ErrorMessages: do not use R from backend

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

app/src/main/java/com/wireguard/android/backend/Backend.java

@@ -41,13 +41,6 @@ public interface Backend {
      */
     Statistics getStatistics(Tunnel tunnel) throws Exception;
 
-    /**
-     * Determine type name of underlying backend.
-     *
-     * @return Type name
-     */
-    String getTypePrettyName();
-
     /**
      * Determine version of underlying backend.
      *

app/src/main/java/com/wireguard/android/backend/BackendException.java

@@ -0,0 +1,31 @@
+/*
+ * Copyright © 2020 WireGuard LLC. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package com.wireguard.android.backend;
+
+public final class BackendException extends Exception {
+    public enum Reason {
+        UNKNOWN_KERNEL_MODULE_NAME,
+        WG_QUICK_CONFIG_ERROR_CODE,
+        TUNNEL_MISSING_CONFIG,
+        VPN_NOT_AUTHORIZED,
+        UNABLE_TO_START_VPN,
+        TUN_CREATION_ERROR,
+        GO_ACTIVATION_ERROR_CODE
+
+    }
+    private final Reason reason;
+    private final Object[] format;
+    public BackendException(final Reason reason, final Object ...format) {
+        this.reason = reason;
+        this.format = format;
+    }
+    public Reason getReason() {
+        return reason;
+    }
+    public Object[] getFormat() {
+        return format;
+    }
+}

app/src/main/java/com/wireguard/android/backend/GoBackend.java

@@ -14,10 +14,8 @@ import androidx.annotation.Nullable;
 import androidx.collection.ArraySet;
 import android.util.Log;
 
-import com.wireguard.android.Application;
-import com.wireguard.android.R;
+import com.wireguard.android.backend.BackendException.Reason;
 import com.wireguard.android.backend.Tunnel.State;
-import com.wireguard.android.util.ExceptionLoggers;
 import com.wireguard.android.util.SharedLibraryLoader;
 import com.wireguard.config.Config;
 import com.wireguard.config.InetNetwork;
@@ -28,7 +26,6 @@ import com.wireguard.crypto.KeyFormatException;
 import java.net.InetAddress;
 import java.util.Collections;
 import java.util.HashSet;
-import java.util.Objects;
 import java.util.Set;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.TimeoutException;
@@ -130,11 +127,6 @@ public final class GoBackend implements Backend {
         return stats;
     }
 
-    @Override
-    public String getTypePrettyName() {
-        return context.getString(R.string.type_name_go_userspace);
-    }
-
     @Override
     public String getVersion() {
         return wgVersion();
@@ -171,10 +163,11 @@ public final class GoBackend implements Backend {
         Log.i(TAG, "Bringing tunnel " + tunnel.getName() + " " + state);
 
         if (state == State.UP) {
-            Objects.requireNonNull(config, context.getString(R.string.no_config_error));
+            if (config == null)
+                throw new BackendException(Reason.TUNNEL_MISSING_CONFIG);
 
             if (VpnService.prepare(context) != null)
-                throw new Exception(context.getString(R.string.vpn_not_authorized_error));
+                throw new BackendException(Reason.VPN_NOT_AUTHORIZED);
 
             final VpnService service;
             if (!vpnService.isDone())
@@ -183,7 +176,9 @@ public final class GoBackend implements Backend {
             try {
                 service = vpnService.get(2, TimeUnit.SECONDS);
             } catch (final TimeoutException e) {
-                throw new Exception(context.getString(R.string.vpn_start_error), e);
+                final Exception be = new BackendException(Reason.UNABLE_TO_START_VPN);
+                be.initCause(e);
+                throw be;
             }
             service.setOwner(this);
 
@@ -225,12 +220,12 @@ public final class GoBackend implements Backend {
             builder.setBlocking(true);
             try (final ParcelFileDescriptor tun = builder.establish()) {
                 if (tun == null)
-                    throw new Exception(context.getString(R.string.tun_create_error));
+                    throw new BackendException(Reason.TUN_CREATION_ERROR);
                 Log.d(TAG, "Go backend v" + wgVersion());
                 currentTunnelHandle = wgTurnOn(tunnel.getName(), tun.detachFd(), goConfig);
             }
             if (currentTunnelHandle < 0)
-                throw new Exception(context.getString(R.string.tunnel_on_error, currentTunnelHandle));
+                throw new BackendException(Reason.GO_ACTIVATION_ERROR_CODE, currentTunnelHandle);
 
             currentTunnel = tunnel;
             currentConfig = config;

app/src/main/java/com/wireguard/android/backend/WgQuickBackend.java

@@ -5,12 +5,13 @@
 
 package com.wireguard.android.backend;
 
