mirror of
https://github.com/kevinveenbirkenbach/computer-playbook.git
synced 2026-11-06 02:54:26 +00:00
kevinveenbirkenbachandClaude Opus 5
4d79f7c19f
`ruff`'s B905 wants every `zip()` to say whether it tolerates operands of different length. Here it never sees one: both operands are the `packed` form of an address from the same network, so both are four bytes for IPv4 and sixteen for IPv6. `strict=True` states that, and turns a silently truncated - and therefore too permissive - regex into an error should the invariant ever break. The three other files carry `ruff format` reflows the same run produced. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
70 lines
2.2 KiB
Python
70 lines
2.2 KiB
Python
"""Derive an address-matching regex from a role's local subnet.
|
|
|
|
A swarm task is attached to several site-local networks at once, so a service
|
|
that must bind to one specific network cannot be told "pick a site-local
|
|
address" - it needs a matcher for the one subnet it owns.
|
|
"""
|
|
|
|
from __future__ import annotations
|
|
|
|
import ipaddress
|
|
|
|
|
|
def _octet_pattern(low: int, high: int) -> str:
|
|
if low == high:
|
|
return str(low)
|
|
if (low, high) == (0, 255):
|
|
return r"\d+"
|
|
return "(" + "|".join(str(value) for value in range(low, high + 1)) + ")"
|
|
|
|
|
|
def subnet_address_regex(subnet: str) -> str:
|
|
"""Return a regex matching every address inside ``subnet``, and no other.
|
|
|
|
A prefix mask leaves a contiguous run of low bits free, so per octet the
|
|
addresses span exactly ``network_address`` to ``broadcast_address``. The
|
|
cross product of those four ranges is the network, which makes the octet
|
|
decomposition exact for any prefix length, aligned or not.
|
|
|
|
Args:
|
|
subnet: IPv4 network in CIDR notation, e.g. ``192.168.24.0/24``.
|
|
|
|
Returns:
|
|
A regex over dotted octets, e.g. ``192\\.168\\.24\\.\\d+`` for a /24 or
|
|
``192\\.168\\.(24|25)\\.\\d+`` for a /23.
|
|
|
|
Raises:
|
|
ValueError: the notation is malformed or carries host bits.
|
|
"""
|
|
network = ipaddress.ip_network(subnet, strict=True)
|
|
return r"\.".join(
|
|
_octet_pattern(low, high)
|
|
for low, high in zip(
|
|
network.network_address.packed,
|
|
network.broadcast_address.packed,
|
|
strict=True,
|
|
)
|
|
)
|
|
|
|
|
|
def subnet_gateway(subnet: str) -> str:
|
|
"""Return the address Docker assigns as the gateway of ``subnet``.
|
|
|
|
Args:
|
|
subnet: IPv4 network in CIDR notation, e.g. ``192.168.24.0/24``.
|
|
|
|
Returns:
|
|
The first usable address, e.g. ``192.168.24.1``.
|
|
|
|
Raises:
|
|
ValueError: the notation is malformed, carries host bits, or the network
|
|
is too small to hold a gateway.
|
|
"""
|
|
network = ipaddress.ip_network(subnet, strict=True)
|
|
try:
|
|
return str(network[1])
|
|
except IndexError as exc:
|
|
raise ValueError(
|
|
f"subnet {subnet} is a /{network.prefixlen} and holds no gateway address"
|
|
) from exc
|