client6: new async DHCPv6 client like #250.

- Race-condition-averse.
- Supports multiple concurrent requests.
- Tested.
- Requires a fully compatible net.PacketConn.

Signed-off-by: Christopher Koch <[email protected]>

dhcpv6/client6/client.go

@@ -199,7 +199,11 @@ func (c *Client) sendReceive(ifname string, packet dhcpv6.DHCPv6, expectedType d
 // an error if any. The modifiers will be applied to the Solicit before sending
 // it, see modifiers.go
 func (c *Client) Solicit(ifname string, modifiers ...dhcpv6.Modifier) (dhcpv6.DHCPv6, dhcpv6.DHCPv6, error) {
-	solicit, err := dhcpv6.NewSolicitForInterface(ifname)
+	iface, err := net.InterfaceByName(ifname)
+	if err != nil {
+		return nil, nil, err
+	}
+	solicit, err := dhcpv6.NewSolicit(iface.HardwareAddr)
 	if err != nil {
 		return nil, nil, err
 	}

dhcpv6/dhcpv6.go

@@ -16,6 +16,11 @@ type DHCPv6 interface {
 	String() string
 	Summary() string
 	IsRelay() bool
+
+	// GetInnerMessage returns the innermost encapsulated DHCPv6 message.
+	//
+	// If it is already a message, it will be returned. If it is a relay
+	// message, the encapsulated message will be recursively extracted.
 	GetInnerMessage() (*Message, error)
 
 	GetOption(code OptionCode) []Option
@@ -108,11 +113,11 @@ func DecapsulateRelay(l DHCPv6) (DHCPv6, error) {
 	}
 	opt := l.GetOneOption(OptionRelayMsg)
 	if opt == nil {
-		return nil, fmt.Errorf("No OptRelayMsg found")
+		return nil, fmt.Errorf("malformed Relay message: no OptRelayMsg found")
 	}
 	relayOpt := opt.(*OptRelayMsg)
 	if relayOpt.RelayMessage() == nil {
-		return nil, fmt.Errorf("Relay message cannot be nil")
+		return nil, fmt.Errorf("malformed Relay message: encapsulated message is empty")
 	}
 	return relayOpt.RelayMessage(), nil
 }

dhcpv6/dhcpv6message.go

@@ -70,18 +70,14 @@ func NewSolicitWithCID(duid Duid, modifiers ...Modifier) (*Message, error) {
 	return m, nil
 }
 
-// NewSolicitForInterface creates a new SOLICIT message with DUID-LLT, using the
+// NewSolicit creates a new SOLICIT message with DUID-LLT, using the
 // given network interface's hardware address and current time
-func NewSolicitForInterface(ifname string, modifiers ...Modifier) (*Message, error) {
-	iface, err := net.InterfaceByName(ifname)
-	if err != nil {
-		return nil, err
-	}
+func NewSolicit(ifaceHWAddr net.HardwareAddr, modifiers ...Modifier) (*Message, error) {
 	duid := Duid{
 		Type:          DUID_LLT,
 		HwType:        iana.HWTypeEthernet,
 		Time:          GetTime(),
-		LinkLayerAddr: iface.HardwareAddr,
+		LinkLayerAddr: ifaceHWAddr,
 	}
 	return NewSolicitWithCID(duid, modifiers...)
 }

dhcpv6/modifiers.go

@@ -99,6 +99,11 @@ func WithDomainSearchList(searchlist ...string) Modifier {
 	}
 }
 
+// WithRapidCommit adds the rapid commit option to a message.
+func WithRapidCommit(d DHCPv6) {
+	d.UpdateOption(&OptionGeneric{OptionCode: OptionRapidCommit})
+}
+
 // WithRequestedOptions adds requested options to the packet
 func WithRequestedOptions(optionCodes ...OptionCode) Modifier {
 	return func(d DHCPv6) {