Add reverse_pointer filter.

plugins/filter/reverse_pointer.py

@@ -0,0 +1,84 @@
+# -*- coding: utf-8 -*-
+
+# Copyright (c) 2020-2021, Felix Fontein <felix@fontein.de>
+# GNU General Public License v3.0+ (see LICENSES/GPL-3.0-or-later.txt or https://www.gnu.org/licenses/gpl-3.0.txt)
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+from __future__ import absolute_import, division, print_function
+__metaclass__ = type
+
+
+DOCUMENTATION = r"""
+name: reverse_pointer
+short_description: Convert an IP address into a DNS name for reverse lookup
+version_added: 3.1.0
+description:
+  - Given an IPv4 or IPv6 address, such as V(192.168.1.2), converts it to a DNS name to use for
+    reverse lookups, such as V(2.1.168.192.in-addr.arpa).
+options:
+  _input:
+    description:
+      - The IP address.
+    type: string
+    required: true
+author:
+  - Felix Fontein (@felixfontein)
+seealso:
+  - name: RFC 1035, Section 3.5
+    link: https://www.rfc-editor.org/rfc/rfc1035.html#section-3.5
+    description: Describes C(in-addr.arpa).
+  - name: RFC 3152
+    link: https://www.rfc-editor.org/rfc/rfc3152.html
+    description: Describes C(ip6.arpa).
+"""
+
+EXAMPLES = r"""
+- name: Convert IP address to DNS name for reverse lookup
+  ansible.builtin.set_fact:
+    dns_name: "{{ ip_address | community.dns.reverse_pointer }}"
+    # Should result in '2.1.168.192.in-addr.arpa.'
+  vars:
+    ip_address: 192.168.1.2
+"""
+
+RETURN = r"""
+_value:
+  description: The DNS name.
+  type: string
+"""
+
+
+from ansible.errors import AnsibleFilterError
+from ansible.module_utils.common.text.converters import to_text
+from ansible.module_utils.six import string_types
+
+from ansible_collections.community.dns.plugins.plugin_utils.ips import assert_requirements_present
+
+try:
+    import ipaddress
+except ImportError:
+    # handled by assert_requirements_present
+    pass
+
+
+def reverse_pointer(ip):
+    assert_requirements_present('community.dns.reverse_pointer', 'filter')
+    if not isinstance(ip, string_types):
+        raise AnsibleFilterError('Input for community.dns.reverse_pointer must be a string')
+    try:
+        ipaddr = ipaddress.ip_address(to_text(ip))
+    except Exception as e:
+        raise AnsibleFilterError('Cannot parse IP address: {error}'.format(error=e))
+    res = ipaddr.reverse_pointer
+    if not res.endswith(u'.'):
+        res += u'.'
+    return res
+
+
+class FilterModule(object):
+    '''Ansible jinja2 filters'''
+
+    def filters(self):
+        return {
+            'reverse_pointer': reverse_pointer,
+        }

tests/integration/targets/filter_reverse_pointer/aliases

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+# Copyright (c) Ansible Project
+# GNU General Public License v3.0+ (see LICENSES/GPL-3.0-or-later.txt or https://www.gnu.org/licenses/gpl-3.0.txt)
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+shippable/posix/group1

tests/integration/targets/filter_reverse_pointer/tasks/main.yml

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+---
+# Copyright (c) Ansible Project
+# GNU General Public License v3.0+ (see LICENSES/GPL-3.0-or-later.txt or https://www.gnu.org/licenses/gpl-3.0.txt)
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+- name: Compute reverse pointer
+  ansible.builtin.set_fact:
+    reverse_ipv4: >-
+      {{ '192.168.1.2' | community.dns.reverse_pointer }}
+    reverse_ipv6: >-
+      {{ 'a::B' | community.dns.reverse_pointer }}
+
+- name: Check results
+  assert:
+    that:
+      - reverse_ipv4 == '2.1.168.192.in-addr.arpa.'
+      - reverse_ipv6 == 'b.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.a.0.0.0.ip6.arpa.'
+
+- name: Process invalid IP address
+  ansible.builtin.set_fact:
+    reverse_nope: >-
+      {{ 'foo.com' | community.dns.reverse_pointer }}
+  ignore_errors: true
+  register: invalid_ip
+
+- name: Process non-string
+  ansible.builtin.set_fact:
+    reverse_nope: >-
+      {{ 42 | community.dns.reverse_pointer }}
+  ignore_errors: true
+  register: non_string
+
+- name: Check results
+  assert:
+    that:
+      - invalid_ip is failed
+      - >-
+        "Cannot parse IP address: 'foo.com' does not appear to be an IPv4 or IPv6 address" in invalid_ip.msg
+      - non_string is failed
+      - >-
+        "Input for community.dns.reverse_pointer must be a string" in non_string.msg