dhcpv6: add DHCPv4-over-DHCPv6 support

Add message types, options, and modifier for handling DHCPv4-over-DHCPv6.

Refer to RFC 7341

Signed-off-by: Mikael Magnusson <mikma@users.sourceforge.net>

9 files changed, 293 insertions, 0 deletions

diff --git a/dhcpv6/dhcpv6message.go b/dhcpv6/dhcpv6message.go
index 56f8627..2ec3203 100644
--- a/dhcpv6/dhcpv6message.go
+++ b/dhcpv6/dhcpv6message.go
@@ -193,6 +193,19 @@ func (mo MessageOptions) FQDN() *OptFQDN {
 	return nil
 }
 
+// DHCP4oDHCP6Server returns the DHCP 4o6 Server Address option as
+// defined by RFC 7341.
+func (mo MessageOptions) DHCP4oDHCP6Server() *OptDHCP4oDHCP6Server {
+	opt := mo.Options.GetOne(OptionDHCP4oDHCP6Server)
+	if opt == nil {
+		return nil
+	}
+	if server, ok := opt.(*OptDHCP4oDHCP6Server); ok {
+		return server
+	}
+	return nil
+}
+
 // Message represents a DHCPv6 Message as defined by RFC 3315 Section 6.
 type Message struct {
 	MessageType   MessageType
diff --git a/dhcpv6/modifiers.go b/dhcpv6/modifiers.go
index 14bfe51..549ec38 100644
--- a/dhcpv6/modifiers.go
+++ b/dhcpv6/modifiers.go
@@ -119,3 +119,13 @@ func WithRequestedOptions(codes ...OptionCode) Modifier {
 		}
 	}
 }
+
+// WithDHCP4oDHCP6Server adds or updates an OptDHCP4oDHCP6Server
+func WithDHCP4oDHCP6Server(addrs ...net.IP) Modifier {
+	return func(d DHCPv6) {
+		opt := OptDHCP4oDHCP6Server{
+			DHCP4oDHCP6Servers: addrs,
+		}
+		d.UpdateOption(&opt)
+	}
+}
diff --git a/dhcpv6/modifiers_test.go b/dhcpv6/modifiers_test.go
index b99d4a2..c240067 100644
--- a/dhcpv6/modifiers_test.go
+++ b/dhcpv6/modifiers_test.go
@@ -92,3 +92,18 @@ func TestWithFQDN(t *testing.T) {
 	require.Equal(t, uint8(4), ofqdn.Flags)
 	require.Equal(t, "cnos.localhost", ofqdn.DomainName)
 }
+
+func TestWithDHCP4oDHCP6Server(t *testing.T) {
+	var d Message
+	WithDHCP4oDHCP6Server([]net.IP{
+		net.ParseIP("fe80::1"),
+		net.ParseIP("fe80::2"),
+	}...)(&d)
+	require.Equal(t, 1, len(d.Options.Options))
+	opt := d.Options.DHCP4oDHCP6Server()
+	require.Equal(t, OptionDHCP4oDHCP6Server, opt.Code())
+	require.Equal(t, 2, len(opt.DHCP4oDHCP6Servers))
+	require.Equal(t, net.ParseIP("fe80::1"), opt.DHCP4oDHCP6Servers[0])
+	require.Equal(t, net.ParseIP("fe80::2"), opt.DHCP4oDHCP6Servers[1])
+	require.NotEqual(t, net.ParseIP("fe80::1"), opt.DHCP4oDHCP6Servers[1])
+}
diff --git a/dhcpv6/option_dhcpv4_msg.go b/dhcpv6/option_dhcpv4_msg.go
new file mode 100644
index 0000000..0a1a2b3
--- /dev/null
+++ b/dhcpv6/option_dhcpv4_msg.go
@@ -0,0 +1,39 @@
+package dhcpv6
+
+import (
+	"fmt"
+
+	"github.com/insomniacslk/dhcp/dhcpv4"
+)
+
+// OptDHCPv4Msg represents a OptionDHCPv4Msg option
+//
+// This module defines the OptDHCPv4Msg structure.
+// https://www.ietf.org/rfc/rfc7341.txt
+type OptDHCPv4Msg struct {
+	Msg *dhcpv4.DHCPv4
+}
+
+// Code returns the option code
+func (op *OptDHCPv4Msg) Code() OptionCode {
+	return OptionDHCPv4Msg
+}
+
+// ToBytes returns the option serialized to bytes.
+func (op *OptDHCPv4Msg) ToBytes() []byte {
+	return op.Msg.ToBytes()
