implement VPN backend

endpoints/vpn/backend.go

@@ -2,15 +2,19 @@ package vpn
 
 import (
 	"encoding/json"
-	"fmt"
+	"github.com/net-byte/vtun/common/config"
+	"github.com/net-byte/vtun/tun"
 	_ "github.com/net-byte/vtun/tun"
+	"github.com/net-byte/water"
 	"github.com/openziti/sdk-golang/ziti"
 	"github.com/openziti/sdk-golang/ziti/edge"
 	"github.com/openziti/zrok/endpoints"
+	cmap "github.com/orcaman/concurrent-map/v2"
 	"github.com/pkg/errors"
 	"github.com/sirupsen/logrus"
 	"github.com/songgao/water/waterutil"
 	"net"
+	"sync/atomic"
 	"time"
 )
 
@@ -21,11 +25,20 @@ type BackendConfig struct {
 	RequestsChan    chan *endpoints.Request
 }
 
+type client struct {
+	conn net.Conn
+}
+
 type Backend struct {
 	cfg      *BackendConfig
 	listener edge.Listener
 
 	cidr net.IPAddr
+	tun  *water.Interface
+	mtu  int
+
+	counter atomic.Uint32
+	clients cmap.ConcurrentMap[dest, *client]
 }
 
 func NewBackend(cfg *BackendConfig) (*Backend, error) {
@@ -49,14 +62,66 @@ func NewBackend(cfg *BackendConfig) (*Backend, error) {
 	b := &Backend{
 		cfg:      cfg,
 		listener: listener,
+		mtu:      ZROK_VPN_MTU,
+		clients: cmap.NewWithCustomShardingFunction[dest, *client](func(key dest) uint32 {
+			return key.toInt32()
+		}),
 	}
+	b.counter.Store(1)
 	return b, nil
 }
 
+func (b *Backend) readTun() {
+	buf := make([]byte, ZROK_VPN_MTU)
+	for {
+		n, err := b.tun.Read(buf)
+		if err != nil {
+			logrus.WithError(err).Error("failed to read tun device")
+			// handle? error
+			panic(err)
+			return
+		}
+		pkt := packet(buf[:n])
+		if !waterutil.IsIPv4(pkt) {
+			continue
+		}
+
+		logrus.WithField("packet", pkt).Trace("read from tun device")
+		dest := pkt.destination()
+
+		if clt, ok := b.clients.Get(dest); ok {
+			_, err := clt.conn.Write(pkt)
+			if err != nil {
+				logrus.WithError(err).Errorf("failed to write packet to clt[%v]", dest)
+				_ = clt.conn.Close()
+				b.clients.Remove(dest)
+			}
+		} else {
+			logrus.Errorf("no client with address[%v]", dest)
+		}
+	}
+}
+
 func (b *Backend) Run() error {
 	logrus.Info("started")
 	defer logrus.Info("exited")
 
+	tunCfg := config.Config{
+		ServerIP:   "192.168.127.1",
+		ServerIPv6: "fced::ffff:c0a8:7f01",
+		CIDR:       "192.168.127.1/24",
+		CIDRv6:     "fced::ffff:c0a8:7f01/64",
+		MTU:        ZROK_VPN_MTU,
+		Verbose:    true,
+	}
+
+	b.tun = tun.CreateTun(tunCfg)
+	defer func() {
+		_ = b.tun.Close()
+	}()
+
+	go b.readTun()
+
 	for {
 		if conn, err := b.listener.Accept(); err == nil {
 			go b.handle(conn)
@@ -66,47 +131,54 @@ func (b *Backend) Run() error {
 	}
 }
 
-type ipProto waterutil.IPProtocol
-
-func (p ipProto) String() string {
-	switch p {
-	case waterutil.TCP:
-		return "tcp"
-	case waterutil.UDP:
-		return "udp"
-	case waterutil.ICMP:
-		return "icmp"
-	default:
-		return fmt.Sprintf("proto[%d]", p)
-	}
-}
-
 func (b *Backend) handle(conn net.Conn) {
 	defer func(conn net.Conn) {
 		_ = conn.Close()
 	}(conn)
 
+	num := uint32(0)
+	for num == 0 || num == 1 {
+		num = b.counter.Add(1)
+		num = num % 256
+	}
+
+	ipv4 := net.IPv4(192, 168, 127, byte(num))
+	ip := ipToDest(ipv4)
+
 	cfg := &ClientConfig{
 		Greeting: "Welcome to zrok VPN",
+		IP:       ipv4.String(),
+		ServerIP: "192.168.127.1",
+		CIDR:     ipv4.String() + "/24",
+		MTU:      b.mtu,
 	}
+
 	j, err := json.Marshal(&cfg)
 	if err != nil {
+		logrus.WithError(err).Error("failed to write client VPN config")
+		return
+	}
+	_, err = conn.Write(j)
+	if err != nil {
+		logrus.WithError(err).Error("failed to write client VPN config")
 		return
 	}
-	conn.Write(j)
 
