huge tap/bridge overhaul; udp node; dhcp node; DHCP example

examples/bridge/main.go

@@ -0,0 +1,189 @@
+package main
+
+import (
+	"crypto/rand"
+	"encoding/binary"
+	"fmt"
+	"net"
+	"net/netip"
+	"os"
+	"time"
+
+	"github.com/soypat/lneto"
+	"github.com/soypat/lneto/arp"
+	"github.com/soypat/lneto/dhcpv4"
+	"github.com/soypat/lneto/ethernet"
+	"github.com/soypat/lneto/internal/ltesto"
+	"github.com/soypat/lneto/internet"
+	"github.com/soypat/lneto/internet/pcap"
+)
+
+func main() {
+	err := run()
+	if err != nil {
+		fmt.Println(err)
+		os.Exit(1)
+	}
+	fmt.Println("success")
+}
+
+func run() (err error) {
+	br := ltesto.NewHTTPTapClient("http://127.0.0.1:7070")
+	defer br.Close()
+
+	nicHW := br.HardwareAddr6()
+
+	brHW := nicHW
+	brHW[5]++ // We'll be using a similar HW address but with NIC specific identifier modified.
+	mtu := br.MTU()
+	nicAddr := br.IPPrefix()
+
+	fmt.Println("NIC hardware address:", net.HardwareAddr(nicHW[:]).String(), "bridgeHW:", net.HardwareAddr(brHW[:]).String(), "mtu:", mtu, "addr:", nicAddr.String())
+	var stack Stack
+	err = stack.Reset(brHW, nicAddr.Addr().Next(), uint16(mtu))
+	if err != nil {
+		return err
+	}
+	err = stack.BeginDHCPRequest()
+	if err != nil {
+		return err
+	}
+	var shark pcap.PacketBreakdown
+	buf := make([]byte, mtu)
+	var iframes []pcap.Frame
+	lastAction := time.Now()
+	for {
+		clear(buf)
+		nwrite, err := stack.Encapsulate(buf[:], 0)
+		if err != nil {
+			fmt.Println("ERR:ENCAPSULATE", err)
+		} else if nwrite > 0 {
+			iframes, err = shark.CaptureEthernet(iframes[:0], buf[:nwrite], 0)
+			if err != nil {
+				fmt.Println("OU", iframes, err.Error())
+			} else {
+				fmt.Println("OU", iframes)
+			}
+			n, err := br.Write(buf[:nwrite])
+			if err != nil {
+				return err
+			} else if n != nwrite {
+				return fmt.Errorf("mismatch written bytes %d!=%d", nwrite, n)
+			}
+		}
+
+		clear(buf)
+		nread, err := br.Read(buf)
+		if err != nil {
+			return err
+		} else if nread > 0 {
+			iframes, err = shark.CaptureEthernet(iframes[:0], buf[:nread], 0)
+			if err != nil {
+				fmt.Println("IN", iframes, err.Error())
+			} else {
+				fmt.Println("IN", iframes)
+			}
+			err = stack.Demux(buf[:nread], 0)
+			if err != nil {
+				fmt.Println("ERR:DEMUX", err)
+			}
+		}
+
+		if nread == 0 && nwrite == 0 && time.Since(lastAction) > 4*time.Second {
+			time.Sleep(5 * time.Millisecond)
+		} else {
+			lastAction = time.Now()
+		}
+	}
+	return nil
+}
+
+type Stack struct {
+	link internet.StackEthernet
+	ip   internet.StackIP
+	arp  internet.NodeARP
+	udps internet.StackPorts
+	dhcp dhcpv4.Client
+}
+
+func (s *Stack) Demux(b []byte, _ int) error {
+	return s.link.Demux(b, 0)
+}
+
+func (s *Stack) Encapsulate(b []byte, _ int) (int, error) {
+	return s.link.Encapsulate(b, 0)
+}
+
+func (s *Stack) Reset(mac [6]byte, addr netip.Addr, mtu uint16) error {
+	err := s.link.Reset6(mac, ethernet.BroadcastAddr(), int(mtu))
+	if err != nil {
+		return err
+	}
+	err = s.ip.Reset(addr)
+	if err != nil {
+		return err
+	}
+	ipaddr := addr.AsSlice()
+	proto := ethernet.TypeIPv4
+	if addr.Is6() {
+		proto = ethernet.TypeIPv6
+	}
+	err = s.arp.Reset(arp.HandlerConfig{
+		HardwareAddr: mac[:],
+		ProtocolAddr: ipaddr,
+		MaxQueries:   3,
+		MaxPending:   3,
+		HardwareType: 1,
+		ProtocolType: proto,
+	})
+	if err != nil {
+		return err
+	}
+	err = s.udps.Reset(uint64(lneto.IPProtoUDP), 2)
+	if err != nil {
+		return err
+	}
+
+	// Now setup stacks.
+	err = s.link.Register(&s.arp) // ARP.
+	if err != nil {
+		return err
+	}
+	err = s.link.Register(&s.ip) // IPv4 | IPv6
+	if err != nil {
+		return err
+	}
+	err = s.ip.Register(&s.udps)
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+func (s *Stack) BeginDHCPRequest() error {
+	addr4 := s.ip.Addr().As4()
+	var buf [4]byte
+	rand.Read(buf[:])
+	xid := binary.LittleEndian.Uint32(buf[:])
+	err := s.dhcp.BeginRequest(xid, dhcpv4.RequestConfig{
+		RequestedAddr:      addr4,
+		ClientHardwareAddr: s.link.HardwareAddr6(),
+		Hostname:           "lneto",
+	})
+	if err != nil {
+		return err
+	}
+	var u internet.StackUDPPort
+	u.SetStackNode(&s.dhcp, dhcpv4.DefaultServerPort)
+	err = s.udps.Register(&u)
+	if err != nil {
+		return err
+	}
+	return err
+}
+
+func clear(buf []byte) {
+	for i := range buf {
+		buf[i] = 0
+	}
+}