed to parse the host as a numeric address, so it must be a DNS hostname/FQDN.
+                                }
+                                // use the first SRV record and break out of loop
+                                break;
+                            }
+                        } else {
+                            System.out.println("SRV lookup failed: " + lookup.getErrorString());
+                        }
+                    } catch (final TextParseException | UnknownHostException e) {
+                        System.out.println("SRV lookup failed: " + e.getMessage());
+                    }
+                }
+                if (resolved == null) {
+                    try {
+                        // Prefer v4 endpoints over v6 to work around DNS64 and IPv6 NAT issues.
+                        final InetAddress[] candidates = InetAddress.getAllByName(target[0]);
+                        InetAddress address = candidates[0];
+                        for (final InetAddress candidate : candidates) {
+                            if (candidate instanceof Inet4Address) {
+                                address = candidate;
+                                break;
+                            }
                         }
+                        resolved = new InetEndpoint(address.getHostAddress(), true, targetPort[0]);
+                        lastResolution = Instant.now();
+                    } catch (final UnknownHostException e) {
+                        System.out.println("DNS lookup failed: " + e.getMessage());
                     }
-                    resolved = new InetEndpoint(address.getHostAddress(), true, port);
-                    lastResolution = Instant.now();
-                } catch (final UnknownHostException e) {
-                    resolved = null;
                 }
             }
             return Optional.ofNullable(resolved);
@@ -121,6 +176,9 @@ public int hashCode() {
     @Override
     public String toString() {
         final boolean isBareIpv6 = isResolved && BARE_IPV6.matcher(host).matches();
-        return (isBareIpv6 ? '[' + host + ']' : host) + ':' + port;
+        // Only show the port if it's non-zero
+        if (port > 0)
+            return (isBareIpv6 ? '[' + host + ']' : host) + ':' + port;
+        return (isBareIpv6 ? '[' + host + ']' : host);
     }
 }

ui/src/main/java/com/wireguard/android/fragment/TunnelDetailFragment.kt

@@ -113,6 +113,17 @@ class TunnelDetailFragment : BaseFragment(), MenuProvider {
             for (i in 0 until binding.peersLayout.childCount) {
                 val peer: TunnelDetailPeerBinding = DataBindingUtil.getBinding(binding.peersLayout.getChildAt(i))
                     ?: continue
+                if (binding.config != null && i < binding.config!!.peers.size) {
+                    val endpoint = binding.config!!.peers[i].endpoint.get()
+                    val resolved = endpoint.resolved.get()
+                    if (resolved.host != endpoint.host) {
+                        if (endpoint.port != 0) {
+                            peer.endpointText.text = "${endpoint.host}:${endpoint.port}\n${resolved.host}:${resolved.port}"
+                        } else {
+                            peer.endpointText.text = "${endpoint.host}\n${resolved.host}:${resolved.port}"
+                        }
+                    }
+                }
                 val publicKey = peer.item!!.publicKey
                 val peerStats = statistics.peer(publicKey)
                 if (peerStats == null || (peerStats.rxBytes == 0L && peerStats.txBytes == 0L)) {