Add random_mac string filter (#39775)

Add new filter to generate random MAC addresses from
string prefix. See docs/docsite/rst/user_guide/playbooks_filters.rst
for more detailed infos.

changelogs/fragments/add_random_mac_filtter.yaml

@@ -0,0 +1,6 @@
+---
+minor_changes:
+  - Added new filter to generate random MAC addresses from a given
+    string acting as a prefix. Refer to the appropriate entry
+    which has been added to user_guide playbook_filters.rst
+    document.

docs/docsite/rst/user_guide/playbooks_filters.rst

@@ -243,6 +243,22 @@ An example of using this filter with ``loop``::
         key: "{{ lookup('file', item.1) }}"
       loop: "{{ users|subelements('authorized') }}"
 
+.. _random_mac_filter:
+
+Random Mac Address Filter
+`````````````````````````
+
+.. versionadded:: 2.6
+
+This filter can be used to generate a random MAC address from a string prefix.
+
+To get a random MAC address from a string prefix starting with '52:54:00'::
+
+    "{{ '52:54:00'|random_mac }}"
+    # => '52:54:00:ef:1c:03'
+
+Note that if anything is wrong with the prefix string, the filter will issue an error.
+
 .. _random_filter:
 
 Random Number Filter

lib/ansible/plugins/filter/core.py

@@ -37,7 +37,7 @@ import yaml
 from collections import MutableMapping, MutableSequence
 import datetime
 from functools import partial
-from random import Random, SystemRandom, shuffle
+from random import Random, SystemRandom, shuffle, random
 
 from jinja2.filters import environmentfilter, do_groupby as _do_groupby
 
@@ -532,6 +532,39 @@ def dict_to_list_of_dict_key_value_elements(mydict):
     return ret
 
 
+def random_mac(value):
+    ''' takes string prefix, and return it completed with random bytes
+        to get a complete 6 bytes MAC address '''
+
+    if not isinstance(value, string_types):
+        raise AnsibleFilterError('Invalid value type (%s) for random_mac (%s)' % (type(value), value))
+
+    value = value.lower()
+    mac_items = value.split(':')
+
+    if len(mac_items) > 5:
+        raise AnsibleFilterError('Invalid value (%s) for random_mac: 5 colon(:) separated items max' % value)
+
+    err = ""
+    for mac in mac_items:
+        if len(mac) == 0:
+            err += ",empty item"
+            continue
+        if not re.match('[a-f0-9]{2}', mac):
+            err += ",%s not hexa byte" % mac
+    err = err.strip(',')
+
+    if len(err):
+        raise AnsibleFilterError('Invalid value (%s) for random_mac: %s' % (value, err))
+
+    # Generate random float and make it int
+    v = int(random() * 10.0**10)
+    # Select first n chars to complement input prefix
+    remain = 2 * (6 - len(mac_items))
+    rnd = ('%x' % v)[:remain]
+    return value + re.sub(r'(..)', r':\1', rnd)
+
+
 class FilterModule(object):
     ''' Ansible core jinja2 filters '''
 
@@ -621,4 +654,7 @@ class FilterModule(object):
             'flatten': flatten,
             'dict2items': dict_to_list_of_dict_key_value_elements,
             'subelements': subelements,
+
+            # Misc
+            'random_mac': random_mac,
         }

test/integration/targets/filters/tasks/main.yml

@@ -193,3 +193,45 @@
     - "'QW5zaWJsZSAtIOOBj+OCieOBqOOBvwo=' | b64decode == 'Ansible - くらとみ\n'"
     - "'Ansible - くらとみ\n' | b64encode(encoding='utf-16-le') == 'QQBuAHMAaQBiAGwAZQAgAC0AIABPMIkwaDB/MAoA'"
     - "'QQBuAHMAaQBiAGwAZQAgAC0AIABPMIkwaDB/MAoA' | b64decode(encoding='utf-16-le') == 'Ansible - くらとみ\n'"
+
+- name: Test random_mac filter bad argument type
+  debug:
+    var: "0 | random_mac"
+  register: _bad_random_mac_filter
+  ignore_errors: yes
+
+- name: Verify random_mac filter showed a bad argument type error message
+  assert:
+    that:
+      - _bad_random_mac_filter is failed
+      - "_bad_random_mac_filter.msg is match('Invalid value type (.*int.*) for random_mac .*')"
+
+- name: Test random_mac filter bad argument value
+  debug:
+    var: "'dummy' | random_mac"
+  register: _bad_random_mac_filter
+  ignore_errors: yes
+
+- name: Verify random_mac filter showed a bad argument value error message
+  assert:
+    that:
+      - _bad_random_mac_filter is failed
+      - "_bad_random_mac_filter.msg is match('Invalid value (.*) for random_mac: .* not hexa byte')"
+
+- name: Test random_mac filter prefix too big
+  debug:
+    var: "'00:00:00:00:00:00' | random_mac"
+  register: _bad_random_mac_filter
+  ignore_errors: yes
+
+- name: Verify random_mac filter showed a prefix too big error message
+  assert:
+    that:
+      - _bad_random_mac_filter is failed
+      - "_bad_random_mac_filter.msg is match('Invalid value (.*) for random_mac: 5 colon.* separated items max')"
+
+- name:  Verify random_mac filter
+  assert:
+    that:
+            - "'00:00:00' | random_mac is match('^00:00:00:[a-f0-9][a-f0-9]:[a-f0-9][a-f0-9]:[a-f0-9][a-f0-9]$')"
+            - "'00:00:00' | random_mac != '00:00:00' | random_mac"