Merge branch 'master' into bsdp-acks

7 files changed, 453 insertions, 114 deletions

diff --git a/dhcpv4/bsdp/bsdp.go b/dhcpv4/bsdp/bsdp.go
index 3402b0c..e15c59c 100644
--- a/dhcpv4/bsdp/bsdp.go
+++ b/dhcpv4/bsdp/bsdp.go
@@ -40,7 +40,7 @@ func ParseBootImageListFromAck(ack dhcpv4.DHCPv4) ([]BootImage, error) {
 	if err != nil {
 		return nil, err
 	}
-	bootImageOpts := vendorOpt.GetOptions(OptionBootImageList)
+	bootImageOpts := vendorOpt.GetOption(OptionBootImageList)
 	for _, opt := range bootImageOpts {
 		images = append(images, opt.(*OptBootImageList).Images...)
 	}
@@ -53,8 +53,30 @@ func needsReplyPort(replyPort uint16) bool {
 
 // NewInformListForInterface creates a new INFORM packet for interface ifname
 // with configuration options specified by config.
-func NewInformListForInterface(iface string, replyPort uint16) (*dhcpv4.DHCPv4, error) {
-	d, err := dhcpv4.NewInformForInterface(iface /* needsBroadcast = */, false)
+func NewInformListForInterface(ifname string, replyPort uint16) (*dhcpv4.DHCPv4, error) {
+	iface, err := net.InterfaceByName(ifname)
+	if err != nil {
+		return nil, err
+	}
+	// Get currently configured IP.
+	addrs, err := iface.Addrs()
+	if err != nil {
+		return nil, err
+	}
+	localIPs, err := dhcpv4.GetExternalIPv4Addrs(addrs)
+	if err != nil {
+		return nil, fmt.Errorf("could not get local IPv4 addr for %s: %v", iface.Name, err)
+	}
+	if localIPs == nil || len(localIPs) == 0 {
+		return nil, fmt.Errorf("could not get local IPv4 addr for %s", iface.Name)
+	}
+	return NewInformList(iface.HardwareAddr, localIPs[0], replyPort)
+}
+
+// NewInformList creates a new INFORM packet for interface with hardware address
+// `hwaddr` and IP `localIP`. Packet will be sent out on port `replyPort`.
+func NewInformList(hwaddr net.HardwareAddr, localIP net.IP, replyPort uint16) (*dhcpv4.DHCPv4, error) {
+	d, err := dhcpv4.NewInform(hwaddr, localIP)
 	if err != nil {
 		return nil, err
 	}
@@ -91,7 +113,7 @@ func NewInformListForInterface(iface string, replyPort uint16) (*dhcpv4.DHCPv4,
 }
 
 // InformSelectForAck constructs an INFORM[SELECT] packet given an ACK to the
-// previously-sent INFORM[LIST] with Config config.
+// previously-sent INFORM[LIST].
 func InformSelectForAck(ack dhcpv4.DHCPv4, replyPort uint16, selectedImage BootImage) (*dhcpv4.DHCPv4, error) {
 	d, err := dhcpv4.New()
 	if err != nil {
diff --git a/dhcpv4/bsdp/bsdp_option_generic_test.go b/dhcpv4/bsdp/bsdp_option_generic_test.go
index 5abcfbd..27436dd 100644
--- a/dhcpv4/bsdp/bsdp_option_generic_test.go
+++ b/dhcpv4/bsdp/bsdp_option_generic_test.go
@@ -10,6 +10,16 @@ func TestParseOptGeneric(t *testing.T) {
 	// Empty bytestream produces error
 	_, err := ParseOptGeneric([]byte{})
 	require.Error(t, err, "error from empty bytestream")
+
+	// Good parse
+	o, err := ParseOptGeneric([]byte{1, 1, 1})
+	require.NoError(t, err)
+	require.Equal(t, OptionMessageType, o.Code())
+	require.Equal(t, MessageTypeList, MessageType(o.Data[0]))
+
+	// Bad parse
+	o, err = ParseOptGeneric([]byte{1, 2, 1})
+	require.Error(t, err, "invalid length")
 }
 
 func TestOptGenericCode(t *testing.T) {
diff --git a/dhcpv4/bsdp/bsdp_test.go b/dhcpv4/bsdp/bsdp_test.go
index fc1aedf..6029d49 100644
--- a/dhcpv4/bsdp/bsdp_test.go
+++ b/dhcpv4/bsdp/bsdp_test.go
@@ -52,43 +52,31 @@ func TestNeedsReplyPort(t *testing.T) {
 	require.False(t, needsReplyPort(dhcpv4.ClientPort))
 }
 
-// TODO(get9): Remove when #99 lands.
-func newInform() *dhcpv4.DHCPv4 {
-	p, _ := dhcpv4.New()
-	p.SetClientIPAddr(net.IP{1, 2, 3, 4})
-	p.SetGatewayIPAddr(net.IP{4, 3, 2, 1})
-	p.SetHwType(iana.HwTypeEthernet)
-	hwAddr := [16]byte{1, 2, 3, 4, 5, 6}
-	p.SetClientHwAddr(hwAddr[:])
-	p.SetHwAddrLen(6)
-	return p
-}
-
-func TestNewReplyForInformList_NoDefaultImage(t *testing.T) {
+func TestNewReplyForInformSelect_NoSelectedImage(t *testing.T) {
 	inform := newInform()
-	_, err := NewReplyForInformList(inform, ReplyConfig{})
+	_, err := NewReplyForInformSelect(inform, ReplyConfig{})
 	require.Error(t, err)
 }
 
