From aa8923b2c63b8b915762adb60566affb4c77a548 Mon Sep 17 00:00:00 2001
From: Razvan Dimescu <ssaricu@gmail.com>
Date: Mon, 30 Mar 2026 01:31:51 +0300
Subject: [PATCH] fix: add debug logging for DoT SERVFAIL serialization
 failure, TC-bit TODO

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 src/ctx.rs | 2 ++
 src/dot.rs | 1 +
 2 files changed, 3 insertions(+)

diff --git a/src/ctx.rs b/src/ctx.rs
index 5ad1bbc..d3d4eb0 100644
--- a/src/ctx.rs
+++ b/src/ctx.rs
@@ -310,6 +310,8 @@ pub async fn resolve_query(
     );
 
     // Serialize response
+    // TODO: TC bit is UDP-specific; DoT connections could carry up to 65535 bytes.
+    // Once BytePacketBuffer supports larger buffers, skip truncation for TCP/TLS.
     let mut resp_buffer = BytePacketBuffer::new();
     if response.write(&mut resp_buffer).is_err() {
         // Response too large — set TC bit and send header + question only
diff --git a/src/dot.rs b/src/dot.rs
index e10e7b7..d780727 100644
--- a/src/dot.rs
+++ b/src/dot.rs
@@ -175,6 +175,7 @@ where
                 resp.header.rescode = ResultCode::SERVFAIL;
                 let mut buf = BytePacketBuffer::new();
                 if resp.write(&mut buf).is_err() {
+                    debug!("DoT: failed to serialize SERVFAIL for {}", remote_addr);
                     break;
                 }
                 buf