fix OptInterfaceId (#29)

2 files changed, 36 insertions, 3 deletions

diff --git a/dhcpv6/option_interfaceid.go b/dhcpv6/option_interfaceid.go
index 4ba83f5..2634d9f 100644
--- a/dhcpv6/option_interfaceid.go
+++ b/dhcpv6/option_interfaceid.go
@@ -19,7 +19,7 @@ func (op *OptInterfaceId) Code() OptionCode {
 func (op *OptInterfaceId) ToBytes() []byte {
 	buf := make([]byte, 4)
 	binary.BigEndian.PutUint16(buf[0:2], uint16(OPTION_INTERFACE_ID))
-	binary.BigEndian.PutUint16(buf[2:4], 2)
+	binary.BigEndian.PutUint16(buf[2:4], uint16(len(op.interfaceId)))
 	buf = append(buf, op.interfaceId...)
 	return buf
 }
@@ -33,7 +33,7 @@ func (op *OptInterfaceId) SetInterfaceID(interfaceId []byte) {
 }
 
 func (op *OptInterfaceId) Length() int {
-	return 4 + len(op.interfaceId)
+	return len(op.interfaceId)
 }
 
 func (op *OptInterfaceId) String() string {
@@ -44,6 +44,6 @@ func (op *OptInterfaceId) String() string {
 // The input data does not include option code and length bytes.
 func ParseOptInterfaceId(data []byte) (*OptInterfaceId, error) {
 	opt := OptInterfaceId{}
-	opt.interfaceId = append([]byte(nil), data[4:]...)
+	opt.interfaceId = append([]byte(nil), data...)
 	return &opt, nil
 }
diff --git a/dhcpv6/option_interfaceid_test.go b/dhcpv6/option_interfaceid_test.go
new file mode 100644
index 0000000..21de822
--- /dev/null
+++ b/dhcpv6/option_interfaceid_test.go
@@ -0,0 +1,33 @@
+package dhcpv6
+
+import (
+	"bytes"
+	"testing"
+)
+
+func TestOptInterfaceId(t *testing.T) {
+	expected := []byte("DSLAM01 eth2/1/01/21")
+	opt, err := ParseOptInterfaceId(expected)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if optLen := opt.Length(); optLen != len(expected) {
+		t.Fatalf("Invalid length. Expected %v, got %v", len(expected), optLen)
+	}
+	if url := opt.InterfaceID(); !bytes.Equal(url, expected) {
+		t.Fatalf("Invalid Interface ID. Expected %v, got %v", expected, url)
+	}
+}
+
+func TestOptInterfaceIdToBytes(t *testing.T) {
+	interfaceId := []byte("DSLAM01 eth2/1/01/21")
+	expected := []byte{00, 18, 00, byte(len(interfaceId))}
+	expected = append(expected, interfaceId...)
+	opt := OptInterfaceId{
+		interfaceId: interfaceId,
+	}
+	toBytes := opt.ToBytes()
+	if !bytes.Equal(toBytes, expected) {
+		t.Fatalf("Invalid ToBytes result. Expected %v, got %v", expected, toBytes)
+	}
+}