core/io: doh cache headers

GD2021 · Sep 27, 2024 · 45c0799 · 45c0799
1 parent cc6e798
commit 45c0799
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diff --git a/src/commons/dnsutil.js b/src/commons/dnsutil.js
@@ -377,6 +377,11 @@ export function isAnswerQuad0(packet) {
   return isAnswerBlocked(packet.answers);
 }
 
+export function ttl(packet) {
+  if (!hasAnswers(packet)) return 0;
+  return packet.answers[0].ttl || 0;
+}
+
 /**
  * @param {any} dnsPacket
  * @returns {string[]}

diff --git a/src/core/io-state.js b/src/core/io-state.js
@@ -191,6 +191,7 @@ export default class IOState {
     return util.concatHeaders(
       util.dnsHeaders(),
       util.contentLengthHeader(b),
+      this.cacheHeaders(),
       xNileRegion,
       xNileFlags,
       xNileFlagsOk
@@ -215,6 +216,16 @@ export default class IOState {
     }
   }
 
+  // set cache from ttl in decoded-dns-packet
+  cacheHeaders() {
+    const ttl = dnsutil.ttl(this.decodedDnsPacket);
+    if (ttl <= 0) return null;
+
+    return {
+      "cache-control": "public, max-age=" + ttl,
+    };
+  }
+
   assignBlockResponse() {
     let done = this.initFlagsAndAnswers();
     done = done && this.addData();