dns: make `dns.setServers` support customized port

allow `dns.setServers` parameter to contain port

e.g.

```
dns.setServers([ '103.238.225.181:666' ]);
```

And `dns.getServers` will return IP with port if not the default port.

PR-URL: https://github.com/nodejs/node/pull/13723
Refs: https://github.com/nodejs/node/issues/7903
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

1 files changed, 20 insertions, 8 deletions

diff --git a/lib/dns.js b/lib/dns.js
index e2af27863e..8f84a07950 100644
--- a/lib/dns.js
+++ b/lib/dns.js
@@ -60,6 +60,7 @@ function errnoException(err, syscall, hostname) {
   return ex;
 }
 
+const IANA_DNS_PORT = 53;
 const digits = [
   0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 0-15
   0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 16-31
@@ -301,7 +302,13 @@ function resolve(hostname, rrtype, callback) {
 
 
 function getServers() {
-  return cares.getServers();
+  const ret = cares.getServers();
+  return ret.map((val) => {
+    if (!val[1] || val[1] === IANA_DNS_PORT) return val[0];
+
+    const host = isIP(val[0]) === 6 ? `[${val[0]}]` : val[0];
+    return `${host}:${val[1]}`;
+  });
 }
 
 
@@ -311,26 +318,31 @@ function setServers(servers) {
   const orig = cares.getServers();
   const newSet = [];
   const IPv6RE = /\[(.*)\]/;
-  const addrSplitRE = /:\d+$/;
+  const addrSplitRE = /(^.+?)(?::(\d+))?$/;
 
   servers.forEach((serv) => {
     var ipVersion = isIP(serv);
     if (ipVersion !== 0)
-      return newSet.push([ipVersion, serv]);
+      return newSet.push([ipVersion, serv, IANA_DNS_PORT]);
 
     const match = serv.match(IPv6RE);
     // we have an IPv6 in brackets
     if (match) {
       ipVersion = isIP(match[1]);
-      if (ipVersion !== 0)
-        return newSet.push([ipVersion, match[1]]);
+      if (ipVersion !== 0) {
+        const port =
+          parseInt(serv.replace(addrSplitRE, '$2')) ||
+          IANA_DNS_PORT;
+        return newSet.push([ipVersion, match[1], port]);
+      }
     }
 
-    const s = serv.split(addrSplitRE)[0];
+    const [, s, p] = serv.match(addrSplitRE);
     ipVersion = isIP(s);
 
-    if (ipVersion !== 0)
-      return newSet.push([ipVersion, s]);
+    if (ipVersion !== 0) {
+      return newSet.push([ipVersion, s, parseInt(p)]);
+    }
 
     throw new Error(`IP address is not properly formatted: ${serv}`);
   });