-func TestNewReplyForInformList_NoImages(t *testing.T) {
+func TestNewReplyForInformSelect_NoImages(t *testing.T) {
 	inform := newInform()
 	fakeImage := BootImage{
 		ID: BootImageID{ImageType: BootImageTypeMacOSX},
 	}
-	_, err := NewReplyForInformList(inform, ReplyConfig{
-		Images:       []BootImage{},
-		DefaultImage: &fakeImage,
+	_, err := NewReplyForInformSelect(inform, ReplyConfig{
+		Images:        []BootImage{},
+		SelectedImage: &fakeImage,
 	})
 	require.Error(t, err)
 
-	_, err = NewReplyForInformList(inform, ReplyConfig{
+	_, err = NewReplyForInformSelect(inform, ReplyConfig{
 		Images:        nil,
 		SelectedImage: &fakeImage,
 	})
+	require.Error(t, err)
 }
 
-// TODO (get9): clean up when #99 lands.
-func TestNewReplyForInformList(t *testing.T) {
+func TestNewReplyForInformSelect(t *testing.T) {
 	inform := newInform()
 	images := []BootImage{
 		BootImage{
@@ -110,12 +98,12 @@ func TestNewReplyForInformList(t *testing.T) {
 	}
 	config := ReplyConfig{
 		Images:         images,
-		DefaultImage:   &images[0],
+		SelectedImage:  &images[0],
 		ServerIP:       net.IP{9, 9, 9, 9},
 		ServerHostname: "bsdp.foo.com",
 		ServerPriority: 0x7070,
 	}
-	ack, err := NewReplyForInformList(inform, config)
+	ack, err := NewReplyForInformSelect(inform, config)
 	require.NoError(t, err)
 	require.Equal(t, net.IP{1, 2, 3, 4}, ack.ClientIPAddr())
 	require.Equal(t, net.IPv4zero, ack.YourIPAddr())
@@ -144,62 +132,221 @@ func TestNewReplyForInformList(t *testing.T) {
 	vendorOpts := ack.GetOneOption(dhcpv4.OptionVendorSpecificInformation).(*OptVendorSpecificInformation)
 	require.Equal(
 		t,
-		&OptMessageType{Type: MessageTypeList},
+		&OptMessageType{Type: MessageTypeSelect},
 		vendorOpts.GetOneOption(OptionMessageType).(*OptMessageType),
 	)
 	require.Equal(
 		t,
-		&OptServerPriority{Priority: 0x7070},
-		vendorOpts.GetOneOption(OptionServerPriority).(*OptServerPriority),
-	)
-	require.Equal(
-		t,
-		&OptDefaultBootImageID{ID: images[0].ID},
-		vendorOpts.GetOneOption(OptionDefaultBootImageID).(*OptDefaultBootImageID),
-	)
-	require.Equal(
-		t,
-		&OptBootImageList{Images: images},
-		vendorOpts.GetOneOption(OptionBootImageList).(*OptBootImageList),
-	)
-
-	// Add in selected boot image, ensure it's in the generated ACK.
-	config.SelectedImage = &images[0]
-	ack, err = NewReplyForInformList(inform, config)
-	require.NoError(t, err)
-	vendorOpts = ack.GetOneOption(dhcpv4.OptionVendorSpecificInformation).(*OptVendorSpecificInformation)
-	require.Equal(
-		t,
 		&OptSelectedBootImageID{ID: images[0].ID},
 		vendorOpts.GetOneOption(OptionSelectedBootImageID).(*OptSelectedBootImageID),
 	)
 }
 
