ansible/library/system/sysctl

#!/usr/bin/python
# -*- coding: utf-8 -*-

# (c) 2012, David "DaviXX" CHANIAL <david.chanial@gmail.com>
# (c) 2014, James Tanner <tanner.jc@gmail.com>
#
# This file is part of Ansible
#
# Ansible is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# Ansible is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with Ansible.  If not, see <http://www.gnu.org/licenses/>.
#

DOCUMENTATION = '''
---
module: sysctl
short_description: Manage entries in sysctl.conf.
description:
    - This module manipulates sysctl entries and optionally performs a C(/sbin/sysctl -p) after changing them.
version_added: "1.0"
options:
    name:
        description:
            - The dot-separated path (aka I(key)) specifying the sysctl variable.
        required: true
        default: null
        aliases: [ 'key' ]
    value:
        description:
            - Desired value of the sysctl key.
        required: false
        default: null
        aliases: [ 'val' ]
    state:
        description:
            - Whether the entry should be present or absent in the sysctl file.
        choices: [ "present", "absent" ]
        default: present
    reload:
        description:
            - If C(yes), performs a I(/sbin/sysctl -p) if the C(sysctl_file) is
              updated. If C(no), does not reload I(sysctl) even if the
              C(sysctl_file) is updated.
        choices: [ "yes", "no" ]
        default: "yes"
    sysctl_file:
        description:
            - Specifies the absolute path to C(sysctl.conf), if not C(/etc/sysctl.conf).
        required: false
        default: /etc/sysctl.conf
    sysctl_set:
        description:
            - Verify token value with the sysctl command and set with -w if necessary
        choices: [ "yes", "no" ]
        required: false
        version_added: 1.5
        default: False
notes: []
requirements: []
author: David "DaviXX" CHANIAL <david.chanial@gmail.com>
'''

EXAMPLES = '''
# Set vm.swappiness to 5 in /etc/sysctl.conf
- sysctl: name=vm.swappiness value=5 state=present

# Remove kernel.panic entry from /etc/sysctl.conf
- sysctl: name=kernel.panic state=absent sysctl_file=/etc/sysctl.conf

# Set kernel.panic to 3 in /tmp/test_sysctl.conf
- sysctl: name=kernel.panic value=3 sysctl_file=/tmp/test_sysctl.conf reload=no

# Set ip fowarding on in /proc and do not reload the sysctl file
- sysctl: name="net.ipv4.ip_forward" value=1 sysctl_set=yes

# Set ip forwarding on in /proc and in the sysctl file and reload if necessary
- sysctl: name="net.ipv4.ip_forward" value=1 sysctl_set=yes state=present reload=yes
'''

# ==============================================================

import os
import tempfile
import re

class SysctlModule(object):

    def __init__(self, module):
        self.module = module 
        self.args = self.module.params

        self.sysctl_cmd = self.module.get_bin_path('sysctl', required=True)
        self.sysctl_file = self.args['sysctl_file']

        self.proc_value = None  # current token value in proc fs
        self.file_value = None  # current token value in file
        self.file_lines = []    # all lines in the file
        self.file_values = {}   # dict of token values

        self.changed = False    # will change occur
        self.set_proc = False   # does sysctl need to set value
        self.write_file = False # does the sysctl file need to be reloaded

        self.process()

    # ==============================================================
    #   LOGIC
    # ==============================================================

    def process(self):

        # Whitespace is bad
        self.args['name'] = self.args['name'].strip()
        if self.args['value'] is not None:
            self.args['value'] = self.args['value'].strip()
        else:
            self.args['value'] = ""

        thisname = self.args['name']

        # get the current proc fs value
        self.proc_value = self.get_token_curr_value(thisname)

        # get the currect sysctl file value
        self.read_sysctl_file()
        if thisname not in self.file_values:
            self.file_values[thisname] = None

        # update file contents with desired token/value
        self.fix_lines()

        # what do we need to do now?
        if self.file_values[thisname] is None and self.args['state'] == "present":
            self.changed = True
            self.write_file = True
        elif self.file_values[thisname] != self.args['value']:
            self.changed = True
            self.write_file = True
        if self.args['sysctl_set']:            
            if self.proc_value is None:
                self.changed = True
            elif self._compare_values(self.proc_value, self.args['value']):
                self.changed = True 
                self.set_proc = True

