core-extra/daemon/core/nodes/client.py

"""
client.py: implementation of the VnodeClient class for issuing commands
over a control channel to the vnoded process running in a network namespace.
The control channel can be accessed via calls using the vcmd shell.
"""

import logging
import os
from subprocess import PIPE, Popen

from core import constants, utils
from core.errors import CoreCommandError


class VnodeClient(object):
    """
    Provides client functionality for interacting with a virtual node.
    """

    def __init__(self, name, ctrlchnlname):
        """
        Create a VnodeClient instance.

        :param str name: name for client
        :param str ctrlchnlname: control channel name
        """
        self.name = name
        self.ctrlchnlname = ctrlchnlname

    def _verify_connection(self):
        """
        Checks that the vcmd client is properly connected.

        :return: nothing
        :raises IOError: when not connected
        """
        if not self.connected():
            raise IOError("vcmd not connected")

    def connected(self):
        """
        Check if node is connected or not.

        :return: True if connected, False otherwise
        :rtype: bool
        """
        return True

    def close(self):
        """
        Close the client connection.

        :return: nothing
        """
        pass

    def _cmd_args(self):
        return [constants.VCMD_BIN, "-c", self.ctrlchnlname, "--"]

    def cmd(self, args, wait=True):
        """
        Execute a command on a node and return the status (return code).

        :param list[str]|str args: command arguments
        :param bool wait: wait for command to end or not
        :return: command status
        :rtype: int
        """
        self._verify_connection()
        args = utils.split_args(args)

        # run command, return process when not waiting
        cmd = self._cmd_args() + args
        logging.debug("cmd wait(%s): %s", wait, cmd)
        p = Popen(cmd, stdout=PIPE, stderr=PIPE)
        if not wait:
            return 0

        # wait for and return exit status
        return p.wait()

    def cmd_output(self, args):
        """
        Execute a command on a node and return a tuple containing the
        exit status and result string. stderr output
        is folded into the stdout result string.

        :param list[str]|str args: command to run
        :return: command status and combined stdout and stderr output
        :rtype: tuple[int, str]
        """
        p, stdin, stdout, stderr = self.popen(args)
        stdin.close()
        output = stdout.read() + stderr.read()
        stdout.close()
        stderr.close()
        status = p.wait()
        return status, output.decode("utf-8").strip()

    def check_cmd(self, args):
        """
        Run command and return exit status and combined stdout and stderr.

        :param list[str]|str args: command to run
        :return: combined stdout and stderr
        :rtype: str
        :raises core.CoreCommandError: when there is a non-zero exit status
        """
        status, output = self.cmd_output(args)
        if status != 0:
            raise CoreCommandError(status, args, output)
        return output.strip()

    def popen(self, args):
        """
        Execute a popen command against the node.

        :param list[str]|str args: command arguments
        :return: popen object, stdin, stdout, and stderr
        :rtype: tuple
        """
        self._verify_connection()
        args = utils.split_args(args)
        cmd = self._cmd_args() + args
        logging.debug("popen: %s", cmd)
        p = Popen(cmd, stdout=PIPE, stderr=PIPE, stdin=PIPE)
        return p, p.stdin, p.stdout, p.stderr

    def icmd(self, args):
        """
        Execute an icmd against a node.

        :param list[str]|str args: command arguments
        :return: command result
        :rtype: int
        """
        args = utils.split_args(args)
        return os.spawnlp(
            os.P_WAIT,
            constants.VCMD_BIN,
            constants.VCMD_BIN,
            "-c",
            self.ctrlchnlname,
            "--",
            *args
        )

    def term(self, sh="/bin/sh"):
        """
        Open a terminal on a node.

        :param str sh: shell to open terminal with
        :return: terminal command result
        :rtype: int
        """
        args = (
            "xterm",
            "-ut",
            "-title",
            self.name,
            "-e",
            constants.VCMD_BIN,
            "-c",
            self.ctrlchnlname,
            "--",
            sh,
        )
        if "SUDO_USER" in os.environ:
            args = (
                "su",
                "-s",
                "/bin/sh",
                "-c",
                "exec " + " ".join(map(lambda x: "'%s'" % x, args)),
                os.environ["SUDO_USER"],
            )
        return os.spawnvp(os.P_NOWAIT, args[0], args)

    def termcmdstring(self, sh="/bin/sh"):
        """
        Create a terminal command string.

        :param str sh: shell to execute command in
        :return: str
        """
        return "%s -c %s -- %s" % (constants.VCMD_BIN, self.ctrlchnlname, sh)