SSH窗口大小如何影响paramiko

问题描述

我正在构建一个应用程序，其中它通过SSH连接到Cisco设备以收集show命令的输出.我正在python中使用paramiko模块来完成此操作.

I am building an application where it SSHs to Cisco devices to collect output of show commands. I am using paramiko module in python to get this done.

在将命令输出与plink的输出进行比较时，知道paramiko的输出被截断了.尝试使用无缓冲和增加的缓冲区大小，但没有帮助.后来，尝试使用window_size参数，它似乎可以正常工作.

While comparing the command output with that of plink, got to know that the output from paramiko is truncated. Tried with unbuffering and increased buffer size and it didn't help. Later, just tried with window_size parameter and it seems to work.

下面是我的代码:

import paramiko
sshclient = None
try:
    sshclient = paramiko.SSHClient()
    sshclient.set_missing_host_key_policy(paramiko.AutoAddPolicy())
    sshclient.connect('mydevice', username='admin', password='admin12345')
    chan = sshclient.get_transport().open_session(window_size=500000)
    chan.settimeout(10800)
    chan.exec_command('show tech-support fcip')

    value = chan.recv(1024)
    while value:
        print(value)
        value = chan.recv(1024)

finally:
    if sshclient:
        sshclient.close()

按照运输，default_window_size=2097152;比默认值小1597152.

As per paramiko document for Transport, default_window_size=2097152; 1597152 lesser than the default_value.

另外，使用default_window_size=2097152的部分日志输出是:

Also the partial log output with default_window_size=2097152 is:

Authentication (password) successful!
[chan 0] Max packet in: 32768 bytes
[chan 0] Max packet out: 32768 bytes
Secsh channel 0 opened.
[chan 0] Sesch channel 0 request ok
EOF in transport thread

与window_size=500000相同的是:

Authentication (password) successful!
[chan 0] Max packet in: 32768 bytes
[chan 0] Max packet out: 32768 bytes
Secsh channel 0 opened.
[chan 0] Sesch channel 0 request ok
[chan 0] EOF received (0)
EOF in transport thread

在这里，当window_size为默认值时，甚至在服务器发出终止信号之前，通道也已关闭.

Here it looks like, when the window_size is default value, the channel is being closed even before the termination signal from the server.

专家，请告诉我SSH中window_size减少的后果，它将如何影响我的应用程序?

Experts, please advise me the consequences of reduced window_size in SSH and how will it affect my application?

推荐答案

通过修改window_size，可以影响输入返回字符之前一行的最大长度.如果您的应用程序要求您执行一些解析，并且您想要调用

By modifying the window_size, you effect the maximum length a line can be before a return character is entered. If your application requires you to perform some parsing, and you want to call something like

value.split('\n')

您可能会发现字符串分割的频率比您预期的要多/少.

You may find that the strings are being split more/less frequently than you predicted.

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