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: #13723
Refs: #7903
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

doc/api/dns.md

@@ -59,8 +59,21 @@ the [Implementation considerations section][] for more information.
 added: v0.11.3
 -->
 
-Returns an array of IP address strings that are being used for name
-resolution.
+Returns an array of IP address strings, formatted according to [rfc5952][],
+that are currently configured for DNS resolution. A string will include a port
+section if a custom port is used.
+
+For example:
+
+<!-- eslint-disable -->
+```js
+[
+  '4.4.4.4',
+  '2001:4860:4860::8888',
+  '4.4.4.4:1053',
+  '[2001:4860:4860::8888]:1053'
+]
+```
 
 ## dns.lookup(hostname[, options], callback)
 <!-- YAML
@@ -482,12 +495,22 @@ one of the [DNS error codes][].
 <!-- YAML
 added: v0.11.3
 -->
-- `servers` {string[]}
+- `servers` {string[]} array of [rfc5952][] formatted addresses
+
+Sets the IP address and port of servers to be used when performing DNS
+resolution. The `servers` argument is an array of [rfc5952][] formatted
+addresses. If the port is the IANA default DNS port (53) it can be omitted.
 
-Sets the IP addresses of the servers to be used when resolving. The `servers`
-argument is an array of IPv4 or IPv6 addresses.
+For example:
 
-If a port is specified on the address, it will be removed.
+```js
+dns.setServers([
+  '4.4.4.4',
+  '[2001:4860:4860::8888]',
+  '4.4.4.4:1053',
+  '[2001:4860:4860::8888]:1053'
+]);
+```
 
 An error will be thrown if an invalid address is provided.
 
@@ -583,3 +606,4 @@ uses. For instance, _they do not use the configuration from `/etc/hosts`_.
 [supported `getaddrinfo` flags]: #dns_supported_getaddrinfo_flags
 [the official libuv documentation]: http://docs.libuv.org/en/latest/threadpool.html
 [`util.promisify()`]: util.html#util_util_promisify_original
+[rfc5952]: https://tools.ietf.org/html/rfc5952#section-6

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}`);
   });

src/cares_wrap.cc

@@ -442,9 +442,9 @@ void AresEnsureServers(Environment* env) {
   }
 
   ares_channel channel = env->cares_channel();
-  ares_addr_node* servers = nullptr;
+  ares_addr_port_node* servers = nullptr;
 
-  ares_get_servers(channel, &servers);
+  ares_get_servers_ports(channel, &servers);
 
   /* if no server or multi-servers, ignore */
   if (servers == nullptr) return;
@@ -456,7 +456,9 @@ void AresEnsureServers(Environment* env) {
 
   /* if the only server is not 127.0.0.1, ignore */
   if (servers[0].family != AF_INET ||
-      servers[0].addr.addr4.s_addr != htonl(INADDR_LOOPBACK)) {
+      servers[0].addr.addr4.s_addr != htonl(INADDR_LOOPBACK) ||
+      servers[0].tcp_port != 0 ||
+      servers[0].udp_port != 0) {
     ares_free_data(servers);
     env->set_cares_is_servers_default(false);
     return;
@@ -1924,12 +1926,12 @@ void GetServers(const FunctionCallbackInfo<Value>& args) {
 
   Local<Array> server_array = Array::New(env->isolate());
 
-  ares_addr_node* servers;
+  ares_addr_port_node* servers;
 
-  int r = ares_get_servers(env->cares_channel(), &servers);
+  int r = ares_get_servers_ports(env->cares_channel(), &servers);
   CHECK_EQ(r, ARES_SUCCESS);
 
-  ares_addr_node* cur = servers;
+  ares_addr_port_node* cur = servers;
 
   for (uint32_t i = 0; cur != nullptr; ++i, cur = cur->next) {
     char ip[INET6_ADDRSTRLEN];
@@ -1938,8 +1940,11 @@ void GetServers(const FunctionCallbackInfo<Value>& args) {
     int err = uv_inet_ntop(cur->family, caddr, ip, sizeof(ip));
     CHECK_EQ(err, 0);
 
