Add Support for resolving DNS using search list for host-name loopkup.

lib: dns.js - passing the search field form the options object to
              QueryReqWrap object.

src:
base_object.h - added GetField function to read fields from the
                persistent object (persistent QueryReqWrap object).

cares_wrap.cc - added a AresSearch function.
              - QueryAWrap (resolve4) and QueryAaaaWrap (resolve6)
              utilizes the AresSearch when options.search is true.

doc/api: added search option to the resolve4 and resolve6 documentation

Fixes: nodejs#17850

doc/api/dns.md

@@ -285,6 +285,9 @@ changes:
     When `true`, the callback receives an array of
     `{ address: '1.2.3.4', ttl: 60 }` objects rather than an array of strings,
     with the TTL expressed in seconds.
+  - `search` {boolean} Resolve the DNS using the local domain name or the search 
+    list for host-name lookup.
+    When `true`, the resolve will use the search list which can create extra dns queries.
 - `callback` {Function}
   - `err` {Error}
   - `addresses` {string[] | Object[]}
@@ -310,6 +313,9 @@ changes:
     When `true`, the callback receives an array of
     `{ address: '0:1:2:3:4:5:6:7', ttl: 60 }` objects rather than an array of
     strings, with the TTL expressed in seconds.
+  - `search` {boolean} Resolve the DNS using the local domain name or the search 
+    list for host-name lookup.
+    When `true`, the resolve will use the search list which can create extra dns queries.
 - `callback` {Function}
   - `err` {Error}
   - `addresses` {string[] | Object[]}

lib/dns.js

@@ -228,6 +228,7 @@ function resolver(bindingName) {
     req.hostname = name;
     req.oncomplete = onresolve;
     req.ttl = !!(options && options.ttl);
+    req.search = !!(options && options.search);
     var err = this._handle[bindingName](req, name);
     if (err) throw dnsException(err, bindingName);
     return req;

src/base_object-inl.h

@@ -52,6 +52,15 @@ inline v8::Local<v8::Object> BaseObject::object() {
 }
 
 
+inline v8::MaybeLocal<v8::Value> BaseObject::GetField(
+        std::string const&  field) {
+    return object()->Get(env()->context(),
+                    v8::String::NewFromUtf8(env()->isolate(),
+                    field.c_str(),
+                    v8::NewStringType::kNormal).ToLocalChecked());
+}
+
+
 inline Environment* BaseObject::env() const {
   return env_;
 }

src/base_object.h

@@ -40,6 +40,8 @@ class BaseObject {
   // persistent.IsEmpty() is true.
   inline v8::Local<v8::Object> object();
 
+  inline v8::MaybeLocal<v8::Value> GetField(std::string const& field);
+
   inline Persistent<v8::Object>& persistent();
 
   inline Environment* env() const;

src/cares_wrap.cc

@@ -619,6 +619,14 @@ class QueryWrap : public AsyncWrap {
                static_cast<void*>(this));
   }
 
+  void AresSearch(const char* name,
+                  int dnsclass,
+                  int type) {
+    channel_->EnsureServers();
+    ares_search(channel_->cares_channel(), name, dnsclass, type, Callback,
+                static_cast<void*>(this));
+  }
+
   static void CaresAsyncClose(uv_handle_t* handle) {
     uv_async_t* async = reinterpret_cast<uv_async_t*>(handle);
     auto data = static_cast<struct CaresAsyncData*>(async->data);
@@ -1360,7 +1368,20 @@ class QueryAWrap: public QueryWrap {
   }
 
   int Send(const char* name) override {
-    AresQuery(name, ns_c_in, ns_t_a);
+    auto prop_value = GetField("search");
+    bool bSearch = false;
+
+    if (!prop_value.IsEmpty()) {
+      auto search_prop = prop_value.ToLocalChecked()->ToBoolean();
+      bSearch = search_prop->Value();
+    }
+
+    if (bSearch) {
+      AresSearch(name, ns_c_in, ns_t_a);
+    } else {
+      AresQuery(name, ns_c_in, ns_t_a);
+    }
+
     return 0;
   }
 
@@ -1404,7 +1425,20 @@ class QueryAaaaWrap: public QueryWrap {
   }
 
   int Send(const char* name) override {
-    AresQuery(name, ns_c_in, ns_t_aaaa);
+    auto prop_value = GetField("search");
+    bool bSearch = false;
+
+    if (!prop_value.IsEmpty()) {
+      auto search_prop = prop_value.ToLocalChecked()->ToBoolean();
+      bSearch = search_prop->Value();
+    }
+
+    if (bSearch) {
+      AresSearch(name, ns_c_in, ns_t_a);
+    } else {
+      AresQuery(name, ns_c_in, ns_t_a);
+    }
+
     return 0;
   }
 

test/internet/test-dns.js

@@ -76,7 +76,7 @@ TEST(function test_reverse_bogus(done) {
 
 TEST(function test_resolve4_ttl(done) {
   const req = dns.resolve4(addresses.INET4_HOST, {
-    ttl: true
+    ttl: true, search: false
   }, function(err, result) {
     assert.ifError(err);
     assert.ok(result.length > 0);
@@ -99,7 +99,7 @@ TEST(function test_resolve4_ttl(done) {
 
 TEST(function test_resolve6_ttl(done) {
   const req = dns.resolve6(addresses.INET6_HOST, {
-    ttl: true
+    ttl: true, search: false
   }, function(err, result) {
     assert.ifError(err);
     assert.ok(result.length > 0);