dhcpv6: Implement RelayPort option

This is a simple 1-value option used in relay messages for RFC8357, specifying
the UDP port on which messages should be sent to the relay

Signed-off-by: Anatole Denis <natolumin@unverle.fr>

1 files changed, 42 insertions, 0 deletions

diff --git a/dhcpv6/option_relayport.go b/dhcpv6/option_relayport.go
new file mode 100644
index 0000000..fd51948
--- /dev/null
+++ b/dhcpv6/option_relayport.go
@@ -0,0 +1,42 @@
+// This module defines the optRelayPort structure.
+// https://www.ietf.org/rfc/rfc8357.txt
+
+package dhcpv6
+
+import (
+	"fmt"
+
+	"github.com/u-root/uio/uio"
+)
+
+// OptRelayPort specifies an UDP port to use for the downstream relay
+func OptRelayPort(port uint16) Option {
+	return &optRelayPort{DownstreamSourcePort: port}
+}
+
+type optRelayPort struct {
+	DownstreamSourcePort uint16
+}
+
+func (op *optRelayPort) Code() OptionCode {
+	return OptionRelayPort
+}
+
+func (op *optRelayPort) ToBytes() []byte {
+	buf := uio.NewBigEndianBuffer(nil)
+	buf.Write16(op.DownstreamSourcePort)
+	return buf.Data()
+}
+
+func (op *optRelayPort) String() string {
+	return fmt.Sprintf("RelayPort: %d", op.DownstreamSourcePort)
+}
+
+// build an optRelayPort structure from a sequence of bytes.
+// The input data does not include option code and length bytes.
+func parseOptRelayPort(data []byte) (*optRelayPort, error) {
+	var opt optRelayPort
+	buf := uio.NewBigEndianBuffer(data)
+	opt.DownstreamSourcePort = buf.Read16()
+	return &opt, buf.FinError()
+}