ipnet - IP addresses and CIDR networks

Import with import "ipnet.j" as ipnet;. Parse and reason about IPv4 and IPv6 addresses and CIDR blocks: canonical formatting, membership tests, and subnet math (netmask, broadcast). Addresses are held as raw bytes (4 for IPv4, 16 for IPv6); the math is bitwise. Pure Jennifer over strings + convert; runs on both binaries.

import "ipnet.j" as ipnet;

def net as ipnet.Network init ipnet.parse("192.168.1.0/24");
def ip as ipnet.Address init ipnet.parseAddress("192.168.1.42");
def inside as bool init ipnet.contains($net, $ip);   # true

Runnable: examples/modules/ipnet_demo.j.

Types

Both structs have public fields (read them directly), and the builder functions are the conventional way to construct them.

def struct ipnet.Address { version as int, octets as bytes };   # version 4 or 6
def struct ipnet.Network { addr as Address, prefix as int };

• Address.version is 4 or 6; Address.octets is the raw address bytes (4 or 16), in network byte order.
• Network.addr is the base address with host bits zeroed; Network.prefix is the prefix length (0..32 for IPv4, 0..128 for IPv6).

Addresses

parseAddress accepts IPv6 with :: zero-compression and a trailing embedded IPv4 (::ffff:192.168.1.1). toString renders IPv6 canonically per RFC 5952: lowercase, no leading zeros, and the longest run of two-or-more zero groups compressed to :: (leftmost on a tie). Because equal compares bytes, two different spellings of the same address compare equal.

CIDR networks

parse zeroes the host bits, so ipnet.parse("192.168.1.42/24") has base 192.168.1.0. contains returns false for a version mismatch (an IPv4 address is never inside an IPv6 network). broadcast sets every host bit: for IPv4 that is the broadcast address, for IPv6 the last address in the block.

def allowed as list of ipnet.Network init [ipnet.parse("10.0.0.0/8"), ipnet.parse("192.168.0.0/16")];
def client as ipnet.Address init ipnet.parseAddress("10.4.5.6");
def ok as bool init false;
for (def net in $allowed) {
    if (ipnet.contains($net, $client)) { $ok = true; }
}

Errors

Malformed input throws Error{kind: "ipnet"} (a bad octet, too few / many groups, multiple ::, a bad hex digit, a missing /prefix, or an out-of-range prefix) - catch it with try / catch.

Scope

• Address and prefix math, not a resolver. No DNS, no interface enumeration; hostname / interface lookups live in the net library.
• Lenient decimal octets. parseAddress reads IPv4 octets as plain decimal, so leading zeros are accepted as decimal (192.168.001.001 = 192.168.1.1), not rejected or read as octal.
• IPv4-mapped IPv6 renders as hex. ::ffff:192.168.1.1 round-trips at the byte level but toString renders it in pure hex form (::ffff:c0a8:101), not the dotted-quad convenience form.
• No subnet-of-subnet test in v1. contains tests an address in a network; network-in-network containment is not modelled yet.

See also

• net.md - sockets, TLS, and DNS lookups.
• strings.md - the text surface the parser builds on.
• modules/index.md - the module catalog and import rules.