[client] Fix/pkg loss (#3338)

The Relayed connection setup is optimistic. It does not have any confirmation of an established end-to-end connection. Peers start sending WireGuard handshake packets immediately after the successful offer-answer handshake.
Meanwhile, for successful P2P connection negotiation, we change the WireGuard endpoint address, but this change does not trigger new handshake initiation. Because the peer switched from Relayed connection to P2P, the packets from the Relay server are dropped and must wait for the next WireGuard handshake via P2P.

To avoid this scenario, the relayed WireGuard proxy no longer drops the packets. Instead, it rewrites the source address to the new P2P endpoint and continues forwarding the packets.

We still have one corner case: if the Relayed server negotiation chooses a server that has not been used before. In this case, one side of the peer connection will be slower to reach the Relay server, and the Relay server will drop the handshake packet.

If everything goes well we should see exactly 5 seconds improvements between the WireGuard configuration time and the handshake time.

client/iface/wgproxy/proxy_test.go

@@ -1,5 +1,3 @@
-//go:build linux
-
 package wgproxy
 
 import (
@@ -7,12 +5,9 @@ import (
 	"io"
 	"net"
 	"os"
-	"runtime"
 	"testing"
 	"time"
 
-	"github.com/netbirdio/netbird/client/iface/wgproxy/ebpf"
-	udpProxy "github.com/netbirdio/netbird/client/iface/wgproxy/udp"
 	"github.com/netbirdio/netbird/util"
 )
 
@@ -22,6 +17,14 @@ func TestMain(m *testing.M) {
 	os.Exit(code)
 }
 
+type proxyInstance struct {
+	name         string
+	proxy        Proxy
+	wgPort       int
+	endpointAddr *net.UDPAddr
+	closeFn      func() error
+}
+
 type mocConn struct {
 	closeChan chan struct{}
 	closed    bool
@@ -78,41 +81,21 @@ func (m *mocConn) SetWriteDeadline(t time.Time) error {
 func TestProxyCloseByRemoteConn(t *testing.T) {
 	ctx := context.Background()
 
-	tests := []struct {
-		name  string
-		proxy Proxy
-	}{
-		{
-			name:  "userspace proxy",
-			proxy: udpProxy.NewWGUDPProxy(51830, 1280),
-		},
+	tests, err := seedProxyForProxyCloseByRemoteConn()
+	if err != nil {
+		t.Fatalf("error: %v", err)
 	}
 
-	if runtime.GOOS == "linux" && os.Getenv("GITHUB_ACTIONS") != "true" {
-		ebpfProxy := ebpf.NewWGEBPFProxy(51831, 1280)
-		if err := ebpfProxy.Listen(); err != nil {
-			t.Fatalf("failed to initialize ebpf proxy: %s", err)
-		}
-		defer func() {
-			if err := ebpfProxy.Free(); err != nil {
-				t.Errorf("failed to free ebpf proxy: %s", err)
-			}
-		}()
-		proxyWrapper := ebpf.NewProxyWrapper(ebpfProxy)
-
-		tests = append(tests, struct {
-			name  string
-			proxy Proxy
-		}{
-			name:  "ebpf proxy",
-			proxy: proxyWrapper,
-		})
-	}
+	relayedConn, _ := net.Dial("udp", "127.0.0.1:1234")
+	defer func() {
+		_ = relayedConn.Close()
+	}()
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
+			addr, _ := net.ResolveUDPAddr("udp", "100.108.135.221:51892")
 			relayedConn := newMockConn()
-			err := tt.proxy.AddTurnConn(ctx, nil, relayedConn)
+			err := tt.proxy.AddTurnConn(ctx, addr, relayedConn)
 			if err != nil {
 				t.Errorf("error: %v", err)
 			}
@@ -124,3 +107,104 @@ func TestProxyCloseByRemoteConn(t *testing.T) {
 		})
 	}
 }
+
+// TestProxyRedirect todo extend the proxies with Bind proxy
+func TestProxyRedirect(t *testing.T) {
+	tests, err := seedProxies()
+	if err != nil {
+		t.Fatalf("error: %v", err)
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			redirectTraffic(t, tt.proxy, tt.wgPort, tt.endpointAddr)
+			if err := tt.closeFn(); err != nil {
+				t.Errorf("error: %v", err)
+			}
+		})
+	}
+}
+
+func redirectTraffic(t *testing.T, proxy Proxy, wgPort int, endPointAddr *net.UDPAddr) {
+	t.Helper()
+
+	msgHelloFromRelay := []byte("hello from relay")
+	msgRedirected := [][]byte{
+		[]byte("hello 1. to p2p"),
+		[]byte("hello 2. to p2p"),
+		[]byte("hello 3. to p2p"),
+	}
+
+	dummyWgListener, err := net.ListenUDP("udp", &net.UDPAddr{
+		IP:   net.IPv4(127, 0, 0, 1),
+		Port: wgPort})
+	if err != nil {
+		t.Fatalf("failed to listen on udp port: %s", err)
+	}
+
+	relayedServer, _ := net.ListenUDP("udp",
+		&net.UDPAddr{
+			IP:   net.IPv4(127, 0, 0, 1),
+			Port: 1234,
+		},
+	)
+
+	relayedConn, _ := net.Dial("udp", "127.0.0.1:1234")
+
+	defer func() {
+		_ = dummyWgListener.Close()
+		_ = relayedConn.Close()
+		_ = relayedServer.Close()
+	}()
+
+	if err := proxy.AddTurnConn(context.Background(), endPointAddr, relayedConn); err != nil {
+		t.Errorf("error: %v", err)
+	}
+	defer func() {
+		if err := proxy.CloseConn(); err != nil {
+			t.Errorf("error: %v", err)
+		}
+	}()
+
+	proxy.Work()
+
+	if _, err := relayedServer.WriteTo(msgHelloFromRelay, relayedConn.LocalAddr()); err != nil {
+		t.Errorf("error relayedServer.Write(msgHelloFromRelay): %v", err)
+	}
+
+	n, err := dummyWgListener.Read(make([]byte, 1024))
+	if err != nil {
+		t.Errorf("error: %v", err)
+	}
+
+	if n != len(msgHelloFromRelay) {
+		t.Errorf("expected %d bytes, got %d", len(msgHelloFromRelay), n)
+	}
+
+	p2pEndpointAddr := &net.UDPAddr{
+		IP:   net.IPv4(192, 168, 0, 56),
+		Port: 1234,
+	}
+	proxy.RedirectAs(p2pEndpointAddr)
+
+	for _, msg := range msgRedirected {
+		if _, err := relayedServer.WriteTo(msg, relayedConn.LocalAddr()); err != nil {
+			t.Errorf("error: %v", err)
+		}
+	}
+
+	for i := 0; i < len(msgRedirected); i++ {
+		buf := make([]byte, 1024)
+		n, rAddr, err := dummyWgListener.ReadFrom(buf)
+		if err != nil {
+			t.Errorf("error: %v", err)
+		}
+
+		if rAddr.String() != p2pEndpointAddr.String() {
+			t.Errorf("expected %s, got %s", p2pEndpointAddr.String(), rAddr.String())
+		}
+		if string(buf[:n]) != string(msgRedirected[i]) {
+			t.Errorf("expected %s, got %s", string(msgRedirected[i]), string(buf[:n]))
+		}
+	}
+}