-func TestNewReplyForInformSelect_NoSelectedImage(t *testing.T) {
+func TestNewInformList_NoReplyPort(t *testing.T) {
+	hwAddr := net.HardwareAddr{1, 2, 3, 4, 5, 6}
+	localIP := net.IPv4(10, 10, 11, 11)
+	m, err := NewInformList(hwAddr, localIP, 0)
+
+	require.NoError(t, err)
+	require.True(t, dhcpv4.HasOption(m, dhcpv4.OptionVendorSpecificInformation))
+	require.True(t, dhcpv4.HasOption(m, dhcpv4.OptionParameterRequestList))
+	require.True(t, dhcpv4.HasOption(m, dhcpv4.OptionMaximumDHCPMessageSize))
+	require.True(t, dhcpv4.HasOption(m, dhcpv4.OptionEnd))
+
+	opt := m.GetOneOption(dhcpv4.OptionVendorSpecificInformation)
+	require.NotNil(t, opt, "vendor opts not present")
+	vendorInfo := opt.(*OptVendorSpecificInformation)
+	require.True(t, dhcpv4.HasOption(vendorInfo, OptionMessageType))
+	require.True(t, dhcpv4.HasOption(vendorInfo, OptionVersion))
+
+	opt = vendorInfo.GetOneOption(OptionMessageType)
+	require.Equal(t, MessageTypeList, opt.(*OptMessageType).Type)
+}
+
+func TestNewInformList_ReplyPort(t *testing.T) {
+	hwAddr := net.HardwareAddr{1, 2, 3, 4, 5, 6}
+	localIP := net.IPv4(10, 10, 11, 11)
+	replyPort := uint16(11223)
+
+	// Bad reply port
+	_, err := NewInformList(hwAddr, localIP, replyPort)
+	require.Error(t, err)
+
+	// Good reply port
+	replyPort = uint16(999)
+	m, err := NewInformList(hwAddr, localIP, replyPort)
+	require.NoError(t, err)
+
+	opt := m.GetOneOption(dhcpv4.OptionVendorSpecificInformation)
+	vendorInfo := opt.(*OptVendorSpecificInformation)
+	require.True(t, dhcpv4.HasOption(vendorInfo, OptionReplyPort))
+
+	opt = vendorInfo.GetOneOption(OptionReplyPort)
+	require.Equal(t, replyPort, opt.(*OptReplyPort).Port)
+}
+
+func newAck(hwAddr []byte, transactionID uint32) *dhcpv4.DHCPv4 {
+	ack, _ := dhcpv4.New()
+	ack.SetTransactionID(transactionID)
+	ack.SetHwType(iana.HwTypeEthernet)
+	ack.SetClientHwAddr(hwAddr)
+	ack.SetHwAddrLen(uint8(len(hwAddr)))
+	ack.AddOption(&dhcpv4.OptMessageType{MessageType: dhcpv4.MessageTypeAck})
+	ack.AddOption(&dhcpv4.OptionGeneric{OptionCode: dhcpv4.OptionEnd})
+	return ack
+}
+
+func TestInformSelectForAck_Broadcast(t *testing.T) {
+	hwAddr := []byte{0x11, 0x22, 0x33, 0x44, 0x55, 0x66}
+	tid := uint32(22)
+	serverID := net.IPv4(1, 2, 3, 4)
+	bootImage := BootImage{
+		ID: BootImageID{
+			IsInstall: true,
+			ImageType: BootImageTypeMacOSX,
+			Index:     0x1000,
+		},
+		Name: "bsdp-1",
+	}
+	ack := newAck(hwAddr, tid)
+	ack.SetBroadcast()
+	ack.AddOption(&dhcpv4.OptServerIdentifier{ServerID: serverID})
+
+	m, err := InformSelectForAck(*ack, 0, bootImage)
+	require.NoError(t, err)
+	require.Equal(t, dhcpv4.OpcodeBootRequest, m.Opcode())
+	require.Equal(t, ack.HwType(), m.HwType())
+	require.Equal(t, ack.ClientHwAddr(), m.ClientHwAddr())
+	require.Equal(t, ack.TransactionID(), m.TransactionID())
+	require.True(t, m.IsBroadcast())
+
+	// Validate options.
+	require.True(t, dhcpv4.HasOption(m, dhcpv4.OptionClassIdentifier))
+	require.True(t, dhcpv4.HasOption(m, dhcpv4.OptionParameterRequestList))
+	require.True(t, dhcpv4.HasOption(m, dhcpv4.OptionDHCPMessageType))
+	opt := m.GetOneOption(dhcpv4.OptionDHCPMessageType)
+	require.Equal(t, dhcpv4.MessageTypeInform, opt.(*dhcpv4.OptMessageType).MessageType)
+	require.True(t, dhcpv4.HasOption(m, dhcpv4.OptionEnd))
+
+	// Validate vendor opts.
+	require.True(t, dhcpv4.HasOption(m, dhcpv4.OptionVendorSpecificInformation))
+	opt = m.GetOneOption(dhcpv4.OptionVendorSpecificInformation)
+	vendorInfo := opt.(*OptVendorSpecificInformation)
+	require.True(t, dhcpv4.HasOption(vendorInfo, OptionMessageType))
+	opt = vendorInfo.GetOneOption(OptionMessageType)
+	require.Equal(t, MessageTypeSelect, opt.(*OptMessageType).Type)
+	require.True(t, dhcpv4.HasOption(vendorInfo, OptionVersion))
+	require.True(t, dhcpv4.HasOption(vendorInfo, OptionSelectedBootImageID))
+	opt = vendorInfo.GetOneOption(OptionSelectedBootImageID)
+	require.Equal(t, bootImage.ID, opt.(*OptSelectedBootImageID).ID)
+	require.True(t, dhcpv4.HasOption(vendorInfo, OptionServerIdentifier))
+	opt = vendorInfo.GetOneOption(OptionServerIdentifier)
+	require.True(t, serverID.Equal(opt.(*OptServerIdentifier).ServerID))
+}
+
+func TestInformSelectForAck_NoServerID(t *testing.T) {
+	hwAddr := []byte{0x11, 0x22, 0x33, 0x44, 0x55, 0x66}
+	tid := uint32(22)
+	bootImage := BootImage{
+		ID: BootImageID{
+			IsInstall: true,
+			ImageType: BootImageTypeMacOSX,
+			Index:     0x1000,
+		},
+		Name: "bsdp-1",
+	}
+	ack := newAck(hwAddr, tid)
+
+	_, err := InformSelectForAck(*ack, 0, bootImage)
+	require.Error(t, err, "expect error for no server identifier option")
+}
+
+func TestInformSelectForAck_BadReplyPort(t *testing.T) {
+	hwAddr := []byte{0x11, 0x22, 0x33, 0x44, 0x55, 0x66}
+	tid := uint32(22)
+	serverID := net.IPv4(1, 2, 3, 4)
+	bootImage := BootImage{
+		ID: BootImageID{
+			IsInstall: true,
+			ImageType: BootImageTypeMacOSX,
+			Index:     0x1000,
+		},
+		Name: "bsdp-1",
+	}
+	ack := newAck(hwAddr, tid)
+	ack.SetBroadcast()
+	ack.AddOption(&dhcpv4.OptServerIdentifier{ServerID: serverID})
+
+	_, err := InformSelectForAck(*ack, 11223, bootImage)
+	require.Error(t, err, "expect error for > 1024 replyPort")
+}
+
+func TestInformSelectForAck_ReplyPort(t *testing.T) {
+	hwAddr := []byte{0x11, 0x22, 0x33, 0x44, 0x55, 0x66}
+	tid := uint32(22)
+	serverID := net.IPv4(1, 2, 3, 4)
+	bootImage := BootImage{
+		ID: BootImageID{
+			IsInstall: true,
+			ImageType: BootImageTypeMacOSX,
+			Index:     0x1000,
+		},
+		Name: "bsdp-1",
+	}
+	ack := newAck(hwAddr, tid)
+	ack.SetBroadcast()
+	ack.AddOption(&dhcpv4.OptServerIdentifier{ServerID: serverID})
+
+	replyPort := uint16(999)
+	m, err := InformSelectForAck(*ack, replyPort, bootImage)
+	require.NoError(t, err)
+
+	require.True(t, dhcpv4.HasOption(m, dhcpv4.OptionVendorSpecificInformation))
+	opt := m.GetOneOption(dhcpv4.OptionVendorSpecificInformation)
+	vendorInfo := opt.(*OptVendorSpecificInformation)
+	require.True(t, dhcpv4.HasOption(vendorInfo, OptionReplyPort))
+	opt = vendorInfo.GetOneOption(OptionReplyPort)
+	require.Equal(t, replyPort, opt.(*OptReplyPort).Port)
+}
+
+// TODO(get9): Remove when #99 lands.
+func newInform() *dhcpv4.DHCPv4 {
+	p, _ := dhcpv4.New()
+	p.SetClientIPAddr(net.IP{1, 2, 3, 4})
+	p.SetGatewayIPAddr(net.IP{4, 3, 2, 1})
+	p.SetHwType(iana.HwTypeEthernet)
+	hwAddr := [16]byte{1, 2, 3, 4, 5, 6}
+	p.SetClientHwAddr(hwAddr[:])
+	p.SetHwAddrLen(6)
+	return p
+}
+
+func TestNewReplyForInformList_NoDefaultImage(t *testing.T) {
 	inform := newInform()
-	_, err := NewReplyForInformSelect(inform, ReplyConfig{})
+	_, err := NewReplyForInformList(inform, ReplyConfig{})
 	require.Error(t, err)
 }
 
