CumulusNetworks-ifupdown2/ifupdown/utils.py

#!/usr/bin/python
#
# Copyright 2014 Cumulus Networks, Inc. All rights reserved.
# Author: Roopa Prabhu, roopa@cumulusnetworks.com
#
# utils --
#    helper class
#

import os
import re
import shlex
import fcntl
import signal
import logging
import subprocess
import ifupdownflags

from functools import partial

def signal_handler_f(ps, sig, frame):
    if ps:
        ps.send_signal(sig)
    if sig == signal.SIGINT:
        raise KeyboardInterrupt

class utils():
    logger = logging.getLogger('ifupdown')
    DEVNULL = open(os.devnull, 'w')

    @classmethod
    def importName(cls, modulename, name):
        """ Import a named object """
        try:
            module = __import__(modulename, globals(), locals(), [name])
        except ImportError:
            return None
        return getattr(module, name)

    @classmethod
    def lockFile(cls, lockfile):
        try:
            fp = os.open(lockfile, os.O_CREAT | os.O_TRUNC | os.O_WRONLY)
            fcntl.flock(fp, fcntl.LOCK_EX | fcntl.LOCK_NB)
            fcntl.fcntl(fp, fcntl.F_SETFD, fcntl.FD_CLOEXEC)
        except IOError:
            return False
        return True

    @classmethod
    def parse_iface_range(cls, name):
        range_match = re.match("^([\w\.]+)\[([\d]+)-([\d]+)\]", name)
        if range_match:
            range_groups = range_match.groups()
            if range_groups[1] and range_groups[2]:
                return (range_groups[0], int(range_groups[1], 10),
                        int(range_groups[2], 10))
        return None

    @classmethod
    def expand_iface_range(cls, name):
        ifacenames = []
        iface_range = cls.parse_iface_range(name)
        if iface_range:
            for i in range(iface_range[1], iface_range[2]):
                ifacenames.append('%s-%d' %(iface_range[0], i))
        return ifacenames

    @classmethod
    def check_ifname_size_invalid(cls, name=''):
        """ IFNAMSIZ in include/linux/if.h is 16 so we check this """
        IFNAMSIZ = 16
        if len(name) > IFNAMSIZ - 1:
            return True
        else:
            return False

    @classmethod
    def enable_subprocess_signal_forwarding(cls, ps, sig):
        signal.signal(sig, partial(signal_handler_f, ps))

    @classmethod
    def disable_subprocess_signal_forwarding(cls, sig):
        signal.signal(sig, signal.SIG_DFL)

    @classmethod
    def _log_command_exec(cls, cmd, stdin):
        if stdin:
            cls.logger.info('executing %s [%s]' % (cmd, stdin))
        else:
            cls.logger.info('executing %s' % cmd)

    @classmethod
    def _format_error(cls, cmd, cmd_returncode, cmd_output, stdin):
        if type(cmd) is list:
            cmd = ' '.join(cmd)
        if stdin:
            cmd = '%s [%s]' % (cmd, stdin)
        if cmd_output:
            return 'cmd \'%s\' failed: returned %d (%s)' % \
                   (cmd, cmd_returncode, cmd_output)
        else:
            return 'cmd \'%s\' failed: returned %d' % (cmd, cmd_returncode)

    @classmethod
    def _execute_subprocess(cls, cmd,
                            env=None,
                            shell=False,
                            close_fds=False,
                            stdout=True,
                            stdin=None,
                            stderr=subprocess.STDOUT):
        """
        exec's commands using subprocess Popen
            Args:
                cmd, should be shlex.split if not shell
        returns: output

        Note: close_fds=True is affecting performance (2~3 times slower)
        """
        if ifupdownflags.flags.DRYRUN:
            return ''

        cmd_output = None
        try:
            ch = subprocess.Popen(cmd,
                                  env=env,
                                  shell=shell,
                                  close_fds=close_fds,
                                  stdin=subprocess.PIPE if stdin else None,
                                  stdout=subprocess.PIPE if stdout else cls.DEVNULL,
                                  stderr=stderr)
            utils.enable_subprocess_signal_forwarding(ch, signal.SIGINT)
            if stdout or stdin:
                cmd_output = ch.communicate(input=stdin)[0]
            cmd_returncode = ch.wait()
        except Exception as e:
            raise Exception('cmd \'%s\' failed (%s)' % (' '.join(cmd), str(e)))
        finally:
            utils.disable_subprocess_signal_forwarding(signal.SIGINT)
        if cmd_returncode != 0:
            raise Exception(cls._format_error(cmd,
                                              cmd_returncode,
                                              cmd_output,
                                              stdin))
        return cmd_output

    @classmethod
    def exec_user_command(cls, cmd, close_fds=False, stdout=True,
                          stdin=None, stderr=subprocess.STDOUT):
        cls._log_command_exec(cmd, stdin)
        return cls._execute_subprocess(cmd,
                                       shell=True,
                                       close_fds=close_fds,
                                       stdout=stdout,
                                       stdin=stdin,
                                       stderr=stderr)

    @classmethod
    def exec_command(cls, cmd, env=None, close_fds=False, stdout=True,
                     stdin=None, stderr=subprocess.STDOUT):
        cls._log_command_exec(cmd, stdin)
        return cls._execute_subprocess(shlex.split(cmd),
                                       env=env,
                                       close_fds=close_fds,
                                       stdout=stdout,
                                       stdin=stdin,
                                       stderr=stderr)

    @classmethod
    def exec_commandl(cls, cmdl, env=None, close_fds=False, stdout=True,
                      stdin=None, stderr=subprocess.STDOUT):
        cls._log_command_exec(' '.join(cmdl), stdin)
        return cls._execute_subprocess(cmdl,
                                       env=env,
                                       close_fds=close_fds,
                                       stdout=stdout,
                                       stdin=stdin,
                                       stderr=stderr)

fcntl.fcntl(utils.DEVNULL, fcntl.F_SETFD, fcntl.FD_CLOEXEC)