-    Local<String> addr = OneByteString(env->isolate(), ip);
-    server_array->Set(i, addr);
+    Local<Array> ret = Array::New(env->isolate(), 2);
+    ret->Set(0, OneByteString(env->isolate(), ip));
+    ret->Set(1, Integer::New(env->isolate(), cur->udp_port));
+
+    server_array->Set(i, ret);
   }
 
   ares_free_data(servers);
@@ -1962,8 +1967,8 @@ void SetServers(const FunctionCallbackInfo<Value>& args) {
     return args.GetReturnValue().Set(rv);
   }
 
-  ares_addr_node* servers = new ares_addr_node[len];
-  ares_addr_node* last = nullptr;
+  ares_addr_port_node* servers = new ares_addr_port_node[len];
+  ares_addr_port_node* last = nullptr;
 
   int err;
 
@@ -1974,12 +1979,15 @@ void SetServers(const FunctionCallbackInfo<Value>& args) {
 
     CHECK(elm->Get(0)->Int32Value());
     CHECK(elm->Get(1)->IsString());
+    CHECK(elm->Get(2)->Int32Value());
 
     int fam = elm->Get(0)->Int32Value();
     node::Utf8Value ip(env->isolate(), elm->Get(1));
+    int port = elm->Get(2)->Int32Value();
 
-    ares_addr_node* cur = &servers[i];
+    ares_addr_port_node* cur = &servers[i];
 
+    cur->tcp_port = cur->udp_port = port;
     switch (fam) {
       case 4:
         cur->family = AF_INET;
@@ -2005,7 +2013,7 @@ void SetServers(const FunctionCallbackInfo<Value>& args) {
   }
 
   if (err == 0)
-    err = ares_set_servers(env->cares_channel(), &servers[0]);
+    err = ares_set_servers_ports(env->cares_channel(), &servers[0]);
   else
     err = ARES_EBADSTR;
 

test/parallel/test-dns.js

@@ -35,6 +35,8 @@ assert.doesNotThrow(() => {
   servers[0] = '127.0.0.1';
   servers[2] = '0.0.0.0';
   dns.setServers(servers);
+
+  assert.deepStrictEqual(dns.getServers(), ['127.0.0.1', '0.0.0.0']);
 });
 
 assert.doesNotThrow(() => {
@@ -53,6 +55,11 @@ assert.doesNotThrow(() => {
   });
 
   dns.setServers(servers);
+  assert.deepStrictEqual(dns.getServers(), [
+    '127.0.0.1',
+    '192.168.1.1',
+    '0.0.0.0'
+  ]);
 });
 
 const goog = [
@@ -63,6 +70,8 @@ assert.doesNotThrow(() => dns.setServers(goog));
 assert.deepStrictEqual(dns.getServers(), goog);
 assert.throws(() => dns.setServers(['foobar']),
               /^Error: IP address is not properly formatted: foobar$/);
+assert.throws(() => dns.setServers(['127.0.0.1:va']),
+              /^Error: IP address is not properly formatted: 127\.0\.0\.1:va$/);
 assert.deepStrictEqual(dns.getServers(), goog);
 
 const goog6 = [
@@ -79,10 +88,14 @@ assert.deepStrictEqual(dns.getServers(), goog6);
 const ports = [
   '4.4.4.4:53',
   '[2001:4860:4860::8888]:53',
+  '103.238.225.181:666',
+  '[fe80::483a:5aff:fee6:1f04]:666'
 ];
 const portsExpected = [
   '4.4.4.4',
   '2001:4860:4860::8888',
+  '103.238.225.181:666',
+  '[fe80::483a:5aff:fee6:1f04]:666'
 ];
 dns.setServers(ports);
 assert.deepStrictEqual(dns.getServers(), portsExpected);