Re: [PATCH v4 4/9] dts: add ssh pexpect library

[Bruce Richardson <bruce.richardson@intel.com>]

On Fri, Jul 29, 2022 at 10:55:45AM +0000, Juraj Linkeš wrote:
> The library 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>

Comments inline below.
Thanks,
/Bruce

> ---
>  dts/framework/exception.py   |  57 ++++++++++
>  dts/framework/ssh_pexpect.py | 205 +++++++++++++++++++++++++++++++++++
>  dts/framework/utils.py       |  12 ++
>  3 files changed, 274 insertions(+)
>  create mode 100644 dts/framework/exception.py
>  create mode 100644 dts/framework/ssh_pexpect.py
>  create mode 100644 dts/framework/utils.py
> 
> diff --git a/dts/framework/exception.py b/dts/framework/exception.py
> new file mode 100644
> index 0000000000..35e81a4d99
> --- /dev/null
> +++ b/dts/framework/exception.py
> @@ -0,0 +1,57 @@
> +# 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
> +#
> +
> +"""
> +User-defined exceptions used across the framework.
> +"""
> +
> +
> +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"
> diff --git a/dts/framework/ssh_pexpect.py b/dts/framework/ssh_pexpect.py
> new file mode 100644
> index 0000000000..e8f64515c0
> --- /dev/null
> +++ b/dts/framework/ssh_pexpect.py
> @@ -0,0 +1,205 @@
> +# 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 typing import Optional
> +
> +from pexpect import pxssh
> +
> +from .exception import SSHConnectionException, SSHSessionDeadException, TimeoutException
> +from .logger import DTSLOG
> +from .utils import GREEN, RED
> +
> +"""
> +The module handles ssh sessions to TG and SUT.
> +It implements the send_expect function to send commands and get output data.
> +"""
> +
> +
> +class SSHPexpect:
> +    username: str
> +    password: str
> +    node: str
> +    logger: DTSLOG
> +    magic_prompt: str
> +
> +    def __init__(
> +        self,
> +        node: str,
> +        username: str,
> +        password: Optional[str],
> +        logger: DTSLOG,
> +    ):
> +        self.magic_prompt = "MAGIC PROMPT"
> +        self.logger = logger
> +
> +        self.node = node
> +        self.username = username
> +        self.password = password or ""
> +        self.logger.info(f"ssh {self.username}@{self.node}")
> +
> +        self._connect_host()
> +
> +    def _connect_host(self) -> None:
> +        """
> +        Create connection to assigned node.
> +        """
> +        retry_times = 10
> +        try:
> +            if ":" in self.node:

Should this check and the relevant splitting below to assign to self.ip and
self.port, not be don at init when the node is passed in? Certainly the
splitting should probably be done outside the loop, rather than re-doing
the split into ip and port 10 times?

> +                while retry_times:
> +                    self.ip = self.node.split(":")[0]
> +                    self.port = int(self.node.split(":")[1])
> +                    self.session = pxssh.pxssh(encoding="utf-8")
> +                    try:
> +                        self.session.login(
> +                            self.ip,
> +                            self.username,
> +                            self.password,
> +                            original_prompt="[$#>]",
> +                            port=self.port,
> +                            login_timeout=20,
> +                            password_regex=r"(?i)(?:password:)|(?:passphrase for key)|(?i)(password for .+:)",
> +                        )
> +                    except Exception as e:
> +                        print(e)
> +                        time.sleep(2)
> +                        retry_times -= 1
> +                        print("retry %d times connecting..." % (10 - retry_times))
> +                    else:
> +                        break
> +                else:
> +                    raise Exception("connect to %s:%s failed" % (self.ip, self.port))
> +            else:
> +                self.session = pxssh.pxssh(encoding="utf-8")
> +                self.session.login(
> +                    self.node,
> +                    self.username,
> +                    self.password,
> +                    original_prompt="[$#>]",
> +                    password_regex=r"(?i)(?:password:)|(?:passphrase for key)|(?i)(password for .+:)",
> +                )
> +                self.logger.info(f"Connection to {self.node} 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 = (
> +                    "\nSuggession: Check if the firewall on [ %s ] " % self.ip
> +                    + "is stopped\n"
> +                )

I'd suggest using f-strings here to avoid splitting error messages across
lines. They can also be used for strings above too to increase readability.

