Add DNS fallback system.

app/build.gradle

@@ -341,6 +341,7 @@ dependencies {
         exclude group: 'com.fasterxml.jackson.core'
         exclude group: 'org.freemarker'
     }
+    implementation 'dnsjava:dnsjava:2.1.9'
 
     flipperImplementation 'com.facebook.flipper:flipper:0.32.2'
     flipperImplementation 'com.facebook.soloader:soloader:0.8.2'

app/src/main/java/org/thoughtcrime/securesms/giph/net/GiphyLoader.java

@@ -16,6 +16,7 @@ import org.thoughtcrime.securesms.giph.model.GiphyImage;
 import org.thoughtcrime.securesms.giph.model.GiphyResponse;
 import org.thoughtcrime.securesms.net.ContentProxySelector;
 import org.thoughtcrime.securesms.net.UserAgentInterceptor;
+import org.thoughtcrime.securesms.push.SignalServiceNetworkAccess;
 import org.thoughtcrime.securesms.util.AsyncLoader;
 import org.thoughtcrime.securesms.util.JsonUtils;
 
@@ -43,6 +44,7 @@ public abstract class GiphyLoader extends AsyncLoader<List<GiphyImage>> {
     this.client       = new OkHttpClient.Builder()
                                         .proxySelector(new ContentProxySelector())
                                         .addInterceptor(new UserAgentInterceptor())
+                                        .dns(SignalServiceNetworkAccess.DNS)
                                         .build();
   }
 

app/src/main/java/org/thoughtcrime/securesms/glide/ChunkedImageUrlLoader.java

@@ -11,7 +11,9 @@ import com.bumptech.glide.load.model.MultiModelLoaderFactory;
 import org.thoughtcrime.securesms.giph.model.ChunkedImageUrl;
 import org.thoughtcrime.securesms.net.ContentProxySafetyInterceptor;
 import org.thoughtcrime.securesms.net.ContentProxySelector;
+import org.thoughtcrime.securesms.net.CustomDns;
 import org.thoughtcrime.securesms.net.UserAgentInterceptor;
+import org.thoughtcrime.securesms.push.SignalServiceNetworkAccess;
 
 import java.io.InputStream;
 
@@ -46,6 +48,7 @@ public class ChunkedImageUrlLoader implements ModelLoader<ChunkedImageUrl, Input
                                      .addInterceptor(new UserAgentInterceptor())
                                      .addNetworkInterceptor(new ContentProxySafetyInterceptor())
                                      .addNetworkInterceptor(new PaddedHeadersInterceptor())
+                                     .dns(SignalServiceNetworkAccess.DNS)
                                      .build();
     }
 

app/src/main/java/org/thoughtcrime/securesms/glide/OkHttpUrlLoader.java

@@ -11,6 +11,7 @@ import com.bumptech.glide.load.model.MultiModelLoaderFactory;
 
 import org.thoughtcrime.securesms.net.ContentProxySelector;
 import org.thoughtcrime.securesms.net.UserAgentInterceptor;
+import org.thoughtcrime.securesms.push.SignalServiceNetworkAccess;
 
 import java.io.InputStream;
 
@@ -48,6 +49,7 @@ public class OkHttpUrlLoader implements ModelLoader<GlideUrl, InputStream> {
             internalClient = new OkHttpClient.Builder()
                                              .proxySelector(new ContentProxySelector())
                                              .addInterceptor(new UserAgentInterceptor())
+                                             .dns(SignalServiceNetworkAccess.DNS)
                                              .build();
           }
         }

app/src/main/java/org/thoughtcrime/securesms/linkpreview/LinkPreviewRepository.java

