fix: draining remote stream after port-forward connection broken

Signed-off-by: Nic <qianyong@api7.ai>

staging/src/k8s.io/client-go/tools/portforward/portforward.go

@@ -406,6 +406,11 @@ func (pf *PortForwarder) handleConnection(conn net.Conn, port ForwardedPort) {
 	case <-remoteDone:
 	case <-localError:
 	}
+	/*
+		reset dataStream to discard any unsent data, preventing port forwarding from being blocked.
+		we must reset dataStream before waiting on errorChan, otherwise, the blocking data will affect errorStream and cause <-errorChan to block indefinitely.
+	*/
+	_ = dataStream.Reset()
 
 	// always expect something on errorChan (it may be nil)
 	err = <-errorChan

test/e2e/kubectl/portforward.go

@@ -25,6 +25,7 @@ import (
 	"fmt"
 	"io"
 	"net"
+	"net/http"
 	"os/exec"
 	"regexp"
 	"strconv"
@@ -123,6 +124,36 @@ func pfPod(expectedClientData, chunks, chunkSize, chunkIntervalMillis string, bi
 	}
 }
 
+func testWebServerPod() *v1.Pod {
+	return &v1.Pod{
+		ObjectMeta: metav1.ObjectMeta{
+			Name:   podName,
+			Labels: map[string]string{"name": podName},
+		},
+		Spec: v1.PodSpec{
+			Containers: []v1.Container{
+				{
+					Name:  "testwebserver",
+					Image: imageutils.GetE2EImage(imageutils.Agnhost),
+					Args:  []string{"test-webserver"},
+					Ports: []v1.ContainerPort{{ContainerPort: int32(80)}},
+					ReadinessProbe: &v1.Probe{
+						ProbeHandler: v1.ProbeHandler{
+							HTTPGet: &v1.HTTPGetAction{
+								Path: "/",
+								Port: intstr.FromInt32(int32(80)),
+							},
+						},
+						InitialDelaySeconds: 5,
+						TimeoutSeconds:      3,
+						FailureThreshold:    10,
+					},
+				},
+			},
+		},
+	}
+}
+
 // WaitForTerminatedContainer waits till a given container be terminated for a given pod.
 func WaitForTerminatedContainer(ctx context.Context, f *framework.Framework, pod *v1.Pod, containerName string) error {
 	return e2epod.WaitForPodCondition(ctx, f.ClientSet, f.Namespace.Name, pod.Name, "container terminated", framework.PodStartTimeout, func(pod *v1.Pod) (bool, error) {
@@ -493,6 +524,69 @@ var _ = SIGDescribe("Kubectl Port forwarding", func() {
 			doTestOverWebSockets(ctx, "localhost", f)
 		})
 	})
+
+	ginkgo.Describe("Shutdown client connection while the remote stream is writing data to the port-forward connection", func() {
+		ginkgo.It("port-forward should keep working after detect broken connection", func(ctx context.Context) {
+			ginkgo.By("Creating the target pod")
+			pod := testWebServerPod()
+			if _, err := f.ClientSet.CoreV1().Pods(f.Namespace.Name).Create(ctx, pod, metav1.CreateOptions{}); err != nil {
+				framework.Failf("Couldn't create pod: %v", err)
+			}
+			if err := e2epod.WaitTimeoutForPodReadyInNamespace(ctx, f.ClientSet, pod.Name, f.Namespace.Name, framework.PodStartTimeout); err != nil {
+				framework.Failf("Pod did not start running: %v", err)
+			}
+
+			ginkgo.By("Running 'kubectl port-forward'")
+			cmd := runPortForward(f.Namespace.Name, pod.Name, 80)
+			defer cmd.Stop()
+
+			ginkgo.By("Send a http request to verify port-forward working")
+			client := http.Client{
+				Timeout: 5 * time.Second,
+			}
+			resp, err := client.Get(fmt.Sprintf("http://127.0.0.1:%d/", cmd.port))
+			if err != nil {
+				framework.Failf("Couldn't get http response from port-forward: %v", err)
+			}
+			if resp.StatusCode != http.StatusOK {
+				framework.Failf("Expected status code %d, got %d", http.StatusOK, resp.StatusCode)
+			}
+
+			ginkgo.By("Dialing the local port")
+			conn, err := net.Dial("tcp", fmt.Sprintf("127.0.0.1:%d", cmd.port))
+			if err != nil {
+				framework.Failf("Couldn't connect to port %d: %v", cmd.port, err)
+			}
+
+			// use raw tcp connection to emulate client close connection without reading response
+			ginkgo.By("Request agohost binary file (40MB+)")
+			requestLines := []string{"GET /agnhost HTTP/1.1", "Host: localhost", ""}
+			for _, line := range requestLines {
+				if _, err := conn.Write(append([]byte(line), []byte("\r\n")...)); err != nil {
+					framework.Failf("Couldn't write http request to local connection: %v", err)
+				}
+			}
+
+			ginkgo.By("Read only one byte from the connection")
+			if _, err := conn.Read(make([]byte, 1)); err != nil {
+				framework.Logf("Couldn't reading from the local connection: %v", err)
+			}
+
+			ginkgo.By("Close client connection without reading remain data")
+			if err := conn.Close(); err != nil {
+				framework.Failf("Couldn't close local connection: %v", err)
+			}
+
+			ginkgo.By("Send another http request through port-forward again")
+			resp, err = client.Get(fmt.Sprintf("http://127.0.0.1:%d/", cmd.port))
+			if err != nil {
+				framework.Failf("Couldn't get http response from port-forward: %v", err)
+			}
+			if resp.StatusCode != http.StatusOK {
+				framework.Failf("Expected status code %d, got %d", http.StatusOK, resp.StatusCode)
+			}
+		})
+	})
 })
 
 func wsRead(conn *websocket.Conn) (byte, []byte, error) {