We should probably look to standardize all strings used in DTS to a single
format - either f-strings or the style given here, rather than using a mix.

> +                print(GREEN(suggestion))
> +
> +            raise SSHConnectionException(self.node)
> +
> +    def send_expect_base(self, command: str, expected: str, timeout: float) -> str:
> +        self.clean_session()
> +        self.session.PROMPT = expected
> +        self.__sendline(command)
> +        self.__prompt(command, timeout)
> +
> +        before = self.get_output_before()
> +        return before
> +
> +    def send_expect(
> +        self, command: str, expected: str, timeout: float = 15, verify: bool = False
> +    ) -> str | int:
> +
> +        try:
> +            ret = self.send_expect_base(command, expected, timeout)
> +            if verify:
> +                ret_status = self.send_expect_base("echo $?", expected, timeout)
> +                if not int(ret_status):
> +                    return ret
> +                else:
> +                    self.logger.error("Command: %s failure!" % command)
> +                    self.logger.error(ret)
> +                    return int(ret_status)
> +            else:
> +                return ret
> +        except Exception as e:
> +            print(
> +                RED(
> +                    "Exception happened in [%s] and output is [%s]"
> +                    % (command, self.get_output_before())
> +                )
> +            )
> +            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_session_before(timeout=timeout)
> +        self.session.PROMPT = self.session.UNIQUE_PROMPT
> +        self.session.prompt(0.1)
> +
> +        return output
> +
> +    def clean_session(self) -> None:
> +        self.get_session_before(timeout=0.01)
> +
> +    def get_session_before(self, timeout: float = 15) -> str:
> +        """
> +        Get all output before timeout
> +        """
> +        self.session.PROMPT = self.magic_prompt
> +        try:
> +            self.session.prompt(timeout)
> +        except Exception as e:
> +            pass
> +
> +        before = self.get_output_all()
> +        self.__flush()
> +
> +        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_all()) from None
> +
> +    def __sendline(self, command: str) -> None:
> +        if not self.isalive():
> +            raise SSHSessionDeadException(self.node)
> +        if len(command) == 2 and command.startswith("^"):
> +            self.session.sendcontrol(command[1])
> +        else:
> +            self.session.sendline(command)
> +
> +    def get_output_before(self) -> str:
> +        if not self.isalive():
> +            raise SSHSessionDeadException(self.node)
> +        before: list[str] = self.session.before.rsplit("\r\n", 1)

The cast in the middle of pyton code seems strange. Does rsplit not always
return a list value? In quick testing here even doing "".rsplit("x",1)
returns a list with the empty string.

> +        if before[0] == "[PEXPECT]":
> +            before[0] = ""
> +
> +        return before[0]

Might be slightly more readable as:
	retval = self.session.before.rsplit("\r\n", 1)[0]
	if retval == "[PEXPECT]"
		return ""
	return retval

> +
> +    def get_output_all(self) -> str:
> +        output: str = self.session.before
> +        output.replace("[PEXPECT]", "")
> +        return output
> +

This function is missing the isalive() check in the previous function
above.
Also, could you rewrite "get_output_before" to use "get_output_all" to
avoid having checks for [PEXPECT] in multiple places - and also checks for
isalive().

> +    def close(self, force: bool = False) -> None:
> +        if force is True:
> +            self.session.close()
> +        else:
> +            if self.isalive():
> +                self.session.logout()
> +
> +    def isalive(self) -> bool:
> +        return self.session.isalive()
> diff --git a/dts/framework/utils.py b/dts/framework/utils.py
> new file mode 100644
> index 0000000000..db87349827
> --- /dev/null
> +++ b/dts/framework/utils.py
> @@ -0,0 +1,12 @@
> +# 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
>