Add option IPv6OnlyPreferred (RFC 8925)

Signed-off-by: Brian Candler <[email protected]>

dhcpv4/dhcpv4.go

@@ -730,6 +730,22 @@ func (d *DHCPv4) IPAddressRebindingTime(def time.Duration) time.Duration {
 	return time.Duration(dur)
 }
 
+// IPv6OnlyPreferred returns true if this option is present, and the
+// V6ONLY_WAIT duration if it is.
+//
+// The IPv6-Only Preferred option is described by RFC 8195, Section 3.1.
+func (d *DHCPv4) IPv6OnlyPreferred() (bool, time.Duration) {
+	v := d.Options.Get(OptionIPv6OnlyPreferred)
+	if v == nil {
+		return false, 0
+	}
+	var dur Duration
+	if err := dur.FromBytes(v); err != nil {
+		return false, 0
+	}
+	return true, time.Duration(dur)
+}
+
 // MaxMessageSize returns the DHCP Maximum Message Size if present.
 //
 // The Maximum DHCP Message Size option is described by RFC 2132, Section 9.10.

dhcpv4/modifiers.go

@@ -159,6 +159,11 @@ func WithLeaseTime(leaseTime uint32) Modifier {
 	return WithOption(OptIPAddressLeaseTime(time.Duration(leaseTime) * time.Second))
 }
 
+// WithIPv6OnlyPreferred adds or updates an OptIPv6OnlyPreferred
+func WithIPv6OnlyPreferred(v6OnlyWait uint32) Modifier {
+	return WithOption(OptIPv6OnlyPreferred(time.Duration(v6OnlyWait) * time.Second))
+}
+
 // WithDomainSearchList adds or updates an OptionDomainSearch
 func WithDomainSearchList(searchList ...string) Modifier {
 	return WithOption(OptDomainSearch(&rfc1035label.Labels{

dhcpv4/option_ipv6_only_preferred.go

@@ -0,0 +1,10 @@
+package dhcpv4
+
+import (
+	"time"
+)
+
+// The IPv6-Only Preferred option is described by RFC 8925, Section 3.1
+func OptIPv6OnlyPreferred(d time.Duration) Option {
+	return Option{Code: OptionIPv6OnlyPreferred, Value: Duration(d)}
+}

dhcpv4/option_ipv6_only_preferred_test.go

@@ -0,0 +1,43 @@
+package dhcpv4
+
+import (
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestOptIPv6OnlyPreferred(t *testing.T) {
+	o := OptIPv6OnlyPreferred(43200 * time.Second)
+	require.Equal(t, OptionIPv6OnlyPreferred, o.Code, "Code")
+	require.Equal(t, []byte{0, 0, 168, 192}, o.Value.ToBytes(), "ToBytes")
+	require.Equal(t, "IPv6-Only Preferred: 12h0m0s", o.String(), "String")
+}
+
+func TestOptIPv6OnlyPreferredZero(t *testing.T) {
+	o := OptIPv6OnlyPreferred(0)
+	require.Equal(t, OptionIPv6OnlyPreferred, o.Code, "Code")
+	require.Equal(t, []byte{0, 0, 0, 0}, o.Value.ToBytes(), "ToBytes")
+	require.Equal(t, "IPv6-Only Preferred: 0s", o.String(), "String")
+}
+
+func TestGetIPv6OnlyPreferred(t *testing.T) {
+	m, _ := New(WithGeneric(OptionIPv6OnlyPreferred, []byte{0, 0, 168, 192}))
+	found, v6onlyWait := m.IPv6OnlyPreferred()
+	require.True(t, found)
+	require.Equal(t, 43200*time.Second, v6onlyWait)
+
+	// Too short.
+	m, _ = New(WithGeneric(OptionIPv6OnlyPreferred, []byte{168, 192}))
+	found, v6onlyWait = m.IPv6OnlyPreferred()
+	require.False(t, found)
+
+	// Too long.
+	m, _ = New(WithGeneric(OptionIPv6OnlyPreferred, []byte{1, 1, 1, 1, 1}))
+	found, v6onlyWait = m.IPv6OnlyPreferred()
+	require.False(t, found)
+
+	// Empty.
+	m, _ = New()
+	require.False(t, found)
+}

dhcpv4/options.go

@@ -336,7 +336,7 @@ func getOption(code OptionCode, data []byte, vendorDecoder OptionDecoder) fmt.St
 	case OptionDNSDomainSearchList:
 		d = &rfc1035label.Labels{}
 
-	case OptionIPAddressLeaseTime:
+	case OptionIPAddressLeaseTime, OptionIPv6OnlyPreferred:
 		var dur Duration
 		d = &dur
 

dhcpv4/types.go

@@ -238,6 +238,8 @@ const (
 	OptionGeoConfCivic                optionCode = 99
 	OptionIEEE10031TZString           optionCode = 100
 	OptionReferenceToTZDatabase       optionCode = 101
+	// Option 108 returned in RFC 8925
+	OptionIPv6OnlyPreferred optionCode = 108
 	// Options 102-111 returned in RFC 3679
 	OptionNetInfoParentServerAddress optionCode = 112
 	OptionNetInfoParentServerTag     optionCode = 113
@@ -401,6 +403,8 @@ var optionCodeToString = map[OptionCode]string{
 	OptionGeoConfCivic:                "GEOCONF_CIVIC",
 	OptionIEEE10031TZString:           "IEEE 1003.1 TZ String",
 	OptionReferenceToTZDatabase:       "Reference to the TZ Database",
+	// Option 108 returned in RFC 8925
+	OptionIPv6OnlyPreferred: "IPv6-Only Preferred",
 	// Options 102-111 returned in RFC 3679
 	OptionNetInfoParentServerAddress: "NetInfo Parent Server Address",
 	OptionNetInfoParentServerTag:     "NetInfo Parent Server Tag",