add lease&release support for nclient4

Signed-off-by: Hu Jun <hujun.work@gmail.com>

1 files changed, 270 insertions, 0 deletions

diff --git a/dhcpv4/nclient4/lease.go b/dhcpv4/nclient4/lease.go
new file mode 100644
index 0000000..b5cb6b0
--- /dev/null
+++ b/dhcpv4/nclient4/lease.go
@@ -0,0 +1,270 @@
+/*
+An example, bind to eth0, using option82/remote-id for client identification:
+
+
+    package main
+
+    import (
+        "context"
+        "log"
+
+        "github.com/insomniacslk/dhcp/dhcpv4"
+        "github.com/insomniacslk/dhcp/dhcpv4/nclient4"
+    )
+
+    func main() {
+        ifname := "eth0"
+        remote_id := "client-1"
+        var idoptlist dhcpv4.OptionCodeList
+        //specify option82 is part of client identification used by DHCPv4 server
+        idoptlist.Add(dhcpv4.OptionRelayAgentInformation)
+        clnt_options := []nclient4.ClientOpt{nclient4.WithClientIdOptions(idoptlist), nclient4.WithDebugLogger()}
+        clnt, err := nclient4.New(ifname, clnt_options...)
+        if err != nil {
+            log.Fatalf("failed to create dhcpv4 client,%v", err)
+        }
+        //adding option82/remote-id option to discovery and request
+        remote_id_sub_opt := dhcpv4.OptGeneric(dhcpv4.AgentRemoteIDSubOption, []byte(remote_id))
+        option82 := dhcpv4.OptRelayAgentInfo(remote_id_sub_opt)
+        _, _, err = clnt.RequestSavingLease(context.Background(), dhcpv4.WithOption(option82))
+        if err != nil {
+            log.Fatal(err)
+        }
+        //print the lease
+        log.Printf("Got lease:\n%v", clnt.GetLease())
+        //release the lease
+        log.Print("Releasing lease...")
+        err = clnt.Release()
+        if err != nil {
+            log.Fatal(err)
+        }
+        log.Print("done")
+    }
+
+
+*/
+package nclient4
+
+import (
+	"context"
+	"fmt"
+	"net"
+	"time"
+
+	"github.com/insomniacslk/dhcp/dhcpv4"
+	"github.com/vishvananda/netlink"
+)
+
+const (
+	//default lease time if server doesn't return lease time option or return zero
+	defaultLeaseTime = time.Hour
+)
+
+//DHCPv4ClientLease contains a DHCPv4 lease after DORA,
+//could be used for creating a new Client with NewWithLease()
+type DHCPv4ClientLease struct {
+	IfName         string
+	MACAddr        net.HardwareAddr
+	ServerAddr     net.UDPAddr
+	AssignedIP     net.IP
+	AssignedIPMask net.IPMask
+	CreationTime   time.Time
+	LeaseDuration  time.Duration
+	RenewInterval  time.Duration
+	RebindInterval time.Duration
+	IdOptions      dhcpv4.Options //DHCPv4 options to identify the client like client-id, option82/remote-id
+	AckOptions     dhcpv4.Options //DHCPv4 options in ACK, could be used for applying lease
+
+}
+
+//return a string representation
+func (lease DHCPv4ClientLease) String() string {
+	const FMTSTR = "%-35s\t%-35s\n"
+	const TIME_FMT = "01/02/2006 15:04:05.000"
+	rstr := fmt.Sprintf(FMTSTR, fmt.Sprintf("Interface:%v", lease.IfName), fmt.Sprintf("MAC:%v", lease.MACAddr))
+	rstr += fmt.Sprintf(FMTSTR, fmt.Sprintf("Svr:%v", lease.ServerAddr.IP), fmt.Sprintf("Created:%v", lease.CreationTime.Format(TIME_FMT)))
+	prefix_len, _ := lease.AssignedIPMask.Size()
+	rstr += fmt.Sprintf(FMTSTR, fmt.Sprintf("IP:%v/%v", lease.AssignedIP, prefix_len), fmt.Sprintf("Lease time:%v", lease.LeaseDuration))
+	rstr += fmt.Sprintf(FMTSTR, fmt.Sprintf("Renew interval:%v", lease.RenewInterval), fmt.Sprintf("Rebind interval:%v", lease.RebindInterval))
+	rstr += fmt.Sprintf("Id options:\n%v", lease.IdOptions)
+	rstr += fmt.Sprintf("ACK options:\n%v", lease.AckOptions)
+	return rstr
+}
+
+// WithClientIdOptions configures a list of DHCPv4 option code that DHCP server
+// uses to identify client, beside the MAC address.
