Error reading SSH protocol banner

I’m hoping someone here can guide me in the right direction to solve a looping error.

I have some python:

for name in instanceNames:
    print(f'\nChecking {name} ...')
    c = Connection(name)
        try:
            print('Exec hostname')
            r = c.run('hostname', warn=True)
            print(f'{r}')
        except:
            print('SSH session error')

Runs along fine until it hits a particular system and then:

Exception: Error reading SSH protocol banner
Traceback (most recent call last):
  File "/root/.local/lib/python3.7/site-packages/paramiko/transport.py", line 2211, in _check_banner
    buf = self.packetizer.readline(timeout)
  File "/root/.local/lib/python3.7/site-packages/paramiko/packet.py", line 380, in readline
    buf += self._read_timeout(timeout)
  File "/root/.local/lib/python3.7/site-packages/paramiko/packet.py", line 622, in _read_timeout
    raise socket.timeout()
_socket.timeout

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/root/.local/lib/python3.7/site-packages/paramiko/transport.py", line 2039, in run
    self._check_banner()
  File "/root/.local/lib/python3.7/site-packages/paramiko/transport.py", line 2216, in _check_banner
    "Error reading SSH protocol banner" + str(e)
paramiko.ssh_exception.SSHException: Error reading SSH protocol banner

Exception: Error reading SSH protocol banner
Traceback (most recent call last):
  File "/root/.local/lib/python3.7/site-packages/paramiko/transport.py", line 2211, in _check_banner
    buf = self.packetizer.readline(timeout)
  File "/root/.local/lib/python3.7/site-packages/paramiko/packet.py", line 380, in readline
    buf += self._read_timeout(timeout)
  File "/root/.local/lib/python3.7/site-packages/paramiko/packet.py", line 622, in _read_timeout
    raise socket.timeout()
_socket.timeout

During handling of the above exception, another exception occurred:
...

This goes on until I CTRL-C, after which all other host items throw an exception.

I don’t really care at the moment about the banner exception on that particular host (I will deal with that later) but for now I’d like to avoid the retries and subsequent failures. Any tips?

[davidjmemmett]

Hi @Gary-Armstrong,

It looks like it might be worth passing banner_timeout to Connection.connect_kwargs and seeing if that helps.

A quick example (untested):

c = Connection(
    host="hostname",
    user="username",
    connect_kwargs={
        "banner_timeout": 60,
    },
)

A couple of people appear to have had a similar issue to yours before, and adding a reasonable banner_timeout appears to have helped. Let me know how you get on!

Cheers, David

[npfoss]

In case this helps anyone like me who wasn’t creating a Connection manually, it was just through the magic of fabric:

you can create a fabric.yml with a bunch of config settings including banner_timeout, and put it in the dir you’re calling fab from, e.g.

connect_kwargs:
    banner_timeout: 60

and you can confirm that the settings are being used by adding this in your imports to turn on paramiko debug logging:

import logging
logging.basicConfig(level=logging.DEBUG)