ansible/library/sysctl

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

# (c) 2012, David "DaviXX" CHANIAL <david.chanial@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: Permit to handle sysctl.conf entries
description:
    - This module manipulates sysctl entries and performs a I(/sbin/sysctl -p) after changing them.
version_added: "0.6"
options:
    name:
        description:
            - "this is the short path, decimal seperated, to the sysctl entry, ex: C(vm.swappiness)"
        required: true
        default: null
        aliases: [ 'key' ]
    value:
        description:
            - set the sysctl value to this entry
        required: false
        default: null
        aliases: [ 'val' ]
    state:
        description:
            - whether the entry should be present or absent
        choices: [ "present", "absent" ]
        default: present
    checks:
        description:
            - if C(checks)=I(none) no smart/facultative checks will be made
            - if C(checks)=I(before) some checks performed before any update (ie. does the sysctl key is writable ?)
            - if C(checks)=I(after) some checks performed after an update (ie. does kernel give back the setted value ?)
            - if C(checks)=I(both) all the smart checks I(before and after) are performed
        choices: [ "none", "before", "after", "both" ]
        default: both
    reload:
        description:
            - if C(reload=yes), performs a I(/sbin/sysctl -p) if the C(sysctl_file) is updated
            - if C(reload=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 /etc/sysctl.conf
        required: false
        default: /etc/sysctl.conf
examples:
    - code: "sysctl: name=vm.swappiness value=5 state=present"
      description: "Set vm.swappiness to 5 in /etc/sysctl.conf"
    - code: "sysctl: name=kernel.panic state=absent sysctl_file=/etc/sysctl.conf"
      description: "Remove kernel.panic entry from /etc/sysctl.conf"
    - code: "sysctl: name=kernel.panic value=3 sysctl_file=/tmp/test_sysctl.conf check=before reload=no"
      description: Set kernel.panic to 3 in /tmp/test_sysctl.conf, check if the sysctl key seems writable, but do not reload sysctl, and do not check kernel value after (not needed, because not the real /etc/sysctl.conf updated)
notes: []
requirements: []
author: David "DaviXX" CHANIAL <david.chanial@gmail.com>
'''

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

import os
import tempfile

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

def reload_sysctl(**sysctl_args):
    # update needed ?
    if not sysctl_args['reload']:
        return 0, ''

    # do it
    cmd = [ '/sbin/sysctl', '-p' ]
    call = subprocess.Popen(cmd, shell=False, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
    out, err = call.communicate()
    if call.returncode == 0:
        return 0, ''
    else:
        return call.returncode, out+err

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

def write_sysctl(module, lines, **sysctl_args):
    # open a tmp file
    fd, tmp_path = tempfile.mkstemp('.conf', '.ansible_m_sysctl_', os.path.dirname(sysctl_args['sysctl_file']))
    f = open(tmp_path,"w")
    try:
        for l in lines:
            f.write(l)
    except IOError, e:
        module.fail_json(msg="Failed to write to file %s: %s" % (tmp_path, str(e)))
    f.flush()
    f.close()
    
    # replace the real one
    module.atomic_replace(tmp_path, sysctl_args['sysctl_file']) 
    
    # end
    return sysctl_args

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

def sysctl_args_expand(**sysctl_args):
    # key_path
    sysctl_args['key_path'] = sysctl_args['name'].replace('.' ,'/')
    sysctl_args['key_path'] = '/proc/sys/' + sysctl_args['key_path'];
    
    # end
    return sysctl_args

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

def sysctl_args_collapse(**sysctl_args):
    # go ahead
    if sysctl_args.get('key_path') is not None:
        del sysctl_args['key_path']
    if sysctl_args['state'] == 'absent' and 'value' in sysctl_args:
        del sysctl_args['value']
    
    # end
    return sysctl_args

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

def sysctl_check(current_step, **sysctl_args):
    # checking coherence
    if sysctl_args['state'] == 'absent' and sysctl_args['value'] is not None:
        return 1, 'value=x must not be supplied when state=absent'
    
    if sysctl_args['state'] == 'present' and sysctl_args['value'] is None:
        return 1, 'value=x must be supplied when state=present'
    
    if not sysctl_args['reload'] and sysctl_args['checks'] in ['after', 'both']:
        return 1, 'checks cannot be set to after or both if reload=no'

    # getting file stat
    if not os.access(sysctl_args['key_path'], os.F_OK):
        return 1, 'key_path is not an existing file, key seems invalid'
    if not os.access(sysctl_args['key_path'], os.R_OK):
        return 1, 'key_path is not a readable file, key seems to be uncheckable'
    
