Merge pull request #2 from Jigsaw-Code/bemasc-srvfail

Fix query construction error

choir_test.go

@@ -288,6 +288,12 @@ func TestFormat(t *testing.T) {
 	if err := msg.Unpack(query); err != nil {
 		t.Fatal(err)
 	}
+	if msg.Header.OpCode != 0 {
+		t.Error("Message is not a question")
+	}
+	if !msg.Header.RecursionDesired {
+		t.Error("Query doesn't request recursion")
+	}
 	question := msg.Questions[0]
 	expectedQuestion := dnsmessage.Question{
 		Name:  dnsmessage.MustNewName(name + "."),

client.go

@@ -153,6 +153,7 @@ func formatQuery(name string) ([]byte, error) {
 	binary.BigEndian.PutUint16(ecsPayload[2:], ecsPrefixLength)
 
 	msg := &dnsmessage.Message{
+		Header: dnsmessage.Header{RecursionDesired: true},
 		Questions: []dnsmessage.Question{{
 			Name:  n,
 			Type:  dnsmessage.TypeTXT,

example/example_client.go

@@ -83,10 +83,31 @@ func (s udpDNSReportSender) Send(r choir.Report) error {
 	log.Printf("Querying %s via %s\n", name, s.serverAddress)
 	c, err := net.Dial("udp", s.serverAddress)
 	if err != nil {
-		log.Fatal("Failed to reach resolver:", err)
+		return fmt.Errorf("Failed to reach resolver: %w", err)
 	}
-	c.Write(query)
-	c.Close()
+	defer c.Close()
+
+	if _, err := c.Write(query); err != nil {
+		return fmt.Errorf("Query failed: %w", err)
+	}
+
+	var buf [4096]byte
+	c.SetReadDeadline(time.Now().Add(5 * time.Second))
+	n, err := c.Read(buf[:])
+	if err != nil {
+		return fmt.Errorf("Reading response failed: %w", err)
+	}
+
+	var response dnsmessage.Message
+	if err := response.Unpack(buf[:n]); err != nil {
+		return fmt.Errorf("Bad response: %w", err)
+	}
+	if response.Header.RCode != dnsmessage.RCodeNameError {
+		// We expect an NXDOMAIN response.  Anything else is surprising.
+		return fmt.Errorf("Unexpected response: %v", response.Header.RCode)
+	}
+
+	log.Printf("Report complete")
 	return nil
 }