fix(Message): Honour rcode when serialising message (#135)

By working around bug in dns-packet.

src/lib/utils/dns/Message.spec.ts

@@ -219,12 +219,12 @@ describe('Message', () => {
   describe('serialise', () => {
     describe('Header', () => {
       test('RCODE should be honoured', () => {
-        const message = new Message({ rcode: RCODE_IDS.NOERROR }, [], []);
+        const message = new Message({ rcode: RCODE_IDS.NXDOMAIN }, [], []);
 
         const serialisation = message.serialise();
 
         const messageDeserialised = decode(serialisation);
-        expect(messageDeserialised.rcode).toBe('NOERROR');
+        expect(messageDeserialised.rcode).toBe('NXDOMAIN');
       });
     });
 

src/lib/utils/dns/Message.ts

@@ -14,7 +14,7 @@ import { DnsError } from './DnsError.js';
 import type { IanaRrTypeName } from './ianaRrTypes.js';
 import type { DnsClassName } from './ianaClasses.js';
 import type { RcodeName } from './ianaRcodes.js';
-import { getRcodeId, getRcodeName } from './ianaRcodes.js';
+import { getRcodeId } from './ianaRcodes.js';
 import { getRrTypeName } from './ianaRrTypes.js';
 import { getDnsClassName } from './ianaClasses.js';
 
@@ -46,7 +46,7 @@ export class Message {
           answer.type,
           answer.class as DnsClassName,
           answer.ttl!,
-          answer.data as object,
+          answer.data,
         ),
     );
     return new Message({ rcode }, questions, answers);
@@ -59,7 +59,6 @@ export class Message {
   ) {}
 
   public serialise(): Uint8Array {
-    const rcode = getRcodeName(this.header.rcode);
     const questions: DpQuestion[] = this.questions.map((question) => ({
       name: question.name,
       type: question.getTypeName(),
@@ -71,7 +70,11 @@ export class Message {
       class: getDnsClassName(answer.classId) as RecordClass,
       data: answer.dataFields,
     }));
-    return encode({ rcode, questions, answers });
+    return encode({
+      flags: this.header.rcode, // `rcode` field has no effect, so we have to pass it in the flags
+      questions,
+      answers,
+    });
   }
 
   /**

src/lib/utils/dns/ianaRcodes.spec.ts

@@ -1,5 +1,5 @@
 import type { RcodeIdOrName } from './ianaRcodes.js';
-import { getRcodeId, getRcodeName, RCODE_IDS } from './ianaRcodes.js';
+import { getRcodeId, RCODE_IDS } from './ianaRcodes.js';
 import { DnsError } from './DnsError.js';
 
 describe('getRcodeId', () => {
@@ -24,18 +24,3 @@ describe('getRcodeId', () => {
     );
   });
 });
-
-describe('getRcodeName', () => {
-  test('Id should be converted to name', () => {
-    expect(getRcodeName(RCODE_IDS.NOERROR)).toBe('NOERROR');
-  });
-
-  test('Id not defined by IANA should cause an error', () => {
-    const invalidId = Math.max(...Object.values(RCODE_IDS)) + 1;
-
-    expect(() => getRcodeName(invalidId)).toThrowWithMessage(
-      DnsError,
-      `DNS RCode id ${invalidId} is not defined by IANA`,
-    );
-  });
-});

src/lib/utils/dns/ianaRcodes.ts

@@ -37,10 +37,6 @@ const RCODE_IDS_NORMALISED: { readonly [name: string]: number } = Object.entries
   {},
 );
 
-const RCODE_NAMES: { readonly [name: number]: RcodeName } = Object.fromEntries(
-  Object.entries(RCODE_IDS_NORMALISED).map(([name, id]) => [id, name as RcodeName]),
-);
-
 export function getRcodeId(codeName: RcodeIdOrName): number {
   if (typeof codeName === 'number') {
     return codeName;
@@ -54,11 +50,3 @@ export function getRcodeId(codeName: RcodeIdOrName): number {
 
   return id;
 }
-
-export function getRcodeName(codeId: number): RcodeName {
-  const name = RCODE_NAMES[codeId] as RcodeName | undefined;
-  if (!name) {
-    throw new DnsError(`DNS RCode id ${codeId} is not defined by IANA`);
-  }
-  return name;
-}