    # sysctl file exists and openable ?
    # TODO choose if prefered to use os.access() instead try/catch on open
    if current_step == 'before':
        try:
            with open(sysctl_args['sysctl_file']) as f: pass
        except IOError as e:
            return 1, 'unable to open supplied sysctl.conf'
   
    # no smart checks at this step ?
    if sysctl_args['checks'] == 'none':
        return 0, ''
    if current_step == 'before' and sysctl_args['checks'] not in ['before', 'both']:
        return 0, ''
    if current_step == 'after' and sysctl_args['checks'] not in ['after', 'both']:
        return 0, ''

    # checks before
    if current_step == 'before' and sysctl_args['checks'] in ['before', 'both']:
        
        if not os.access(sysctl_args['key_path'], os.W_OK):
            return 1, 'key_path is not a writable file, key seems to be read only'
        return 0, ''

    # checks after
    if current_step == 'after' and sysctl_args['checks'] in ['after', 'both']:

        if sysctl_args['value'] is not None:
            with open(sysctl_args['key_path'],'r') as f:
                output = f.read()
                output = output.strip(' \t\n\r')
                if output != sysctl_args['value']:
                    return 1, 'key seems not set to value even after update/sysctl, founded : <%s>, wanted : <%s>' % (output, sysctl_args['value'])
        
        return 0, ''
    
    # weird end
    return 1, 'unexpected position reached'

# ==============================================================
# 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']),
            checks = dict(default='both', choices=['none', 'before', 'after', 'both']),
            reload = dict(default=True, choices=BOOLEANS),
            sysctl_file = dict(default='/etc/sysctl.conf')
        )
    )

    # defaults
    sysctl_args = {
        'changed': False,
        'name': module.params['name'],
        'state': module.params['state'],
        'checks': module.params['checks'],
        'reload': module.boolean(module.params.get('reload', True)),
        'value': module.params.get('value'),
        'sysctl_file': module.params['sysctl_file']
    }
    
    # prepare vars
    sysctl_args = sysctl_args_expand(**sysctl_args)
    new_line = "%s = %s\n" % (sysctl_args['name'], sysctl_args['value'])
    to_write = []
    founded = False
   
    # make checks before act
    res,msg = sysctl_check('before', **sysctl_args)
    if res != 0:
        module.fail_json(msg='checks_before failed with: ' + msg)

    # reading the file
    for line in open(sysctl_args['sysctl_file'], 'r').readlines():
        if not line.strip():
            to_write.append(line)
            continue
        if line.strip().startswith('#'):
            to_write.append(line)
            continue
        if len(line.split('=')) != 2:
            # not sure what this is or why it is here
            # but it is not our fault so leave it be
            to_write.append(line)
            continue

        # write line if not the one searched
        ld = {}
        ld['name'], ld['val'] = line.split('=')
        ld['name'] = ld['name'].strip()

        if ld['name'] != sysctl_args['name']:
            to_write.append(line)
            continue

        # should be absent ?
        if sysctl_args['state'] == 'absent':
            # not writing the founded line
            # mark as changed
            sysctl_args['changed'] = True
                
        # should be present
        if sysctl_args['state'] == 'present':
            # is the founded line equal to the wanted one ?
            ld['val'] = ld['val'].strip()
            if ld['val'] == sysctl_args['value']:
                # line is equal, writing it without update (but cancel repeats)
                if sysctl_args['changed'] == False and founded == False:
                    to_write.append(line)
                    founded = True
            else:
                # update the line (but cancel repeats)
                if sysctl_args['changed'] == False and founded == False:
                    to_write.append(new_line)
                    sysctl_args['changed'] = True
                continue

    # if not changed, but should be present, so we have to add it
    if sysctl_args['state'] == 'present' and sysctl_args['changed'] == False and founded == False:
        to_write.append(new_line)
        sysctl_args['changed'] = True

    # has changed ?
    res = 0
    if sysctl_args['changed'] == True:
        sysctl_args = write_sysctl(module, to_write, **sysctl_args)
        res,msg = reload_sysctl(**sysctl_args)
        
        # make checks after act
        res,msg = sysctl_check('after', **sysctl_args)
        if res != 0:
            module.fail_json(msg='checks_after failed with: ' + msg)

    # look at the next link to avoid this workaround
    # https://groups.google.com/forum/?fromgroups=#!topic/ansible-project/LMY-dwF6SQk
    changed = sysctl_args['changed']
    del sysctl_args['changed']

    # end
    sysctl_args = sysctl_args_collapse(**sysctl_args)
    module.exit_json(changed=changed, **sysctl_args)
    sys.exit(0)

# this is magic, see lib/ansible/module_common.py
#<<INCLUDE_ANSIBLE_MODULE_COMMON>>
main()