-import android.content.Context;
 import androidx.annotation.Nullable;
+
+import android.content.Context;
 import android.util.Log;
 
 import com.wireguard.android.Application;
-import com.wireguard.android.R;
+import com.wireguard.android.backend.BackendException.Reason;
 import com.wireguard.android.backend.Tunnel.State;
 import com.wireguard.config.Config;
 import com.wireguard.crypto.Key;
@@ -40,13 +41,11 @@ public final class WgQuickBackend implements Backend {
     private static final String TAG = "WireGuard/" + WgQuickBackend.class.getSimpleName();
 
     private final File localTemporaryDir;
-    private final Context context;
     private final Map<Tunnel, Config> runningConfigs = new HashMap<>();
     private final Set<TunnelStateChangeNotificationReceiver> notifiers = new HashSet<>();
 
     public WgQuickBackend(final Context context) {
         localTemporaryDir = new File(context.getCacheDir(), "tmp");
-        this.context = context;
     }
 
     @Override
@@ -92,17 +91,12 @@ public final class WgQuickBackend implements Backend {
         return stats;
     }
 
-    @Override
-    public String getTypePrettyName() {
-        return context.getString(R.string.type_name_kernel_module);
-    }
-
     @Override
     public String getVersion() throws Exception {
         final List<String> output = new ArrayList<>();
         if (Application.getRootShell()
                 .run(output, "cat /sys/module/wireguard/version") != 0 || output.isEmpty())
-            throw new Exception(context.getString(R.string.module_version_error));
+            throw new BackendException(Reason.UNKNOWN_KERNEL_MODULE_NAME);
         return output.get(0);
     }
 
@@ -150,7 +144,7 @@ public final class WgQuickBackend implements Backend {
         // noinspection ResultOfMethodCallIgnored
         tempFile.delete();
         if (result != 0)
-            throw new Exception(context.getString(R.string.tunnel_config_error, result));
+            throw new BackendException(Reason.WG_QUICK_CONFIG_ERROR_CODE, result);
 
         if (state == State.UP)
             runningConfigs.put(tunnel, config);

app/src/main/java/com/wireguard/android/preference/VersionPreference.java

@@ -16,21 +16,32 @@ import android.util.AttributeSet;
 import com.wireguard.android.Application;
 import com.wireguard.android.BuildConfig;
 import com.wireguard.android.R;
+import com.wireguard.android.backend.Backend;
+import com.wireguard.android.backend.GoBackend;
+import com.wireguard.android.backend.WgQuickBackend;
 
 import java.util.Locale;
 
 public class VersionPreference extends Preference {
     @Nullable private String versionSummary;
 
+    private String getBackendPrettyName(final Context context, final Backend backend) {
+        if (backend instanceof GoBackend)
+            return context.getString(R.string.type_name_kernel_module);
+        if (backend instanceof WgQuickBackend)
+            return context.getString(R.string.type_name_go_userspace);
+        return "";
+    }
+
     public VersionPreference(final Context context, final AttributeSet attrs) {
         super(context, attrs);
 
         Application.getBackendAsync().thenAccept(backend -> {
-            versionSummary = getContext().getString(R.string.version_summary_checking, backend.getTypePrettyName().toLowerCase(Locale.ENGLISH));
+            versionSummary = getContext().getString(R.string.version_summary_checking, getBackendPrettyName(context, backend).toLowerCase(Locale.ENGLISH));
             Application.getAsyncWorker().supplyAsync(backend::getVersion).whenComplete((version, exception) -> {
                 versionSummary = exception == null
-                        ? getContext().getString(R.string.version_summary, backend.getTypePrettyName(), version)
-                        : getContext().getString(R.string.version_summary_unknown, backend.getTypePrettyName().toLowerCase(Locale.ENGLISH));
+                        ? getContext().getString(R.string.version_summary, getBackendPrettyName(context, backend), version)
+                        : getContext().getString(R.string.version_summary_unknown, getBackendPrettyName(context, backend).toLowerCase(Locale.ENGLISH));
                 notifyChanged();
             });
         });

app/src/main/java/com/wireguard/android/util/ErrorMessages.java

@@ -12,9 +12,9 @@ import androidx.annotation.Nullable;
 