-func TestNewReplyForInformSelect_NoImages(t *testing.T) {
+func TestNewReplyForInformList_NoImages(t *testing.T) {
 	inform := newInform()
 	fakeImage := BootImage{
 		ID: BootImageID{ImageType: BootImageTypeMacOSX},
 	}
-	_, err := NewReplyForInformSelect(inform, ReplyConfig{
-		Images:        []BootImage{},
-		SelectedImage: &fakeImage,
+	_, err := NewReplyForInformList(inform, ReplyConfig{
+		Images:       []BootImage{},
+		DefaultImage: &fakeImage,
 	})
 	require.Error(t, err)
 
-	_, err = NewReplyForInformSelect(inform, ReplyConfig{
+	_, err = NewReplyForInformList(inform, ReplyConfig{
 		Images:        nil,
 		SelectedImage: &fakeImage,
 	})
 	require.Error(t, err)
 }
 
-func TestNewReplyForInformSelect(t *testing.T) {
+// TODO (get9): clean up when #99 lands.
+func TestNewReplyForInformList(t *testing.T) {
 	inform := newInform()
 	images := []BootImage{
 		BootImage{
@@ -221,12 +368,12 @@ func TestNewReplyForInformSelect(t *testing.T) {
 	}
 	config := ReplyConfig{
 		Images:         images,
-		SelectedImage:  &images[0],
+		DefaultImage:   &images[0],
 		ServerIP:       net.IP{9, 9, 9, 9},
 		ServerHostname: "bsdp.foo.com",
 		ServerPriority: 0x7070,
 	}
-	ack, err := NewReplyForInformSelect(inform, config)
+	ack, err := NewReplyForInformList(inform, config)
 	require.NoError(t, err)
 	require.Equal(t, net.IP{1, 2, 3, 4}, ack.ClientIPAddr())
 	require.Equal(t, net.IPv4zero, ack.YourIPAddr())
@@ -255,11 +402,32 @@ func TestNewReplyForInformSelect(t *testing.T) {
 	vendorOpts := ack.GetOneOption(dhcpv4.OptionVendorSpecificInformation).(*OptVendorSpecificInformation)
 	require.Equal(
 		t,
-		&OptMessageType{Type: MessageTypeSelect},
+		&OptMessageType{Type: MessageTypeList},
 		vendorOpts.GetOneOption(OptionMessageType).(*OptMessageType),
 	)
 	require.Equal(
 		t,
+		&OptServerPriority{Priority: 0x7070},
+		vendorOpts.GetOneOption(OptionServerPriority).(*OptServerPriority),
+	)
+	require.Equal(
+		t,
+		&OptDefaultBootImageID{ID: images[0].ID},
+		vendorOpts.GetOneOption(OptionDefaultBootImageID).(*OptDefaultBootImageID),
+	)
+	require.Equal(
+		t,
+		&OptBootImageList{Images: images},
+		vendorOpts.GetOneOption(OptionBootImageList).(*OptBootImageList),
+	)
+
+	// Add in selected boot image, ensure it's in the generated ACK.
+	config.SelectedImage = &images[0]
+	ack, err = NewReplyForInformList(inform, config)
+	require.NoError(t, err)
+	vendorOpts = ack.GetOneOption(dhcpv4.OptionVendorSpecificInformation).(*OptVendorSpecificInformation)
+	require.Equal(
+		t,
 		&OptSelectedBootImageID{ID: images[0].ID},
 		vendorOpts.GetOneOption(OptionSelectedBootImageID).(*OptSelectedBootImageID),
 	)
diff --git a/dhcpv4/bsdp/option_vendor_specific_information.go b/dhcpv4/bsdp/option_vendor_specific_information.go
index 645f0c8..e735b57 100644
--- a/dhcpv4/bsdp/option_vendor_specific_information.go
+++ b/dhcpv4/bsdp/option_vendor_specific_information.go
@@ -131,8 +131,8 @@ func (o *OptVendorSpecificInformation) Length() int {
 	return length
 }
 
