From 930786ed2e1bfbf34e6ee72d8cfcfd84c31aa2e5 Mon Sep 17 00:00:00 2001
From: Ximon Eighteen <3304436+ximon18@users.noreply.github.com>
Date: Thu, 3 Oct 2024 13:34:55 +0200
Subject: [PATCH] FIX: Servers should drop received DNS response messages, not
 propagate them for processing. (#381)

---
 src/net/server/connection.rs | 10 ++++++++++
 src/net/server/dgram.rs      | 13 ++++++++++++-
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/src/net/server/connection.rs b/src/net/server/connection.rs
index ec1f0a38..2997828d 100644
--- a/src/net/server/connection.rs
+++ b/src/net/server/connection.rs
@@ -670,6 +670,7 @@ where
 
                 match Message::from_octets(buf) {
                     Err(err) => {
+                        // TO DO: Count this event?
                         tracing::warn!(
                             "Failed while parsing request message: {err}"
                         );
@@ -678,6 +679,15 @@ where
                         ));
                     }
 
+                    // https://datatracker.ietf.org/doc/html/rfc1035#section-4.1.1
+                    // 4.1.1. Header section format
+                    //   "QR   A one bit field that specifies whether this
+                    //         message is a query (0), or a response (1)."
+                    Ok(msg) if msg.header().qr() => {
+                        // TO DO: Count this event?
+                        trace!("Ignoring received message because it is a reply, not a query.");
+                    }
+
                     Ok(msg) => {
                         let ctx = NonUdpTransportContext::new(Some(
                             self.config.load().idle_timeout,
diff --git a/src/net/server/dgram.rs b/src/net/server/dgram.rs
index cac9fc25..253a43f7 100644
--- a/src/net/server/dgram.rs
+++ b/src/net/server/dgram.rs
@@ -511,7 +511,18 @@ where
                     tokio::spawn(async move {
                         match Message::from_octets(buf) {
                             Err(err) => {
-                                tracing::warn!("Failed while parsing request message: {err}");
+                                // TO DO: Count this event?
+                                warn!("Failed while parsing request message: {err}");
+                            }
+
+                            // https://datatracker.ietf.org/doc/html/rfc1035#section-4.1.1
+                            // 4.1.1. Header section format
+                            //   "QR   A one bit field that specifies whether
+                            //         this message is a query (0), or a
+                            //         response (1)."
+                            Ok(msg) if msg.header().qr() => {
+                                // TO DO: Count this event?
+                                trace!("Ignoring received message because it is a reply, not a query.");
                             }
 
                             Ok(msg) => {