dns: make dns.setServers support customized port

Make `dns.setServers` parameter may be strings contain IP and port which
split by `:`.

eg.

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

And `dns.getServers` will return IP with port if that server is not use
default port.

Refs: nodejs#7903

lib/dns.js

@@ -301,7 +301,13 @@ function resolve(hostname, rrtype, callback) {
 
 
 function getServers() {
-  return cares.getServers();
+  const ret = cares.getServers();
+  return ret.map((val) => {
+    if (!val[1] || val[1] === 53) return val[0];
+
+    const ipVersion = isIP(val[0]);
+    return ipVersion === 6 ? `[${val[0]}]:${val[1]}` : `${val[0]}:${val[1]}`;
+  });
 }
 
 
@@ -311,26 +317,33 @@ 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, 53]);
 
     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 portMatch = serv.match(addrSplitRE) || [];
+        return newSet.push([ipVersion, match[1], parseInt(portMatch[1] || 53)]);
+      }
     }
 
     const s = serv.split(addrSplitRE)[0];
     ipVersion = isIP(s);
 
-    if (ipVersion !== 0)
-      return newSet.push([ipVersion, s]);
+    if (ipVersion !== 0) {
+      return newSet.push([
+        ipVersion,
+        s,
+        parseInt(serv.substr(serv.indexOf(':') + 1))
+      ]);
+    }
 
     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;