-// GetOptions returns all suboptions that match the given OptionCode code.
-func (o *OptVendorSpecificInformation) GetOptions(code dhcpv4.OptionCode) []dhcpv4.Option {
+// GetOption returns all suboptions that match the given OptionCode code.
+func (o *OptVendorSpecificInformation) GetOption(code dhcpv4.OptionCode) []dhcpv4.Option {
 	var opts []dhcpv4.Option
 	for _, opt := range o.Options {
 		if opt.Code() == code {
@@ -142,9 +142,9 @@ func (o *OptVendorSpecificInformation) GetOptions(code dhcpv4.OptionCode) []dhcp
 	return opts
 }
 
-// GetOption returns the first suboption that matches the OptionCode code.
+// GetOneOption returns the first suboption that matches the OptionCode code.
 func (o *OptVendorSpecificInformation) GetOneOption(code dhcpv4.OptionCode) dhcpv4.Option {
-	opts := o.GetOptions(code)
+	opts := o.GetOption(code)
 	if len(opts) == 0 {
 		return nil
 	}
diff --git a/dhcpv4/bsdp/option_vendor_specific_information_test.go b/dhcpv4/bsdp/option_vendor_specific_information_test.go
index bcd28ca..5e7689d 100644
--- a/dhcpv4/bsdp/option_vendor_specific_information_test.go
+++ b/dhcpv4/bsdp/option_vendor_specific_information_test.go
@@ -71,6 +71,17 @@ func TestParseOptVendorSpecificInformation(t *testing.T) {
 	}
 	o, err = ParseOptVendorSpecificInformation(data)
 	require.Error(t, err)
+
+	// Bad option
+	data = []byte{
+		43,      // code
+		7,       // length
+		1, 1, 1, // List option
+		2, 2, 1, // Version option
+		5, 3, 1, 1, 1, // Reply port option
+	}
+	o, err = ParseOptVendorSpecificInformation(data)
+	require.Error(t, err)
 }
 
 func TestOptVendorSpecificInformationString(t *testing.T) {
@@ -125,7 +136,7 @@ func TestOptVendorSpecificInformationGetOptions(t *testing.T) {
 			&OptVersion{Version1_1},
 		},
 	}
-	foundOpts := o.GetOptions(OptionBootImageList)
+	foundOpts := o.GetOption(OptionBootImageList)
 	require.Empty(t, foundOpts, "should not get any options")
 
 	// One option
@@ -135,7 +146,7 @@ func TestOptVendorSpecificInformationGetOptions(t *testing.T) {
 			&OptVersion{Version1_1},
 		},
 	}
-	foundOpts = o.GetOptions(OptionMessageType)
+	foundOpts = o.GetOption(OptionMessageType)
 	require.Equal(t, 1, len(foundOpts), "should only get one option")
 	require.Equal(t, MessageTypeList, foundOpts[0].(*OptMessageType).Type)
 
@@ -147,7 +158,7 @@ func TestOptVendorSpecificInformationGetOptions(t *testing.T) {
 			&OptVersion{Version1_0},
 		},
 	}
-	foundOpts = o.GetOptions(OptionVersion)
+	foundOpts = o.GetOption(OptionVersion)
 	require.Equal(t, 2, len(foundOpts), "should get two options")
 	require.Equal(t, Version1_1, foundOpts[0].(*OptVersion).Version)
 	require.Equal(t, Version1_0, foundOpts[1].(*OptVersion).Version)
diff --git a/dhcpv4/dhcpv4.go b/dhcpv4/dhcpv4.go
index ad6e319..2519e2c 100644
--- a/dhcpv4/dhcpv4.go
+++ b/dhcpv4/dhcpv4.go
@@ -45,11 +45,21 @@ type Modifier func(d *DHCPv4) *DHCPv4
 // IPv4AddrsForInterface obtains the currently-configured, non-loopback IPv4
 // addresses for iface.
 func IPv4AddrsForInterface(iface *net.Interface) ([]net.IP, error) {
+	if iface == nil {
+		return nil, errors.New("IPv4AddrsForInterface: iface cannot be nil")
+	}
 	addrs, err := iface.Addrs()
-	var v4addrs []net.IP
 	if err != nil {
-		return v4addrs, err
+		return nil, err
 	}
+	return GetExternalIPv4Addrs(addrs)
+}
+
+// GetExternalIPv4Addrs obtains the currently-configured, non-loopback IPv4
+// addresses from `addrs` coming from a particular interface (e.g.
+// net.Interface.Addrs).
+func GetExternalIPv4Addrs(addrs []net.Addr) ([]net.IP, error) {
+	var v4addrs []net.IP
 	for _, addr := range addrs {
 		var ip net.IP
 		switch v := addr.(type) {
@@ -125,19 +135,25 @@ func New() (*DHCPv4, error) {
 // Ethernet HW type and the hardware address obtained from the specified
 // interface.
 func NewDiscoveryForInterface(ifname string) (*DHCPv4, error) {
-	d, err := New()
+	iface, err := net.InterfaceByName(ifname)
 	if err != nil {
 		return nil, err
 	}
-	// get hw addr
-	iface, err := net.InterfaceByName(ifname)
+	return NewDiscovery(iface.HardwareAddr)
+}
+
+// NewDiscovery builds a new DHCPv4 Discovery message, with a default Ethernet
+// HW type and specified hardware address.
+func NewDiscovery(hwaddr net.HardwareAddr) (*DHCPv4, error) {
+	d, err := New()
 	if err != nil {
 		return nil, err
 	}
+	// get hw addr
 	d.SetOpcode(OpcodeBootRequest)
 	d.SetHwType(iana.HwTypeEthernet)
-	d.SetHwAddrLen(uint8(len(iface.HardwareAddr)))
-	d.SetClientHwAddr(iface.HardwareAddr)
+	d.SetHwAddrLen(uint8(len(hwaddr)))
+	d.SetClientHwAddr(hwaddr)
 	d.SetBroadcast()
 	d.AddOption(&OptMessageType{MessageType: MessageTypeDiscover})
 	d.AddOption(&OptParameterRequestList{
@@ -155,34 +171,44 @@ func NewDiscoveryForInterface(ifname string) (*DHCPv4, error) {
 // Ethernet HW type and the hardware address obtained from the specified
 // interface.
 func NewInformForInterface(ifname string, needsBroadcast bool) (*DHCPv4, error) {
-	d, err := New()
+	// get hw addr
+	iface, err := net.InterfaceByName(ifname)
 	if err != nil {
 		return nil, err
 	}
 
