src,dns: refactor cares_wrap to avoid global state

PR-URL: #14518
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>

Author: addaleax

lib/dns.js

@@ -28,11 +28,16 @@ const uv = process.binding('uv');
 const internalNet = require('internal/net');
 const { customPromisifyArgs } = require('internal/util');
 
-const GetAddrInfoReqWrap = cares.GetAddrInfoReqWrap;
-const GetNameInfoReqWrap = cares.GetNameInfoReqWrap;
-const QueryReqWrap = cares.QueryReqWrap;
+const {
+  GetAddrInfoReqWrap,
+  GetNameInfoReqWrap,
+  QueryReqWrap,
+  ChannelWrap,
+  isIP
+} = cares;
+
+const defaultChannel = new ChannelWrap();
 
-const isIP = cares.isIP;
 const isLegalPort = internalNet.isLegalPort;
 
 
@@ -240,8 +245,6 @@ function onresolve(err, result, ttls) {
 
 
 function resolver(bindingName) {
-  var binding = cares[bindingName];
-
   return function query(name, /* options, */ callback) {
     var options;
     if (arguments.length > 2) {
@@ -261,7 +264,7 @@ function resolver(bindingName) {
     req.hostname = name;
     req.oncomplete = onresolve;
     req.ttl = !!(options && options.ttl);
-    var err = binding(req, name);
+    var err = defaultChannel[bindingName](req, name);
     if (err) throw errnoException(err, bindingName);
     return req;
   };
@@ -303,7 +306,7 @@ function resolve(hostname, type_, callback_) {
 
 
 function getServers() {
-  const ret = cares.getServers();
+  const ret = defaultChannel.getServers();
   return ret.map((val) => {
     if (!val[1] || val[1] === IANA_DNS_PORT) return val[0];
 
@@ -316,7 +319,7 @@ function getServers() {
 function setServers(servers) {
   // cache the original servers because in the event of an error setting the
   // servers cares won't have any servers available for resolution
-  const orig = cares.getServers();
+  const orig = defaultChannel.getServers();
   const newSet = [];
   const IPv6RE = /\[(.*)\]/;
   const addrSplitRE = /(^.+?)(?::(\d+))?$/;
@@ -348,11 +351,11 @@ function setServers(servers) {
     throw new Error(`IP address is not properly formatted: ${serv}`);
   });
 
-  const errorNumber = cares.setServers(newSet);
+  const errorNumber = defaultChannel.setServers(newSet);
 
   if (errorNumber !== 0) {
     // reset the servers to the old servers, because ares probably unset them
-    cares.setServers(orig.join(','));
+    defaultChannel.setServers(orig.join(','));
 
     var err = cares.strerror(errorNumber);
     throw new Error(`c-ares failed to set servers: "${err}" [${servers}]`);

src/async-wrap.h

@@ -36,6 +36,7 @@ namespace node {
 
 #define NODE_ASYNC_NON_CRYPTO_PROVIDER_TYPES(V)                               \
   V(NONE)                                                                     \
+  V(DNSCHANNEL)                                                               \
   V(FSEVENTWRAP)                                                              \
   V(FSREQWRAP)                                                                \
   V(GETADDRINFOREQWRAP)                                                       \