dhcpv6: easier option parsing

- move option parsing to uio buffer library.
- move option code and length reading into FromBytes rather than
implementing it in each OptionParser.

1 files changed, 12 insertions, 14 deletions

diff --git a/dhcpv6/option_clientid.go b/dhcpv6/option_clientid.go
index fc68ae7..92ceb24 100644
--- a/dhcpv6/option_clientid.go
+++ b/dhcpv6/option_clientid.go
@@ -1,14 +1,15 @@
 package dhcpv6
 
-// This module defines the OptClientId and DUID structures.
-// https://www.ietf.org/rfc/rfc3315.txt
-
 import (
-	"encoding/binary"
 	"fmt"
+
+	"github.com/u-root/u-root/pkg/uio"
 )
 
 // OptClientId represents a Client ID option
+//
+// This module defines the OptClientId and DUID structures.
+// https://www.ietf.org/rfc/rfc3315.txt
 type OptClientId struct {
 	Cid Duid
 }
@@ -17,12 +18,13 @@ func (op *OptClientId) Code() OptionCode {
 	return OptionClientID
 }
 
+// ToBytes marshals the Client ID option as defined by RFC 3315, Section 22.2.
 func (op *OptClientId) ToBytes() []byte {
-	buf := make([]byte, 4)
-	binary.BigEndian.PutUint16(buf[0:2], uint16(OptionClientID))
-	binary.BigEndian.PutUint16(buf[2:4], uint16(op.Length()))
-	buf = append(buf, op.Cid.ToBytes()...)
-	return buf
+	buf := uio.NewBigEndianBuffer(nil)
+	buf.Write16(uint16(OptionClientID))
+	buf.Write16(uint16(op.Length()))
+	buf.WriteBytes(op.Cid.ToBytes())
+	return buf.Data()
 }
 
 func (op *OptClientId) Length() int {
@@ -37,11 +39,7 @@ func (op *OptClientId) String() string {
 // of bytes. The input data does not include option code and length
 // bytes.
 func ParseOptClientId(data []byte) (*OptClientId, error) {
-	if len(data) < 2 {
-		// at least the DUID type is necessary to continue
-		return nil, fmt.Errorf("Invalid OptClientId data: shorter than 2 bytes")
-	}
-	opt := OptClientId{}
+	var opt OptClientId
 	cid, err := DuidFromBytes(data)
 	if err != nil {
 		return nil, err