-	// get hw addr
-	iface, err := net.InterfaceByName(ifname)
+	// Set Client IP as iface's currently-configured IP.
+	localIPs, err := IPv4AddrsForInterface(iface)
+	if err != nil || len(localIPs) == 0 {
+		return nil, fmt.Errorf("could not get local IPs for iface %s", ifname)
+	}
+	pkt, err := NewInform(iface.HardwareAddr, localIPs[0])
 	if err != nil {
 		return nil, err
 	}
-	d.SetOpcode(OpcodeBootRequest)
-	d.SetHwType(iana.HwTypeEthernet)
-	d.SetHwAddrLen(uint8(len(iface.HardwareAddr)))
-	d.SetClientHwAddr(iface.HardwareAddr)
 
 	if needsBroadcast {
-		d.SetBroadcast()
+		pkt.SetBroadcast()
 	} else {
-		d.SetUnicast()
+		pkt.SetUnicast()
 	}
+	return pkt, nil
+}
 
-	// Set Client IP as iface's currently-configured IP.
-	localIPs, err := IPv4AddrsForInterface(iface)
-	if err != nil || len(localIPs) == 0 {
-		return nil, fmt.Errorf("could not get local IPs for iface %s", ifname)
+// NewInform builds a new DHCPv4 Informational message with default Ethernet HW
+// type and specified hardware address. It does NOT put a DHCP End option at the
+// end.
+func NewInform(hwaddr net.HardwareAddr, localIP net.IP) (*DHCPv4, error) {
+	d, err := New()
+	if err != nil {
+		return nil, err
 	}
-	d.SetClientIPAddr(localIPs[0])
 
+	d.SetOpcode(OpcodeBootRequest)
+	d.SetHwType(iana.HwTypeEthernet)
+	d.SetHwAddrLen(uint8(len(hwaddr)))
+	d.SetClientHwAddr(hwaddr)
+	d.SetClientIPAddr(localIP)
 	d.AddOption(&OptMessageType{MessageType: MessageTypeInform})
 	return d, nil
 }
@@ -728,3 +754,15 @@ func (d *DHCPv4) ToBytes() []byte {
 	}
 	return ret
 }
+
+// OptionGetter is a interface that knows how to retrieve an option from a
+// structure of options given an OptionCode.
+type OptionGetter interface {
+	GetOption(OptionCode) []Option
+	GetOneOption(OptionCode) Option
+}
+
+// HasOption checks whether the OptionGetter `o` has the given `opcode` Option.
+func HasOption(o OptionGetter, opcode OptionCode) bool {
+	return o.GetOneOption(opcode) != nil
+}
diff --git a/dhcpv4/dhcpv4_test.go b/dhcpv4/dhcpv4_test.go
index eaa9266..28f38d4 100644
--- a/dhcpv4/dhcpv4_test.go
+++ b/dhcpv4/dhcpv4_test.go
@@ -8,10 +8,25 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
-func RequireEqualIPAddr(t *testing.T, a, b net.IP, msg ...interface{}) {
-	if !net.IP.Equal(a, b) {
-		t.Fatalf("Invalid %s. %v != %v", msg, a, b)
+func TestGetExternalIPv4Addrs(t *testing.T) {
+	addrs4and6 := []net.Addr{
+		&net.IPAddr{IP: net.IP{1, 2, 3, 4}},
+		&net.IPAddr{IP: net.IP{4, 3, 2, 1}},
+		&net.IPNet{IP: net.IP{4, 3, 2, 0}},
+		&net.IPAddr{IP: net.IP{1, 2, 3, 4, 1, 1, 1, 1}},
+		&net.IPAddr{IP: net.IP{4, 3, 2, 1, 1, 1, 1, 1}},
+		&net.IPAddr{},                         // nil IP
+		&net.IPAddr{IP: net.IP{127, 0, 0, 1}}, // loopback IP
 	}
+
+	expected := []net.IP{
+		net.IP{1, 2, 3, 4},
+		net.IP{4, 3, 2, 1},
+		net.IP{4, 3, 2, 0},
+	}
+	actual, err := GetExternalIPv4Addrs(addrs4and6)
+	require.NoError(t, err)
+	require.Equal(t, expected, actual)
 }
 
