[client] Eliminate UDP proxy in user-space mode (#2712)

In the case of user space WireGuard mode, use in-memory proxy between the TURN/Relay connection and the WireGuard Bind. We keep the UDP proxy and eBPF proxy for kernel mode.

The key change is the new wgproxy/bind and the iface/bind/ice_bind changes. Everything else is just to fulfill the dependencies.

client/iface/wgproxy/bind/proxy.go

@@ -0,0 +1,137 @@
+package bind
+
+import (
+	"context"
+	"fmt"
+	"net"
+	"net/netip"
+	"sync"
+
+	log "github.com/sirupsen/logrus"
+
+	"github.com/netbirdio/netbird/client/iface/bind"
+)
+
+type ProxyBind struct {
+	Bind *bind.ICEBind
+
+	wgAddr     *net.UDPAddr
+	wgEndpoint *bind.Endpoint
+	remoteConn net.Conn
+	ctx        context.Context
+	cancel     context.CancelFunc
+	closeMu    sync.Mutex
+	closed     bool
+
+	pausedMu  sync.Mutex
+	paused    bool
+	isStarted bool
+}
+
+// AddTurnConn adds a new connection to the bind.
+// endpoint is the NetBird address of the remote peer. The SetEndpoint return with the address what will be used in the
+// WireGuard configuration.
+func (p *ProxyBind) AddTurnConn(ctx context.Context, nbAddr *net.UDPAddr, remoteConn net.Conn) error {
+	addr, err := p.Bind.SetEndpoint(nbAddr, remoteConn)
+	if err != nil {
+		return err
+	}
+
+	p.wgAddr = addr
+	p.wgEndpoint = addrToEndpoint(addr)
+	p.remoteConn = remoteConn
+	p.ctx, p.cancel = context.WithCancel(ctx)
+	return err
+
+}
+func (p *ProxyBind) EndpointAddr() *net.UDPAddr {
+	return p.wgAddr
+}
+
+func (p *ProxyBind) Work() {
+	if p.remoteConn == nil {
+		return
+	}
+
+	p.pausedMu.Lock()
+	p.paused = false
+	p.pausedMu.Unlock()
+
+	// Start the proxy only once
+	if !p.isStarted {
+		p.isStarted = true
+		go p.proxyToLocal(p.ctx)
+	}
+}
+
+func (p *ProxyBind) Pause() {
+	if p.remoteConn == nil {
+		return
+	}
+
+	p.pausedMu.Lock()
+	p.paused = true
+	p.pausedMu.Unlock()
+}
+
+func (p *ProxyBind) CloseConn() error {
+	if p.cancel == nil {
+		return fmt.Errorf("proxy not started")
+	}
+	return p.close()
+}
+
+func (p *ProxyBind) close() error {
+	p.closeMu.Lock()
+	defer p.closeMu.Unlock()
+
+	if p.closed {
+		return nil
+	}
+	p.closed = true
+
+	p.cancel()
+
+	p.Bind.RemoveEndpoint(p.wgAddr)
+
+	return p.remoteConn.Close()
+}
+
+func (p *ProxyBind) proxyToLocal(ctx context.Context) {
+	defer func() {
+		if err := p.close(); err != nil {
+			log.Warnf("failed to close remote conn: %s", err)
+		}
+	}()
+
+	buf := make([]byte, 1500)
+	for {
+		n, err := p.remoteConn.Read(buf)
+		if err != nil {
+			if ctx.Err() != nil {
+				return
+			}
+			log.Errorf("failed to read from remote conn: %s, %s", p.remoteConn.RemoteAddr(), err)
+			return
+		}
+
+		p.pausedMu.Lock()
+		if p.paused {
+			p.pausedMu.Unlock()
+			continue
+		}
+
+		msg := bind.RecvMessage{
+			Endpoint: p.wgEndpoint,
+			Buffer:   buf[:n],
+		}
+		p.Bind.RecvChan <- msg
+		p.pausedMu.Unlock()
+	}
+}
+
+func addrToEndpoint(addr *net.UDPAddr) *bind.Endpoint {
+	ip, _ := netip.AddrFromSlice(addr.IP.To4())
+	addrPort := netip.AddrPortFrom(ip, uint16(addr.Port))
+	return &bind.Endpoint{AddrPort: addrPort}
+}