Fix setting the rdlength for compressed names

RawSetRdlength was working with a 0xC00 bitmask which
should have been 0xC0.

TODO.markdown

@@ -8,6 +8,10 @@ need to be fixed.
 * Add handy zone data structure (r/b tree)? Or not...
 * Use the Exchange structure to deal with errors when resolving, esp. Timeout
 * Add tsig check in 'q'?
+* tsig and ip blocks should be handled in the library! Other configs may be
+  stored outside and are up to the programmer
+* Query source address, for axfr n stuff is something others
+* Compression is not working correctly
 
 ## Examples to add
 

ex/reflect/reflect.go

@@ -29,7 +29,10 @@ import (
 	"strconv"
 )
 
-var printf *bool
+var (
+	printf *bool
+	compress *bool
+)
 
 const dom = "whoami.miek.nl."
 
@@ -42,6 +45,7 @@ func handleReflect(w dns.ResponseWriter, r *dns.Msg) {
 	)
 	m := new(dns.Msg)
 	m.SetReply(r)
+	m.Compress = *compress
 	if ip, ok := w.RemoteAddr().(*net.UDPAddr); ok {
 		str = "Port: " + strconv.Itoa(ip.Port) + " (udp)"
 		a = ip.IP
@@ -103,6 +107,7 @@ func serve(net string) {
 func main() {
 	cpuprofile := flag.String("cpuprofile", "", "write cpu profile to file")
 	printf = flag.Bool("print", false, "print replies")
+	compress = flag.Bool("compress", false, "compress replies")
 	flag.Usage = func() {
 		flag.PrintDefaults()
 	}

msg.go

@@ -193,26 +193,20 @@ var Rcode_str = map[int]string{
 
 // PackDomainName packs a domain name s into msg[off:].
 // If compression is wanted compress must be true and the compression
-// map, needs to hold a mapping between domain names and offsets
+// map needs to hold a mapping between domain names and offsets
 // pointing into msg[].
 func PackDomainName(s string, msg []byte, off int, compression map[string]int, compress bool) (off1 int, ok bool) {
 	// Add trailing dot to canonicalize name.
 	lenmsg := len(msg)
 	if n := len(s); n == 0 || s[n-1] != '.' {
-		//println("hier? s", s)
-		//return lenmsg, false // This is an error, should be fqdn
+		// Make it fully qualified
 		s += "."
 	}
-
 	// Each dot ends a segment of the name.
 	// We trade each dot byte for a length byte.
 	// Except for escaped dots (\.), which are normal dots.
 	// There is also a trailing zero.
-	// Check that we have all the space we need.
-	tot := len(s) + 1 // TODO: this too much for compression...
-	if off+tot > lenmsg {
-		return lenmsg, false
-	}
+
 	// Compression
 	nameoffset := -1
 	pointer := -1
@@ -238,9 +232,15 @@ func PackDomainName(s string, msg []byte, off int, compression map[string]int, c
 			msg[off] = byte(i - begin)
 			offset := off
 			off++
+			if off > lenmsg {
+				return lenmsg, false
+			}
 			for j := begin; j < i; j++ {
 				msg[off] = bs[j]
 				off++
+				if off > lenmsg {
+					return lenmsg, false
+				}
 			}
 			// Dont try to compress '.'
 			if string(bs[begin:]) != "." && compression != nil {
@@ -259,7 +259,7 @@ func PackDomainName(s string, msg []byte, off int, compression map[string]int, c
 					if pointer == -1 && compress {
 						pointer = p         // Where to point to
 						nameoffset = offset // Where to point from
-						// println("Compressing:", string(bs[begin:]))
+						break
 					}
 				}
 			}

rawmsg.go

@@ -24,7 +24,7 @@ Loop:
 		}
 		c := int(msg[off])
 		off++
-		switch c & 0xC00 {
+		switch c & 0xC0 {
 		case 0x00:
 			if c == 0x00 {
 				// End of the domainname