[cloud] ec2_group fix CIDR with host bits set - fixes #25403 (#29605)

* WIP adds network subnetting functions

* adds functions to convert between netmask and masklen
* adds functions to verify netmask and masklen
* adds function to dtermine network and subnet from address / mask pair

* network_common: add a function to get the first 48 bits in a IPv6 address.

ec2_group: only use network bits of a CIDR.

* Add tests for CIDRs with host bits set.

* ec2_group: add warning if CIDR isn't the networking address.

* Fix pep8.

* Improve wording.

* fix import for network utils

* Update tests to use pytest instead of unittest

* add test for to_ipv6_network()

* Fix PEP8

lib/ansible/module_utils/network/common/utils.py

@@ -31,8 +31,11 @@ import operator
 import socket
 
 from itertools import chain
+from struct import pack
+from socket import inet_aton, inet_ntoa
 
 from ansible.module_utils.six import iteritems, string_types
+from ansible.module_utils.six.moves import zip
 from ansible.module_utils.basic import AnsibleFallbackNotFound
 
 try:
@@ -45,6 +48,7 @@ except ImportError:
 
 OPERATORS = frozenset(['ge', 'gt', 'eq', 'neq', 'lt', 'le'])
 ALIASES = frozenset([('min', 'ge'), ('max', 'le'), ('exactly', 'eq'), ('neq', 'ne')])
+VALID_MASKS = [2**8 - 2**i for i in range(0, 9)]
 
 
 def to_list(val):
@@ -426,3 +430,106 @@ class Template:
                 if marker in data:
                     return True
         return False
+
+
+def is_netmask(val):
+    parts = str(val).split('.')
+    if not len(parts) == 4:
+        return False
+    for part in parts:
+        try:
+            if int(part) not in VALID_MASKS:
+                raise ValueError
+        except ValueError:
+            return False
+    return True
+
+
+def is_masklen(val):
+    try:
+        return 0 <= int(val) <= 32
+    except ValueError:
+        return False
+
+
+def to_bits(val):
+    """ converts a netmask to bits """
+    bits = ''
+    for octet in val.split('.'):
+        bits += bin(int(octet))[2:].zfill(8)
+    return str
+
+
+def to_netmask(val):
+    """ converts a masklen to a netmask """
+    if not is_masklen(val):
+        raise ValueError('invalid value for masklen')
+
+    bits = 0
+    for i in range(32 - int(val), 32):
+        bits |= (1 << i)
+
+    return inet_ntoa(pack('>I', bits))
+
+
+def to_masklen(val):
+    """ converts a netmask to a masklen """
+    if not is_netmask(val):
+        raise ValueError('invalid value for netmask: %s' % val)
+
+    bits = list()
+    for x in val.split('.'):
+        octet = bin(int(x)).count('1')
+        bits.append(octet)
+
+    return sum(bits)
+
+
+def to_subnet(addr, mask, dotted_notation=False):
+    """ coverts an addr / mask pair to a subnet in cidr notation """
+    try:
+        if not is_masklen(mask):
+            raise ValueError
+        cidr = int(mask)
+        mask = to_netmask(mask)
+    except ValueError:
+        cidr = to_masklen(mask)
+
+    addr = addr.split('.')
+    mask = mask.split('.')
+
+    network = list()
+    for s_addr, s_mask in zip(addr, mask):
+        network.append(str(int(s_addr) & int(s_mask)))
+
+    if dotted_notation:
+        return '%s %s' % ('.'.join(network), to_netmask(cidr))
+    return '%s/%s' % ('.'.join(network), cidr)
+
+
+def to_ipv6_network(addr):
+    """ IPv6 addresses are eight groupings. The first three groupings (48 bits) comprise the network address. """
+
+    # Split by :: to identify omitted zeros
+    ipv6_prefix = addr.split('::')[0]
+
+    # Get the first three groups, or as many as are found + ::
+    found_groups = []
+    for group in ipv6_prefix.split(':'):
+        found_groups.append(group)
+        if len(found_groups) == 3:
+            break
+    if len(found_groups) < 3:
+        found_groups.append('::')
+
+    # Concatenate network address parts
+    network_addr = ''
+    for group in found_groups:
+        if group != '::':
+            network_addr += str(group)
+        network_addr += str(':')
+
+    # Ensure network address ends with ::
+    if not network_addr.endswith('::'):
+        network_addr += str(':')
+    return network_addr