        # Do the work
        if not self.module.check_mode:
            if self.write_file:
                self.write_sysctl()
            if self.write_file and self.args['reload']:
                self.reload_sysctl()
            if self.set_proc:
                self.set_token_value(self.args['name'], self.args['value'])

    def _compare_values(self, a, b):
        """Expects two string values. It will split the string by whitespace
        and compare each value. It will return True if both lists are the same,
        contain the same elements and the same order."""
        if a is None or b is None:
            return False

        a = a.split()
        b = b.split()

        if len(a) != len(b):
            return False

        return len([i for i, j in zip(a, b) if i == j]) != len(a)

    # ==============================================================
    #   SYSCTL COMMAND MANAGEMENT
    # ==============================================================

    # Use the sysctl command to find the current value 
    def get_token_curr_value(self, token):
        thiscmd = "%s -e -n %s" % (self.sysctl_cmd, token)
        rc,out,err = self.module.run_command(thiscmd)    
        if rc != 0:
            return None
        else:
            return out

    # Use the sysctl command to set the current value
    def set_token_value(self, token, value):
        if len(value.split()) > 0:
            value = '"' + value + '"'
        thiscmd = "%s -w %s=%s" % (self.sysctl_cmd, token, value)
        rc,out,err = self.module.run_command(thiscmd)
        if rc != 0:
            self.module.fail_json(msg='setting %s failed: %s' (token, out + err))
        else:
            return rc

    # Run sysctl -p
    def reload_sysctl(self):
        # do it
        if get_platform().lower() == 'freebsd':
            # freebsd doesn't support -p, so reload the sysctl service
            rc,out,err = self.module.run_command('/etc/rc.d/sysctl reload')
        else:
            # system supports reloading via the -p flag to sysctl, so we'll use that 
            rc,out,err = self.module.run_command([self.sysctl_cmd, '-p', self.sysctl_file])

        if rc != 0:            
            self.module.fail_json(msg="Failed to reload sysctl: %s" % str(out) + str(err))

    # ==============================================================
    #   SYSCTL FILE MANAGEMENT
    # ==============================================================

    # Get the token value from the sysctl file
    def read_sysctl_file(self):
        lines = open(self.sysctl_file, "r").readlines()
        for line in lines:
            line = line.strip()
            self.file_lines.append(line)

            # don't split empty lines or comments
            if not line or line.startswith("#"):
                continue 

            k, v = line.split('=',1)
            k = k.strip()
            v = v.strip()
            self.file_values[k] = v.strip()

    # Fix the value in the sysctl file content
    def fix_lines(self):
        checked = []
        self.fixed_lines = []
        for line in self.file_lines:
            if not line.strip() or line.strip().startswith("#"):
                self.fixed_lines.append(line)
                continue
            tmpline = line.strip()            
            k, v = line.split('=',1)
            k = k.strip()
            v = v.strip()
            if k not in checked:
                checked.append(k)
                if k == self.args['name']:
                    if self.args['state'] == "present":
                        new_line = "%s = %s\n" % (k, self.args['value'])
                        self.fixed_lines.append(new_line)                    
                else:
                    new_line = "%s = %s\n" % (k, v)
                    self.fixed_lines.append(new_line)                    

        if self.args['name'] not in checked and self.args['state'] == "present":
            new_line = "%s = %s\n" % (self.args['name'], self.args['value'])
            self.fixed_lines.append(new_line)                    

    # Completely rewrite the sysctl file
    def write_sysctl(self):
        # open a tmp file
        fd, tmp_path = tempfile.mkstemp('.conf', '.ansible_m_sysctl_', os.path.dirname(self.sysctl_file))
        f = open(tmp_path,"w")
        try:
            for l in self.fixed_lines:
                f.write(l.strip() + "\n")
        except IOError, e:
            self.module.fail_json(msg="Failed to write to file %s: %s" % (tmp_path, str(e)))
        f.flush()
        f.close()

        # replace the real one
        self.module.atomic_move(tmp_path, self.sysctl_file) 


# ==============================================================
# main

def main():

    # defining module
    module = AnsibleModule(
        argument_spec = dict(
            name = dict(aliases=['key'], required=True),
            value = dict(aliases=['val'], required=False),
            state = dict(default='present', choices=['present', 'absent']),
            reload = dict(default=True, type='bool'),
            sysctl_set = dict(default=False, type='bool'),
            sysctl_file = dict(default='/etc/sysctl.conf')
        ),
        supports_check_mode=True
    )

    result = SysctlModule(module)    

    module.exit_json(changed=result.changed)
    sys.exit(0)

# import module snippets
from ansible.module_utils.basic import *
main()