@@ -12,7 +12,6 @@ import com.bumptech.glide.request.FutureTarget;
 
 import org.thoughtcrime.securesms.attachments.Attachment;
 import org.thoughtcrime.securesms.attachments.UriAttachment;
-import org.thoughtcrime.securesms.blurhash.BlurHash;
 import org.thoughtcrime.securesms.database.AttachmentDatabase;
 import org.thoughtcrime.securesms.dependencies.ApplicationDependencies;
 import org.thoughtcrime.securesms.giph.model.ChunkedImageUrl;
@@ -23,7 +22,6 @@ import org.thoughtcrime.securesms.net.CompositeRequestController;
 import org.thoughtcrime.securesms.net.ContentProxySafetyInterceptor;
 import org.thoughtcrime.securesms.net.ContentProxySelector;
 import org.thoughtcrime.securesms.net.RequestController;
-import org.thoughtcrime.securesms.net.UserAgentInterceptor;
 import org.thoughtcrime.securesms.providers.BlobProvider;
 import org.thoughtcrime.securesms.stickers.StickerRemoteUri;
 import org.thoughtcrime.securesms.stickers.StickerUrl;

app/src/main/java/org/thoughtcrime/securesms/logsubmit/SubmitDebugLogRepository.java

@@ -14,6 +14,7 @@ import org.thoughtcrime.securesms.dependencies.ApplicationDependencies;
 import org.thoughtcrime.securesms.logging.Log;
 import org.thoughtcrime.securesms.logsubmit.util.Scrubber;
 import org.thoughtcrime.securesms.net.UserAgentInterceptor;
+import org.thoughtcrime.securesms.push.SignalServiceNetworkAccess;
 import org.thoughtcrime.securesms.util.concurrent.SignalExecutors;
 import org.whispersystems.libsignal.util.guava.Optional;
 
@@ -88,7 +89,7 @@ public class SubmitDebugLogRepository {
     }
 
     try {
-      OkHttpClient client   = new OkHttpClient.Builder().addInterceptor(new UserAgentInterceptor()).build();
+      OkHttpClient client   = new OkHttpClient.Builder().addInterceptor(new UserAgentInterceptor()).dns(SignalServiceNetworkAccess.DNS).build();
       Response     response = client.newCall(new Request.Builder().url(API_ENDPOINT).get().build()).execute();
       ResponseBody body     = response.body();
 

app/src/main/java/org/thoughtcrime/securesms/net/CustomDns.java

@@ -0,0 +1,62 @@
+package org.thoughtcrime.securesms.net;
+
+import androidx.annotation.NonNull;
+
+import com.annimon.stream.Stream;
+
+import org.xbill.DNS.ARecord;
+import org.xbill.DNS.Lookup;
+import org.xbill.DNS.Record;
+import org.xbill.DNS.Resolver;
+import org.xbill.DNS.SimpleResolver;
+import org.xbill.DNS.TextParseException;
+import org.xbill.DNS.Type;
+
+import java.net.InetAddress;
+import java.net.UnknownHostException;
+import java.util.List;
+
+import okhttp3.Dns;
+
+/**
+ * A {@link Dns} implementation that specifies the hostname of a specific DNS.
+ */
+public class CustomDns implements Dns {
+
+  private final String dnsHostname;
+
+  public CustomDns(@NonNull String dnsHostname) {
+    this.dnsHostname = dnsHostname;
+  }
+
+  @Override
+  public @NonNull List<InetAddress> lookup(@NonNull String hostname) throws UnknownHostException {
+    Resolver resolver = new SimpleResolver(dnsHostname);
+    Lookup   lookup   = doLookup(hostname);
+
+    lookup.setResolver(resolver);
+
+    Record[] records = lookup.run();
+
+    if (records != null) {
+      List<InetAddress> ipv4Addresses = Stream.of(records)
+                                              .filter(r -> r.getType() == Type.A)
+                                              .map(r -> (ARecord) r)
+                                              .map(ARecord::getAddress)
+                                              .toList();
+      if (ipv4Addresses.size() > 0) {
+        return ipv4Addresses;
+      }
+    }
+
+    throw new UnknownHostException(hostname);
+  }
+
+  private static @NonNull Lookup doLookup(@NonNull String hostname) throws UnknownHostException {
+    try {
+      return new Lookup(hostname);
+    } catch (TextParseException e) {
+      throw new UnknownHostException();
+    }
+  }
+}

