Merge pull request #117764 from aojea/tcp_rst

e2e agnhost functionality to RST TCP connections

test/images/agnhost/README.md

@@ -621,6 +621,29 @@ Usage:
     kubectl exec test-agnhost -- /agnhost serve-hostname [--tcp] [--udp] [--http] [--close] [--port <port>]
 ```
 
+### tcp-reset
+
+Starts a simple TCP servers that reads only one byte of the connection and then closes it,
+having the effect of sending a TCP RST to the client.
+
+The subcommand can accept the following flags:
+
+- `port` (default: `8080`): The port number to listen to.
+
+Usage:
+
+```console
+    kubectl exec test-agnhost -- /agnhost tcp-reset [--port <port>]
+```
+
+Important: This behavior only works if the client send more than 1 byte and is OS
+dependant, it is guaranteed to work on Linux.
+
+```console
+echo -n 1 | nc 192.168.1.4:8080  # FIN
+echo -n 12 | nc 192.168.1.4:8080 # RST
+```
+
 ### test-webserver
 
 Starts a simple HTTP fileserver which serves any file specified in the URL path, if it exists.

test/images/agnhost/VERSION

@@ -1 +1 @@
-2.43
+2.44

test/images/agnhost/agnhost.go

@@ -45,6 +45,7 @@ import (
 	"k8s.io/kubernetes/test/images/agnhost/porter"
 	resconsumerctrl "k8s.io/kubernetes/test/images/agnhost/resource-consumer-controller"
 	servehostname "k8s.io/kubernetes/test/images/agnhost/serve-hostname"
+	tcpreset "k8s.io/kubernetes/test/images/agnhost/tcp-reset"
 	testwebserver "k8s.io/kubernetes/test/images/agnhost/test-webserver"
 	"k8s.io/kubernetes/test/images/agnhost/webhook"
 )
@@ -81,6 +82,7 @@ func main() {
 	rootCmd.AddCommand(resconsumerctrl.CmdResourceConsumerController)
 	rootCmd.AddCommand(servehostname.CmdServeHostname)
 	rootCmd.AddCommand(testwebserver.CmdTestWebserver)
+	rootCmd.AddCommand(tcpreset.CmdTCPReset)
 	rootCmd.AddCommand(webhook.CmdWebhook)
 	rootCmd.AddCommand(openidmetadata.CmdTestServiceAccountIssuerDiscovery)
 	rootCmd.AddCommand(grpchealthchecking.CmdGrpcHealthChecking)

test/images/agnhost/tcp-reset/tcp_reset.go

@@ -0,0 +1,78 @@
+/*
+Copyright 2023 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// A small utility to send RST on the TCP connection
+// Ref: https://gosamples.dev/connection-reset-by-peer/
+
+package tcpreset
+
+import (
+	"fmt"
+	"log"
+	"net"
+	"os"
+	"os/signal"
+	"syscall"
+
+	"github.com/spf13/cobra"
+)
+
+// CmdTCPReset is used by agnhost Cobra.
+var CmdTCPReset = &cobra.Command{
+	Use:   "tcp-reset",
+	Short: "Serves on a tcp port and RST the connections received",
+	Long:  `Serves on a tcp port and RST the connections received.`,
+	Args:  cobra.MaximumNArgs(0),
+	Run:   main,
+}
+
+var (
+	port int
+)
+
+func init() {
+	CmdTCPReset.Flags().IntVar(&port, "port", 8080, "Port number.")
+}
+
+func main(cmd *cobra.Command, args []string) {
+
+	listener, err := net.Listen("tcp", fmt.Sprintf(":%d", port))
+	if err != nil {
+		log.Fatalf("Error from net.Listen(): %s", err)
+	}
+	go func() {
+		for {
+			conn, err := listener.Accept()
+			if err != nil {
+				log.Fatalf("Error from Accept(): %s", err)
+			}
+			// if there are still data in the buffer to read
+			// and the connection is closed, it will send a RST.
+			buf := make([]byte, 1)
+			conn.Read(buf)
+			conn.Close()
+			log.Printf("TCP request from %s", conn.RemoteAddr().String())
+		}
+	}()
+
+	log.Printf("Serving on port %d.\n", port)
+	signals := make(chan os.Signal, 1)
+	signal.Notify(signals, syscall.SIGTERM)
+	sig := <-signals
+	log.Printf("Shutting down after receiving signal: %s.\n", sig)
+	log.Printf("Awaiting pod deletion.\n")
+
+}