It is working now

_examples/q/fp.go

@@ -20,22 +20,22 @@ const (
 )
 
 func startParse(addr string) {
-        l := &lexer {
-                addr: addr,
-                client: dns.NewClient(),
-                fp: new(fingerprint),
-                items: make(chan item),
-                state: lexAlive,
-        }
+	l := &lexer{
+		addr:   addr,
+		client: dns.NewClient(),
+		fp:     new(fingerprint),
+		items:  make(chan item),
+		state:  dnsAlive,
+	}
 
-        l.run()
+	l.run()
 
-        // Not completely sure about this code..
+	// Not completely sure about this code..
 	for {
 		item := <-l.items
 		fmt.Printf("%v\n", item)
-	        if l.state == nil {
-                        break
+		if l.state == nil {
+			break
 		}
 	}
 }
@@ -46,14 +46,14 @@ func sendProbe(c *dns.Client, addr string, f *fingerprint, q dns.Question) *fing
 	m := f.toProbe(q)
 	r, err := c.Exchange(m, addr)
 	if err != nil {
-                return errorToFingerprint(err)
+		return errorToFingerprint(err)
 	}
 	return msgToFingerprint(r)
 }
 
 // This leads to strings like: "QUERY,NOERROR,qr,aa,tc,RD,ad,cd,z,1,0,0,1,DO,4096"
 type fingerprint struct {
-	Error             string
+	Error             os.Error
 	Opcode            int
 	Rcode             int
 	Response          bool
@@ -159,10 +159,21 @@ func (f *fingerprint) setString(str string) {
 	return
 }
 
+func (f *fingerprint) ok() bool {
+	return f.Error == nil
+}
+
+func (f *fingerprint) error() string {
+	if f.Error == nil {
+		panic("error is nil")
+	}
+	return f.Error.String()
+}
+
 func errorToFingerprint(e os.Error) *fingerprint {
-        f := new(fingerprint)
-        f.Error = e.String()
-        return f
+	f := new(fingerprint)
+	f.Error = e
+	return f
 }
 
 func msgToFingerprint(m *dns.Msg) *fingerprint {

_examples/q/lex.go

@@ -1,3 +1,7 @@
+// We handle the checking as a lexing program.
+// We use the lexer like Rob Pike lectures about in this
+// clip: http://www.youtube.com/watch?v=HxaD_trXwRE
+
 package main
 
 import (
@@ -6,16 +10,13 @@ import (
 
 type itemType int
 
-// We handle the checking as a lexing program.
-// We use the lexer like Rob Pike lectures about in this
-// clip: http://www.youtube.com/watch?v=HxaD_trXwRE
 type item struct {
 	typ itemType
 	val string
 }
 
 const (
-	_              itemType = iota
+	itemError      itemType = iota
 	itemVender              // software vendor
 	itemSoftware            // the name of the DNS server software
 	itemVersionMin          // the minimum version of the software (empty if not determined)
@@ -32,7 +33,6 @@ type lexer struct {
 	q      dns.Question // question to ask.
 	items  chan item    // channel of scanned items.
 	state  stateFn      // the next function to enter.
-	error  string       // error text.
 }
 
 func (l *lexer) probe() *fingerprint {
@@ -51,39 +51,42 @@ func (l *lexer) setQuestion(name string, t uint16, c uint16) {
 	l.q = dns.Question{name, t, c}
 }
 
-// Set the error
-func (l *lexer) setError(s string) {
-	l.error = s
-}
-
 func (l *lexer) run() {
 	go func() {
 		for l.state != nil {
-                        l.state = l.state(l)
+			l.state = l.state(l)
 		}
 		close(l.items)
 	}()
 }
 
-// "Lexer" functions
+// "Lexer" functions, prefixed with dns
 
 // Check if the server responds
-func lexAlive(l *lexer) stateFn {
+func dnsAlive(l *lexer) stateFn {
 	println("lexAlive")
+	l.setString("QUERY,NOERROR,qr,aa,tc,rd,ad,cd,z,1,0,0,0,do,0")
+	l.setQuestion(".", dns.TypeNS, dns.ClassINET)
 
-	//l.fp.SetString("QUERY,NOERROR,qr,aa,tc,RD,ad,cd,z,1,0,0,0,DO,0")
-	//l.q = dns.Question{".", dns.TypeNS, dns.ClassINET}
-	return lexDoBitMirror
+	f := l.probe()
+
+	if f.ok() {
+		return dnsDoBitMirror
+	}
+	l.emit(&item{itemError, f.error()})
+	return nil
 }
 
 // Check if the server returns the DO-bit when set in the request. 
-func lexDoBitMirror(l *lexer) stateFn {
+func dnsDoBitMirror(l *lexer) stateFn {
 	println("lexDoBitMirror")
 
 	// The important part here is that the DO bit is on
 	l.setString("QUERY,NOERROR,qr,aa,tc,RD,ad,cd,z,1,0,0,0,DO,0")
 	l.setQuestion(".", dns.TypeNS, dns.ClassINET)
-	if l.probe().Do {
+
+	f := l.probe()
+	if f.Do {
 		l.emit(&item{itemSoftware, NSD})
 	}
 	l.emit(&item{itemSoftware, BIND})