add support for connection migration (#4960)

integrationtests/self/connection_migration_test.go

@@ -0,0 +1,144 @@
+package self_test
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"net"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"github.com/quic-go/quic-go"
+	quicproxy "github.com/quic-go/quic-go/integrationtests/tools/proxy"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestConnectionMigration(t *testing.T) {
+	ln, err := quic.ListenAddr("localhost:0", tlsConfig, getQuicConfig(nil))
+	require.NoError(t, err)
+	defer ln.Close()
+
+	tr1 := &quic.Transport{Conn: newUDPConnLocalhost(t)}
+	defer tr1.Close()
+	tr2 := &quic.Transport{Conn: newUDPConnLocalhost(t)}
+	defer tr2.Close()
+
+	var packetsPath1, packetsPath2 atomic.Int64
+
+	const rtt = 5 * time.Millisecond
+	proxy := quicproxy.Proxy{
+		Conn:       newUDPConnLocalhost(t),
+		ServerAddr: ln.Addr().(*net.UDPAddr),
+		DelayPacket: func(dir quicproxy.Direction, from, to net.Addr, _ []byte) time.Duration {
+			var port int
+			switch dir {
+			case quicproxy.DirectionIncoming:
+				port = from.(*net.UDPAddr).Port
+			case quicproxy.DirectionOutgoing:
+				port = to.(*net.UDPAddr).Port
+			}
+			switch port {
+			case tr1.Conn.LocalAddr().(*net.UDPAddr).Port:
+				packetsPath1.Add(1)
+			case tr2.Conn.LocalAddr().(*net.UDPAddr).Port:
+				packetsPath2.Add(1)
+			default:
+				fmt.Println("address not found", from)
+			}
+			return rtt / 2
+		},
+	}
+	require.NoError(t, proxy.Start())
+	defer proxy.Close()
+
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+
+	conn, err := tr1.Dial(ctx, proxy.LocalAddr(), getTLSClientConfig(), getQuicConfig(nil))
+	require.NoError(t, err)
+	defer conn.CloseWithError(0, "")
+
+	sconn, err := ln.Accept(ctx)
+	require.NoError(t, err)
+	defer sconn.CloseWithError(0, "")
+
+	sendAndReceiveFile := func(t *testing.T) {
+		t.Helper()
+		str, err := conn.OpenUniStream()
+		require.NoError(t, err)
+
+		errChan := make(chan error, 1)
+		go func() {
+			defer close(errChan)
+			sstr, err := sconn.AcceptUniStream(ctx)
+			if err != nil {
+				errChan <- fmt.Errorf("accepting stream: %w", err)
+				return
+			}
+			data, err := io.ReadAll(sstr)
+			if err != nil {
+				errChan <- fmt.Errorf("reading stream data: %w", err)
+				return
+			}
+			if !bytes.Equal(data, PRData) {
+				errChan <- errors.New("unexpected data")
+			}
+		}()
+
+		_, err = str.Write(PRData)
+		require.NoError(t, err)
+		require.NoError(t, str.Close())
+
+		select {
+		case err := <-errChan:
+			require.NoError(t, err)
+		case <-time.After(time.Second):
+			t.Fatal("timed out waiting for data")
+		}
+	}
+
+	sendAndReceiveFile(t) // stream 2
+	require.NotZero(t, packetsPath1.Load())
+	require.Zero(t, packetsPath2.Load())
+
+	// probing the path causes a few packets to be sent on path 2
+	path, err := conn.AddPath(tr2)
+	require.NoError(t, err)
+	require.ErrorIs(t, path.Switch(), quic.ErrPathNotValidated)
+	require.NoError(t, path.Probe(ctx))
+	require.Less(t, int(packetsPath2.Load()), 5)
+
+	// make sure that no more packets are sent on path 2 before switching to the path
+	c2 := packetsPath2.Load()
+	sendAndReceiveFile(t) // stream 6
+	require.Equal(t, packetsPath2.Load(), c2)
+
+	time.Sleep(3 * rtt) // wait for ACKs
+
+	// now switch and make sure that no packets are sent on path 1
+	require.NoError(t, path.Switch())
+	sendAndReceiveFile(t) // stream 10
+	c1 := packetsPath1.Load()
+	require.Equal(t, c1, packetsPath1.Load())
+	require.Greater(t, packetsPath2.Load(), c2)
+	require.Equal(t, tr2.Conn.LocalAddr(), conn.LocalAddr())
+
+	// switch back to the handshake path
+	time.Sleep(3 * rtt) // wait for ACKs
+	c1BeforeSwitch := packetsPath1.Load()
+	c2BeforeSwitch := packetsPath2.Load()
+	path2, err := conn.AddPath(tr1)
+	require.NoError(t, err)
+	require.NoError(t, path2.Probe(ctx))
+	time.Sleep(3 * rtt) // wait for ACKs
+	require.NoError(t, path2.Switch())
+	sendAndReceiveFile(t) // stream 14
+	require.Greater(t, packetsPath1.Load(), c1BeforeSwitch)
+	// some path probing might have happened
+	require.Less(t, int(packetsPath2.Load()-c2BeforeSwitch), 20)
+	require.Equal(t, tr1.Conn.LocalAddr(), conn.LocalAddr())
+}