-	buf := make([]byte, 16*1024)
+	clt := &client{conn: conn}
+	b.clients.Set(ip, clt)
+
+	buf := make([]byte, b.mtu)
 	for {
 		read, err := conn.Read(buf)
 		if err != nil {
 			logrus.Error("read error", err)
 			return
 		}
-		pkt := buf[:read]
+		pkt := packet(buf[:read])
-		logrus.Infof("read packet %d bytes %v %v:%v -> %v:%v", read,
+		logrus.WithField("packet", pkt).Info("read from ziti")
-			ipProto(waterutil.IPv4Protocol(pkt)),
+		_, err = b.tun.Write(pkt)
-			waterutil.IPv4Source(pkt), waterutil.IPv4SourcePort(pkt),
+		if err != nil {
-			waterutil.IPv4Destination(pkt), waterutil.IPv4DestinationPort(pkt))
+			logrus.WithError(err).Error("failed to write packet to tun")
-
+		}
 	}
 }

endpoints/vpn/vpn.go

@@ -1,9 +1,63 @@
 package vpn
 
+import (
+	"fmt"
+	"github.com/songgao/water/waterutil"
+	"net"
+	"strconv"
+)
+
+const ZROK_VPN_MTU = 16 * 1024
+
 type ClientConfig struct {
 	Greeting string
 	IP       string
 	CIDR     string
 	ServerIP string
 	Routes   []string
+	MTU      int
+}
+
+type dest struct {
+	addr [4]byte
+}
+
+func (d dest) String() string {
+	return net.IP(d.addr[:]).String()
+}
+
+func (d dest) toInt32() uint32 {
+	return uint32(d.addr[0])<<24 + uint32(d.addr[1])<<16 + uint32(d.addr[2])<<8 + uint32(d.addr[3])
+}
+
+func ipToDest(addr net.IP) dest {
+	return dest{
+		addr: [4]byte{addr[0], addr[1], addr[2], addr[3]},
+	}
+}
+
+type packet []byte
+
+func (p packet) destination() dest {
+	return ipToDest(waterutil.IPv4Destination(p))
+}
+
+func (p packet) String() string {
+	return fmt.Sprintf("%s %s:%d -> %s:%d %d bytes", p.proto(),
+		waterutil.IPv4Source(p), waterutil.IPv4SourcePort(p),
+		waterutil.IPv4Destination(p), waterutil.IPv4DestinationPort(p), len(waterutil.IPv4Payload(p)))
+}
+
+func (p packet) proto() string {
+	proto := waterutil.IPv4Protocol(p)
+	switch proto {
+	case waterutil.TCP:
+		return "tcp"
+	case waterutil.UDP:
+		return "udp"
+	case waterutil.ICMP:
+		return "icmp"
+	default:
+		return strconv.Itoa(int(proto))
+	}
 }

go.mod

@@ -31,6 +31,7 @@ require (
 	github.com/michaelquigley/pfxlog v0.6.10
 	github.com/muesli/reflow v0.3.0
 	github.com/net-byte/vtun v1.7.0
+	github.com/net-byte/water v0.0.7
 	github.com/nxadm/tail v1.4.8
 	github.com/openziti/channel/v2 v2.0.121
 	github.com/openziti/edge-api v0.26.12
@@ -38,6 +39,7 @@ require (
 	github.com/openziti/identity v1.0.72
 	github.com/openziti/sdk-golang v0.23.10
 	github.com/openziti/transport/v2 v2.0.124
+	github.com/orcaman/concurrent-map/v2 v2.0.1
 	github.com/pkg/errors v0.9.1
 	github.com/rabbitmq/amqp091-go v1.8.1
 	github.com/rubenv/sql-migrate v1.6.0
@@ -166,7 +168,6 @@ require (
 	github.com/muesli/termenv v0.13.0 // indirect
 	github.com/muhlemmer/gu v0.3.1 // indirect
 	github.com/net-byte/go-gateway v0.0.2 // indirect
-	github.com/net-byte/water v0.0.7 // indirect
 	github.com/oklog/ulid v1.3.1 // indirect
 	github.com/onsi/ginkgo/v2 v2.9.5 // indirect
 	github.com/opentracing/opentracing-go v1.2.0 // indirect
@@ -174,7 +175,6 @@ require (
 	github.com/openziti/metrics v1.2.47 // indirect
 	github.com/openziti/secretstream v0.1.17 // indirect
 	github.com/openziti/storage v0.2.6 // indirect
-	github.com/orcaman/concurrent-map/v2 v2.0.1 // indirect
 	github.com/parallaxsecond/parsec-client-go v0.0.0-20221025095442-f0a77d263cf9 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/power-devops/perfstat v0.0.0-20221212215047-62379fc7944b // indirect