add OptDomainSearch (#111)

6 files changed, 115 insertions, 5 deletions

diff --git a/dhcpv4/option_domain_search.go b/dhcpv4/option_domain_search.go
new file mode 100644
index 0000000..daade0a
--- /dev/null
+++ b/dhcpv4/option_domain_search.go
@@ -0,0 +1,63 @@
+package dhcpv4
+
+// This module defines the OptDomainSearch structure.
+// https://tools.ietf.org/html/rfc3397
+
+import (
+	"fmt"
+
+	"github.com/insomniacslk/dhcp/rfc1035label"
+)
+
+// OptDomainSearch represents an option encapsulating a domain search list.
+type OptDomainSearch struct {
+	DomainSearch []string
+}
+
+// Code returns the option code.
+func (op *OptDomainSearch) Code() OptionCode {
+	return OptionDNSDomainSearchList
+}
+
+// ToBytes returns a serialized stream of bytes for this option.
+func (op *OptDomainSearch) ToBytes() []byte {
+	buf := []byte{byte(op.Code()), byte(op.Length())}
+	buf = append(buf, rfc1035label.LabelsToBytes(op.DomainSearch)...)
+	return buf
+}
+
+// Length returns the length of the data portion (excluding option code an byte
+// length). 
+func (op *OptDomainSearch) Length() int {
+	var length int
+	for _, label := range op.DomainSearch {
+		length += len(label) + 2 // add the first and the last length bytes
+	}
+	return length
+}
+
+// String returns a human-readable string.
+func (op *OptDomainSearch) String() string {
+	return fmt.Sprintf("DNS Domain Search List -> %v", op.DomainSearch)
+}
+
+// ParseOptDomainSearch returns a new OptDomainSearch from a byte stream, or
+// error if any.
+func ParseOptDomainSearch(data []byte) (*OptDomainSearch, error) {
+	if len(data) < 2 {
+		return nil, ErrShortByteStream
+	}
+	code := OptionCode(data[0])
+	if code != OptionDNSDomainSearchList {
+		return nil, fmt.Errorf("expected code %v, got %v", OptionDNSDomainSearchList, code)
+	}
+	length := int(data[1])
+	if len(data) < 2+length {
+		return nil, ErrShortByteStream
+	}
+	domainSearch, err := rfc1035label.LabelsFromBytes(data[2:length+2])
+	if err != nil {
+		return nil, err
+	}
+	return &OptDomainSearch{DomainSearch: domainSearch}, nil
+}
diff --git a/dhcpv4/option_domain_search_test.go b/dhcpv4/option_domain_search_test.go
new file mode 100644
index 0000000..4848a83
--- /dev/null
+++ b/dhcpv4/option_domain_search_test.go
@@ -0,0 +1,37 @@
+package dhcpv4
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestParseOptDomainSearch(t *testing.T) {
+	data := []byte{
+		119, // OptionDNSDomainSearchList
+		33,  // length
+		7, 'e', 'x', 'a', 'm', 'p', 'l', 'e', 3, 'c', 'o', 'm', 0,
+		6, 's', 'u', 'b', 'n', 'e', 't', 7, 'e', 'x', 'a', 'm', 'p', 'l', 'e', 3, 'o', 'r', 'g', 0,
+	}
+	opt, err := ParseOptDomainSearch(data)
+	require.NoError(t, err)
+	require.Equal(t, len(opt.DomainSearch), 2)
+	require.Equal(t, opt.DomainSearch[0], "example.com")
+	require.Equal(t, opt.DomainSearch[1], "subnet.example.org")
+}
+
+func TestOptDomainSearchToBytes(t *testing.T) {
+	expected := []byte{
+		119, // OptionDNSDomainSearchList
+		33,  // length
+		7, 'e', 'x', 'a', 'm', 'p', 'l', 'e', 3, 'c', 'o', 'm', 0,
+		6, 's', 'u', 'b', 'n', 'e', 't', 7, 'e', 'x', 'a', 'm', 'p', 'l', 'e', 3, 'o', 'r', 'g', 0,
+	}
+	opt := OptDomainSearch{
+		DomainSearch: []string{
+			"example.com",
+			"subnet.example.org",
+		},
+	}
+	require.Equal(t, opt.ToBytes(), expected)
+}
diff --git a/dhcpv4/options.go b/dhcpv4/options.go
index 22e6eee..0be494f 100644
--- a/dhcpv4/options.go
+++ b/dhcpv4/options.go
@@ -76,6 +76,8 @@ func ParseOption(data []byte) (Option, error) {
 		opt, err = ParseOptBootfileName(data)
 	case OptionUserClassInformation:
 		opt, err = ParseOptUserClass(data)
+	case OptionDNSDomainSearchList:
+		opt, err = ParseOptDomainSearch(data)
 	default:
 		opt, err = ParseOptionGeneric(data)
 	}
diff --git a/dhcpv6/option_domainsearchlist.go b/dhcpv6/option_domainsearchlist.go
index 6e5504c..a3c6f28 100644
--- a/dhcpv6/option_domainsearchlist.go
+++ b/dhcpv6/option_domainsearchlist.go
@@ -6,6 +6,8 @@ package dhcpv6
 import (
 	"encoding/binary"
 	"fmt"
+
+	"github.com/insomniacslk/dhcp/rfc1035label"
 )
 
