implement resolvePtr

src/node/dns.ts

@@ -13,7 +13,6 @@ import {
   resolve6,
   resolveAny,
   resolveNaptr,
-  resolvePtr,
   resolveSoa,
   resolveSrv,
   setDefaultResultOrder,
@@ -33,7 +32,6 @@ export {
   resolve6,
   resolveAny,
   resolveNaptr,
-  resolvePtr,
   resolveSoa,
   resolveSrv,
   setDefaultResultOrder,
@@ -47,6 +45,7 @@ export const resolveCaa = callbackify(dns.resolveCaa.bind(dns));
 export const resolveMx = callbackify(dns.resolveMx.bind(dns));
 export const resolveCname = callbackify(dns.resolveCname.bind(dns));
 export const resolveNs = callbackify(dns.resolveNs.bind(dns));
+export const resolvePtr = callbackify(dns.resolvePtr.bind(dns));
 
 export default {
   getServers,

src/node/dns/promises.ts

@@ -6,6 +6,7 @@ import {
   resolveMx,
   resolveCname,
   resolveNs,
+  resolvePtr,
 } from 'node-internal:internal_dns';
 
 export * from 'node-internal:internal_dns_constants';
@@ -16,6 +17,7 @@ export {
   resolveMx,
   resolveCname,
   resolveNs,
+  resolvePtr,
 } from 'node-internal:internal_dns';
 
 export default {
@@ -25,5 +27,6 @@ export default {
   resolveMx,
   resolveCname,
   resolveNs,
+  resolvePtr,
   ...errorCodes,
 };

src/node/internal/internal_dns.ts

@@ -124,16 +124,28 @@ export function resolveNs(name: string): Promise<string[]> {
   return sendDnsRequest(name, 'NS').then((json) => {
     if (!('Answer' in json)) {
       // DNS request should contain an "Answer" attribute, but it didn't.
-      throw new DnsError(name, errorCodes.NOTFOUND, 'queryMx');
+      throw new DnsError(name, errorCodes.NOTFOUND, 'queryNs');
     }
 
     // Cloudflare DNS appends "." at the end whereas Node.js doesn't.
     return json.Answer.map((a) => a.data.slice(0, -1));
   });
 }
 
-export function resolvePtr(): void {
-  throw new Error('Not implemented');
+export function resolvePtr(name: string): Promise<string[]> {
+  validateString(name, 'name');
+
+  // Validation errors needs to be sync.
+  // Return a promise rather than using async qualifier.
+  return sendDnsRequest(name, 'PTR').then((json) => {
+    if (!('Answer' in json)) {
+      // DNS request should contain an "Answer" attribute, but it didn't.
+      throw new DnsError(name, errorCodes.NOTFOUND, 'queryPtr');
+    }
+
+    // Cloudflare DNS appends "." at the end whereas Node.js doesn't.
+    return json.Answer.map((a) => a.data.slice(0, -1));
+  });
 }
 
 export function resolveSoa(): void {

src/workerd/api/node/tests/dns-nodejs-test.js

@@ -183,3 +183,20 @@ export const resolveNs = {
     validateResult(await dnsPromises.resolveNs(addresses.NS_HOST));
   },
 };
+
+// Tests are taken from
+// https://github.com/nodejs/node/blob/d7fdbb994cda8b2e1da4240eb97270c6abbaa9dd/test/internet/test-dns.js#L268
+export const resolvePtr = {
+  async test() {
+    function validateResult(result) {
+      ok(result.length > 0);
+
+      for (const item of result) {
+        ok(item);
+        strictEqual(typeof item, 'string');
+      }
+    }
+
+    validateResult(await dnsPromises.resolvePtr(addresses.PTR_HOST));
+  },
+};