3 files changed, 168 insertions, 0 deletions
diff --git a/dhcpv4/option_vivc.go b/dhcpv4/option_vivc.go
new file mode 100644
index 0000000..9be8557
--- /dev/null
+++ b/dhcpv4/option_vivc.go
@@ -0,0 +1,102 @@
+package dhcpv4
+
+import (
+	"bytes"
+	"encoding/binary"
+	"fmt"
+)
+
+// This option implements the Vendor-Identifying Vendor Class Option
+// https://tools.ietf.org/html/rfc3925
+
+// VIVCIdentifier represents one Vendor-Identifying vendor class option.
+type VIVCIdentifier struct {
+	EntID uint32
+	Data  []byte
+}
+
+// OptVIVC represents the DHCP message type option.
+type OptVIVC struct {
+	Identifiers []VIVCIdentifier
+}
+
+// ParseOptVIVC contructs an OptVIVC tsruct from a sequence of bytes and returns
+// it, or an error.
+func ParseOptVIVC(data []byte) (*OptVIVC, error) {
+	if len(data) < 2 {
+		return nil, ErrShortByteStream
+	}
+	code := OptionCode(data[0])
+	if code != OptionVendorIdentifyingVendorClass {
+		return nil, fmt.Errorf("expected code %v, got %v", OptionVendorIdentifyingVendorClass, code)
+	}
+	length := int(data[1])
+	data = data[2:]
+
+	if length != len(data) {
+		return nil, ErrShortByteStream
+	}
+
+	ids := []VIVCIdentifier{}
+	for len(data) > 5 {
+		entID := binary.BigEndian.Uint32(data[0:4])
+		idLen := int(data[4])
+		data = data[5:]
+
+		if idLen > len(data) {
+			return nil, ErrShortByteStream
+		}
+
+		ids = append(ids, VIVCIdentifier{EntID: entID, Data: data[:idLen]})
+		data = data[idLen:]
+	}
+
+	if len(data) != 0 {
+		return nil, ErrShortByteStream
+	}
+
+	return &OptVIVC{Identifiers: ids}, nil
+}
+
+// Code returns the option code.
+func (o *OptVIVC) Code() OptionCode {
+	return OptionVendorIdentifyingVendorClass
+}
+
+// ToBytes returns a serialized stream of bytes for this option.
+func (o *OptVIVC) ToBytes() []byte {
+	buf := make([]byte, o.Length()+2)
+	copy(buf[0:], []byte{byte(o.Code()), byte(o.Length())})
+
+	b := buf[2:]
+	for _, id := range o.Identifiers {
+		binary.BigEndian.PutUint32(b[0:4], id.EntID)
+		b[4] = byte(len(id.Data))
+		copy(b[5:], id.Data)
+		b = b[len(id.Data)+5:]
+	}
+	return buf
+}
+
+// String returns a human-readable string for this option.
+func (o *OptVIVC) String() string {
+	buf := bytes.Buffer{}
+	fmt.Fprintf(&buf, "Vendor-Identifying Vendor Class ->")
+
+	for _, id := range o.Identifiers {
+		fmt.Fprintf(&buf, " %d:'%s',", id.EntID, id.Data)
+	}
+
+	return buf.String()[:buf.Len()-1]
+}
+
+// Length returns the length of the data portion (excluding option code and byte
+// for length, if any).
+func (o *OptVIVC) Length() int {
+	n := 0
+	for _, id := range o.Identifiers {
+		// each class has a header of endID (4 bytes) and length (1 byte)
+		n += 5 + len(id.Data)
+	}
+	return n
+}
diff --git a/dhcpv4/option_vivc_test.go b/dhcpv4/option_vivc_test.go
new file mode 100644
index 0000000..14ded61
--- /dev/null
+++ b/dhcpv4/option_vivc_test.go
@@ -0,0 +1,64 @@
+package dhcpv4
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+var (
+	sampleVIVCOpt = OptVIVC{
+		Identifiers: []VIVCIdentifier{
+			{EntID: 9, Data: []byte("CiscoIdentifier")},
+			{EntID: 18, Data: []byte("WellfleetIdentifier")},
+		},
+	}
+	sampleVIVCOptRaw = []byte{
+		byte(OptionVendorIdentifyingVendorClass), 44, // option header
+		0x0, 0x0, 0x0, 0x9, // enterprise id 9
+		0xf, // length
+		'C', 'i', 's', 'c', 'o', 'I', 'd', 'e', 'n', 't', 'i', 'f', 'i', 'e', 'r',
+		0x0, 0x0, 0x0, 0x12, // enterprise id 18
+		0x13, // length
+		'W', 'e', 'l', 'l', 'f', 'l', 'e', 'e', 't', 'I', 'd', 'e', 'n', 't', 'i', 'f', 'i', 'e', 'r',
+	}
+)
+
+func TestOptVIVCInterfaceMethods(t *testing.T) {
+	require.Equal(t, OptionVendorIdentifyingVendorClass, sampleVIVCOpt.Code(), "Code")
+	require.Equal(t, 44, sampleVIVCOpt.Length(), "Length")
+	require.Equal(t, sampleVIVCOptRaw, sampleVIVCOpt.ToBytes(), "ToBytes")
+}
+
+func TestParseOptVICO(t *testing.T) {
+	o, err := ParseOptVIVC(sampleVIVCOptRaw)
+	require.NoError(t, err)
+	require.Equal(t, &sampleVIVCOpt, o)
+
+	// Short byte stream
+	data := []byte{byte(OptionVendorIdentifyingVendorClass)}
+	_, err = ParseOptVIVC(data)
+	require.Error(t, err, "should get error from short byte stream")
+
+	// Wrong code
+	data = []byte{54, 2, 1, 1}
+	_, err = ParseOptVIVC(data)
+	require.Error(t, err, "should get error from wrong code")
+
+	// Bad length
+	data = []byte{byte(OptionVendorIdentifyingVendorClass), 6, 1, 1, 1}
+	_, err = ParseOptVIVC(data)
+	require.Error(t, err, "should get error from bad length")
+
+	// Identifier len too long
+	data = make([]byte, len(sampleVIVCOptRaw))
+	copy(data, sampleVIVCOptRaw)
+	data[6] = 40
+	_, err = ParseOptVIVC(data)
+	require.Error(t, err, "should get error from bad length")
+}
+
+func TestOptVIVCString(t *testing.T) {
+	require.Equal(t, "Vendor-Identifying Vendor Class -> 9:'CiscoIdentifier', 18:'WellfleetIdentifier'",
+		sampleVIVCOpt.String())
+}
diff --git a/dhcpv4/options.go b/dhcpv4/options.go
index efbfb74..528c175 100644
--- a/dhcpv4/options.go
+++ b/dhcpv4/options.go
@@ -56,6 +56,8 @@ func ParseOption(data []byte) (Option, error) {
 		opt, err = ParseOptClassIdentifier(data)
 	case OptionDomainName:
 		opt, err = ParseOptDomainName(data)
+	case OptionVendorIdentifyingVendorClass:
+		opt, err = ParseOptVIVC(data)
 	default:
 		opt, err = ParseOptionGeneric(data)
 	}