5 files changed, 100 insertions, 0 deletions
diff --git a/dhcpv6/modifiers.go b/dhcpv6/modifiers.go
index efd14a5..06eb9d9 100644
--- a/dhcpv6/modifiers.go
+++ b/dhcpv6/modifiers.go
@@ -43,6 +43,14 @@ func WithNetboot(d DHCPv6) {
 	msg.UpdateOption(oro)
 }
 
+// WithFQDN adds a fully qualified domain name option to the packet
+func WithFQDN(flags uint8, domainname string) Modifier {
+	return func(d DHCPv6) {
+		ofqdn := OptFQDN{Flags: flags, DomainName: domainname}
+		d.AddOption(&ofqdn)
+	}
+}
+
 // WithUserClass adds a user class option to the packet
 func WithUserClass(uc []byte) Modifier {
 	// TODO let the user specify multiple user classes
diff --git a/dhcpv6/modifiers_test.go b/dhcpv6/modifiers_test.go
index 324c425..dfef08c 100644
--- a/dhcpv6/modifiers_test.go
+++ b/dhcpv6/modifiers_test.go
@@ -95,3 +95,13 @@ func TestWithDomainSearchList(t *testing.T) {
 	require.Equal(t, "slackware.it", labels[0])
 	require.Equal(t, "dhcp.slackware.it", labels[1])
 }
+
+func TestWithFQDN(t *testing.T) {
+	var d Message
+	WithFQDN(4, "cnos.localhost")(&d)
+	require.Equal(t, 1, len(d.Options))
+	ofqdn := d.Options[0].(*OptFQDN)
+	require.Equal(t, OptionFQDN, ofqdn.Code())
+	require.Equal(t, uint8(4), ofqdn.Flags)
+	require.Equal(t, "cnos.localhost", ofqdn.DomainName)
+}
diff --git a/dhcpv6/option_fqdn.go b/dhcpv6/option_fqdn.go
new file mode 100644
index 0000000..82d1254
--- /dev/null
+++ b/dhcpv6/option_fqdn.go
@@ -0,0 +1,41 @@
+package dhcpv6
+
+import (
+	"fmt"
+
+	"github.com/u-root/u-root/pkg/uio"
+)
+
+// OptFQDN implements OptionFQDN option.
+//
+// https://tools.ietf.org/html/rfc4704
+type OptFQDN struct {
+	Flags      uint8
+	DomainName string
+}
+
+// Code returns the option code.
+func (op *OptFQDN) Code() OptionCode {
+	return OptionFQDN
+}
+
+// ToBytes serializes the option and returns it as a sequence of bytes
+func (op *OptFQDN) ToBytes() []byte {
+	buf := uio.NewBigEndianBuffer(nil)
+	buf.Write8(op.Flags)
+	buf.WriteBytes([]byte(op.DomainName))
+	return buf.Data()
+}
+
+func (op *OptFQDN) String() string {
+	return fmt.Sprintf("OptFQDN{flags=%d, domainname=%s}", op.Flags, op.DomainName)
+}
+
+// ParseOptFQDN deserializes from bytes to build a OptFQDN structure.
+func ParseOptFQDN(data []byte) (*OptFQDN, error) {
+	var opt OptFQDN
+	buf := uio.NewBigEndianBuffer(data)
+	opt.Flags = buf.Read8()
+	opt.DomainName = string(buf.ReadAll())
+	return &opt, buf.FinError()
+}
diff --git a/dhcpv6/option_fqdn_test.go b/dhcpv6/option_fqdn_test.go
new file mode 100644
index 0000000..870ed9d
--- /dev/null
+++ b/dhcpv6/option_fqdn_test.go
@@ -0,0 +1,39 @@
+package dhcpv6
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestParseOptFQDN(t *testing.T) {
+	data := []byte{
+		0, // Flags
+		'c', 'n', 'o', 's', '.', 'l', 'o', 'c', 'a', 'l',
+		'h', 'o', 's', 't',
+	}
+	opt, err := ParseOptFQDN(data)
+
+	require.NoError(t, err)
+	require.Equal(t, OptionFQDN, opt.Code())
+	require.Equal(t, uint8(0), opt.Flags)
+	require.Equal(t, "cnos.localhost", opt.DomainName)
+	require.Equal(t, "OptFQDN{flags=0, domainname=cnos.localhost}", opt.String())
+}
+
+func TestOptFQDNToBytes(t *testing.T) {
+	opt := OptFQDN{
+		Flags:      0,
+		DomainName: "cnos.localhost",
+	}
+	want := []byte{
+		0, // Flags
+		'c', 'n', 'o', 's', '.', 'l', 'o', 'c', 'a', 'l',
+		'h', 'o', 's', 't',
+	}
+	b := opt.ToBytes()
+	if !bytes.Equal(b, want) {
+		t.Fatalf("opt.ToBytes()=%v, want %v", b, want)
+	}
+}
diff --git a/dhcpv6/options.go b/dhcpv6/options.go
index fb36a38..e653c01 100644
--- a/dhcpv6/options.go
+++ b/dhcpv6/options.go
@@ -73,6 +73,8 @@ func ParseOption(code OptionCode, optData []byte) (Option, error) {
 		opt, err = ParseOptIAPrefix(optData)
 	case OptionRemoteID:
 		opt, err = ParseOptRemoteId(optData)
+	case OptionFQDN:
+		opt, err = ParseOptFQDN(optData)
 	case OptionBootfileURL:
 		opt, err = ParseOptBootFileURL(optData)
 	case OptionBootfileParam: