[relay] Feature/relay integration (#2244)

This update adds new relay integration for NetBird clients. The new relay is based on web sockets and listens on a single port.

- Adds new relay implementation with websocket with single port relaying mechanism
- refactor peer connection logic, allowing upgrade and downgrade from/to P2P connection
- peer connections are faster since it connects first to relay and then upgrades to P2P
- maintains compatibility with old clients by not using the new relay
- updates infrastructure scripts with new relay service

relay/testec2/tun/proxy.go

@@ -0,0 +1,72 @@
+//go:build linux || darwin
+
+package tun
+
+import (
+	"net"
+	"sync/atomic"
+
+	log "github.com/sirupsen/logrus"
+)
+
+type Proxy struct {
+	Device       *Device
+	PConn        net.PacketConn
+	DstAddr      net.Addr
+	shutdownFlag atomic.Bool
+}
+
+func (p *Proxy) Start() {
+	go p.readFromDevice()
+	go p.readFromConn()
+}
+
+func (p *Proxy) Close() {
+	p.shutdownFlag.Store(true)
+}
+
+func (p *Proxy) readFromDevice() {
+	buf := make([]byte, 1500)
+	for {
+		n, err := p.Device.Read(buf)
+		if err != nil {
+			if p.shutdownFlag.Load() {
+				return
+			}
+			log.Errorf("failed to read from device: %s", err)
+			return
+		}
+
+		_, err = p.PConn.WriteTo(buf[:n], p.DstAddr)
+		if err != nil {
+			if p.shutdownFlag.Load() {
+				return
+			}
+			log.Errorf("failed to write to conn: %s", err)
+			return
+		}
+	}
+}
+
+func (p *Proxy) readFromConn() {
+	buf := make([]byte, 1500)
+	for {
+		n, _, err := p.PConn.ReadFrom(buf)
+		if err != nil {
+			if p.shutdownFlag.Load() {
+				return
+			}
+			log.Errorf("failed to read from conn: %s", err)
+			return
+		}
+
+		_, err = p.Device.Write(buf[:n])
+		if err != nil {
+			if p.shutdownFlag.Load() {
+				return
+			}
+			log.Errorf("failed to write to device: %s", err)
+			return
+		}
+	}
+}

relay/testec2/tun/tun.go

@@ -0,0 +1,110 @@
+//go:build linux || darwin
+
+package tun
+
+import (
+	"net"
+
+	log "github.com/sirupsen/logrus"
+	"github.com/songgao/water"
+	"github.com/vishvananda/netlink"
+)
+
+type Device struct {
+	Name    string
+	IP      string
+	PConn   net.PacketConn
+	DstAddr net.Addr
+
+	iFace *water.Interface
+	proxy *Proxy
+}
+
+func (d *Device) Up() error {
+	cfg := water.Config{
+		DeviceType: water.TUN,
+		PlatformSpecificParams: water.PlatformSpecificParams{
+			Name: d.Name,
+		},
+	}
+	iFace, err := water.New(cfg)
+	if err != nil {
+		return err
+	}
+	d.iFace = iFace
+
+	err = d.assignIP()
+	if err != nil {
+		return err
+	}
+
+	err = d.bringUp()
+	if err != nil {
+		return err
+	}
+
+	d.proxy = &Proxy{
+		Device:  d,
+		PConn:   d.PConn,
+		DstAddr: d.DstAddr,
+	}
+	d.proxy.Start()
+	return nil
+}
+
+func (d *Device) Close() error {
+	if d.proxy != nil {
+		d.proxy.Close()
+	}
+	if d.iFace != nil {
+		return d.iFace.Close()
+	}
+	return nil
+}
+
+func (d *Device) Read(b []byte) (int, error) {
+	return d.iFace.Read(b)
+}
+
+func (d *Device) Write(b []byte) (int, error) {
+	return d.iFace.Write(b)
+}
+
+func (d *Device) assignIP() error {
+	iface, err := netlink.LinkByName(d.Name)
+	if err != nil {
+		log.Errorf("failed to get TUN device: %v", err)
+		return err
+	}
+
+	ip := net.IPNet{
+		IP:   net.ParseIP(d.IP),
+		Mask: net.CIDRMask(24, 32),
+	}
+
+	addr := &netlink.Addr{
+		IPNet: &ip,
+	}
+	err = netlink.AddrAdd(iface, addr)
+	if err != nil {
+		log.Errorf("failed to add IP address: %v", err)
+		return err
+	}
+	return nil
+}
+
+func (d *Device) bringUp() error {
+	iface, err := netlink.LinkByName(d.Name)
+	if err != nil {
+		log.Errorf("failed to get device: %v", err)
+		return err
+	}
+
+	// Bring the interface up
+	err = netlink.LinkSetUp(iface)
+	if err != nil {
+		log.Errorf("failed to set device up: %v", err)
+		return err
+	}
+	return nil
+}