 func TestFromBytes(t *testing.T) {
@@ -53,9 +68,9 @@ func TestFromBytes(t *testing.T) {
 	require.Equal(t, d.TransactionID(), uint32(0xaabbccdd))
 	require.Equal(t, d.NumSeconds(), uint16(3))
 	require.Equal(t, d.Flags(), uint16(1))
-	RequireEqualIPAddr(t, d.ClientIPAddr(), net.IPv4zero)
-	RequireEqualIPAddr(t, d.YourIPAddr(), net.IPv4zero)
-	RequireEqualIPAddr(t, d.GatewayIPAddr(), net.IPv4zero)
+	require.True(t, d.ClientIPAddr().Equal(net.IPv4zero))
+	require.True(t, d.YourIPAddr().Equal(net.IPv4zero))
+	require.True(t, d.GatewayIPAddr().Equal(net.IPv4zero))
 	clientHwAddr := d.ClientHwAddr()
 	require.Equal(t, clientHwAddr[:], []byte{0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0})
 	hostname := d.ServerHostName()
@@ -153,6 +168,8 @@ func TestSettersAndGetters(t *testing.T) {
 	require.Equal(t, uint8(6), d.HwAddrLen())
 	d.SetHwAddrLen(12)
 	require.Equal(t, uint8(12), d.HwAddrLen())
+	d.SetHwAddrLen(22)
+	require.Equal(t, uint8(16), d.HwAddrLen())
 
 	// getter/setter for HopCount
 	require.Equal(t, uint8(3), d.HopCount())
@@ -175,24 +192,24 @@ func TestSettersAndGetters(t *testing.T) {
 	require.Equal(t, uint16(0), d.Flags())
 
 	// getter/setter for ClientIPAddr
-	RequireEqualIPAddr(t, net.IPv4(1, 2, 3, 4), d.ClientIPAddr())
+	require.True(t, d.ClientIPAddr().Equal(net.IPv4(1, 2, 3, 4)))
 	d.SetClientIPAddr(net.IPv4(4, 3, 2, 1))
-	RequireEqualIPAddr(t, net.IPv4(4, 3, 2, 1), d.ClientIPAddr())
+	require.True(t, d.ClientIPAddr().Equal(net.IPv4(4, 3, 2, 1)))
 
 	// getter/setter for YourIPAddr
-	RequireEqualIPAddr(t, net.IPv4(5, 6, 7, 8), d.YourIPAddr())
+	require.True(t, d.YourIPAddr().Equal(net.IPv4(5, 6, 7, 8)))
 	d.SetYourIPAddr(net.IPv4(8, 7, 6, 5))
-	RequireEqualIPAddr(t, net.IPv4(8, 7, 6, 5), d.YourIPAddr())
+	require.True(t, d.YourIPAddr().Equal(net.IPv4(8, 7, 6, 5)))
 
 	// getter/setter for ServerIPAddr
-	RequireEqualIPAddr(t, net.IPv4(9, 10, 11, 12), d.ServerIPAddr())
+	require.True(t, d.ServerIPAddr().Equal(net.IPv4(9, 10, 11, 12)))
 	d.SetServerIPAddr(net.IPv4(12, 11, 10, 9))
-	RequireEqualIPAddr(t, net.IPv4(12, 11, 10, 9), d.ServerIPAddr())
+	require.True(t, d.ServerIPAddr().Equal(net.IPv4(12, 11, 10, 9)))
 
 	// getter/setter for GatewayIPAddr
-	RequireEqualIPAddr(t, net.IPv4(13, 14, 15, 16), d.GatewayIPAddr())
+	require.True(t, d.GatewayIPAddr().Equal(net.IPv4(13, 14, 15, 16)))
 	d.SetGatewayIPAddr(net.IPv4(16, 15, 14, 13))
-	RequireEqualIPAddr(t, net.IPv4(16, 15, 14, 13), d.GatewayIPAddr())
+	require.True(t, d.GatewayIPAddr().Equal(net.IPv4(16, 15, 14, 13)))
 
 	// getter/setter for ClientHwAddr
 	hwaddr := d.ClientHwAddr()
@@ -240,6 +257,8 @@ func TestToStringMethods(t *testing.T) {
 	require.Equal(t, "Ethernet", d.HwTypeToString())
 	d.SetHwType(iana.HwTypeARCNET)
 	require.Equal(t, "ARCNET", d.HwTypeToString())
+	d.SetHwType(iana.HwTypeType(0))
+	require.Equal(t, "Invalid", d.HwTypeToString())
 
 	// FlagsToString
 	d.SetUnicast()
@@ -253,6 +272,8 @@ func TestToStringMethods(t *testing.T) {
 	d.SetHwAddrLen(6)
 	d.SetClientHwAddr([]byte{0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0})
 	require.Equal(t, "aa:bb:cc:dd:ee:ff", d.ClientHwAddrToString())
+	d.SetClientHwAddr([]byte{1, 2, 3, 4, 1, 2, 3, 4, 1, 2, 3, 4, 1, 2, 3, 4, 1, 2, 3, 4}) // 20 bytes
+	require.Equal(t, "01:02:03:04:01:02", d.ClientHwAddrToString())
 
 	// ServerHostNameToString
 	d.SetServerHostName([]byte("my.host.local"))
@@ -309,11 +330,11 @@ func TestGetOption(t *testing.T) {
 	}
 
 	hostnameOpt := &OptionGeneric{OptionCode: OptionHostName, Data: []byte("darkstar")}
-	bootFileOpt1 := &OptionGeneric{OptionCode: OptionBootfileName, Data: []byte("boot.img")}
-	bootFileOpt2 := &OptionGeneric{OptionCode: OptionBootfileName, Data: []byte("boot2.img")}
+	bootFileOpt1 := &OptBootfileName{[]byte("boot.img")}
+	bootFileOpt2 := &OptBootfileName{[]byte("boot2.img")}
 	d.AddOption(hostnameOpt)
-	d.AddOption(bootFileOpt1)
-	d.AddOption(bootFileOpt2)
+	d.AddOption(&OptBootfileName{[]byte("boot.img")})
+	d.AddOption(&OptBootfileName{[]byte("boot2.img")})
 
 	require.Equal(t, d.GetOption(OptionHostName), []Option{hostnameOpt})
 	require.Equal(t, d.GetOption(OptionBootfileName), []Option{bootFileOpt1, bootFileOpt2})
@@ -342,15 +363,57 @@ func TestAddOption(t *testing.T) {
 	require.Equal(t, options[3].Code(), OptionEnd)
 }
 