+}
+
+func (op *OptDHCPv4Msg) String() string {
+	return fmt.Sprintf("OptDHCPv4Msg{%v}", op.Msg)
+}
+
+// ParseOptDHCPv4Msg builds an OptDHCPv4Msg structure
+// from a sequence of bytes. The input data does not include option code and length
+// bytes.
+func ParseOptDHCPv4Msg(data []byte) (*OptDHCPv4Msg, error) {
+	var opt OptDHCPv4Msg
+	var err error
+	opt.Msg, err = dhcpv4.FromBytes(data)
+	return &opt, err
+}
diff --git a/dhcpv6/option_dhcpv4_msg_test.go b/dhcpv6/option_dhcpv4_msg_test.go
new file mode 100644
index 0000000..1ffa17a
--- /dev/null
+++ b/dhcpv6/option_dhcpv4_msg_test.go
@@ -0,0 +1,105 @@
+package dhcpv6
+
+import (
+	"bytes"
+	"net"
+	"testing"
+
+	"github.com/insomniacslk/dhcp/dhcpv4"
+	"github.com/insomniacslk/dhcp/iana"
+	"github.com/stretchr/testify/require"
+)
+
+var magicCookie = [4]byte{99, 130, 83, 99}
+
+func TestParseOptDHCPv4Msg(t *testing.T) {
+	data := []byte{
+		1,                      // dhcp request
+		1,                      // ethernet hw type
+		6,                      // hw addr length
+		3,                      // hop count
+		0xaa, 0xbb, 0xcc, 0xdd, // transaction ID, big endian (network)
+		0, 3, // number of seconds
+		0, 1, // broadcast
+		0, 0, 0, 0, // client IP address
+		0, 0, 0, 0, // your IP address
+		0, 0, 0, 0, // server IP address
+		0, 0, 0, 0, // gateway IP address
+		0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // client MAC address + padding
+	}
+
+	// server host name
+	expectedHostname := []byte{}
+	for i := 0; i < 64; i++ {
+		expectedHostname = append(expectedHostname, 0)
+	}
+	data = append(data, expectedHostname...)
+	// boot file name
+	expectedBootfilename := []byte{}
+	for i := 0; i < 128; i++ {
+		expectedBootfilename = append(expectedBootfilename, 0)
+	}
+	data = append(data, expectedBootfilename...)
+	// magic cookie, then no options
+	data = append(data, magicCookie[:]...)
+
+	opt, err := ParseOptDHCPv4Msg(data)
+	d := opt.Msg
+	require.NoError(t, err)
+	require.Equal(t, d.OpCode, dhcpv4.OpcodeBootRequest)
+	require.Equal(t, d.HWType, iana.HWTypeEthernet)
+	require.Equal(t, d.HopCount, byte(3))
+	require.Equal(t, d.TransactionID, dhcpv4.TransactionID{0xaa, 0xbb, 0xcc, 0xdd})
+	require.Equal(t, d.NumSeconds, uint16(3))
+	require.Equal(t, d.Flags, uint16(1))
+	require.True(t, d.ClientIPAddr.Equal(net.IPv4zero))
+	require.True(t, d.YourIPAddr.Equal(net.IPv4zero))
+	require.True(t, d.GatewayIPAddr.Equal(net.IPv4zero))
+	require.Equal(t, d.ClientHWAddr, net.HardwareAddr{0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff})
+	require.Equal(t, d.ServerHostName, "")
+	require.Equal(t, d.BootFileName, "")
+	// no need to check Magic Cookie as it is already validated in FromBytes
+	// above
+}
+
+func TestOptDHCPv4MsgToBytes(t *testing.T) {
+	// the following bytes match what dhcpv4.New would create. Keep them in
+	// sync!
+	expected := []byte{
+		1,                      // Opcode BootRequest
+		1,                      // HwType Ethernet
+		6,                      // HwAddrLen
