PCAPGraph/netutils.py at main · RedSideSecurity/PCAPGraph · GitHub

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"""Shared network helpers: internal/external classification and subnets."""

from __future__ import annotations

import ipaddress
from functools import lru_cache


@lru_cache(maxsize=100_000)
def is_internal(ip: str) -> bool:
    """True for private / loopback / link-local / multicast / reserved hosts.

    Everything routable on the public internet is 'external'.
    """
    try:
        addr = ipaddress.ip_address(ip)
    except ValueError:
        return False
    return (
        addr.is_private
        or addr.is_loopback
        or addr.is_link_local
        or addr.is_multicast
        or addr.is_reserved
        or addr.is_unspecified
    )


@lru_cache(maxsize=100_000)
def is_noise(ip: str) -> bool:
    """Multicast / broadcast / unspecified addresses — not real hosts.

    These (e.g. SSDP 239.255.255.250, 224.0.0.x, 255.255.255.255, 0.0.0.0) are
    filtered out of the graph so they don't show up as bogus 'internal hosts'.
    """
    try:
        addr = ipaddress.ip_address(ip)
    except ValueError:
        return False
    return addr.is_multicast or addr.is_unspecified or ip == "255.255.255.255"


def is_public(ip: str) -> bool:
    try:
        ipaddress.ip_address(ip)
    except ValueError:
        return False
    return not is_internal(ip)


@lru_cache(maxsize=100_000)
def subnet_of(ip: str) -> str:
    """The /24 (IPv4) or /64 (IPv6) the host belongs to, as a label."""
    try:
        addr = ipaddress.ip_address(ip)
    except ValueError:
        return "unknown"
    if addr.version == 4:
        return str(ipaddress.ip_network(f"{ip}/24", strict=False))
    return str(ipaddress.ip_network(f"{ip}/64", strict=False))