app/src/main/java/org/thoughtcrime/securesms/net/SequentialDns.java

@@ -0,0 +1,45 @@
+package org.thoughtcrime.securesms.net;
+
+import androidx.annotation.NonNull;
+
+import org.thoughtcrime.securesms.logging.Log;
+
+import java.net.InetAddress;
+import java.net.UnknownHostException;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Locale;
+
+import okhttp3.Dns;
+
+/**
+ * Iterates through an ordered list of {@link Dns}, trying each one in sequence.
+ */
+public class SequentialDns implements Dns {
+
+  private static final String TAG = Log.tag(SequentialDns.class);
+
+  private List<Dns> dnsList;
+
+  public SequentialDns(Dns... dns) {
+    this.dnsList = Arrays.asList(dns);
+  }
+
+  @Override
+  public @NonNull List<InetAddress> lookup(@NonNull String hostname) throws UnknownHostException {
+    for (Dns dns : dnsList) {
+      try {
+        List<InetAddress> addresses = dns.lookup(hostname);
+        if (addresses.size() > 0) {
+          return addresses;
+        } else {
+          Log.w(TAG, String.format(Locale.ENGLISH, "Didn't find any addresses for %s using %s. Continuing.", hostname, dns.getClass().getSimpleName()));
+        }
+      } catch (UnknownHostException e) {
+        Log.w(TAG, String.format(Locale.ENGLISH, "Failed to resolve %s using %s. Continuing.", hostname, dns.getClass().getSimpleName()));
+      }
+    }
+    Log.w(TAG, "Failed to resolve using any DNS.");
+    throw new UnknownHostException(hostname);
+  }
+}

app/src/main/java/org/thoughtcrime/securesms/net/StaticDns.java

@@ -0,0 +1,35 @@
+package org.thoughtcrime.securesms.net;
+
+import androidx.annotation.NonNull;
+
+import java.net.InetAddress;
+import java.net.UnknownHostException;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+
+import okhttp3.Dns;
+
+/**
+ * A super simple {@link Dns} implementation that maps hostnames to a static IP addresses.
+ */
+public class StaticDns implements Dns {
+
+  private final Map<String, String> hostnameMap;
+
+  public StaticDns(@NonNull Map<String, String> hostnameMap) {
+    this.hostnameMap = hostnameMap;
+  }
+
+  @Override
+  public @NonNull List<InetAddress> lookup(@NonNull String hostname) throws UnknownHostException {
+    String ip = hostnameMap.get(hostname);
+
+    if (ip != null) {
+      return Collections.singletonList(InetAddress.getByName(ip));
+    } else {
+      throw new UnknownHostException(hostname);
+    }
+
+  }
+}

app/src/main/java/org/thoughtcrime/securesms/push/SignalServiceNetworkAccess.java

@@ -6,9 +6,12 @@ import android.content.Context;
 import androidx.annotation.Nullable;
 
 import org.thoughtcrime.securesms.BuildConfig;
+import org.thoughtcrime.securesms.net.CustomDns;
+import org.thoughtcrime.securesms.net.SequentialDns;
 import org.thoughtcrime.securesms.net.UserAgentInterceptor;
 import org.thoughtcrime.securesms.util.Base64;
 import org.thoughtcrime.securesms.util.TextSecurePreferences;
+import org.whispersystems.libsignal.util.guava.Optional;
 import org.whispersystems.signalservice.api.push.TrustStore;
 import org.whispersystems.signalservice.internal.configuration.SignalCdnUrl;
 import org.whispersystems.signalservice.internal.configuration.SignalContactDiscoveryUrl;
@@ -25,6 +28,7 @@ import java.util.Map;
 
 import okhttp3.CipherSuite;
 import okhttp3.ConnectionSpec;
+import okhttp3.Dns;
 import okhttp3.Interceptor;
 import okhttp3.TlsVersion;
 
@@ -33,6 +37,8 @@ public class SignalServiceNetworkAccess {
   @SuppressWarnings("unused")
   private static final String TAG = SignalServiceNetworkAccess.class.getSimpleName();
 