 import com.wireguard.android.Application;
 import com.wireguard.android.R;
+import com.wireguard.android.backend.BackendException;
 import com.wireguard.config.BadConfigException;
 import com.wireguard.config.BadConfigException.Location;
-import com.wireguard.config.BadConfigException.Reason;
 import com.wireguard.config.InetEndpoint;
 import com.wireguard.config.InetNetwork;
 import com.wireguard.config.ParseException;
@@ -29,16 +29,25 @@ import java.util.Map;
 import java9.util.Maps;
 
 public final class ErrorMessages {
-    private static final Map<Reason, Integer> BCE_REASON_MAP = new EnumMap<>(Maps.of(
-            Reason.INVALID_KEY, R.string.bad_config_reason_invalid_key,
-            Reason.INVALID_NUMBER, R.string.bad_config_reason_invalid_number,
-            Reason.INVALID_VALUE, R.string.bad_config_reason_invalid_value,
-            Reason.MISSING_ATTRIBUTE, R.string.bad_config_reason_missing_attribute,
-            Reason.MISSING_SECTION, R.string.bad_config_reason_missing_section,
-            Reason.MISSING_VALUE, R.string.bad_config_reason_missing_value,
-            Reason.SYNTAX_ERROR, R.string.bad_config_reason_syntax_error,
-            Reason.UNKNOWN_ATTRIBUTE, R.string.bad_config_reason_unknown_attribute,
-            Reason.UNKNOWN_SECTION, R.string.bad_config_reason_unknown_section
+    private static final Map<BadConfigException.Reason, Integer> BCE_REASON_MAP = new EnumMap<>(Maps.of(
+            BadConfigException.Reason.INVALID_KEY, R.string.bad_config_reason_invalid_key,
+            BadConfigException.Reason.INVALID_NUMBER, R.string.bad_config_reason_invalid_number,
+            BadConfigException.Reason.INVALID_VALUE, R.string.bad_config_reason_invalid_value,
+            BadConfigException.Reason.MISSING_ATTRIBUTE, R.string.bad_config_reason_missing_attribute,
+            BadConfigException.Reason.MISSING_SECTION, R.string.bad_config_reason_missing_section,
+            BadConfigException.Reason.MISSING_VALUE, R.string.bad_config_reason_missing_value,
+            BadConfigException.Reason.SYNTAX_ERROR, R.string.bad_config_reason_syntax_error,
+            BadConfigException.Reason.UNKNOWN_ATTRIBUTE, R.string.bad_config_reason_unknown_attribute,
+            BadConfigException.Reason.UNKNOWN_SECTION, R.string.bad_config_reason_unknown_section
+    ));
+    private static final Map<BackendException.Reason, Integer> BE_REASON_MAP = new EnumMap<>(Maps.of(
+            BackendException.Reason.UNKNOWN_KERNEL_MODULE_NAME, R.string.module_version_error,
+            BackendException.Reason.WG_QUICK_CONFIG_ERROR_CODE, R.string.tunnel_config_error,
+            BackendException.Reason.TUNNEL_MISSING_CONFIG, R.string.no_config_error,
+            BackendException.Reason.VPN_NOT_AUTHORIZED, R.string.vpn_not_authorized_error,
+            BackendException.Reason.UNABLE_TO_START_VPN, R.string.vpn_start_error,
+            BackendException.Reason.TUN_CREATION_ERROR, R.string.tun_create_error,
+            BackendException.Reason.GO_ACTIVATION_ERROR_CODE, R.string.tunnel_on_error
     ));
     private static final Map<Format, Integer> KFE_FORMAT_MAP = new EnumMap<>(Maps.of(
             Format.BASE64, R.string.key_length_explanation_base64,
@@ -77,6 +86,9 @@ public final class ErrorMessages {
                             bce.getLocation().getName());
             final String explanation = getBadConfigExceptionExplanation(resources, bce);
             message = resources.getString(R.string.bad_config_error, reason, context) + explanation;
+        } else if (rootCause instanceof BackendException) {
+            final BackendException be = (BackendException) rootCause;
+            message = resources.getString(BE_REASON_MAP.get(be.getReason()), be.getFormat());
         } else if (rootCause.getMessage() != null) {
             message = rootCause.getMessage();
         } else {
@@ -123,7 +135,7 @@ public final class ErrorMessages {
     private static Throwable rootCause(final Throwable throwable) {
         Throwable cause = throwable;
         while (cause.getCause() != null) {
-            if (cause instanceof BadConfigException)
+            if (cause instanceof BadConfigException || cause instanceof BackendException)
                 break;
             final Throwable nextCause = cause.getCause();
             if (nextCause instanceof RemoteException)