1 files changed, 51 insertions, 0 deletions
diff --git a/filter_plugins/ipv4.py b/filter_plugins/ipv4.py
new file mode 100644
index 0000000..1c42e82
--- /dev/null
+++ b/filter_plugins/ipv4.py
@@ -0,0 +1,51 @@
+"""Custom Jinja2 filters for IPv4 address math."""
+import struct
+import socket
+
+
+def _ip_to_int(ip):
+    return struct.unpack("!I", socket.inet_aton(ip))[0]
+
+
+def _int_to_ip(n):
+    return socket.inet_ntoa(struct.pack("!I", n))
+
+
+def ipv4_network(cidr):
+    """Return the network address of a CIDR. '10.0.20.2/24' -> '10.0.20.0'"""
+    ip, prefix = cidr.split("/")
+    mask = (0xFFFFFFFF << (32 - int(prefix))) & 0xFFFFFFFF
+    return _int_to_ip(_ip_to_int(ip) & mask)
+
+
+def ipv4_nth(cidr, n):
+    """Return the nth host address in a network. '10.0.20.0/24' | ipv4_nth(101) -> '10.0.20.101'"""
+    network = ipv4_network(cidr)
+    return _int_to_ip(_ip_to_int(network) + int(n))
+
+
+def ipv4_nth_cidr(cidr, n):
+    """Return the nth host address with the original prefix. '10.0.20.0/24' | ipv4_nth_cidr(101) -> '10.0.20.101/24'"""
+    _, prefix = cidr.split("/")
+    return ipv4_nth(cidr, n) + "/" + prefix
+
+
+def ipv4_host(cidr):
+    """Return just the host part of a CIDR. '10.0.20.2/24' -> '10.0.20.2'"""
+    return cidr.split("/")[0]
+
+
+def ipv4_prefixlen(cidr):
+    """Return just the prefix length. '10.0.20.2/24' -> '24'"""
+    return cidr.split("/")[1]
+
+
+class FilterModule(object):
+    def filters(self):
+        return {
+            "ipv4_network": ipv4_network,
+            "ipv4_nth": ipv4_nth,
+            "ipv4_nth_cidr": ipv4_nth_cidr,
+            "ipv4_host": ipv4_host,
+            "ipv4_prefixlen": ipv4_prefixlen,
+        }