+  public static final Dns DNS = new SequentialDns(Dns.SYSTEM, new CustomDns("1.1.1.1"));
+
   private static final String COUNTRY_CODE_EGYPT = "+20";
   private static final String COUNTRY_CODE_UAE   = "+971";
   private static final String COUNTRY_CODE_OMAN  = "+968";
@@ -146,6 +152,8 @@ public class SignalServiceNetworkAccess {
     final SignalStorageUrl qatarGoogleStorage    = new SignalStorageUrl("https://www.google.com.qa/storage", SERVICE_REFLECTOR_HOST, trustStore, GMAIL_CONNECTION_SPEC);
 
     final List<Interceptor> interceptors = Collections.singletonList(new UserAgentInterceptor());
+    final Optional<Dns>     dns          = Optional.of(DNS);
+
     final byte[] zkGroupServerPublicParams;
 
     try {
@@ -161,6 +169,7 @@ public class SignalServiceNetworkAccess {
                                                              new SignalKeyBackupServiceUrl[] {egyptGoogleKbs, baseGoogleKbs, baseAndroidKbs, mapsOneAndroidKbs, mapsTwoAndroidKbs, mailAndroidKbs},
                                                              new SignalStorageUrl[] {egyptGoogleStorage, baseGoogleStorage, baseAndroidStorage, mapsOneAndroidStorage, mapsTwoAndroidStorage, mailAndroidStorage},
                                                              interceptors,
+                                                             dns,
                                                              zkGroupServerPublicParams));
 
       put(COUNTRY_CODE_UAE, new SignalServiceConfiguration(new SignalServiceUrl[] {uaeGoogleService, baseAndroidService, baseGoogleService, mapsOneAndroidService, mapsTwoAndroidService, mailAndroidService},
@@ -169,6 +178,7 @@ public class SignalServiceNetworkAccess {
                                                            new SignalKeyBackupServiceUrl[] {uaeGoogleKbs, baseGoogleKbs, baseAndroidKbs, mapsOneAndroidKbs, mapsTwoAndroidKbs, mailAndroidKbs},
                                                            new SignalStorageUrl[] {uaeGoogleStorage, baseGoogleStorage, baseAndroidStorage, mapsOneAndroidStorage, mapsTwoAndroidStorage, mailAndroidStorage},
                                                            interceptors,
+                                                           dns,
                                                            zkGroupServerPublicParams));
 
       put(COUNTRY_CODE_OMAN, new SignalServiceConfiguration(new SignalServiceUrl[] {omanGoogleService, baseAndroidService, baseGoogleService, mapsOneAndroidService, mapsTwoAndroidService, mailAndroidService},
@@ -177,6 +187,7 @@ public class SignalServiceNetworkAccess {
                                                             new SignalKeyBackupServiceUrl[] {omanGoogleKbs, baseGoogleKbs, baseAndroidKbs, mapsOneAndroidKbs, mapsTwoAndroidKbs, mailAndroidKbs},
                                                             new SignalStorageUrl[] {omanGoogleStorage, baseGoogleStorage, baseAndroidStorage, mapsOneAndroidStorage, mapsTwoAndroidStorage, mailAndroidStorage},
                                                             interceptors,
+                                                            dns,
                                                             zkGroupServerPublicParams));
 
 
@@ -186,6 +197,7 @@ public class SignalServiceNetworkAccess {
                                                              new SignalKeyBackupServiceUrl[] {qatarGoogleKbs, baseGoogleKbs, baseAndroidKbs, mapsOneAndroidKbs, mapsTwoAndroidKbs, mailAndroidKbs},
                                                              new SignalStorageUrl[] {qatarGoogleStorage, baseGoogleStorage, baseAndroidStorage, mapsOneAndroidStorage, mapsTwoAndroidStorage, mailAndroidStorage},
                                                              interceptors,
+                                                             dns,
                                                              zkGroupServerPublicParams));
     }};
 
@@ -195,6 +207,7 @@ public class SignalServiceNetworkAccess {
                                                                   new SignalKeyBackupServiceUrl[] { new SignalKeyBackupServiceUrl(BuildConfig.SIGNAL_KEY_BACKUP_URL, new SignalServiceTrustStore(context)) },
                                                                   new SignalStorageUrl[] {new SignalStorageUrl(BuildConfig.STORAGE_URL, new SignalServiceTrustStore(context))},
                                                                   interceptors,
+                                                                  dns,
                                                                   zkGroupServerPublicParams);
 
     this.censoredCountries = this.censorshipConfiguration.keySet().toArray(new String[0]);

app/witness-verifications.gradle

@@ -330,6 +330,9 @@ dependencyVerification {
         ['com.tomergoldst.android:tooltips:1.0.6',
          '4c56697dd1ad64b8066535c61f961a6d901e7ae5d97ae27084ba40ad620349b6'],
 
