Timeout for Device.open()

I have been going through the code and scratching my head as to how to get Device to timeout in a reasonable amount of time when I first call open(). The specific scenario is to have netconf enabled on the device via ssh but the protect RE firewall filter does not allow netconf access. On such a device it takes upwards or 2 minutes to timeout the connection on open() which gets extremely annoying when I am trying to connect to many devices.

I would like to have the ability to pass a timeout value to open() to quickly throw an error on a connection that will never open in the first place.

[attila123]

TL;DR: it should be possible to set ssh connect timeout via the “connecttimeout” parameter in ~/.ssh/config (or some other ssh config file with custom path). I did some debugging and looks like:

• PyEZ uses the ncclient library for ssh connections. In ncclient SSHSession.connect() can make use of the “connecttimeout” parameter from an ssh config file, see https://github.com/ncclient/ncclient/blob/v0.6.6/ncclient/transport/ssh.py#L382 (for the current ncclient 0.6.6)
• According to PyEZ documentation https://junos-pyez.readthedocs.io/en/2.2.1/jnpr.junos.html#module-jnpr.junos.device the Device constructor takes an optional parameter: “ssh_config (str) – OPTIONAL The path to the SSH configuration file. This can be used to load SSH information from a configuration file. By default ~/.ssh/config is queried.” I tested it by creating ~/.ssh/config with the following content:

connecttimeout=42

and re-run my debugging. The value 42 was read and applied in https://github.com/ncclient/ncclient/blob/v0.6.6/ncclient/transport/ssh.py#L403 BTW the ssh_config man page (see on your computer or e.g. at https://linux.die.net/man/5/ssh_config) says that the keywords are case-insensitive and indeed it is parsed like that (ncclient uses the config parsing of paramiko (ssh client library) which converts the keywords to lowercase).

Update: to test this I created a “black hole” IP address such that all packets sent to it from my computer will be dropped:

sudo iptables -A OUTPUT -d 10.22.215.174 -j DROP

I verified that the command line ssh client now times out in 42s using this IP:

$  time ssh 10.22.215.174
ssh: connect to host 10.22.215.174 port 22: Connection timed out
ssh 10.22.215.174  0,01s user 0,00s system 0% cpu 42,056 total

So far so good. I also verified that socket connect at https://github.com/ncclient/ncclient/blob/v0.6.6/ncclient/transport/ssh.py#L409 timed out in 42s and there was some timeout exception raised. When not using the “connecttimeout” in ~/.ssh/config then I got the jnpr.junos.exception.ConnectTimeoutError in about 96-99 sec (but in your system it might be different).

Update2: at one occasion I saw the timeout happening in about 11 sec (if I am not mistaken). (then again 42 without any code change) Could be a python (3.7.4) or Linux kernel (5.1.21) issue??? But usually it works correctly, so maybe it was an exceptional case.

[njayarama]

what is current timeout value of the open()? is there any plan to fix this issue, am hitting this one on my network. I need to increase the timeout value.