add address_to_mask and address_to_wildcard

src/netom/__init__.py

@@ -8,6 +8,7 @@
 from pkg_resources import get_distribution
 
 from .exception import NetomValidationError
+from .j2_filters import address_to_mask, address_to_wildcard
 
 # TODO move out of this namespace
 from .models import BgpNeighbor
@@ -57,6 +58,8 @@ def set_search_path(self, search_path):
         self.engine = tmpl.get_engine("jinja2")(search_path=search_path)
         self.engine.engine.filters["make_variable_name"] = make_variable_name
         self.engine.engine.filters["ip_version"] = ip_version
+        self.engine.engine.filters["address_to_mask"] = address_to_mask
+        self.engine.engine.filters["address_to_wildcard"] = address_to_wildcard
         # self.engine.search_path = os.path.dirname(search_path)
 
     def _render(self, filename, data, fobj):

src/netom/j2_filters.py

@@ -0,0 +1,21 @@
+import ipaddress
+from ipaddress import IPv4Address
+
+def address_to_mask(addr):
+    """
+    Transform A.B.C.D/nn into A.B.C.D M.M.M.M subnet mask format.
+    """
+    ipaddr4 = ipaddress.ip_interface(addr)
+    return f"{ipaddr4.ip} {ipaddr4.netmask}"
+
+
+def address_to_wildcard(addr):
+    """
+    Transform A.B.C.D/nn into A.B.C.D W.W.W.W subnet wildcard format.
+
+    credit for the mask shenanigans to George Shuklin
+    https://medium.com/opsops/wildcard-masks-operations-in-python-16acf1c35683
+    """
+    ipnet4 = ipaddress.ip_network(addr)
+    wildcard = str(IPv4Address(int(IPv4Address(ipnet4.netmask))^(2**32-1)))
+    return f"{ipnet4.network_address} {wildcard}"

tests/test_j2_filters.py

@@ -0,0 +1,26 @@
+
+from netom.j2_filters import address_to_mask, address_to_wildcard
+import pytest
+
+
+def test_address_to_mask():
+    assert address_to_mask("192.168.0.1/4") == "192.168.0.1 240.0.0.0"
+    assert address_to_mask("192.168.0.1/8") == "192.168.0.1 255.0.0.0"
+    assert address_to_mask("192.168.0.1/9") == "192.168.0.1 255.128.0.0"
+    assert address_to_mask("192.168.0.1/16") == "192.168.0.1 255.255.0.0"
+    assert address_to_mask("192.168.0.1/24") == "192.168.0.1 255.255.255.0"
+    assert address_to_mask("192.168.0.1/25") == "192.168.0.1 255.255.255.128"
+    assert address_to_mask("192.168.0.1/30") == "192.168.0.1 255.255.255.252"
+    assert address_to_mask("192.168.0.1/31") == "192.168.0.1 255.255.255.254"
+    assert address_to_mask("192.168.0.1/32") == "192.168.0.1 255.255.255.255"
+
+def test_address_to_wildcard():
+    assert address_to_wildcard("192.0.0.0/4") == "192.0.0.0 15.255.255.255"
+    assert address_to_wildcard("192.0.0.0/8") == "192.0.0.0 0.255.255.255"
+    assert address_to_wildcard("192.0.0.0/9") == "192.0.0.0 0.127.255.255"
+    assert address_to_wildcard("192.168.0.0/16") == "192.168.0.0 0.0.255.255"
+    assert address_to_wildcard("192.168.0.0/24") == "192.168.0.0 0.0.0.255"
+    assert address_to_wildcard("192.168.0.0/25") == "192.168.0.0 0.0.0.127"
+    assert address_to_wildcard("192.168.0.0/30") == "192.168.0.0 0.0.0.3"
+    assert address_to_wildcard("192.168.0.0/31") == "192.168.0.0 0.0.0.1"
+    assert address_to_wildcard("192.168.0.0/32") == "192.168.0.0 0.0.0.0"