[relay,client] Relay/fix/wg roaming (#2691)

If a peer connection switches from Relayed to ICE P2P, the Relayed proxy still consumes the data the other peer sends. Because the proxy is operating, the WireGuard switches back to the Relayed proxy automatically, thanks to the roaming feature.

Extend the Proxy implementation with pause/resume functions. Before switching to the p2p connection, pause the WireGuard proxy operation to prevent unnecessary package sources.
Consider waiting some milliseconds after the pause to be sure the WireGuard engine already processed all UDP msg in from the pipe.

client/internal/wgproxy/ebpf/wrapper.go

@@ -4,8 +4,13 @@ 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
@@ -13,20 +18,55 @@ type ProxyWrapper struct {
 	WgeBPFProxy *WGEBPFProxy
 
 	remoteConn net.Conn
-	cancel     context.CancelFunc // with thic cancel function, we stop remoteToLocal thread
+	ctx        context.Context
+	cancel     context.CancelFunc
+
+	wgEndpointAddr *net.UDPAddr
+
+	pausedMu  sync.Mutex
+	paused    bool
+	isStarted bool
 }
 
-func (e *ProxyWrapper) AddTurnConn(ctx context.Context, remoteConn net.Conn) (net.Addr, error) {
-	ctxConn, cancel := context.WithCancel(ctx)
-	addr, err := e.WgeBPFProxy.AddTurnConn(ctxConn, remoteConn)
-
+func (p *ProxyWrapper) AddTurnConn(ctx context.Context, remoteConn net.Conn) error {
+	addr, err := p.WgeBPFProxy.AddTurnConn(remoteConn)
 	if err != nil {
-		cancel()
-		return nil, fmt.Errorf("add turn conn: %w", err)
+		return fmt.Errorf("add turn conn: %w", err)
 	}
-	e.remoteConn = remoteConn
-	e.cancel = cancel
-	return addr, 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
@@ -42,3 +82,45 @@ func (e *ProxyWrapper) CloseConn() error {
 	}
 	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
+}