dns: validate arguments in resolve

Mitigat  C++-land assertion error, add test accordingly.

fix #7070

lib/dns.js

@@ -146,6 +146,11 @@ function resolver(bindingName) {
       if (!status) {
         callback(null, result);
       } else {
+        if (!util.isString(name))
+          throw new Error('Name must be a string')
+        else if (!util.isFunction(callback))
+          throw new Error('Callback must be a function')
+
         callback(errnoException(process._errno, bindingName));
       }
     }

test/simple/test-dns-regress-7070.js

@@ -0,0 +1,27 @@
+// Copyright Joyent, Inc. and other Node contributors.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the
+// "Software"), to deal in the Software without restriction, including
+// without limitation the rights to use, copy, modify, merge, publish,
+// distribute, sublicense, and/or sell copies of the Software, and to permit
+// persons to whom the Software is furnished to do so, subject to the
+// following conditions:
+//
+// The above copyright notice and this permission notice shall be included
+// in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
+// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
+// USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+var common = require('../common');
+var dns = require('dns');
+
+// Should not raise assertion error. Issue #7070
+assert.throws(function () { dns.resolveNs([]) }); // bad name
+assert.throws(function () { dns.resolveNs("") }); // bad callback