2 files changed, 144 insertions, 0 deletions
diff --git a/dhcpv4/option_userclass.go b/dhcpv4/option_userclass.go
new file mode 100644
index 0000000..8aa02d6
--- /dev/null
+++ b/dhcpv4/option_userclass.go
@@ -0,0 +1,78 @@
+package dhcpv4
+
+import (
+	"errors"
+	"fmt"
+	"strings"
+)
+
+// OptUserClass represents a DHCPv4 User Class option
+type OptUserClass struct {
+	UserClasses [][]byte
+}
+
+// Code returns the option code
+func (op *OptUserClass) Code() OptionCode {
+	return OptionUserClassInformation
+}
+
+// ToBytes serializes the option and returns it as a sequence of bytes
+func (op *OptUserClass) ToBytes() []byte {
+	buf := []byte{byte(op.Code()), byte(op.Length())}
+	for _, uc := range op.UserClasses {
+		buf = append(buf, byte(len(uc)))
+		buf = append(buf, uc...)
+	}
+	return buf
+}
+
+// Length returns the option length
+func (op *OptUserClass) Length() int {
+	ret := 0
+	for _, uc := range op.UserClasses {
+		ret += 1 + len(uc)
+	}
+	return ret
+}
+
+func (op *OptUserClass) String() string {
+	ucStrings := make([]string, 0)
+	for _, uc := range op.UserClasses {
+		ucStrings = append(ucStrings, string(uc))
+	}
+	return fmt.Sprintf("OptUserClass{userclass=[%s]}", strings.Join(ucStrings, ", "))
+}
+
+// ParseOptUserClass returns a new OptUserClass from a byte stream or
+// error if any
+func ParseOptUserClass(data []byte) (*OptUserClass, error) {
+	opt := OptUserClass{}
+
+	if len(data) < 4 {
+		return nil, ErrShortByteStream
+	}
+	code := OptionCode(data[0])
+	if code != OptionUserClassInformation {
+		return nil, fmt.Errorf("expected code %v, got %v", OptionUserClassInformation, code)
+	}
+	data = data[2:]
+
+	for {
+		if len(data) == 0 {
+			break
+		}
+		if len(data) < 1 {
+			return nil, errors.New("ParseOptUserClass: short data: missing length field")
+		}
+		ucLen := int(data[0])
+		if len(data) < ucLen+1 {
+			return nil, fmt.Errorf("ParseOptUserClass: short data: less than %d bytes", ucLen+2)
+		}
+		opt.UserClasses = append(opt.UserClasses, data[1:ucLen+1])
+		data = data[1+ucLen:]
+	}
+	if len(opt.UserClasses) < 1 {
+		return nil, errors.New("ParseOptUserClass: at least one user class is required")
+	}
+	return &opt, nil
+}
diff --git a/dhcpv4/option_userclass_test.go b/dhcpv4/option_userclass_test.go
new file mode 100644
index 0000000..fe39b04
--- /dev/null
+++ b/dhcpv4/option_userclass_test.go
@@ -0,0 +1,66 @@
+package dhcpv4
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestOptUserClassToBytes(t *testing.T) {
+	opt := OptUserClass{
+		UserClasses: [][]byte{[]byte("linuxboot")},
+	}
+	data := opt.ToBytes()
+	expected := []byte{
+		77, // OPTION_USER_CLASS
+		10, // length
+		9, 'l', 'i', 'n', 'u', 'x', 'b', 'o', 'o', 't',
+	}
+	require.Equal(t, expected, data)
+}
+
+func TestParseOptUserClassMultiple(t *testing.T) {
+	expected := []byte{
+		77, 15,
+		9, 'l', 'i', 'n', 'u', 'x', 'b', 'o', 'o', 't',
+		4, 't', 'e', 's', 't',
+	}
+	opt, err := ParseOptUserClass(expected)
+	require.NoError(t, err)
+	require.Equal(t, len(opt.UserClasses), 2)
+	require.Equal(t, []byte("linuxboot"), opt.UserClasses[0])
+	require.Equal(t, []byte("test"), opt.UserClasses[1])
+}
+
+func TestParseOptUserClassNone(t *testing.T) {
+	expected := []byte{}
+	_, err := ParseOptUserClass(expected)
+	require.Error(t, err)
+}
+
+func TestParseOptUserClass(t *testing.T) {
+	expected := []byte{
+		77, 10, 9, 'l', 'i', 'n', 'u', 'x', 'b', 'o', 'o', 't',
+	}
+	opt, err := ParseOptUserClass(expected)
+	require.NoError(t, err)
+	require.Equal(t, 1, len(opt.UserClasses))
+	require.Equal(t, []byte("linuxboot"), opt.UserClasses[0])
+}
+
+func TestOptUserClassToBytesMultiple(t *testing.T) {
+	opt := OptUserClass{
+		UserClasses: [][]byte{
+			[]byte("linuxboot"),
+			[]byte("test"),
+		},
+	}
+	data := opt.ToBytes()
+	expected := []byte{
+		77, // OPTION_USER_CLASS
+		15, // length
+		9, 'l', 'i', 'n', 'u', 'x', 'b', 'o', 'o', 't',
+		4, 't', 'e', 's', 't',
+	}
+	require.Equal(t, expected, data)
+}