k8s.io/kubernetes@v1.29.3/test/images/agnhost/port-forward-tester/portforwardtester.go (about) 1 /* 2 Copyright 2015 The Kubernetes Authors. 3 4 Licensed under the Apache License, Version 2.0 (the "License"); 5 you may not use this file except in compliance with the License. 6 You may obtain a copy of the License at 7 8 http://www.apache.org/licenses/LICENSE-2.0 9 10 Unless required by applicable law or agreed to in writing, software 11 distributed under the License is distributed on an "AS IS" BASIS, 12 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 See the License for the specific language governing permissions and 14 limitations under the License. 15 */ 16 17 // A tiny binary for testing port forwarding. The following environment variables 18 // control the binary's logic: 19 // 20 // BIND_PORT - the TCP port to use for the listener 21 // EXPECTED_CLIENT_DATA - data that we expect to receive from the client; may be "". 22 // CHUNKS - how many chunks of data we should send to the client 23 // CHUNK_SIZE - how large each chunk should be 24 // CHUNK_INTERVAL - the delay in between sending each chunk 25 // 26 // Log messages are written to stdout at various stages of the binary's execution. 27 // Test code can retrieve this container's log and validate that the expected 28 // behavior is taking place. 29 30 package portforwardtester 31 32 import ( 33 "fmt" 34 "net" 35 "os" 36 "strconv" 37 "strings" 38 "time" 39 40 "github.com/spf13/cobra" 41 ) 42 43 func getEnvInt(name string) int { 44 s := os.Getenv(name) 45 value, err := strconv.Atoi(s) 46 if err != nil { 47 fmt.Printf("Error parsing %s %q: %v\n", name, s, err) 48 os.Exit(1) 49 } 50 return value 51 } 52 53 // taken from net/http/server.go: 54 // 55 // rstAvoidanceDelay is the amount of time we sleep after closing the 56 // write side of a TCP connection before closing the entire socket. 57 // By sleeping, we increase the chances that the client sees our FIN 58 // and processes its final data before they process the subsequent RST 59 // from closing a connection with known unread data. 60 // This RST seems to occur mostly on BSD systems. (And Windows?) 61 // This timeout is somewhat arbitrary (~latency around the planet). 62 const rstAvoidanceDelay = 500 * time.Millisecond 63 64 // CmdPortForwardTester is used by agnhost Cobra. 65 var CmdPortForwardTester = &cobra.Command{ 66 Use: "port-forward-tester", 67 Short: "Creates a TCP server that sends chunks of data", 68 Long: `Listens for TCP connections on a given address and port, optionally checks the data received, 69 and sends a configurable number of data chunks, with a configurable interval between chunks. 70 71 The subcommand is using the following environment variables: 72 73 - BIND_ADDRESS (optional): The address on which it will start listening for TCP connections (default value: localhost) 74 - BIND_PORT: The port on which it will start listening for TCP connections. 75 - EXPECTED_CLIENT_DATA (optional): If set, it will check that the request sends the same exact data. 76 - CHUNKS: How many chunks of data to write in the response. 77 - CHUNK_SIZE: The expected size of each written chunk of data. If it does not match the actual size of the written data, it will exit with the exit code 4. 78 - CHUNK_INTERVAL: The amount of time to wait in between chunks.`, 79 Args: cobra.MaximumNArgs(0), 80 Run: main, 81 } 82 83 func main(cmd *cobra.Command, args []string) { 84 bindAddress := os.Getenv("BIND_ADDRESS") 85 if bindAddress == "" { 86 bindAddress = "localhost" 87 } 88 bindPort := os.Getenv("BIND_PORT") 89 addr, err := net.ResolveTCPAddr("tcp", net.JoinHostPort(bindAddress, bindPort)) 90 if err != nil { 91 fmt.Printf("Error resolving: %v\n", err) 92 os.Exit(1) 93 } 94 listener, err := net.ListenTCP("tcp", addr) 95 if err != nil { 96 fmt.Printf("Error listening: %v\n", err) 97 os.Exit(1) 98 } 99 100 conn, err := listener.AcceptTCP() 101 if err != nil { 102 fmt.Printf("Error accepting connection: %v\n", err) 103 os.Exit(1) 104 } 105 106 fmt.Println("Accepted client connection") 107 108 expectedClientData := os.Getenv("EXPECTED_CLIENT_DATA") 109 if len(expectedClientData) > 0 { 110 buf := make([]byte, len(expectedClientData)) 111 read, err := conn.Read(buf) 112 if read != len(expectedClientData) { 113 fmt.Printf("Expected to read %d bytes from client, but got %d instead. err=%v\n", len(expectedClientData), read, err) 114 os.Exit(2) 115 } 116 if expectedClientData != string(buf) { 117 fmt.Printf("Expect to read %q, but got %q. err=%v\n", expectedClientData, string(buf), err) 118 os.Exit(3) 119 } 120 if err != nil { 121 fmt.Printf("Read err: %v\n", err) 122 } 123 fmt.Println("Received expected client data") 124 } 125 126 chunks := getEnvInt("CHUNKS") 127 chunkSize := getEnvInt("CHUNK_SIZE") 128 chunkInterval := getEnvInt("CHUNK_INTERVAL") 129 130 stringData := strings.Repeat("x", chunkSize) 131 data := []byte(stringData) 132 133 for i := 0; i < chunks; i++ { 134 written, err := conn.Write(data) 135 if written != chunkSize { 136 fmt.Printf("Expected to write %d bytes from client, but wrote %d instead. err=%v\n", chunkSize, written, err) 137 os.Exit(4) 138 } 139 if err != nil { 140 fmt.Printf("Write err: %v\n", err) 141 } 142 if i+1 < chunks { 143 time.Sleep(time.Duration(chunkInterval) * time.Millisecond) 144 } 145 } 146 147 fmt.Println("Shutting down connection") 148 149 // set linger timeout to flush buffers. This is the official way according to the go api docs. But 150 // there are controversial discussions whether this value has any impact on most platforms 151 // (compare https://codereview.appspot.com/95320043). 152 conn.SetLinger(-1) 153 154 // Flush the connection cleanly, following https://blog.netherlabs.nl/articles/2009/01/18/the-ultimate-so_linger-page-or-why-is-my-tcp-not-reliable: 155 // 1. close write half of connection which sends a FIN packet 156 // 2. give client some time to receive the FIN 157 // 3. close the complete connection 158 conn.CloseWrite() 159 time.Sleep(rstAvoidanceDelay) 160 conn.Close() 161 162 fmt.Println("Done") 163 }