Fix passing DNS server IP to DNS lookup

lib/dns/dns.js

@@ -95,6 +95,15 @@ class Resolver {
     })
   }
 
+  /**
+   * 
+   * @param {string} query Domain to query from DNS server
+   * @param {function(err, ip)} onRecord Callback function, error as first param, found IP as 2nd
+   * @param {string} address DNS server IP
+   * @param {number} port DNS server port
+   * @param {Uint8Array} buf Buffer for DNS response
+   * @returns 
+   */
   lookup (query = 'localhost', onRecord = (err, ip) => {}, address = '127.0.0.1', port = 53, buf = new Uint8Array(65536)) {
     if (this.cache.has(query)) {
       console.log('dns from cache')
@@ -107,10 +116,15 @@ class Resolver {
       onRecord(null, ip)
       return
     }
-    const ips = readResolv()
-    if (ips.length) {
-      address = ips[0]
+    // Default DNS server address is unchanged,
+    // try to read address from `/etc/resolv.conf`
+    if (address === '127.0.0.1') {
+      const ips = readResolv()
+      if (ips.length) {
+        address = ips[0]
+      }
     }
+
     let timer
     const node = new Node(this.loop)
     node.peer(address, port)
@@ -196,3 +210,6 @@ function lookup (hostname) {
 }
 
 export { Resolver, lookup }
+
+
+let resolver = new Resolver()