[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/ebpf/wrapper.go

@@ -0,0 +1,126 @@
+//go:build linux && !android
+
+package ebpf
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"net"
+	"sync"
+
+	log "github.com/sirupsen/logrus"
+)
+
+// ProxyWrapper help to keep the remoteConn instance for net.Conn.Close function call
+type ProxyWrapper struct {
+	WgeBPFProxy *WGEBPFProxy
+
+	remoteConn net.Conn
+	ctx        context.Context
+	cancel     context.CancelFunc
+
+	wgEndpointAddr *net.UDPAddr
+
+	pausedMu  sync.Mutex
+	paused    bool
+	isStarted bool
+}
+
+func (p *ProxyWrapper) AddTurnConn(ctx context.Context, endpoint *net.UDPAddr, remoteConn net.Conn) error {
+	addr, err := p.WgeBPFProxy.AddTurnConn(remoteConn)
+	if err != nil {
+		return fmt.Errorf("add turn conn: %w", err)
+	}
+	p.remoteConn = remoteConn
+	p.ctx, p.cancel = context.WithCancel(ctx)
+	p.wgEndpointAddr = addr
+	return err
+}
+
+func (p *ProxyWrapper) EndpointAddr() *net.UDPAddr {
+	return p.wgEndpointAddr
+}
+
+func (p *ProxyWrapper) Work() {
+	if p.remoteConn == nil {
+		return
+	}
+
+	p.pausedMu.Lock()
+	p.paused = false
+	p.pausedMu.Unlock()
+
+	if !p.isStarted {
+		p.isStarted = true
+		go p.proxyToLocal(p.ctx)
+	}
+}
+
+func (p *ProxyWrapper) Pause() {
+	if p.remoteConn == nil {
+		return
+	}
+
+	log.Tracef("pause proxy reading from: %s", p.remoteConn.RemoteAddr())
+	p.pausedMu.Lock()
+	p.paused = true
+	p.pausedMu.Unlock()
+}
+
+// CloseConn close the remoteConn and automatically remove the conn instance from the map
+func (e *ProxyWrapper) CloseConn() error {
+	if e.cancel == nil {
+		return fmt.Errorf("proxy not started")
+	}
+
+	e.cancel()
+
+	if err := e.remoteConn.Close(); err != nil {
+		return fmt.Errorf("failed to close remote conn: %w", err)
+	}
+	return nil
+}
+
+func (p *ProxyWrapper) proxyToLocal(ctx context.Context) {
+	defer p.WgeBPFProxy.removeTurnConn(uint16(p.wgEndpointAddr.Port))
+
+	buf := make([]byte, 1500)
+	for {
+		n, err := p.readFromRemote(ctx, buf)
+		if err != nil {
+			return
+		}
+
+		p.pausedMu.Lock()
+		if p.paused {
+			p.pausedMu.Unlock()
+			continue
+		}
+
+		err = p.WgeBPFProxy.sendPkg(buf[:n], p.wgEndpointAddr.Port)
+		p.pausedMu.Unlock()
+
+		if err != nil {
+			if ctx.Err() != nil {
+				return
+			}
+			log.Errorf("failed to write out turn pkg to local conn: %v", err)
+		}
+	}
+}
+
+func (p *ProxyWrapper) readFromRemote(ctx context.Context, buf []byte) (int, error) {
+	n, err := p.remoteConn.Read(buf)
+	if err != nil {
+		if ctx.Err() != nil {
+			return 0, ctx.Err()
+		}
+		if !errors.Is(err, io.EOF) {
+			log.Errorf("failed to read from turn conn (endpoint: :%d): %s", p.wgEndpointAddr.Port, err)
+		}
+		return 0, err
+	}
+	return n, nil
+}