fix: filter out duplicate dns results MONGOSH-2027

src/rfc-8252-http-server.spec.ts

@@ -1,4 +1,4 @@
-import { RFC8252HTTPServer } from './rfc-8252-http-server';
+import { getAllInterfaces, RFC8252HTTPServer } from './rfc-8252-http-server';
 import { expect } from 'chai';
 import type { Server as HTTPServer } from 'http';
 import { createServer as createHTTPServer } from 'http';
@@ -485,4 +485,58 @@ describe('RFC8252HTTPServer', function () {
       });
     });
   });
+
+  context('getAllInterfaces', function () {
+    let dnsLookupStub: sinon.SinonStub;
+    this.beforeEach(function () {
+      dnsLookupStub = sinon.stub();
+    });
+
+    it('filters out exact duplicates', async function () {
+      dnsLookupStub.resolves([
+        { address: '127.0.0.1', family: 4 },
+        { address: '127.0.0.1', family: 4 },
+        { address: '[::1]', family: 6 },
+        { address: '[::1]', family: 6 },
+      ]);
+
+      const interfaces = await getAllInterfaces('localhost', dnsLookupStub);
+
+      expect(interfaces).to.have.lengthOf(2);
+      expect(interfaces[0].address).to.equal('127.0.0.1');
+      expect(interfaces[1].address).to.equal('[::1]');
+      expect(interfaces[0].family).to.equal(4);
+      expect(interfaces[1].family).to.equal(6);
+    });
+
+    it('keeps same addresses, different family', async function () {
+      dnsLookupStub.resolves([
+        { address: '127.0.0.1', family: 4 },
+        { address: '127.0.0.1', family: 6 },
+      ]);
+
+      const interfaces = await getAllInterfaces('localhost', dnsLookupStub);
+
+      expect(interfaces).to.have.lengthOf(2);
+      expect(interfaces[0].address).to.equal('127.0.0.1');
+      expect(interfaces[1].address).to.equal('127.0.0.1');
+      expect(interfaces[0].family).to.equal(4);
+      expect(interfaces[1].family).to.equal(6);
+    });
+
+    it('keeps same familes, different address', async function () {
+      dnsLookupStub.resolves([
+        { address: '127.0.0.1', family: 4 },
+        { address: '192.168.1.15', family: 4 },
+      ]);
+
+      const interfaces = await getAllInterfaces('localhost', dnsLookupStub);
+
+      expect(interfaces).to.have.lengthOf(2);
+      expect(interfaces[0].address).to.equal('127.0.0.1');
+      expect(interfaces[1].address).to.equal('192.168.1.15');
+      expect(interfaces[0].family).to.equal(4);
+      expect(interfaces[1].family).to.equal(4);
+    });
+  });
 });

src/rfc-8252-http-server.ts

@@ -29,6 +29,26 @@ export interface RFC8252HTTPServerOptions {
   redirectServerRequestHandler?: RedirectServerRequestHandler;
 }
 
+export async function getAllInterfaces(
+  hostname: string,
+  lookup: typeof dns.lookup = dns.lookup
+): Promise<{ address: string; family: number }[]> {
+  const dnsResults = await lookup(hostname, {
+    all: true,
+    hints: ADDRCONFIG,
+  });
+
+  return dnsResults
+    .filter(
+      (dns, index, arr) =>
+        arr.findIndex(
+          (otherDns) =>
+            dns.address === otherDns.address && dns.family === otherDns.family
+        ) === index
+    )
+    .map(({ address, family }) => ({ address, family }));
+}
+
 /** @internal */
 export class RFC8252HTTPServer {
   private readonly redirectUrl: URL;
@@ -368,14 +388,11 @@ export class RFC8252HTTPServer {
     // to do what Node.js does by default when only a host is provided,
     // namely listening on all interfaces.
     let hostname = this.redirectUrl.hostname;
-    if (hostname.startsWith('[') && hostname.endsWith(']'))
+    if (hostname.startsWith('[') && hostname.endsWith(']')) {
       hostname = hostname.slice(1, -1);
-    const dnsResults = (
-      await dns.lookup(hostname, {
-        all: true,
-        hints: ADDRCONFIG,
-      })
-    ).map(({ address, family }) => ({ address, family }));
+    }
+
+    const dnsResults = await getAllInterfaces(hostname);
 
     this.logger.emit('mongodb-oidc-plugin:local-listen-resolved-hostname', {
       url: this.redirectUrl.toString(),