add test

tests/unit/net_test.ts

@@ -9,6 +9,7 @@ import {
   execCode2,
   tmpUnixSocketPath,
 } from "./test_util.ts";
+import dns2 from "npm:dns2@2.1.0";
 
 // Since these tests may run in parallel, ensure this port is unique to this file
 const listenPort = 4503;
@@ -1327,3 +1328,34 @@ Deno.test(
     // calling [Symbol.dispose] after manual close is a no-op
   },
 );
+
+Deno.test({ permissions: { net: true } }, async function resolveDnsEdns0() {
+  // With EDNS0 enabled, Deno.resolveDns can handle 44 A records.
+  const NUM_RECORD = 44;
+  const { Packet } = dns2;
+  const server = dns2.createServer({
+    udp: true,
+    // deno-lint-ignore no-explicit-any
+    handle(request: any, send: any) {
+      const response = Packet.createResponseFromRequest(request);
+      const { name } = request.questions[0];
+      for (const i of [...Array(NUM_RECORD).keys()]) {
+        response.answers.push({
+          name,
+          type: Packet.TYPE.A,
+          class: Packet.CLASS.IN,
+          ttl: 300,
+          address: "1.2.3." + i,
+        });
+      }
+      send(response);
+    },
+  });
+  const { udp: { port } } = await server.listen({
+    udp: { port: 0, address: "127.0.0.1", type: "udp4" },
+  });
+  const addr = await Deno.resolveDns("example.com", "A", {
+    nameServer: { ipAddr: "127.0.0.1", port },
+  });
+  await server.close();
+});