add OptNTPServers (#115)

4 files changed, 138 insertions, 1 deletions

diff --git a/dhcpv4/option_ntp_servers.go b/dhcpv4/option_ntp_servers.go
new file mode 100644
index 0000000..39881d6
--- /dev/null
+++ b/dhcpv4/option_ntp_servers.go
@@ -0,0 +1,70 @@
+package dhcpv4
+
+import (
+	"fmt"
+	"net"
+)
+
+// This option implements the network time protocol servers option
+// https://tools.ietf.org/html/rfc2132
+
+// OptNTPServers represents an option encapsulating the NTP servers.
+type OptNTPServers struct {
+	NTPServers []net.IP
+}
+
+// ParseOptNTPServers returns a new OptNTPServers from a byte stream, or error if any.
+func ParseOptNTPServers(data []byte) (*OptNTPServers, error) {
+	if len(data) < 2 {
+		return nil, ErrShortByteStream
+	}
+	code := OptionCode(data[0])
+	if code != OptionNTPServers {
+		return nil, fmt.Errorf("expected code %v, got %v", OptionNTPServers, code)
+	}
+	length := int(data[1])
+	if length == 0 || length%4 != 0 {
+		return nil, fmt.Errorf("Invalid length: expected multiple of 4 larger than 4, got %v", length)
+	}
+	if len(data) < 2+length {
+		return nil, ErrShortByteStream
+	}
+	ntpServers := make([]net.IP, 0, length%4)
+	for idx := 0; idx < length; idx += 4 {
+		b := data[2+idx : 2+idx+4]
+		ntpServers = append(ntpServers, net.IPv4(b[0], b[1], b[2], b[3]))
+	}
+	return &OptNTPServers{NTPServers: ntpServers}, nil
+}
+
+// Code returns the option code.
+func (o *OptNTPServers) Code() OptionCode {
+	return OptionNTPServers
+}
+
+// ToBytes returns a serialized stream of bytes for this option.
+func (o *OptNTPServers) ToBytes() []byte {
+	ret := []byte{byte(o.Code()), byte(o.Length())}
+	for _, ntp := range o.NTPServers {
+		ret = append(ret, ntp.To4()...)
+	}
+	return ret
+}
+
+// String returns a human-readable string.
+func (o *OptNTPServers) String() string {
+	var ntpServers string
+	for idx, ntp := range o.NTPServers {
+		ntpServers += ntp.String()
+		if idx < len(o.NTPServers)-1 {
+			ntpServers += ", "
+		}
+	}
+	return fmt.Sprintf("NTP Servers -> %v", ntpServers)
+}
+
+// Length returns the length of the data portion (excluding option code an byte
+// length).
+func (o *OptNTPServers) Length() int {
+	return len(o.NTPServers) * 4
+}
diff --git a/dhcpv4/option_ntp_servers_test.go b/dhcpv4/option_ntp_servers_test.go
new file mode 100644
index 0000000..e7bcefd
--- /dev/null
+++ b/dhcpv4/option_ntp_servers_test.go
@@ -0,0 +1,65 @@
+package dhcpv4
+
+import (
+	"net"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestOptNTPServersInterfaceMethods(t *testing.T) {
+	ntpServers := []net.IP{
+		net.IPv4(192, 168, 0, 10),
+		net.IPv4(192, 168, 0, 20),
+	}
+	o := OptNTPServers{NTPServers: ntpServers}
+	require.Equal(t, OptionNTPServers, o.Code(), "Code")
+	require.Equal(t, net.IPv4len*len(ntpServers), o.Length(), "Length")
+	require.Equal(t, ntpServers, o.NTPServers, "NTPServers")
+}
+
+func TestParseOptNTPServers(t *testing.T) {
+	data := []byte{
+		byte(OptionNTPServers),
+		8,               // Length
+		192, 168, 0, 10, // NTP server #1
+		192, 168, 0, 20, // NTP server #2
+	}
+	o, err := ParseOptNTPServers(data)
+	require.NoError(t, err)
+	ntpServers := []net.IP{
+		net.IPv4(192, 168, 0, 10),
+		net.IPv4(192, 168, 0, 20),
+	}
+	require.Equal(t, &OptNTPServers{NTPServers: ntpServers}, o)
+
+	// Short byte stream
+	data = []byte{byte(OptionNTPServers)}
+	_, err = ParseOptNTPServers(data)
+	require.Error(t, err, "should get error from short byte stream")
+
+	// Wrong code
+	data = []byte{54, 2, 1, 1}
+	_, err = ParseOptNTPServers(data)
+	require.Error(t, err, "should get error from wrong code")
+
+	// Bad length
+	data = []byte{byte(OptionNTPServers), 6, 1, 1, 1}
+	_, err = ParseOptNTPServers(data)
+	require.Error(t, err, "should get error from bad length")
+}
+
+func TestParseOptNTPserversNoNTPServers(t *testing.T) {
+	// RFC2132 requires that at least one NTP server IP is specified
+	data := []byte{
+		byte(OptionNTPServers),
+		0, // Length
+	}
+	_, err := ParseOptNTPServers(data)
+	require.Error(t, err)
+}
+
+func TestOptNTPServersString(t *testing.T) {
+	o := OptNTPServers{NTPServers: []net.IP{net.IPv4(192, 168, 0, 1), net.IPv4(192, 168, 0, 10)}}
+	require.Equal(t, "NTP Servers -> 192.168.0.1, 192.168.0.10", o.String())
+}
diff --git a/dhcpv4/option_router.go b/dhcpv4/option_router.go
index b9bdff1..3154edd 100644
--- a/dhcpv4/option_router.go
+++ b/dhcpv4/option_router.go
@@ -13,7 +13,7 @@ type OptRouter struct {
 	Routers []net.IP
 }
 
-// ParseOptRouter returns a new OptRouter from a byte  stream, or error if any.
+// ParseOptRouter returns a new OptRouter from a byte stream, or error if any.
 func ParseOptRouter(data []byte) (*OptRouter, error) {
 	if len(data) < 2 {
 		return nil, ErrShortByteStream
diff --git a/dhcpv4/options.go b/dhcpv4/options.go
index 53b2ecf..22e6eee 100644
--- a/dhcpv4/options.go
+++ b/dhcpv4/options.go
@@ -46,6 +46,8 @@ func ParseOption(data []byte) (Option, error) {
 		opt, err = ParseOptRouter(data)
 	case OptionHostName:
 		opt, err = ParseOptHostName(data)
+	case OptionNTPServers:
+		opt, err = ParseOptNTPServers(data)
 	case OptionRequestedIPAddress:
 		opt, err = ParseOptRequestedIPAddress(data)
 	case OptionIPAddressLeaseTime: