Add support for MX queries in dns module, works with c-ares upstream patch.

lib/dns.js

@@ -124,6 +124,7 @@ exports.lookup = function (domain, callback) {
 
 exports.resolve4    = function(domain, callback) { channel.query(domain, dns.A, callback) };
 exports.resolve6    = function(domain, callback) { channel.query(domain, dns.AAAA, callback) };
+exports.resolveMx   = function(domain, callback) { channel.query(domain, dns.MX, callback) };
 exports.resolveTxt  = function(domain, callback) { channel.query(domain, dns.TXT, callback) };
 exports.resolveSrv  = function(domain, callback) { channel.query(domain, dns.SRV, callback) };
 exports.reverse     = function(domain, callback) { channel.query(domain, dns.PTR, callback) };
@@ -133,6 +134,7 @@ exports.resolveNs   = function(domain, callback) { channel.query(domain, dns.NS,
 var resolveMap = {
   'A'   : exports.resolve4,
   'AAAA': exports.resolve6,
+  'MX'  : exports.resolveMx,
   'TXT' : exports.resolveTxt,
   'SRV' : exports.resolveSrv,
   'PTR' : exports.resolvePtr,

src/node_cares.cc

@@ -86,6 +86,7 @@ static Persistent<String> weight_symbol;
 static Persistent<String> port_symbol;
 static Persistent<String> name_symbol;
 static Persistent<String> callback_symbol;
+static Persistent<String> exchange_symbol;
 
 
 void Cares::Initialize(Handle<Object> target) {
@@ -105,12 +106,14 @@ void Cares::Initialize(Handle<Object> target) {
   weight_symbol = NODE_PSYMBOL("weight");
   port_symbol = NODE_PSYMBOL("port");
   name_symbol = NODE_PSYMBOL("name");
+  exchange_symbol = NODE_PSYMBOL("exchange");
 
   target->Set(String::NewSymbol("AF_INET"), Integer::New(AF_INET));
   target->Set(String::NewSymbol("AF_INET6"), Integer::New(AF_INET6));
 
   target->Set(String::NewSymbol("A"), Integer::New(ns_t_a));
   target->Set(String::NewSymbol("AAAA"), Integer::New(ns_t_aaaa));
+  target->Set(String::NewSymbol("MX"), Integer::New(ns_t_mx));
   target->Set(String::NewSymbol("NS"), Integer::New(ns_t_ns));
   target->Set(String::NewSymbol("PTR"), Integer::New(ns_t_ptr));
   target->Set(String::NewSymbol("TXT"), Integer::New(ns_t_txt));
@@ -288,6 +291,34 @@ static void ParseAnswerAAAA(QueryArg *arg, unsigned char* abuf, int alen) {
   cb_call(arg->js_cb, 2, argv);
 }
 
+static void ParseAnswerMX(QueryArg *arg, unsigned char* abuf, int alen) {
+  HandleScope scope;
+
+  struct ares_mx_reply *mx_out;
+
+  int status = ares_parse_mx_reply(abuf, alen, &mx_out);
+  if (status != ARES_SUCCESS) {
+    ResolveError(arg->js_cb, status);
+    return;
+  }
+
+  Local<Array> mx_records = Array::New();
+
+  struct ares_mx_reply *current = mx_out;
+  for (int i = 0; current; ++i, current = current->next) {
+    Local<Object> mx = Object::New();
+
+    mx->Set(priority_symbol, Integer::New(current->priority));
+    mx->Set(exchange_symbol, String::New(current->host));
+
+    mx_records->Set(Integer::New(i), mx);
+  }
+  ares_free_data(mx_out);
+
+  Local<Value> argv[2] = { Local<Value>::New(Null()), mx_records };
+  cb_call(arg->js_cb, 2, argv);
+}
+
 
 static void ParseAnswerNS(QueryArg *arg, unsigned char* abuf, int alen) {
   HandleScope scope;
@@ -471,6 +502,10 @@ Handle<Value> Channel::Query(const Arguments& args) {
       parse_cb = ParseAnswerAAAA;
       break;
 
+    case ns_t_mx:
+      parse_cb = ParseAnswerMX;
+      break;
+
     case ns_t_ns:
       parse_cb = ParseAnswerNS;
       break;

test/disabled/test-dns.js

@@ -21,7 +21,7 @@ var hosts = ['example.com', 'example.org',
              '_xmpp-client._tcp.google.com', // SRV
              'oakalynhall.co.uk']; // Multiple PTR replies
 
-var records = ['A', 'AAAA', 'TXT', 'SRV'];
+var records = ['A', 'AAAA', 'MX', 'TXT', 'SRV'];
 
 var i = hosts.length;
 while (i--) {