internal/ndpcmd: implement Nonce handling

Signed-off-by: Matt Layher <mdlayher@gmail.com>

internal/ndpcmd/print.go

@@ -137,7 +137,7 @@ func optStr(o ndp.Option) string {
 
 		return fmt.Sprintf("%s link-layer address: %s", dir, o.Addr.String())
 	case *ndp.MTU:
-		return fmt.Sprintf("MTU: %d", *o)
+		return fmt.Sprintf("MTU: %d", o.MTU)
 	case *ndp.PrefixInformation:
 		var flags []string
 		if o.OnLink {
@@ -174,7 +174,9 @@ func optStr(o ndp.Option) string {
 	case *ndp.DNSSearchList:
 		return fmt.Sprintf("DNS search list: lifetime: %s, domain names: %s", o.Lifetime, strings.Join(o.DomainNames, ", "))
 	case *ndp.CaptivePortal:
-		return fmt.Sprintf("captive portal: %s", *o)
+		return fmt.Sprintf("captive portal: %s", o.URI)
+	case *ndp.Nonce:
+		return fmt.Sprintf("nonce: %s", o)
 	default:
 		panic(fmt.Sprintf("unrecognized option: %v", o))
 	}

option.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"crypto/subtle"
 	"encoding/binary"
+	"encoding/hex"
 	"errors"
 	"fmt"
 	"io"
@@ -774,6 +775,9 @@ func (n *Nonce) Equal(x *Nonce) bool { return subtle.ConstantTimeCompare(n.b, x.
 // Code implements Option.
 func (*Nonce) Code() byte { return optNonce }
 
+// String returns the string representation of a Nonce.
+func (n *Nonce) String() string { return hex.EncodeToString(n.b) }
+
 func (n *Nonce) marshal() ([]byte, error) {
 	if len(n.b) == 0 {
 		return nil, errors.New("ndp: nonce option requires a non-empty nonce value")