Add advanced setting `dnsResolveEnabled`

Default to `true`.

Set to `false` to wholly disable calls to `dns.resolve()` (Firefox-
only). Disabling calls to `dns.resolve()` will prevent cname-uncloaking
and will limit ability to enforce `ipaddress` filter option.

platform/firefox/vapi-background-ext.js

@@ -62,6 +62,7 @@ vAPI.Net = class extends vAPI.Net {
         this.cnameIgnoreExceptions = true;
         this.cnameIgnoreRootDocument = true;
         this.cnameReplayFullURL = false;
+        this.dnsResolveEnabled = true;
     }
 
     setOptions(options) {
@@ -89,6 +90,9 @@ vAPI.Net = class extends vAPI.Net {
         if ( 'cnameReplayFullURL' in options ) {
             this.cnameReplayFullURL = options.cnameReplayFullURL === true;
         }
+        if ( 'dnsResolveEnabled' in options ) {
+            this.dnsResolveEnabled = options.dnsResolveEnabled === true;
+        }
         this.dnsList.fill(null);
         this.dnsDict.clear();
     }
@@ -256,6 +260,7 @@ vAPI.Net = class extends vAPI.Net {
     }
 
     dnsShouldResolve(hn) {
+        if ( this.dnsResolveEnabled === false ) { return false; }
         if ( hn === '' ) { return false; }
         const c0 = hn.charCodeAt(0);
         if ( c0 === 0x5B /* [ */ ) { return false; }

src/js/background.js

@@ -66,6 +66,7 @@ const hiddenSettingsDefault = {
     debugScriptletInjector: false,
     differentialUpdate: true,
     disableWebAssembly: false,
+    dnsResolveEnabled: true,
     extensionUpdateForceReload: false,
     filterAuthorMode: false,
     loggerPopupType: 'popup',

src/js/storage.js

@@ -319,6 +319,7 @@ onBroadcast(msg => {
         cnameIgnoreRootDocument: µbhs.cnameIgnoreRootDocument,
         cnameMaxTTL: µbhs.cnameMaxTTL,
         cnameReplayFullURL: µbhs.cnameReplayFullURL,
+        dnsResolveEnabled: µbhs.dnsResolveEnabled,
     });
 });