set the QUIC version for integration tests using a command line flag

integrationtests/versionnegotiation/rtt_test.go

@@ -0,0 +1,53 @@
+package versionnegotiation
+
+import (
+	"time"
+
+	"github.com/quic-go/quic-go"
+	quicproxy "github.com/quic-go/quic-go/integrationtests/tools/proxy"
+	"github.com/quic-go/quic-go/internal/protocol"
+
+	. "github.com/onsi/ginkgo/v2"
+	. "github.com/onsi/gomega"
+)
+
+var _ = Describe("Handshake RTT tests", func() {
+	const rtt = 400 * time.Millisecond
+
+	expectDurationInRTTs := func(startTime time.Time, num int) {
+		testDuration := time.Since(startTime)
+		rtts := float32(testDuration) / float32(rtt)
+		Expect(rtts).To(SatisfyAll(
+			BeNumerically(">=", num),
+			BeNumerically("<", num+1),
+		))
+	}
+
+	It("fails when there's no matching version, after 1 RTT", func() {
+		if len(protocol.SupportedVersions) == 1 {
+			Skip("Test requires at least 2 supported versions.")
+		}
+
+		serverConfig := &quic.Config{}
+		serverConfig.Versions = protocol.SupportedVersions[:1]
+		ln, err := quic.ListenAddr("localhost:0", getTLSConfig(), serverConfig)
+		Expect(err).ToNot(HaveOccurred())
+		defer ln.Close()
+
+		// start the proxy
+		proxy, err := quicproxy.NewQuicProxy("localhost:0", &quicproxy.Opts{
+			RemoteAddr:  ln.Addr().String(),
+			DelayPacket: func(_ quicproxy.Direction, _ []byte) time.Duration { return rtt / 2 },
+		})
+		Expect(err).ToNot(HaveOccurred())
+
+		startTime := time.Now()
+		_, err = quic.DialAddr(
+			proxy.LocalAddr().String(),
+			getTLSClientConfig(),
+			maybeAddQlogTracer(&quic.Config{Versions: protocol.SupportedVersions[1:2]}),
+		)
+		Expect(err).To(HaveOccurred())
+		expectDurationInRTTs(startTime, 1)
+	})
+})