 // OptDomainSearchList list implements a OptionDomainSearchList option
@@ -21,7 +23,7 @@ func (op *OptDomainSearchList) ToBytes() []byte {
 	buf := make([]byte, 4)
 	binary.BigEndian.PutUint16(buf[0:2], uint16(OptionDomainSearchList))
 	binary.BigEndian.PutUint16(buf[2:4], uint16(op.Length()))
-	buf = append(buf, LabelsToBytes(op.DomainSearchList)...)
+	buf = append(buf, rfc1035label.LabelsToBytes(op.DomainSearchList)...)
 	return buf
 }
 
@@ -42,7 +44,7 @@ func (op *OptDomainSearchList) String() string {
 func ParseOptDomainSearchList(data []byte) (*OptDomainSearchList, error) {
 	opt := OptDomainSearchList{}
 	var err error
-	opt.DomainSearchList, err = LabelsFromBytes(data)
+	opt.DomainSearchList, err = rfc1035label.LabelsFromBytes(data)
 	if err != nil {
 		return nil, err
 	}
diff --git a/dhcpv6/option_rfc1035label.go b/rfc1035label/label.go
index 06870b5..c63b4af 100644
--- a/dhcpv6/option_rfc1035label.go
+++ b/rfc1035label/label.go
@@ -1,10 +1,14 @@
-package dhcpv6
+package rfc1035label
 
 import (
 	"fmt"
 	"strings"
 )
 
+// This implements the compression from RFC 1035, section 4.1.4
+// https://tools.ietf.org/html/rfc1035
+
+// LabelsFromBytes decodes a serialized stream and returns a list of labels
 func LabelsFromBytes(buf []byte) ([]string, error) {
 	var (
 		pos     = 0
@@ -30,9 +34,9 @@ func LabelsFromBytes(buf []byte) ([]string, error) {
 		label += string(buf[pos : pos+length])
 		pos += length
 	}
-	return domains, nil
 }
 
+// LabelToBytes encodes a label and returns a serialized stream of bytes
 func LabelToBytes(label string) []byte {
 	var encodedLabel []byte
 	if len(label) == 0 {
@@ -45,6 +49,8 @@ func LabelToBytes(label string) []byte {
 	return append(encodedLabel, 0)
 }
 
+// LabelsToBytes encodes a list of labels and returns a serialized stream of
+// bytes
 func LabelsToBytes(labels []string) []byte {
 	var encodedLabels []byte
 	for _, label := range labels {
diff --git a/dhcpv6/option_rfc1035label_test.go b/rfc1035label/label_test.go
index f99c209..f91110b 100644
--- a/dhcpv6/option_rfc1035label_test.go
+++ b/rfc1035label/label_test.go
@@ -1,4 +1,4 @@
-package dhcpv6
+package rfc1035label
 
 import (
 	"bytes"