+        ['dnsjava:dnsjava:2.1.9',
+         '072bba34267ffad8907c30a99a6b68f900782f3191454d278e395e289d478446'],
+
         ['me.leolin:ShortcutBadger:1.1.16',
          'e3cb3e7625892129b0c92dd5e4bc649faffdd526d5af26d9c45ee31ff8851774'],
 

libsignal/service/src/main/java/org/whispersystems/signalservice/api/SignalServiceMessageReceiver.java

@@ -221,7 +221,8 @@ public class SignalServiceMessageReceiver {
                                                             urls.getSignalServiceUrls()[0].getTrustStore(),
                                                             Optional.of(credentialsProvider), signalAgent, connectivityListener,
                                                             sleepTimer,
-                                                            urls.getNetworkInterceptors());
+                                                            urls.getNetworkInterceptors(),
+                                                            urls.getDns());
 
     return new SignalServiceMessagePipe(webSocket, Optional.of(credentialsProvider), clientZkProfile);
   }
@@ -231,7 +232,8 @@ public class SignalServiceMessageReceiver {
                                                             urls.getSignalServiceUrls()[0].getTrustStore(),
                                                             Optional.<CredentialsProvider>absent(), signalAgent, connectivityListener,
                                                             sleepTimer,
-                                                            urls.getNetworkInterceptors());
+                                                            urls.getNetworkInterceptors(),
+                                                            urls.getDns());
 
     return new SignalServiceMessagePipe(webSocket, Optional.of(credentialsProvider), clientZkProfile);
   }

libsignal/service/src/main/java/org/whispersystems/signalservice/internal/configuration/SignalServiceConfiguration.java

@@ -1,7 +1,10 @@
 package org.whispersystems.signalservice.internal.configuration;
 
+import org.whispersystems.libsignal.util.guava.Optional;
+
 import java.util.List;
 
+import okhttp3.Dns;
 import okhttp3.Interceptor;
 
 public final class SignalServiceConfiguration {
@@ -12,6 +15,7 @@ public final class SignalServiceConfiguration {
   private final SignalKeyBackupServiceUrl[] signalKeyBackupServiceUrls;
   private final SignalStorageUrl[]          signalStorageUrls;
   private final List<Interceptor>           networkInterceptors;
+  private final Optional<Dns>               dns;
   private final byte[]                      zkGroupServerPublicParams;
 
   public SignalServiceConfiguration(SignalServiceUrl[] signalServiceUrls,
@@ -20,6 +24,7 @@ public final class SignalServiceConfiguration {
                                     SignalKeyBackupServiceUrl[] signalKeyBackupServiceUrls,
                                     SignalStorageUrl[] signalStorageUrls,
                                     List<Interceptor> networkInterceptors,
+                                    Optional<Dns> dns,
                                     byte[] zkGroupServerPublicParams)
   {
     this.signalServiceUrls          = signalServiceUrls;
@@ -28,6 +33,7 @@ public final class SignalServiceConfiguration {
     this.signalKeyBackupServiceUrls = signalKeyBackupServiceUrls;
     this.signalStorageUrls          = signalStorageUrls;
     this.networkInterceptors        = networkInterceptors;
+    this.dns                        = dns;
     this.zkGroupServerPublicParams  = zkGroupServerPublicParams;
   }
 
@@ -55,6 +61,10 @@ public final class SignalServiceConfiguration {
     return networkInterceptors;
   }
 
+  public Optional<Dns> getDns() {
+    return dns;
+  }
+
   public byte[] getZkGroupServerPublicParams() {
     return zkGroupServerPublicParams;
   }

libsignal/service/src/main/java/org/whispersystems/signalservice/internal/push/PushServiceSocket.java