+		0,                      // HopCount
+		0x11, 0x22, 0x33, 0x44, // TransactionID
+		0, 0, // NumSeconds
+		0, 0, // Flags
+		0, 0, 0, 0, // ClientIPAddr
+		0, 0, 0, 0, // YourIPAddr
+		0, 0, 0, 0, // ServerIPAddr
+		0, 0, 0, 0, // GatewayIPAddr
+		0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // ClientHwAddr
+	}
+	// ServerHostName
+	expected = append(expected, bytes.Repeat([]byte{0}, 64)...)
+	// BootFileName
+	expected = append(expected, bytes.Repeat([]byte{0}, 128)...)
+
+	// Magic Cookie
+	expected = append(expected, magicCookie[:]...)
+
+	// Minimum message length padding.
+	//
+	// 236 + 4 byte cookie + 59 bytes padding + 1 byte end.
+	expected = append(expected, bytes.Repeat([]byte{0}, 59)...)
+
+	// End
+	expected = append(expected, 0xff)
+
+	d, err := dhcpv4.New()
+	require.NoError(t, err)
+	// fix TransactionID to match the expected one, since it's randomly
+	// generated in New()
+	d.TransactionID = dhcpv4.TransactionID{0x11, 0x22, 0x33, 0x44}
+	opt := OptDHCPv4Msg{Msg: d}
+	require.Equal(t, expected, opt.ToBytes())
+}
diff --git a/dhcpv6/option_dhcpv4_o_dhcpv6_server.go b/dhcpv6/option_dhcpv4_o_dhcpv6_server.go
new file mode 100644
index 0000000..a46ecac
--- /dev/null
+++ b/dhcpv6/option_dhcpv4_o_dhcpv6_server.go
@@ -0,0 +1,46 @@
+package dhcpv6
+
+import (
+	"fmt"
+	"net"
+
+	"github.com/u-root/u-root/pkg/uio"
+)
+
+// OptDHCP4oDHCP6Server represents a OptionDHCP4oDHCP6Server option
+//
+// This module defines the OptDHCP4oDHCP6Server structure.
+// https://www.ietf.org/rfc/rfc7341.txt
+type OptDHCP4oDHCP6Server struct {
+	DHCP4oDHCP6Servers []net.IP
+}
+
+// Code returns the option code
+func (op *OptDHCP4oDHCP6Server) Code() OptionCode {
+	return OptionDHCP4oDHCP6Server
+}
+
+// ToBytes returns the option serialized to bytes.
+func (op *OptDHCP4oDHCP6Server) ToBytes() []byte {
+	buf := uio.NewBigEndianBuffer(nil)
+	for _, addr := range op.DHCP4oDHCP6Servers {
+		buf.WriteBytes(addr.To16())
+	}
+	return buf.Data()
+}
+
+func (op *OptDHCP4oDHCP6Server) String() string {
+	return fmt.Sprintf("OptDHCP4oDHCP6Server{4o6-servers=%v}", op.DHCP4oDHCP6Servers)
+}
+
+// ParseOptDHCP4oDHCP6Server builds an OptDHCP4oDHCP6Server structure
+// from a sequence of bytes. The input data does not include option code and length
+// bytes.
+func ParseOptDHCP4oDHCP6Server(data []byte) (*OptDHCP4oDHCP6Server, error) {
+	var opt OptDHCP4oDHCP6Server
+	buf := uio.NewBigEndianBuffer(data)
+	for buf.Has(net.IPv6len) {
+		opt.DHCP4oDHCP6Servers = append(opt.DHCP4oDHCP6Servers, buf.CopyN(net.IPv6len))
+	}
+	return &opt, buf.FinError()
+}
diff --git a/dhcpv6/option_dhcpv4_o_dhcpv6_server_test.go b/dhcpv6/option_dhcpv4_o_dhcpv6_server_test.go
new file mode 100644
index 0000000..de86594
--- /dev/null
+++ b/dhcpv6/option_dhcpv4_o_dhcpv6_server_test.go
@@ -0,0 +1,55 @@
+package dhcpv6
+
+import (
+	"net"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestParseOptDHCP4oDHCP6Server(t *testing.T) {
+	data := []byte{
