5 files changed, 105 insertions, 0 deletions
diff --git a/dhcpv6/dhcpv6message.go b/dhcpv6/dhcpv6message.go
index f3ed4ef..0dd219d 100644
--- a/dhcpv6/dhcpv6message.go
+++ b/dhcpv6/dhcpv6message.go
@@ -248,6 +248,21 @@ func (mo MessageOptions) ElapsedTime() time.Duration {
 	return 0
 }
 
+// InformationRefreshTime returns the Information Refresh Time option
+// as defined by RFC 815 Section 21.23.
+//
+// InformationRefreshTime returns the provided default if no option is present.
+func (mo MessageOptions) InformationRefreshTime(def time.Duration) time.Duration {
+	opt := mo.Options.GetOne(OptionInformationRefreshTime)
+	if opt == nil {
+		return def
+	}
+	if t, ok := opt.(*optInformationRefreshTime); ok {
+		return t.InformationRefreshtime
+	}
+	return def
+}
+
 // FQDN returns the FQDN option as defined by RFC 4704.
 func (mo MessageOptions) FQDN() *OptFQDN {
 	opt := mo.Options.GetOne(OptionFQDN)
diff --git a/dhcpv6/modifiers.go b/dhcpv6/modifiers.go
index fbbad23..8c708d9 100644
--- a/dhcpv6/modifiers.go
+++ b/dhcpv6/modifiers.go
@@ -2,6 +2,7 @@ package dhcpv6
 
 import (
 	"net"
+	"time"
 
 	"github.com/insomniacslk/dhcp/iana"
 	"github.com/insomniacslk/dhcp/rfc1035label"
@@ -175,3 +176,9 @@ func WithIAPD(iaid [4]byte, prefixes ...*OptIAPrefix) Modifier {
 func WithClientLinkLayerAddress(ht iana.HWType, lla net.HardwareAddr) Modifier {
 	return WithOption(OptClientLinkLayerAddress(ht, lla))
 }
+
+// WithInformationRefreshTime adds an optInformationRefreshTime to the DHCPv6 packet
+// using the provided duration
+func WithInformationRefreshTime(irt time.Duration) Modifier {
+	return WithOption(OptInformationRefreshTime(irt))
+}
diff --git a/dhcpv6/option_informationrefreshtime.go b/dhcpv6/option_informationrefreshtime.go
new file mode 100644
index 0000000..942d5c7
--- /dev/null
+++ b/dhcpv6/option_informationrefreshtime.go
@@ -0,0 +1,48 @@
+package dhcpv6
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/u-root/u-root/pkg/uio"
+)
+
+// OptInformationRefreshTime implements OptionInformationRefreshTime option.
+// https://tools.ietf.org/html/rfc8415#section-21.23
+func OptInformationRefreshTime(irt time.Duration) *optInformationRefreshTime {
+	return &optInformationRefreshTime{irt}
+}
+
+// optInformationRefreshTime represents an OptionInformationRefreshTime.
+type optInformationRefreshTime struct {
+	InformationRefreshtime time.Duration
+}
+
+// Code returns the option's code
+func (op *optInformationRefreshTime) Code() OptionCode {
+	return OptionInformationRefreshTime
+}
+
+// ToBytes serializes the option and returns it as a sequence of bytes
+func (op *optInformationRefreshTime) ToBytes() []byte {
+	buf := uio.NewBigEndianBuffer(nil)
+	irt := Duration{op.InformationRefreshtime}
+	irt.Marshal(buf)
+	return buf.Data()
+}
+
+func (op *optInformationRefreshTime) String() string {
+	return fmt.Sprintf("InformationRefreshTime: %v", op.InformationRefreshtime)
+}
+
+// parseOptInformationRefreshTime builds an optInformationRefreshTime structure from a sequence
+// of bytes. The input data does not include option code and length bytes.
+func parseOptInformationRefreshTime(data []byte) (*optInformationRefreshTime, error) {
+	var opt optInformationRefreshTime
+	buf := uio.NewBigEndianBuffer(data)
+
+	var irt Duration
+	irt.Unmarshal(buf)
+	opt.InformationRefreshtime = irt.Duration
+	return &opt, buf.FinError()
+}
diff --git a/dhcpv6/option_informationrefreshtime_test.go b/dhcpv6/option_informationrefreshtime_test.go
new file mode 100644
index 0000000..68f0855
--- /dev/null
+++ b/dhcpv6/option_informationrefreshtime_test.go
@@ -0,0 +1,33 @@
+package dhcpv6
+
+import (
+	"bytes"
+	"testing"
+	"time"
+)
+
+func TestOptInformationRefreshTime(t *testing.T) {
+	opt, err := parseOptInformationRefreshTime([]byte{0xaa, 0xbb, 0xcc, 0xdd})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if informationRefreshTime := opt.InformationRefreshtime; informationRefreshTime != time.Duration(0xaabbccdd) * time.Second {
+		t.Fatalf("Invalid information refresh time. Expected 0xaabb, got %v", informationRefreshTime)
+	}
+}
+
+func TestOptInformationRefreshTimeToBytes(t *testing.T) {
+	opt := OptInformationRefreshTime(0)
+	expected := []byte{0, 0, 0, 0}
+	if toBytes := opt.ToBytes(); !bytes.Equal(expected, toBytes) {
+		t.Fatalf("Invalid ToBytes output. Expected %v, got %v", expected, toBytes)
+	}
+}
+
+func TestOptInformationRefreshTimeString(t *testing.T) {
+	opt := OptInformationRefreshTime(3600 * time.Second)
+	expected := "InformationRefreshTime: 1h0m0s"
+	if optString := opt.String(); optString != expected {
+		t.Fatalf("Invalid elapsed time string. Expected %v, got %v", expected, optString)
+	}
+}
diff --git a/dhcpv6/options.go b/dhcpv6/options.go
index 16bc8d7..0ff5148 100644
--- a/dhcpv6/options.go
+++ b/dhcpv6/options.go
@@ -75,6 +75,8 @@ func ParseOption(code OptionCode, optData []byte) (Option, error) {
 		opt, err = ParseOptIAPD(optData)
 	case OptionIAPrefix:
 		opt, err = ParseOptIAPrefix(optData)
+	case OptionInformationRefreshTime:
+		opt, err = parseOptInformationRefreshTime(optData)
 	case OptionRemoteID:
 		opt, err = ParseOptRemoteID(optData)
 	case OptionFQDN: