go - SSH 脚本使用 pty 和 io.Copy 通过菜单流式输出

Question

我有两个问题需要帮助。我想我已经把它缩小到在 goroutine 中使用 io.Copy 。它的行为就像标准输入需要使用回车键“重新激活”。

在循环的第一次迭代中，一切都按预期工作。它登录到 localhost，运行命令，goroutine 打印 stdout 和 stderr。但在随后的迭代中，我必须先按回车键“退出 goroutine”，然后才能在提示符下输入响应。我怀疑它与 os.Stdin 有关。有人可以提供一些建议吗？

我可以在不中断脚本的情况下向 ssh 命令发送 sigterm 吗？例如，我可以中断 ping 输出，然后在菜单提示符处返回吗？

感谢您提供的任何帮助。这是我在这里的第一篇文章。

package main

import (
    "fmt"
    "io"
    "log"
    "net"
    "os"
    "time"

    "golang.org/x/crypto/ssh"
)

var (
    stdout, stderr io.Reader
    stdin          io.WriteCloser
    timeout        = 30 * time.Second
)

func sshConfig() *ssh.ClientConfig {
    config := &ssh.ClientConfig{
        User: MYUSER,
        Auth: []ssh.AuthMethod{
            ssh.Password(MYPASS),
        },
        HostKeyCallback: ssh.HostKeyCallback(func(hostname string, remote net.Addr, key ssh.PublicKey) error { return nil }),
        Timeout:         timeout,
    }
    return config
}

func options() {
  menuString := `
  Enter 1 for "uptime"
  Enter 2 for "ping -c 20 www.google.com"
  Type exit to exit
  `
    for i := 0; i <= 5; i++ {
        var num, cmd string
        fmt.Println(menuString)
        if i == 0 {
            fmt.Print("Select an option from above: ")
        } else {
            fmt.Println("You'll have to press enter before entering your option. Why?")
            fmt.Print("Select an option from above: ")
        }

        fmt.Scanln(&num)
        switch num {
        case "1":
            cmd = "uptime"
            connect(cmd)
        case "2":
            cmd = "ping -c 20 www.google.com"
            connect(cmd)
        case "exit":
            fmt.Println("exiting")
            os.Exit(0)
        default:
            fmt.Println("Invalid response")
            fmt.Println("Select an option from above: ")
        }
    }
}

func connect(c string) {
    config := sshConfig()
    conn, err := ssh.Dial("tcp", "127.0.0.1:22", config)
    defer conn.Close()
    if err != nil {
        log.Fatal("dial target error:", err)
    }
    session, err := conn.NewSession()
    defer session.Close()
    if err != nil {
        log.Fatalf("session failed:%v", err)
    }
    defer session.Close()
    modes := ssh.TerminalModes{
        ssh.ECHO:          0,     // disable echoing
        ssh.TTY_OP_ISPEED: 14400, // input speed = 14.4kbaud
        ssh.TTY_OP_OSPEED: 14400, // output speed = 14.4kbaud
    }
    err = session.RequestPty("xterm", 80, 40, modes)
    if err != nil {
        log.Fatalf("Pty request failed:%v", err)
    }

    stdin, err = session.StdinPipe()
    if err != nil {
        log.Fatalf("Unable to setup stdin for session: %v", err)
    }
    stdout, err = session.StdoutPipe()
    if err != nil {
        log.Fatalf("Unable to setup stdout for session: %v", err)
    }
    stderr, err = session.StderrPipe()
    if err != nil {
        log.Fatalf("Unable to setup stderr for session: %v", err)
    }

    quit := make(chan bool)
    go func() {
        for {
            select {
            case <-quit:
                fmt.Println("exiting goroutine")
                return
            default:
                fmt.Println("go routine is running")
                io.Copy(os.Stdout, stdout)
                io.Copy(stdin, os.Stdin)
                io.Copy(os.Stderr, stderr)
            }
        }
    }()

    if err := session.Run(c); err != nil {
        log.Fatal("Failed to run: " + err.Error())
    }
    fmt.Println("closing the channel")
    close(quit)
    fmt.Println("the channel is closed")
}

func main() {
    options()
}

Answer 1

首先，io.Copy 是一个阻塞调用，它将 io.writer 的缓冲区复制到 io.reader 直到在 src 上达到 EOF 或发生错误。 Here's来自 golang 的 io 模块的片段:

// copyBuffer is the actual implementation of Copy and CopyBuffer.
// if buf is nil, one is allocated.

func copyBuffer(dst Writer, src Reader, buf []byte) (written int64, err error) {
    // If the reader has a WriteTo method, use it to do the copy.
    // Avoids an allocation and a copy.
    if wt, ok := src.(WriterTo); ok {
        return wt.WriteTo(dst)
    }
    // Similarly, if the writer has a ReadFrom method, use it to do the copy.
    if rt, ok := dst.(ReaderFrom); ok {
        return rt.ReadFrom(src)
    }
    if buf == nil {
        size := 32 * 1024
        if l, ok := src.(*LimitedReader); ok && int64(size) > l.N {
            if l.N < 1 {
                size = 1
            } else {
                size = int(l.N)
            }
        }
        buf = make([]byte, size)
    }
    for {
        nr, er := src.Read(buf)
        if nr > 0 {
            nw, ew := dst.Write(buf[0:nr])
            if nw > 0 {
                written += int64(nw)
            }
            if ew != nil {
                err = ew
                break
            }
            if nr != nw {
                err = ErrShortWrite
                break
            }
        }
        if er != nil {
            if er != EOF {
                err = er
            }
            break
        }
    }
    return written, err
}

现在回答你的问题
当在第一次迭代中对 session 的 stdin 和 stderr 进行 io.copy 调用时，它会等到 stderr 和 stdin 上有一条消息被复制并被阻止。
只需将您的 goroutine 替换为复制 stdout 即可为您提供每次迭代的预期行为。类似地，stderr,stdin 需要由它们自己的 goroutine 管理:

go func() {
        for {
            io.Copy(os.Stdout, stdout)
        }
    }()

SigTerm 将用于终止 session ，有一个称为中断的 posix 信号可用于中断 cmd。 Here's一个列表 os all POSIX 表明您使用的 ssh 库支持。
这是中断信号和预期行为的演示:

package main

import (
    "fmt"
    "io"
    "log"
    "net"
    "os"
    "time"

    "golang.org/x/crypto/ssh"
)

var (
    stdout, stderr io.Reader
    stdin          io.WriteCloser
    timeout        = 30 * time.Second
)

const (
    MYUSER = ""
    MYPASS = ""
)

func sshConfig() *ssh.ClientConfig {
    config := &ssh.ClientConfig{
        User: MYUSER,
        Auth: []ssh.AuthMethod{
            ssh.Password(MYPASS),
        },
        HostKeyCallback: ssh.HostKeyCallback(func(hostname string, remote net.Addr, key ssh.PublicKey) error { return nil }),
        Timeout:         timeout,
    }
    return config
}

func options() {
    menuString := `
  Enter 1 for "uptime"
  Enter 2 for "ping -c 20 www.google.com"
  Type exit to exit
  `
    for i := 0; i <= 5; i++ {
        var num, cmd string
        fmt.Println(menuString)
        if i == 0 {
            fmt.Print("Select an option from above: ")
        } else {
            fmt.Println("You'll have to press enter before entering your option. Why?")
            fmt.Print("Select an option from above: ")
        }

        fmt.Scanln(&num)
        switch num {
        case "1":
            cmd = "uptime"
            connect(cmd)
        case "2":
            cmd = "ping -c 20 www.google.com"
            connect(cmd)
        case "exit":
            fmt.Println("exiting")
            os.Exit(0)
        default:
            fmt.Println("Invalid response")
            fmt.Println("Select an option from above: ")
        }
    }
}

func connect(c string) {
    config := sshConfig()
    conn, err := ssh.Dial("tcp", "127.0.0.1:22", config)
    defer conn.Close()
    if err != nil {
        log.Fatal("dial target error:", err)
    }
    session, err := conn.NewSession()
    defer session.Close()
    if err != nil {
        log.Println("session failed:%v", err)
    }
    defer session.Close()
    modes := ssh.TerminalModes{
        ssh.ECHO:          0,     // disable echoing
        ssh.TTY_OP_ISPEED: 14400, // input speed = 14.4kbaud
        ssh.TTY_OP_OSPEED: 14400, // output speed = 14.4kbaud
    }
    err = session.RequestPty("xterm", 80, 40, modes)
    if err != nil {
        log.Fatalf("Pty request failed:%v", err)
    }

    stdin, err = session.StdinPipe()
    if err != nil {
        log.Fatalf("Unable to setup stdin for session: %v", err)
    }
    stdout, err = session.StdoutPipe()
    if err != nil {
        log.Fatalf("Unable to setup stdout for session: %v", err)
    }
    stderr, err = session.StderrPipe()
    if err != nil {
        log.Fatalf("Unable to setup stderr for session: %v", err)
    }

    go func() {
        for {
            io.Copy(os.Stdout, stdout)
        }
    }()

    c = "echo 'go is awesome' && sleep 10 && " + c
    go func() {
        time.Sleep(1 * time.Second)
        session.Signal(ssh.SIGINT)
    }()

    if err := session.Run(c); err != nil {
        log.Println("Failed to run: " + err.Error())
    }
    fmt.Println("closing the channel")
    fmt.Println("the channel is closed")
}

func main() {
    options()
}