RFC correctness improvements

- feat(packet): encode name compression pointers (RFC 1035 §4.1.4)
- feat(server/udp): negotiated UDP payload size with TC=1 on oversize
- feat(server/tcp): pipeline support (RFC 7766 §6.2.1.1)
- feat(packet): EDNS extended RCODE supported
- fix(packet): EDNS default UDP payload size raised to 4096
- fix(packet): clamps TTLs to 2³¹−1
- fix(packet): Label and name length validation (RFC 1035 §2.3.4)
- fix(server/doh): accepts any (or absent) Accept header (RFC 8484 §4.1)
- fix(server/doh): DoH POST requires Content-Type: application/dns-message
- feat(server/doh): DoH responses include TTL-derived Cache-Control
- fix(packet): Packet.Header.toBuffer writes Z=0 (RFC 1035 §4.1.1)

Author: msimerson

CHANGELOG.md

@@ -4,6 +4,18 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/).
 
 ### Unreleased
 
+- feat(packet): encode name compression pointers (RFC 1035 §4.1.4)
+- feat(server/udp): negotiated UDP payload size with TC=1 on oversize
+- feat(server/tcp): pipeline support (RFC 7766 §6.2.1.1)
+- feat(packet): EDNS extended RCODE supported
+- fix(packet): EDNS default UDP payload size raised to 4096
+- fix(packet): clamps TTLs to 2³¹−1
+- fix(packet): Label and name length validation (RFC 1035 §2.3.4)
+- fix(server/doh): accepts any (or absent) Accept header (RFC 8484 §4.1)
+- fix(server/doh): DoH POST requires Content-Type: application/dns-message
+- feat(server/doh): DoH responses include TTL-derived Cache-Control
+- fix(packet): Packet.Header.toBuffer writes Z=0 (RFC 1035 §4.1.1)
+
 ### [2.3.0] - 2026-05-25
 
 - fix(packet): IPv6 `::` compression for leading-zero address #123
@@ -57,5 +69,6 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/).
 - fix(packet): ensure compressed IPv6 is valid #70
 - doc(README): correct `server.listen` options
 
+[2.3.0]: https://github.com/lsongdev/node-dns/releases/tag/v2.3.0
 [2.2.0]: https://github.com/lsongdev/node-dns/releases/tag/v2.2.0
 [2.2.1]: https://github.com/lsongdev/node-dns/releases/tag/v2.2.1

lib/writer.js

@@ -25,6 +25,25 @@ BufferWriter.prototype.writeBuffer = function(b) {
   this.buffer = this.buffer.concat(b.buffer);
 };
 
+// Current write position, in bits.
+BufferWriter.prototype.bitLength = function() {
+  return this.buffer.length;
+};
+
+// Current write position, in bytes. Defined when DNS encoding has stayed on
+// byte boundaries (it always does at the points we expose this).
+BufferWriter.prototype.byteLength = function() {
+  return this.buffer.length / 8;
+};
+
+// Overwrite `size` bits at `bitOffset` with `value`. Used to back-fill
+// placeholders (e.g. RDLENGTH) once the field's contents have been written.
+BufferWriter.prototype.patch = function(bitOffset, value, size) {
+  for (let i = 0; i < size; i++) {
+    this.buffer[bitOffset + i] = (value & Math.pow(2, size - i - 1)) ? 1 : 0;
+  }
+};
+
 /**
  * [toBuffer description]
  * @return {[type]} [description]