From 5790a5028d710bf9507b601b99c29a383fb95b9e Mon Sep 17 00:00:00 2001
From: jared kantrowitz <jared.kantrowitz@gmail.com>
Date: Wed, 20 Dec 2017 12:43:52 -0500
Subject: [PATCH] dns, src: add --preserve-dns-order flag with NODE_OPTIONS
 whitelist

Added flag with NODE_OPTIONS whitelist to allow preserving lookup order
as retrieved from resolver. Still allows individual lookup requests with verbatim
flag assigned explicitly to override the config flag.

Open for suggestions on how to craft a test for this.

Refs: https://github.com/nodejs/node/pull/14731#issuecomment-321513375
---
 lib/dns.js           | 8 ++++++--
 src/node.cc          | 9 +++++++++
 src/node_config.cc   | 3 +++
 src/node_internals.h | 5 +++++
 4 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/lib/dns.js b/lib/dns.js
index 92b55f03595f45..c67823b8ac828a 100644
--- a/lib/dns.js
+++ b/lib/dns.js
@@ -24,6 +24,7 @@
 const util = require('util');
 
 const cares = process.binding('cares_wrap');
+const { preserveDnsOrder } = process.binding('config');
 const { isLegalPort } = require('internal/net');
 const { customPromisifyArgs } = require('internal/util');
 const errors = require('internal/errors');
@@ -128,7 +129,7 @@ function lookup(hostname, options, callback) {
   var hints = 0;
   var family = -1;
   var all = false;
-  var verbatim = false;
+  var verbatim = !!preserveDnsOrder;
 
   // Parse arguments
   if (hostname && typeof hostname !== 'string') {
@@ -143,7 +144,10 @@ function lookup(hostname, options, callback) {
     hints = options.hints >>> 0;
     family = options.family >>> 0;
     all = options.all === true;
-    verbatim = options.verbatim === true;
+
+    if (Object.prototype.hasOwnProperty.call(options, 'verbatim')) {
+      verbatim = options.verbatim === true;
+    }
 
     if (hints !== 0 &&
         hints !== cares.AI_ADDRCONFIG &&
diff --git a/src/node.cc b/src/node.cc
index 0027c0cc7b8fcf..27aab7c1b6675d 100644
--- a/src/node.cc
+++ b/src/node.cc
@@ -258,6 +258,11 @@ std::string config_warning_file;  // NOLINT(runtime/string)
 // that is used by lib/internal/bootstrap_node.js
 bool config_expose_internals = false;
 
+// Set in node.cc by ParseArgs when --preserve-dns-order is used.
+// Used in node_config.cc to set a constant on process.binding('config')
+// that is used by lib/dns.js
+bool config_preserve_dns_order = false;
+
 bool v8_initialized = false;
 
 bool linux_at_secure = false;
@@ -3626,6 +3631,7 @@ static void CheckIfAllowedInEnv(const char* exe, bool is_env,
     "--pending-deprecation",
     "--no-warnings",
     "--napi-modules",
+    "--preserve-dns-order",
     "--expose-http2",   // keep as a non-op through v9.x
     "--experimental-modules",
     "--loader",
@@ -3848,6 +3854,9 @@ static void ParseArgs(int* argc,
     } else if (strcmp(arg, "--expose-http2") == 0 ||
                strcmp(arg, "--expose_http2") == 0) {
       // Keep as a non-op through v9.x
+    } else if (strcmp(arg, "--preserve-dns-order") == 0 ||
+               strcmp(arg, "--preserve_dns_order") == 0) {
+      config_preserve_dns_order = true;
     } else if (strcmp(arg, "-") == 0) {
       break;
     } else if (strcmp(arg, "--") == 0) {
diff --git a/src/node_config.cc b/src/node_config.cc
index bf46444cabd107..238ecebcbf819e 100644
--- a/src/node_config.cc
+++ b/src/node_config.cc
@@ -88,6 +88,9 @@ static void InitConfig(Local<Object> target,
   if (config_expose_internals)
     READONLY_BOOLEAN_PROPERTY("exposeInternals");
 
+  if (config_preserve_dns_order)
+    READONLY_BOOLEAN_PROPERTY("preserveDnsOrder");
+
   READONLY_PROPERTY(target,
                     "bits",
                     Number::New(env->isolate(), 8 * sizeof(intptr_t)));
diff --git a/src/node_internals.h b/src/node_internals.h
index 09bcbba6e0b39f..dde960010946c8 100644
--- a/src/node_internals.h
+++ b/src/node_internals.h
@@ -171,6 +171,11 @@ extern bool config_preserve_symlinks;
 // that is used by lib/module.js
 extern bool config_experimental_modules;
 
+// Set in node.cc by ParseArgs when --preserve-dns-order is used.
+// Used in node_config.cc to set a constant on process.binding('config')
+// that is used by lib/dns.js
+extern bool config_preserve_dns_order;
+
 // Set in node.cc by ParseArgs when --loader is used.
 // Used in node_config.cc to set a constant on process.binding('config')
 // that is used by lib/internal/bootstrap_node.js