xtcp: when connection timeout occurs, support fallback to STCP (#3460)

test/e2e/basic/basic.go

@@ -376,7 +376,7 @@ var _ = ginkgo.Describe("[Feature: Basic]", func() {
 				for _, test := range tests {
 					framework.NewRequestExpect(f).
 						RequestModify(func(r *request.Request) {
-							r.Timeout(5 * time.Second)
+							r.Timeout(10 * time.Second)
 						}).
 						Protocol(protocol).
 						PortName(test.bindPortName).

test/e2e/basic/xtcp.go

@@ -0,0 +1,52 @@
+package basic
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/onsi/ginkgo/v2"
+
+	"github.com/fatedier/frp/test/e2e/framework"
+	"github.com/fatedier/frp/test/e2e/framework/consts"
+	"github.com/fatedier/frp/test/e2e/pkg/port"
+	"github.com/fatedier/frp/test/e2e/pkg/request"
+)
+
+var _ = ginkgo.Describe("[Feature: XTCP]", func() {
+	f := framework.NewDefaultFramework()
+
+	ginkgo.It("Fallback To STCP", func() {
+		serverConf := consts.DefaultServerConfig
+		clientConf := consts.DefaultClientConfig
+
+		bindPortName := port.GenName("XTCP")
+		clientConf += fmt.Sprintf(`
+			[foo]
+			type = stcp
+			local_port = {{ .%s }}
+
+			[foo-visitor]
+			type = stcp
+			role = visitor
+			server_name = foo
+			bind_port = -1
+
+			[bar-visitor]
+			type = xtcp
+			role = visitor
+			server_name = bar
+			bind_port = {{ .%s }}
+			keep_tunnel_open = true
+			fallback_to = foo-visitor
+			fallback_timeout_ms = 200
+			`, framework.TCPEchoServerPort, bindPortName)
+
+		f.RunProcesses([]string{serverConf}, []string{clientConf})
+		framework.NewRequestExpect(f).
+			RequestModify(func(r *request.Request) {
+				r.Timeout(time.Second)
+			}).
+			PortName(bindPortName).
+			Ensure()
+	})
+})