[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
+		}
+	}
+}