Re: [PATCH v5 06/10] dts: add ssh connection module

[Stanislaw Kardach <kda@semihalf.com>]

On Mon, Sep 26, 2022 at 02:17:09PM +0000, Juraj Linkeš wrote:
> The module uses the pexpect python library and implements connection to
> a node and two ways to interact with the node:
> 1. Send a string with specified prompt which will be matched after
>    the string has been sent to the node.
> 2. Send a command to be executed. No prompt is specified here.
> 
> Signed-off-by: Owen Hilyard <ohilyard@iol.unh.edu>
> Signed-off-by: Juraj Linkeš <juraj.linkes@pantheon.tech>
> ---
>  dts/framework/exception.py                    |  48 +++++
>  .../remote_session/session_factory.py         |  16 ++
>  dts/framework/remote_session/ssh_session.py   | 189 ++++++++++++++++++
>  dts/framework/utils.py                        |  13 ++
>  4 files changed, 266 insertions(+)
>  create mode 100644 dts/framework/remote_session/session_factory.py
>  create mode 100644 dts/framework/remote_session/ssh_session.py
>  create mode 100644 dts/framework/utils.py
> 
> diff --git a/dts/framework/exception.py b/dts/framework/exception.py
> index 60fd98c9ca..8466990aa5 100644
> --- a/dts/framework/exception.py
> +++ b/dts/framework/exception.py
> @@ -9,6 +9,54 @@
>  """
>  
>  
> +class TimeoutException(Exception):
> +    """
> +    Command execution timeout.
> +    """
> +
> +    command: str
> +    output: str
> +
> +    def __init__(self, command: str, output: str):
> +        self.command = command
> +        self.output = output
> +
> +    def __str__(self) -> str:
> +        return f"TIMEOUT on {self.command}"
> +
> +    def get_output(self) -> str:
> +        return self.output
> +
> +
> +class SSHConnectionException(Exception):
> +    """
> +    SSH connection error.
> +    """
> +
> +    host: str
> +
> +    def __init__(self, host: str):
> +        self.host = host
> +
> +    def __str__(self) -> str:
> +        return f"Error trying to connect with {self.host}"
> +
> +
> +class SSHSessionDeadException(Exception):
> +    """
> +    SSH session is not alive.
> +    It can no longer be used.
> +    """
> +
> +    host: str
> +
> +    def __init__(self, host: str):
> +        self.host = host
> +
> +    def __str__(self) -> str:
> +        return f"SSH session with {self.host} has died"
> +
> +
>  class ConfigParseException(Exception):
>      """
>      Configuration file parse failure exception.
> diff --git a/dts/framework/remote_session/session_factory.py b/dts/framework/remote_session/session_factory.py
> new file mode 100644
> index 0000000000..ff05df97bf
> --- /dev/null
> +++ b/dts/framework/remote_session/session_factory.py
> @@ -0,0 +1,16 @@
> +# SPDX-License-Identifier: BSD-3-Clause
> +# Copyright(c) 2022 PANTHEON.tech s.r.o.
> +# Copyright(c) 2022 University of New Hampshire
> +#
> +
> +from framework.config import NodeConfiguration
> +from framework.logger import DTSLOG
> +
> +from .remote_session import RemoteSession
> +from .ssh_session import SSHSession
> +
> +
> +def create_remote_session(
> +    node_config: NodeConfiguration, name: str, logger: DTSLOG
> +) -> RemoteSession:
> +    return SSHSession(node_config, name, logger)
> diff --git a/dts/framework/remote_session/ssh_session.py b/dts/framework/remote_session/ssh_session.py
> new file mode 100644
> index 0000000000..e0614e0f90
> --- /dev/null
> +++ b/dts/framework/remote_session/ssh_session.py
> @@ -0,0 +1,189 @@
> +# SPDX-License-Identifier: BSD-3-Clause
> +# Copyright(c) 2010-2014 Intel Corporation
> +# Copyright(c) 2022 PANTHEON.tech s.r.o.
> +# Copyright(c) 2022 University of New Hampshire
> +#
> +
> +
> +import time
> +
> +from pexpect import pxssh
> +
> +from framework.config import NodeConfiguration
> +from framework.exception import (
> +    SSHConnectionException,
> +    SSHSessionDeadException,
> +    TimeoutException,
> +)
> +from framework.logger import DTSLOG
> +from framework.utils import GREEN, RED
> +
> +from .remote_session import RemoteSession
> +
> +
> +class SSHSession(RemoteSession):
> +    """
> +    Module for creating Pexpect SSH sessions to a node.
> +    """
> +
> +    session: pxssh.pxssh
> +    magic_prompt: str
> +
> +    def __init__(
> +        self,
> +        node_config: NodeConfiguration,
> +        session_name: str,
> +        logger: DTSLOG,
> +    ):
> +        self.magic_prompt = "MAGIC PROMPT"
> +        super(SSHSession, self).__init__(node_config, session_name, logger)
> +
> +    def _connect(self) -> None:
> +        """
> +        Create connection to assigned node.
> +        """
> +        retry_attempts = 10
> +        login_timeout = 20 if self.port else 10
> +        password_regex = (
> +            r"(?i)(?:password:)|(?:passphrase for key)|(?i)(password for .+:)"
> +        )
> +        try:
> +            for retry_attempt in range(retry_attempts):
> +                self.session = pxssh.pxssh(encoding="utf-8")
> +                try:
> +                    self.session.login(
> +                        self.ip,
> +                        self.username,
> +                        self.password,
> +                        original_prompt="[$#>]",
> +                        port=self.port,
> +                        login_timeout=login_timeout,
> +                        password_regex=password_regex,
> +                    )