+		0x2a, 0x03, 0x28, 0x80, 0xff, 0xfe, 0x00, 0x0c, 0xfa, 0xce, 0xb0, 0x0c, 0x00, 0x00, 0x00, 0x35,
+	}
+	expected := []net.IP{
+		net.IP(data),
+	}
+	opt, err := ParseOptDHCP4oDHCP6Server(data)
+	require.NoError(t, err)
+	require.Equal(t, expected, opt.DHCP4oDHCP6Servers)
+	require.Equal(t, OptionDHCP4oDHCP6Server, opt.Code())
+	require.Contains(t, opt.String(), "4o6-servers=[2a03:2880:fffe:c:face:b00c:0:35]", "String() should contain the correct DHCP4-over-DHCP6 server output")
+}
+
+func TestOptDHCP4oDHCP6ServerToBytes(t *testing.T) {
+	ip1 := net.ParseIP("2a03:2880:fffe:c:face:b00c:0:35")
+	ip2 := net.ParseIP("2001:4860:4860::8888")
+	servers := []net.IP{ip1, ip2}
+	expected := append([]byte{}, []byte(ip1)...)
+	expected = append(expected, []byte(ip2)...)
+	opt := OptDHCP4oDHCP6Server{DHCP4oDHCP6Servers: servers}
+	require.Equal(t, expected, opt.ToBytes())
+}
+
+func TestParseOptDHCP4oDHCP6ServerParseNoAddr(t *testing.T) {
+	data := []byte{
+	}
+	var expected []net.IP
+	opt, err := ParseOptDHCP4oDHCP6Server(data)
+	require.NoError(t, err)
+	require.Equal(t, expected, opt.DHCP4oDHCP6Servers)
+}
+
+func TestOptDHCP4oDHCP6ServerToBytesNoAddr(t *testing.T) {
+	expected := []byte(nil)
+	opt := OptDHCP4oDHCP6Server{}
+	require.Equal(t, expected, opt.ToBytes())
+}
+
+func TestParseOptDHCP4oDHCP6ServerParseBogus(t *testing.T) {
+	data := []byte{
+		0x2a, 0x03, 0x28, 0x80, 0xff, 0xfe, 0x00, 0x0c, // invalid IPv6 address
+	}
+	_, err := ParseOptDHCP4oDHCP6Server(data)
+	require.Error(t, err, "An invalid IPv6 address should return an error")
+}
diff --git a/dhcpv6/options.go b/dhcpv6/options.go
index 9b76f6d..87a33ff 100644
--- a/dhcpv6/options.go
+++ b/dhcpv6/options.go
@@ -87,6 +87,10 @@ func ParseOption(code OptionCode, optData []byte) (Option, error) {
 		var o OptNetworkInterfaceID
 		err = o.FromBytes(optData)
 		opt = &o
+	case OptionDHCPv4Msg:
+		opt, err = ParseOptDHCPv4Msg(optData)
+	case OptionDHCP4oDHCP6Server:
+		opt, err = ParseOptDHCP4oDHCP6Server(optData)
 	case Option4RD:
 		opt, err = ParseOpt4RD(optData)
 	case Option4RDMapRule:
diff --git a/dhcpv6/types.go b/dhcpv6/types.go
index 560581c..7c4052f 100644
--- a/dhcpv6/types.go
+++ b/dhcpv6/types.go
@@ -36,6 +36,10 @@ const (
 	MessageTypeLeaseQueryReply    MessageType = 15
 	MessageTypeLeaseQueryDone     MessageType = 16
 	MessageTypeLeaseQueryData     MessageType = 17
+	_                             MessageType = 18
+	_                             MessageType = 19
+	MessageTypeDHCPv4Query        MessageType = 20
+	MessageTypeDHCPv4Response     MessageType = 21
 )
 
 // String prints the message type name.
@@ -66,6 +70,8 @@ var messageTypeToStringMap = map[MessageType]string{
 	MessageTypeLeaseQueryReply:    "LEASEQUERY-REPLY",
 	MessageTypeLeaseQueryDone:     "LEASEQUERY-DONE",
 	MessageTypeLeaseQueryData:     "LEASEQUERY-DATA",
+	MessageTypeDHCPv4Query:        "DHCPv4-QUERY",
+	MessageTypeDHCPv4Response:     "DHCPv4-RESPONSE",
 }
 
 // OptionCode is a single byte representing the code for a given Option.