+func TestStrippedOptions(t *testing.T) {
+	// Normal set of options that terminate with OptionEnd.
+	d, err := New()
+	require.NoError(t, err)
+	opts := []Option{
+		&OptBootfileName{[]byte("boot.img")},
+		&OptClassIdentifier{"something"},
+		&OptionGeneric{OptionCode: OptionEnd},
+	}
+	d.SetOptions(opts)
+	stripped := d.StrippedOptions()
+	require.Equal(t, len(opts), len(stripped))
+	for i := range stripped {
+		require.Equal(t, opts[i], stripped[i])
+	}
+
+	// Set of options with additional options after OptionEnd
+	opts = append(opts, &OptMaximumDHCPMessageSize{uint16(1234)})
+	d.SetOptions(opts)
+	stripped = d.StrippedOptions()
+	require.Equal(t, len(opts)-1, len(stripped))
+	for i := range stripped {
+		require.Equal(t, opts[i], stripped[i])
+	}
+}
+
 func TestDHCPv4NewRequestFromOffer(t *testing.T) {
 	offer, err := New()
 	require.NoError(t, err)
+	offer.SetBroadcast()
 	offer.AddOption(&OptMessageType{MessageType: MessageTypeOffer})
-	offer.AddOption(&OptServerIdentifier{ServerID: net.IPv4(192, 168, 0, 1)})
 	req, err := NewRequestFromOffer(offer)
+	require.Error(t, err)
+
+	// Now add the option so it doesn't error out.
+	offer.AddOption(&OptServerIdentifier{ServerID: net.IPv4(192, 168, 0, 1)})
+
+	// Broadcast request
+	req, err = NewRequestFromOffer(offer)
 	require.NoError(t, err)
-	require.NotEqual(t, (*MessageType)(nil), *req.MessageType())
+	require.NotNil(t, req.MessageType())
 	require.Equal(t, MessageTypeRequest, *req.MessageType())
+	require.False(t, req.IsUnicast())
+	require.True(t, req.IsBroadcast())
+
+	// Unicast request
+	offer.SetUnicast()
+	req, err = NewRequestFromOffer(offer)
+	require.NoError(t, err)
+	require.True(t, req.IsUnicast())
+	require.False(t, req.IsBroadcast())
 }
 
 func TestDHCPv4NewRequestFromOfferWithModifier(t *testing.T) {
@@ -391,14 +454,43 @@ func TestNewReplyFromRequestWithModifier(t *testing.T) {
 func TestDHCPv4MessageTypeNil(t *testing.T) {
 	m, err := New()
 	require.NoError(t, err)
-	require.Equal(t, (*MessageType)(nil), m.MessageType())
+	require.Nil(t, m.MessageType())
 }
 
-func TestDHCPv4MessageTypeDiscovery(t *testing.T) {
-	m, err := NewDiscoveryForInterface("lo")
+func TestNewDiscovery(t *testing.T) {
+	hwAddr := net.HardwareAddr{1, 2, 3, 4, 5, 6}
+	m, err := NewDiscovery(hwAddr)
 	require.NoError(t, err)
-	require.NotEqual(t, (*MessageType)(nil), m.MessageType())
+	require.NotNil(t, m.MessageType())
 	require.Equal(t, MessageTypeDiscover, *m.MessageType())
+
+	// Validate fields of DISCOVER packet.
+	require.Equal(t, OpcodeBootRequest, m.Opcode())
+	require.Equal(t, iana.HwTypeEthernet, m.HwType())
+	var expectedHwAddr [16]byte
+	copy(expectedHwAddr[:], hwAddr)
+	require.Equal(t, expectedHwAddr, m.ClientHwAddr())
+	require.Equal(t, len(hwAddr), int(m.HwAddrLen()))
+	require.True(t, m.IsBroadcast())
+	require.True(t, HasOption(m, OptionParameterRequestList))
+	require.True(t, HasOption(m, OptionEnd))
+}
+
+func TestNewInform(t *testing.T) {
+	hwAddr := net.HardwareAddr{1, 2, 3, 4, 5, 6}
+	localIP := net.IPv4(10, 10, 11, 11)
+	m, err := NewInform(hwAddr, localIP)
+
+	require.NoError(t, err)
+	require.Equal(t, OpcodeBootRequest, m.Opcode())
+	require.Equal(t, iana.HwTypeEthernet, m.HwType())
+	var expectedHwAddr [16]byte
+	copy(expectedHwAddr[:], hwAddr)
+	require.Equal(t, expectedHwAddr, m.ClientHwAddr())
+	require.Equal(t, len(hwAddr), int(m.HwAddrLen()))
+	require.NotNil(t, m.MessageType())
+	require.Equal(t, MessageTypeInform, *m.MessageType())
+	require.True(t, m.ClientIPAddr().Equal(localIP))
 }
 
 func TestIsOptionRequested(t *testing.T) {
@@ -412,6 +504,4 @@ func TestIsOptionRequested(t *testing.T) {
 }
 
 // TODO
-//      test broadcast/unicast flags
-//      test Options setter/getter
 //      test Summary() and String()