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src/dns.rs

@@ -16,14 +16,17 @@ const DNS_FLAGS_RA: u16 = 1u16 << 7;
 const DNS_FLAGS_RD: u16 = 1u16 << 8;
 const DNS_FLAGS_CD: u16 = 1u16 << 4;
 const DNS_OFFSET_QUESTION: usize = DNS_HEADER_SIZE;
-const DNS_TYPE_OPT: u16 = 41;
-const DNS_TYPE_TXT: u16 = 16;
-const DNS_TYPE_HINFO: u16 = 13;
-const DNS_CLASS_INET: u16 = 1;
 
-const DNS_RCODE_SERVFAIL: u8 = 2;
-const DNS_RCODE_NXDOMAIN: u8 = 3;
-const DNS_RCODE_REFUSED: u8 = 5;
+pub const DNS_TYPE_A: u16 = 1;
+pub const DNS_TYPE_AAAA: u16 = 28;
+pub const DNS_TYPE_OPT: u16 = 41;
+pub const DNS_TYPE_TXT: u16 = 16;
+pub const DNS_TYPE_HINFO: u16 = 13;
+pub const DNS_CLASS_INET: u16 = 1;
+
+pub const DNS_RCODE_SERVFAIL: u8 = 2;
+pub const DNS_RCODE_NXDOMAIN: u8 = 3;
+pub const DNS_RCODE_REFUSED: u8 = 5;
 
 #[inline]
 pub fn rcode(packet: &[u8]) -> u8 {
@@ -478,6 +481,16 @@ pub fn serve_truncated_response(client_packet: Vec<u8>) -> Result<Vec<u8>, Error
     Ok(packet)
 }
 
+pub fn qtype_qclass(packet: &[u8]) -> Result<(u16, u16), Error> {
+    ensure!(packet.len() >= DNS_HEADER_SIZE, "Short packet");
+    ensure!(qdcount(&packet) == 1, "No question");
+    let offset = skip_name(packet, DNS_HEADER_SIZE)?;
+    ensure!(packet.len() - offset >= 4, "Short packet");
+    let qtype = BigEndian::read_u16(&packet[offset..]);
+    let qclass = BigEndian::read_u16(&packet[offset + 2..]);
+    Ok((qtype, qclass))
+}
+
 pub fn serve_nxdomain_response(client_packet: Vec<u8>) -> Result<Vec<u8>, Error> {
     ensure!(client_packet.len() >= DNS_HEADER_SIZE, "Short packet");
     ensure!(qdcount(&client_packet) == 1, "No question");

src/resolver.rs

@@ -170,12 +170,28 @@ pub async fn get_cached_response_or_resolve(
             return dns::serve_blocked_response(packet.to_vec());
         }
     }
-    if let Some(undelegated_list) = &globals.undelegated_list {
-        if undelegated_list.find(dns::qname_tld(&packet_qname)) {
-            #[cfg(feature = "metrics")]
-            globals.varz.client_queries_rcode_nxdomain.inc();
-            return dns::serve_nxdomain_response(packet.to_vec());
+    let tld = dns::qname_tld(&packet_qname);
+    let synthesize_nxdomain = {
+        if tld.len() == packet_qname.len() {
+            let (qtype, qclass) = dns::qtype_qclass(&packet)?;
+            if qtype == dns::DNS_CLASS_INET
+                && (qclass == dns::DNS_TYPE_A || qclass == dns::DNS_TYPE_AAAA)
+            {
+                dbg!(String::from_utf8_lossy(&packet_qname));
+                true
+            } else {
+                false
+            }
+        } else if let Some(undelegated_list) = &globals.undelegated_list {
+            undelegated_list.find(tld)
+        } else {
+            false
         }
+    };
+    if synthesize_nxdomain {
+        #[cfg(feature = "metrics")]
+        globals.varz.client_queries_rcode_nxdomain.inc();
+        return dns::serve_nxdomain_response(packet.to_vec());
     }
     let original_tid = dns::tid(&packet);
     dns::set_tid(&mut packet, 0);