/geofeed-tuner

Code examples for Python 3

• Use Python 3's built-in ipaddress package, with strict=True passed to constructors where available.
• Be intentional about IPv4 vs IPv6 address parsing—they are not the same for professional network engineers. Use the strongest type/class available.
• Remember that a subnet can contain a single host: use /128 for IPv6 and /32 for IPv4.

IP address and subnet parsing

• Use the convenience factory functions in ipaddress.

  The following ipaddress.ip_address(textAddress) examples parse text into IPv4Address and IPv6Address objects, respectively:

  ipaddress.ip_address('192.168.0.1')
  ipaddress.ip_address('2001:db8::')

  The following ipaddress.ip_network(address, strict=True) example parses a subnet string and returns an IPv4Network or IPv6Network object, failing on invalid input:

  ipaddress.ip_network('192.168.0.0/28', strict=True)

  The following strict-mode call fails (correctly) with ValueError: 192.168.0.1/30 has host bits set. Ask the user to fix such errors; do not guess corrections:

  ipaddress.ip_network('192.168.0.1/30', strict=True)

• Use the strict-form parser ipaddress.ip_network(address, strict=True).

Dictionary of IP subnets

Use a Python dictionary to track subnets and their associated geolocation properties. IPv4Network, IPv6Network, IPv4Address, and IPv6Address are all hashable and can be used as dictionary keys.

Detecting non-public IP ranges

The SKILL.md references is_private for detecting non-public ranges. Use the network's properties:

import ipaddress

def is_non_public(network):
    """Check if a network is non-public (private, loopback, link-local, multicast, or reserved).
    
    Note: In Python < 3.11, is_private may incorrectly flag some ranges
    (e.g., 100.64.0.0/10 CGNAT space). Use is_global as the primary check
    when available, with fallbacks for edge cases.
    """
    addr = network.network_address
    return (
        network.is_private
        or network.is_loopback
        or network.is_link_local
        or network.is_multicast
        or network.is_reserved
        or not network.is_global  # catches most non-routable space
    )

Caution with is_private on Python < 3.11: The 100.64.0.0/10 (Carrier-Grade NAT) range returns is_private=True but is_global=False in older Python versions. Since CGNAT space is not globally routable, flagging it as non-public is correct for RFC 8805 purposes.

ISO 3166-1 country code validation

Read the valid ISO 2-letter country codes from assets/iso3166-1.json, specifically the alpha_2 attribute:

import json

with open('assets/iso3166-1.json') as f:
    data = json.load(f)
    valid_countries = {c['alpha_2'] for c in data['3166-1']}

ISO 3166-2 region code validation

Read the valid region codes from assets/iso3166-2.json, specifically the code attribute. The top-level key is 3166-2 (matching the iso3166-1 pattern):

import json

with open('assets/iso3166-2.json') as f:
    data = json.load(f)
    valid_regions = {r['code'] for r in data['3166-2']}