+func WithClientIdOptions(cidl dhcpv4.OptionCodeList) ClientOpt {
+	return func(c *Client) (err error) {
+		c.clientIdOptions = cidl
+		return
+	}
+}
+
+// WithApplyLeaseHandler specifies a handler function which is called when
+// Client.ApplyLease() is called; without this, a default handler function is called.
+// the default handler will add/remove the assigned address to/from the binding interface;
+// bool parameter is true when lease is applied, false when lease is released
+func WithApplyLeaseHandler(h func(DHCPv4ClientLease, bool) error) ClientOpt {
+	return func(c *Client) (err error) {
+		c.leaseApplyHandler = h
+		return
+	}
+}
+
+//default lease apply handler
+//add/remove address to/from binding interface
+func defaultLeaseApplyHandler(l DHCPv4ClientLease, enable bool) error {
+	link, err := netlink.LinkByName(l.IfName)
+	if err != nil {
+		return err
+	}
+	plen, _ := l.AssignedIPMask.Size()
+	prefix_str := fmt.Sprintf("%v/%v", l.AssignedIP, plen)
+	naddr, err := netlink.ParseAddr(prefix_str)
+	if err != nil {
+		return err
+	}
+	if enable {
+		err = netlink.AddrReplace(link, naddr)
+
+	} else {
+		err = netlink.AddrDel(link, naddr)
+	}
+	return err
+
+}
+
+//Apply the lease, calling the c.leaseApplyHandler
+func (c *Client) ApplyLease(enable bool) error {
+	if c.lease == nil {
+		return fmt.Errorf("no lease to apply")
+	}
+	return c.leaseApplyHandler(c.GetLease(), enable)
+}
+
+//return the lease
+func (c *Client) GetLease() (clease DHCPv4ClientLease) {
+	clease = *c.lease
+	clease.MACAddr = c.ifaceHWAddr
+	clease.IfName = c.ifName
+	clease.ServerAddr = *c.serverAddr
+	return
+}
+
+// RequestRequestSavingLease completes DORA handshake and store&apply the lease
+//
+// Note that modifiers will be applied *both* to Discover and Request packets.
+func (c *Client) RequestSavingLease(ctx context.Context, modifiers ...dhcpv4.Modifier) (offer, ack *dhcpv4.DHCPv4, err error) {
+	offer, err = c.DiscoverOffer(ctx, modifiers...)
+	if err != nil {
+		err = fmt.Errorf("unable to receive an offer: %w", err)
+		return
+	}
+
+	// TODO(chrisko): should this be unicast to the server?
+	request, err := dhcpv4.NewRequestFromOffer(offer, dhcpv4.PrependModifiers(modifiers,
+		dhcpv4.WithOption(dhcpv4.OptMaxMessageSize(MaxMessageSize)))...)