@@ -106,6 +106,7 @@ import javax.net.ssl.X509TrustManager;
 import okhttp3.Call;
 import okhttp3.ConnectionSpec;
 import okhttp3.Credentials;
+import okhttp3.Dns;
 import okhttp3.Interceptor;
 import okhttp3.MediaType;
 import okhttp3.MultipartBody;
@@ -184,16 +185,16 @@ public class PushServiceSocket {
   private final SecureRandom        random;
   private final ClientZkOperations  clientZkOperations;
 
-  public PushServiceSocket(SignalServiceConfiguration signalServiceConfiguration, CredentialsProvider credentialsProvider, String signalAgent) {
+  public PushServiceSocket(SignalServiceConfiguration serviceConfig, CredentialsProvider credentialsProvider, String signalAgent) {
     this.credentialsProvider               = credentialsProvider;
     this.signalAgent                       = signalAgent;
-    this.serviceClients                    = createServiceConnectionHolders(signalServiceConfiguration.getSignalServiceUrls(), signalServiceConfiguration.getNetworkInterceptors());
+    this.serviceClients                    = createServiceConnectionHolders(serviceConfig.getSignalServiceUrls(), serviceConfig.getNetworkInterceptors(), serviceConfig.getDns());
-    this.cdnClients                        = createConnectionHolders(signalServiceConfiguration.getSignalCdnUrls(), signalServiceConfiguration.getNetworkInterceptors());
+    this.cdnClients                        = createConnectionHolders(serviceConfig.getSignalCdnUrls(), serviceConfig.getNetworkInterceptors(), serviceConfig.getDns());
-    this.contactDiscoveryClients           = createConnectionHolders(signalServiceConfiguration.getSignalContactDiscoveryUrls(), signalServiceConfiguration.getNetworkInterceptors());
+    this.contactDiscoveryClients           = createConnectionHolders(serviceConfig.getSignalContactDiscoveryUrls(), serviceConfig.getNetworkInterceptors(), serviceConfig.getDns());
-    this.keyBackupServiceClients           = createConnectionHolders(signalServiceConfiguration.getSignalKeyBackupServiceUrls(), signalServiceConfiguration.getNetworkInterceptors());
+    this.keyBackupServiceClients           = createConnectionHolders(serviceConfig.getSignalKeyBackupServiceUrls(), serviceConfig.getNetworkInterceptors(), serviceConfig.getDns());
-    this.storageClients                    = createConnectionHolders(signalServiceConfiguration.getSignalStorageUrls(), signalServiceConfiguration.getNetworkInterceptors());
+    this.storageClients                    = createConnectionHolders(serviceConfig.getSignalStorageUrls(), serviceConfig.getNetworkInterceptors(), serviceConfig.getDns());
     this.random                            = new SecureRandom();
-    this.clientZkOperations                = FeatureFlags.ZK_GROUPS ? new ClientZkOperations(new ServerPublicParams(signalServiceConfiguration.getZkGroupServerPublicParams())) : null;
+    this.clientZkOperations                = FeatureFlags.ZK_GROUPS ? new ClientZkOperations(new ServerPublicParams(serviceConfig.getZkGroupServerPublicParams())) : null;
   }
 
   public void requestSmsVerificationCode(boolean androidSmsRetriever, Optional<String> captchaToken, Optional<String> challenge) throws IOException {
@@ -1349,29 +1350,32 @@ public class PushServiceSocket {
     throw new NonSuccessfulResponseCodeException("Response: " + response);
   }
 
-  private ServiceConnectionHolder[] createServiceConnectionHolders(SignalUrl[] urls, List<Interceptor> interceptors) {
+  private ServiceConnectionHolder[] createServiceConnectionHolders(SignalUrl[] urls,
+                                                                   List<Interceptor> interceptors,
+                                                                   Optional<Dns> dns)
+  {
     List<ServiceConnectionHolder> serviceConnectionHolders = new LinkedList<>();
 
     for (SignalUrl url : urls) {
-      serviceConnectionHolders.add(new ServiceConnectionHolder(createConnectionClient(url, interceptors),
+      serviceConnectionHolders.add(new ServiceConnectionHolder(createConnectionClient(url, interceptors, dns),
-                                                               createConnectionClient(url, interceptors),
+                                                               createConnectionClient(url, interceptors, dns),
                                                                url.getUrl(), url.getHostHeader()));
     }
 
