Better handle error in pack/unpacking

TODO

@@ -8,5 +8,9 @@ Todo:
 * query-time, server in string ouput of dns.Msg
 
 Issues:
+* completely fix EDNS
 * shortened ipv6 addresses are not parsed correctly
 * quoted quotes in txt records
+* Convience functions?
+    - for new(RR*)
+    - ...

_examples/q/q.go

@@ -1,5 +1,8 @@
 package main
 
+// TODO
+// error handling and dns errors should be displayed
+
 import (
 	"net"
 	"dns"
@@ -10,13 +13,13 @@ import (
         "strings"
 )
 
-var Usage = func() {
-	fmt.Fprintf(os.Stderr, "Usage: %s [@server] [qtype] [qclass] [name ...]\n", os.Args[0])
-	flag.PrintDefaults()
-}
-
 func main() {
 	var dnssec *bool = flag.Bool("dnssec", false, "Set the DO (DNSSEC OK) bit and set the bufsize to 4096")
+        flag.Usage = func() {
+                fmt.Fprintf(os.Stderr, "Usage: %s [@server] [qtype] [qclass] [name ...]\n", os.Args[0])
+                flag.PrintDefaults()
+        }
+
 	nameserver := "127.0.0.1"       // Default nameserver
 	qtype := uint16(dns.TypeA)      // Default qtype
 	qclass := uint16(dns.ClassINET) // Default qclass
@@ -24,9 +27,6 @@ func main() {
 
 	flag.Parse()
 
-	if *dnssec {
-		/* */
-	}
 FLAGS:
 	for i := 0; i < flag.NArg(); i++ {
 		// If it starts with @ it is a nameserver
@@ -67,6 +67,15 @@ FLAGS:
 
 	m := new(dns.Msg)
 	m.Question = make([]dns.Question, 1)
+	if *dnssec {
+                opt := new(dns.RR_OPT)
+                opt.Hdr = dns.RR_Header{Name: "", Rrtype: dns.TypeOPT}
+                opt.Version(0, true)
+                opt.DoBit(true, true)
+                opt.UDPSize(4096, true)
+		m.Extra = make([]dns.RR, 1)
+                m.Extra[0] = opt
+	}
 	for _, v := range qname {
 		m.Question[0] = dns.Question{v, qtype, qclass}
 		qr <- resolver.DnsMsg{m, nil}

msg.go

@@ -476,6 +476,10 @@ func unpackStruct(any interface{}, msg []byte, off int) (off1 int, ok bool) {
 
 // Resource record packer.
 func packRR(rr RR, msg []byte, off int) (off2 int, ok bool) {
+        if rr == nil {
+                return len(msg), false
+        }
+
 	var off1 int
 	// pack twice, once to find end of header
 	// and again to find end of packet.
@@ -647,10 +651,10 @@ func (dns *Msg) Pack() (msg []byte, ok bool) {
 	off := 0
 	off, ok = packStruct(&dh, msg, off)
 	for i := 0; i < len(question); i++ {
-		off, ok = packStruct(&question[i], msg, off)
+                off, ok = packStruct(&question[i], msg, off)
 	}
 	for i := 0; i < len(answer); i++ {
-		off, ok = packRR(answer[i], msg, off)
+                off, ok = packRR(answer[i], msg, off)
 	}
 	for i := 0; i < len(ns); i++ {
 		off, ok = packRR(ns[i], msg, off)
@@ -661,7 +665,7 @@ func (dns *Msg) Pack() (msg []byte, ok bool) {
 	if !ok {
 		return nil, false
 	}
-	return msg[0:off], true
+	return msg[:off], true
 }
 
 func (dns *Msg) Unpack(msg []byte) bool {

resolver/resolver.go

@@ -88,8 +88,9 @@ func query(res *Resolver, msg chan DnsMsg) {
 			out.Dns.Id = uint16(rand.Int()) ^ uint16(time.Nanoseconds())
 			sending, ok := out.Dns.Pack()
 			if !ok {
+                        println("pack failed")
 				msg <- DnsMsg{nil, nil} // todo error
-                                return
+                                continue;
 			}
 
 			for i := 0; i < len(res.Servers); i++ {