recursor_test: backfill a test for CNAMEs which point to nonexistent records

tests/integration-tests/tests/recursor_tests.rs

@@ -24,12 +24,13 @@ use hickory_client::op::{Message, MessageType, Query};
 use hickory_client::rr::{rdata, Name, RData, Record, RecordType};
 use hickory_integration::mock_client::*;
 use hickory_proto::DnsHandle;
-use hickory_proto::error::ProtoError;
+use hickory_proto::error::{ProtoError, ProtoErrorKind};
 use hickory_proto::rr::LowerName;
 use hickory_proto::serialize::txt::Parser;
 use hickory_proto::xfer::{DnsRequest, DnsResponse};
 use hickory_recursor::{ErrorKind, Recursor};
 use hickory_resolver::config::*;
+use hickory_resolver::error::ResolveErrorKind;
 use hickory_resolver::name_server::ConnectionProvider;
 use hickory_resolver::name_server::{NameServer, NameServerPool};
 use hickory_server::authority::{Catalog, LookupError, LookupOptions, ZoneType};
@@ -107,6 +108,7 @@ example-org-cname.example.com. CNAME example.org.
 inline-org-cname.example.com.  CNAME inline.org.
 double-cname.sub.example.com.  CNAME inline-org-cname.example.org.
 cycle-a.example.com.           CNAME cycle-b.org.
+intractable-cname.example.com. CNAME nonexistent.org.
 "#;
 
 const ZONE_ORG: &str = r#"
@@ -604,3 +606,30 @@ fn test_cname_cycle() {
 
     assert!(matches!(lookup_err.kind(), ErrorKind::Timeout));
 }
+
+/// Test that the recursor responds with an error when following CNAMEs to non-existent records,
+/// rather than (for example) returning partial results.
+#[test]
+fn test_cname_to_nonexistent_record() {
+    logger("DEBUG");
+
+    let query = Query::query(Name::from_str("intractable-cname.example.com.").unwrap(), RecordType::A);
+
+    let roots = NameServerPool::from_nameservers(
+        Default::default(),
+        vec![mock_nameserver(NS_ROOT)],
+        vec![],
+    );
+    let recursor = Recursor::new_with_pool(roots, 1024, 1048576).unwrap();
+
+    let now = Instant::now();
+    let lookup_err = block_on(recursor.resolve(query, now)).unwrap_err();
+
+    assert!(matches!(lookup_err.kind(),
+        ErrorKind::Resolve(resolve_error) if matches!(resolve_error.kind(),
+            ResolveErrorKind::Proto(proto_error) if matches!(proto_error.kind(),
+                ProtoErrorKind::NoRecordsFound { .. }
+            )
+        )
+    ));
+}