> +                    break
> +                except Exception as e:
> +                    print(e)
> +                    time.sleep(2)
> +                    print(f"Retrying connection: retry number {retry_attempt + 1}.")
> +            else:
> +                raise Exception(f"Connection to {self.hostname} failed")
> +
> +            self.logger.info(f"Connection to {self.hostname} succeeded")
> +            self.send_expect("stty -echo", "#")
> +            self.send_expect("stty columns 1000", "#")
> +        except Exception as e:
> +            print(RED(str(e)))
> +            if getattr(self, "port", None):
> +                suggestion = (
> +                    f"\nSuggestion: Check if the firewall on {self.hostname} is "
> +                    f"stopped.\n"
> +                )
> +                print(GREEN(suggestion))
> +
> +            raise SSHConnectionException(self.hostname)
> +
> +    def send_expect_base(self, command: str, prompt: str, timeout: float) -> str:
> +        self.clean_session()
> +        original_prompt = self.session.PROMPT
> +        self.session.PROMPT = prompt
> +        self.__sendline(command)
> +        self.__prompt(command, timeout)
> +
> +        before = self._get_output()
> +        self.session.PROMPT = original_prompt
> +        return before
> +
> +    def send_expect(
> +        self, command: str, prompt: str, timeout: float = 15, verify: bool = False
> +    ) -> str | int:
> +        try:
> +            ret = self.send_expect_base(command, prompt, timeout)
> +            if verify:
> +                ret_status = self.send_expect_base("echo $?", prompt, timeout)
> +                try:
> +                    retval = int(ret_status)
> +                    if not retval:
> +                        self.logger.error(f"Command: {command} failure!")
> +                        self.logger.error(ret)
> +                        return retval
> +                    else:
> +                        return ret
Just a minor nit. Isn't the verify logic reversed in this commit?
In V4 "if not retval" was an OK case (returning the output), now it
reports an error.
> +                except ValueError:
> +                    return ret
> +            else:
> +                return ret
> +        except Exception as e:
> +            print(
> +                f"Exception happened in [{command}] and output is "
> +                f"[{self._get_output()}]"
> +            )
> +            raise e
> +
> +    def _send_command(self, command: str, timeout: float = 1) -> str:
> +        try:
> +            self.clean_session()
> +            self.__sendline(command)
> +        except Exception as e:
> +            raise e
> +
> +        output = self.get_output(timeout=timeout)
> +        self.session.PROMPT = self.session.UNIQUE_PROMPT
> +        self.session.prompt(0.1)
> +
> +        return output
> +
> +    def clean_session(self) -> None:
> +        self.get_output(timeout=0.01)
> +
> +    def _get_output(self) -> str:
> +        if not self.is_alive():
> +            raise SSHSessionDeadException(self.hostname)
> +        before = self.session.before.rsplit("\r\n", 1)[0]
> +        if before == "[PEXPECT]":
> +            return ""
> +        return before
> +
> +    def get_output(self, timeout: float = 15) -> str:
> +        """
> +        Get all output before timeout
> +        """
> +        self.session.PROMPT = self.magic_prompt
> +        try:
> +            self.session.prompt(timeout)
> +        except Exception:
> +            pass
> +
> +        before = self._get_output()
> +        self.__flush()
> +
> +        self.logger.debug(before)
> +        return before
> +
> +    def __flush(self) -> None:
> +        """
> +        Clear all session buffer
> +        """
> +        self.session.buffer = ""
> +        self.session.before = ""
> +
> +    def __prompt(self, command: str, timeout: float) -> None:
> +        if not self.session.prompt(timeout):
> +            raise TimeoutException(command, self._get_output()) from None
> +
> +    def __sendline(self, command: str) -> None:
> +        if not self.is_alive():
> +            raise SSHSessionDeadException(self.hostname)
> +        if len(command) == 2 and command.startswith("^"):
> +            self.session.sendcontrol(command[1])
> +        else:
> +            self.session.sendline(command)
> +
> +    def _close(self, force: bool = False) -> None:
> +        if force is True:
> +            self.session.close()
> +        else:
> +            if self.is_alive():
> +                self.session.logout()
> +
> +    def is_alive(self) -> bool:
> +        return self.session.isalive()
> diff --git a/dts/framework/utils.py b/dts/framework/utils.py
> new file mode 100644
> index 0000000000..26b784ebb5
> --- /dev/null
> +++ b/dts/framework/utils.py
> @@ -0,0 +1,13 @@
> +# SPDX-License-Identifier: BSD-3-Clause
> +# Copyright(c) 2010-2014 Intel Corporation
> +# Copyright(c) 2022 PANTHEON.tech s.r.o.
> +# Copyright(c) 2022 University of New Hampshire
> +#
> +
> +
> +def RED(text: str) -> str:
> +    return f"\u001B[31;1m{str(text)}\u001B[0m"
> +
> +
> +def GREEN(text: str) -> str:
> +    return f"\u001B[32;1m{str(text)}\u001B[0m"
> -- 
> 2.30.2
> 

Reviewed-by: Stanislaw Kardach <kda@semihalf.com>

-- 
Best Regards,
Stanislaw Kardach