     return serviceConnectionHolders.toArray(new ServiceConnectionHolder[0]);
   }
 
-  private ConnectionHolder[] createConnectionHolders(SignalUrl[] urls, List<Interceptor> interceptors) {
+  private ConnectionHolder[] createConnectionHolders(SignalUrl[] urls, List<Interceptor> interceptors, Optional<Dns> dns) {
     List<ConnectionHolder> connectionHolders = new LinkedList<>();
 
     for (SignalUrl url : urls) {
-      connectionHolders.add(new ConnectionHolder(createConnectionClient(url, interceptors), url.getUrl(), url.getHostHeader()));
+      connectionHolders.add(new ConnectionHolder(createConnectionClient(url, interceptors, dns), url.getUrl(), url.getHostHeader()));
     }
 
     return connectionHolders.toArray(new ConnectionHolder[0]);
   }
 
-  private OkHttpClient createConnectionClient(SignalUrl url, List<Interceptor> interceptors) {
+  private OkHttpClient createConnectionClient(SignalUrl url, List<Interceptor> interceptors, Optional<Dns> dns) {
     try {
       TrustManager[] trustManagers = BlacklistingTrustManager.createFor(url.getTrustStore());
 
@@ -1380,7 +1384,8 @@ public class PushServiceSocket {
 
       OkHttpClient.Builder builder = new OkHttpClient.Builder()
                                                      .sslSocketFactory(new Tls12SocketFactory(context.getSocketFactory()), (X509TrustManager)trustManagers[0])
-                                                     .connectionSpecs(url.getConnectionSpecs().or(Util.immutableList(ConnectionSpec.RESTRICTED_TLS)));
+                                                     .connectionSpecs(url.getConnectionSpecs().or(Util.immutableList(ConnectionSpec.RESTRICTED_TLS)))
+                                                     .dns(dns.or(Dns.SYSTEM));
 
       for (Interceptor interceptor : interceptors) {
         builder.addInterceptor(interceptor);

libsignal/service/src/main/java/org/whispersystems/signalservice/internal/websocket/WebSocketConnection.java

@@ -33,6 +33,7 @@ import javax.net.ssl.TrustManager;
 import javax.net.ssl.X509TrustManager;
 
 import okhttp3.ConnectionSpec;
+import okhttp3.Dns;
 import okhttp3.Interceptor;
 import okhttp3.OkHttpClient;
 import okhttp3.Request;
@@ -60,6 +61,7 @@ public class WebSocketConnection extends WebSocketListener {
   private final ConnectivityListener          listener;
   private final SleepTimer                    sleepTimer;
   private final List<Interceptor>             interceptors;
+  private final Optional<Dns>                 dns;
 
   private WebSocket           client;
   private KeepAliveSender     keepAliveSender;
@@ -72,7 +74,8 @@ public class WebSocketConnection extends WebSocketListener {
                              String signalAgent,
                              ConnectivityListener listener,
                              SleepTimer timer,
-                             List<Interceptor> interceptors)
+                             List<Interceptor> interceptors,
+                             Optional<Dns> dns)
   {
     this.trustStore          = trustStore;
     this.credentialsProvider = credentialsProvider;
@@ -80,6 +83,7 @@ public class WebSocketConnection extends WebSocketListener {
     this.listener            = listener;
     this.sleepTimer          = timer;
     this.interceptors        = interceptors;
+    this.dns                 = dns;
     this.attempts            = 0;
     this.connected           = false;
 
@@ -108,6 +112,7 @@ public class WebSocketConnection extends WebSocketListener {
                                                            .sslSocketFactory(new Tls12SocketFactory(socketFactory.first()), socketFactory.second())
                                                            .connectionSpecs(Util.immutableList(ConnectionSpec.RESTRICTED_TLS))
                                                            .readTimeout(KEEPALIVE_TIMEOUT_SECONDS + 10, TimeUnit.SECONDS)
+                                                           .dns(dns.or(Dns.SYSTEM))
                                                            .connectTimeout(KEEPALIVE_TIMEOUT_SECONDS + 10, TimeUnit.SECONDS);
 
       for (Interceptor interceptor : interceptors) {