+	if err != nil {
+		err = fmt.Errorf("unable to create a request: %w", err)
+		return
+	}
+
+	ack, err = c.SendAndRead(ctx, c.serverAddr, request, nil)
+	if err != nil {
+		err = fmt.Errorf("got an error while processing the request: %w", err)
+		return
+	}
+	//save lease
+	c.lease = &DHCPv4ClientLease{}
+	c.lease.AssignedIP = ack.YourIPAddr
+	c.lease.AssignedIPMask = ack.SubnetMask()
+	c.lease.CreationTime = time.Now()
+	c.lease.LeaseDuration = ack.IPAddressLeaseTime(0)
+	if c.lease.LeaseDuration == 0 {
+		c.lease.LeaseDuration = defaultLeaseTime
+		c.logger.Printf("warning: server doesn't include Lease Time option or it is zero seconds, setting lease time to default %v", c.lease.LeaseDuration)
+
+	}
+	c.lease.RenewInterval = ack.IPAddressRenewalTime(0)
+	if c.lease.RenewInterval == 0 {
+		//setting default to half of lease time based on RFC2131,section 4.4.5
+		c.lease.RenewInterval = time.Duration(float64(c.lease.LeaseDuration) / 2)
+		c.logger.Printf("warning: server doesn't include Renew Time option or it is zero seconds, setting lease time to default %v", c.lease.RenewInterval)
+
+	}
+	c.lease.RebindInterval = ack.IPAddressRebindingTime(0)
+	if c.lease.RebindInterval == 0 {
+		//setting default to 0.875 of lease time based on RFC2131,section 4.4.5
+		c.lease.RebindInterval = time.Duration(float64(c.lease.LeaseDuration) * 0.875)
+		c.logger.Printf("warning: server doesn't include Renew Time option or it is zero seconds, setting lease time to default %v", c.lease.RebindInterval)
+
+	}
+	c.lease.IdOptions = dhcpv4.Options{}
+	for _, optioncode := range c.clientIdOptions {
+		v := request.Options.Get(optioncode)
+		c.lease.IdOptions.Update(dhcpv4.OptGeneric(optioncode, v))
+	}
+	c.lease.AckOptions = ack.Options
+	//update server address
+	c.serverAddr = &(net.UDPAddr{IP: ack.ServerIdentifier(), Port: 67})
+	c.ApplyLease(true)
+	return
+}
+
+//Release send DHCPv4 release messsage to server.
+//release is sent as unicast per RFC2131, section 4.4.4.
+//The lease need to be applied with c.ApplyLease(true) first before calling Release.
+func (c *Client) Release() error {
+	if c.lease == nil {
+		return fmt.Errorf("There is no lease to release")
+	}
+	req, err := dhcpv4.New()
+	if err != nil {
+		return err
+	}
+	//This is to make sure use same client identification options used during
+	//DORA, so that DHCP server could identify the required lease
+	req.Options = c.lease.IdOptions
+
+	req.UpdateOption(dhcpv4.OptMessageType(dhcpv4.MessageTypeRelease))
+	req.ClientHWAddr = c.ifaceHWAddr
+	req.ClientIPAddr = c.lease.AssignedIP
+	req.UpdateOption(dhcpv4.OptServerIdentifier(c.serverAddr.IP))
+	req.SetUnicast()
+	luaddr, err := net.ResolveUDPAddr("udp4", fmt.Sprintf("%v:%v", c.lease.AssignedIP, 68))
+	if err != nil {
+		return err
+	}
+
+	uniconn, err := net.DialUDP("udp4", luaddr, c.serverAddr)
+	if err != nil {
+		return err
+	}
+	_, err = uniconn.Write(req.ToBytes())
+	if err != nil {
+		return err
+	}
+	c.logger.PrintMessage("sent message:", req)
+	return c.ApplyLease(false)
+}
+
+//NewWithLease return a Client with populated lease.
+//this function could be used to release a saved lease.
+func NewWithLease(clease DHCPv4ClientLease, opts ...ClientOpt) (*Client, error) {
+	clnt_opt_list := []ClientOpt{
+		WithServerAddr(&clease.ServerAddr),
+		WithHWAddr(clease.MACAddr),
+	}
+	clnt_opt_list = append(clnt_opt_list, opts...)
+	clnt, err := New(clease.IfName, clnt_opt_list...)
+	if err != nil {
+		return nil, err
+	}
+	clnt.ifName = clease.IfName
+	clnt.lease = &clease
+	for optioncode, _ := range clease.IdOptions {
+		clnt.clientIdOptions.Add(dhcpv4.GenericOptionCode(optioncode))
+	}
+	return clnt, nil
+
+}