1 files changed, 28 insertions, 42 deletions

diff --git a/dhcpv4/dhcpv4.go b/dhcpv4/dhcpv4.go
index 5005375..d452f6e 100644
--- a/dhcpv4/dhcpv4.go
+++ b/dhcpv4/dhcpv4.go
@@ -42,14 +42,11 @@ type DHCPv4 struct {
 // structures. This is used to simplify packet manipulation
 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) {
-	addrs, err := iface.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
-	if err != nil {
-		return v4addrs, err
-	}
 	for _, addr := range addrs {
 		var ip net.IP
 		switch v := addr.(type) {
@@ -121,23 +118,18 @@ func New() (*DHCPv4, error) {
 	return &d, nil
 }
 
-// NewDiscoveryForInterface builds a new DHCPv4 Discovery message, with a default
-// Ethernet HW type and the hardware address obtained from the specified
-// interface.
-func NewDiscoveryForInterface(ifname string) (*DHCPv4, error) {
+// 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
-	iface, err := net.InterfaceByName(ifname)
-	if err != nil {
-		return nil, err
-	}
 	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{
@@ -151,38 +143,20 @@ func NewDiscoveryForInterface(ifname string) (*DHCPv4, error) {
 	return d, nil
 }
 
-// NewInformForInterface builds a new DHCPv4 Informational message with default
-// Ethernet HW type and the hardware address obtained from the specified
-// interface.
-func NewInformForInterface(ifname string, needsBroadcast bool) (*DHCPv4, error) {
+// 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
 	}
 
-	// get hw addr
-	iface, err := net.InterfaceByName(ifname)
-	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()
-	} else {
-		d.SetUnicast()
-	}
-
-	// 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)
-	}
-	d.SetClientIPAddr(localIPs[0])
-
+	d.SetHwAddrLen(uint8(len(hwaddr)))
+	d.SetClientHwAddr(hwaddr)
+	d.SetClientIPAddr(localIP)
 	d.AddOption(&OptMessageType{MessageType: MessageTypeInform})
 	return d, nil
 }
@@ -715,3 +689,15 @@ 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
+}