always try the complementary DNS resolution strategy if the primary one failed

1 files changed, 67 insertions, 60 deletions

diff --git a/app/src/main/java/se/leap/bitmaskclient/providersetup/connectivity/DnsResolver.java b/app/src/main/java/se/leap/bitmaskclient/providersetup/connectivity/DnsResolver.java
index b50c480d..c6cc5305 100644
--- a/app/src/main/java/se/leap/bitmaskclient/providersetup/connectivity/DnsResolver.java
+++ b/app/src/main/java/se/leap/bitmaskclient/providersetup/connectivity/DnsResolver.java
@@ -1,84 +1,85 @@
- package se.leap.bitmaskclient.providersetup.connectivity;
+package se.leap.bitmaskclient.providersetup.connectivity;
 
- import static java.net.InetAddress.getByName;
+import static java.net.InetAddress.getByName;
 
- import android.util.Log;
+import android.util.Log;
 
- import androidx.annotation.NonNull;
+import androidx.annotation.NonNull;
 
- import java.net.InetAddress;
- import java.net.UnknownHostException;
- import java.util.ArrayList;
- import java.util.List;
+import java.net.InetAddress;
+import java.net.UnknownHostException;
+import java.util.ArrayList;
+import java.util.List;
 
- import de.blinkt.openvpn.core.VpnStatus;
- import okhttp3.Dns;
- import okhttp3.HttpUrl;
- import okhttp3.OkHttpClient;
- import okhttp3.dnsoverhttps.DnsOverHttps;
- import se.leap.bitmaskclient.base.models.Provider;
- import se.leap.bitmaskclient.base.models.ProviderObservable;
- import se.leap.bitmaskclient.base.utils.IPAddress;
+import de.blinkt.openvpn.core.VpnStatus;
+import okhttp3.Dns;
+import okhttp3.HttpUrl;
+import okhttp3.OkHttpClient;
+import okhttp3.dnsoverhttps.DnsOverHttps;
+import se.leap.bitmaskclient.base.models.Provider;
+import se.leap.bitmaskclient.base.models.ProviderObservable;
+import se.leap.bitmaskclient.base.utils.IPAddress;
 
 class DnsResolver implements Dns {
     OkHttpClient dohHttpClient;
-    boolean forceDoH;
+    boolean preferDoH;
 
-    public DnsResolver(OkHttpClient dohHttpClient, boolean forceDoH) {
+    public DnsResolver(OkHttpClient dohHttpClient, boolean preferDoH) {
         this.dohHttpClient = dohHttpClient;
-        this.forceDoH = forceDoH;
+        this.preferDoH = preferDoH;
     }
 
     @NonNull
     @Override
     public List<InetAddress> lookup(@NonNull String hostname) throws UnknownHostException {
         Log.d("DNS", "trying to resolve DNS for " + hostname);
+        List<InetAddress> list = null;
+        if (preferDoH) {
+            if ((list = tryLookupDoH(hostname)) == null) {
+                list  = tryLookupSystemDNS(hostname);
+            }
+        } else {
+            if ((list = tryLookupSystemDNS(hostname)) == null) {
+                list = tryLookupDoH(hostname);
+            }
+        }
+
+        if (list != null) {
+            return list;
+        }
 
+        Log.d("DNS", "try hard coded IPs");
+        // let's check if there's an hard-coded IP we can use
+        ProviderObservable observable = ProviderObservable.getInstance();
+        Provider currentProvider;
+        if (observable.getProviderForDns() != null) {
+            currentProvider = observable.getProviderForDns();
+        } else {
+            currentProvider = observable.getCurrentProvider();
+        }
+        String ip = currentProvider.getIpForHostname(hostname);
+        if (!ip.isEmpty()) {
+            VpnStatus.logWarning("[API] Normal DNS resolution for " + hostname + " seems to be blocked. Circumventing.");
+            ArrayList<InetAddress> addresses = new ArrayList<>();
+            addresses.add(InetAddress.getByAddress(hostname, IPAddress.asBytes(ip)));
+            return addresses;
+        } else {
+            VpnStatus.logWarning("[API] Could not resolve DNS for " + hostname);
+            throw new UnknownHostException("Hostname " + hostname + " not found");
+        }
+    }
+
+    private List<InetAddress> tryLookupSystemDNS(@NonNull String hostname) throws RuntimeException, UnknownHostException {
         try {
-            if (forceDoH) {
-                List<InetAddress> list = lookupDoH(hostname);
-                for (InetAddress address : list) {
-                    Log.d("DNS", "DoH ---> " + address.toString());
-                }
-                return list;
-            }
+            Log.d("DNS", "trying to resolve " + hostname + "with system DNS");
             return Dns.SYSTEM.lookup(hostname);
         } catch (UnknownHostException e) {
             e.printStackTrace();
-            Log.e("DNS", "DoH via cloudflare failed");
-
-            // if not yet tried, do DNS over Https after normal DNS failed
-            if (!forceDoH) {
-                try {
-                   return lookupDoH(hostname);
-                } catch (RuntimeException uhe) {
-                   uhe.printStackTrace();
-                }
-           }
-
-            Log.d("DNS", "try hard coded IPs");
-            // let's check if there's an hard-coded IP we can use
-            ProviderObservable observable = ProviderObservable.getInstance();
-            Provider currentProvider;
-            if (observable.getProviderForDns() != null) {
-                currentProvider = observable.getProviderForDns();
-            } else {
-                currentProvider = observable.getCurrentProvider();
-            }
-            String ip = currentProvider.getIpForHostname(hostname);
-            if (!ip.isEmpty()) {
-                VpnStatus.logWarning("[API] Normal DNS resolution for " + hostname + " seems to be blocked. Circumventing.");
-                ArrayList<InetAddress> addresses = new ArrayList<>();
-                addresses.add(InetAddress.getByAddress(hostname, IPAddress.asBytes(ip)));
-                return addresses;
-            } else {
-                VpnStatus.logWarning("[API] Could not resolve DNS for " + hostname);
-                throw new UnknownHostException("Hostname " + hostname + " not found");
-            }
+            return null;
         }
     }
 
-    private List<InetAddress> lookupDoH(@NonNull String hostname) throws RuntimeException, UnknownHostException {
+    private List<InetAddress> tryLookupDoH(@NonNull String hostname) throws UnknownHostException {
         DnsOverHttps ahablitzDoHClient = new DnsOverHttps.Builder().client(dohHttpClient)
                 .url(HttpUrl.get("https://blitz.ahadns.com"))
                 .build();
@@ -86,7 +87,7 @@ class DnsResolver implements Dns {
             Log.d("DNS", "DoH via blitz.ahadns.com");
             return ahablitzDoHClient.lookup(hostname);
         } catch (UnknownHostException e) {
-             e.printStackTrace();
+            e.printStackTrace();
             Log.e("DNS", "DoH via blitz.ahadns.com failed");
         }
 
@@ -108,7 +109,13 @@ class DnsResolver implements Dns {
                 .bootstrapDnsHosts(getByName("1.1.1.1"), getByName("1.0.0.1"))
                 .build();
 
-        Log.d("DNS", "DoH via cloudflare 1.1.1.1");
-        return cloudFlareDoHClient.lookup(hostname);
+        try {
+            Log.d("DNS", "DoH via cloudflare 1.1.1.1");
+            return cloudFlareDoHClient.lookup(hostname);
+        } catch (UnknownHostException e) {
+            e.printStackTrace();
+            Log.e("DNS", "DoH via cloudflare failed");
+        }
+        return null;
     }
 }