PyTCP-net-proto 3.0.6

The network-protocol packet parse/assemble layer of the PyTCP stack — Ethernet through TCP/UDP — fully usable on its own.

PyTCP-net_proto

The network-protocol packet parse / assemble / validate layer of the PyTCP TCP/IP stack — extracted as its own distribution and usable on its own.

from net_proto import IpProto
from net_proto.protocols.udp.udp__parser import UdpParser
from net_proto.protocols.udp.udp__assembler import UdpAssembler

datagram = UdpAssembler(udp__sport=12345, udp__dport=53, udp__payload=b"query")
parsed = UdpParser(packet_rx)          # raises UdpIntegrityError / UdpSanityError on bad wire input

Why

Strict, RFC-grounded, fully-typed wire-format codecs for the common Internet protocols, with a single clean validation-error tree and no runtime dependencies beyond the address library it is built on.

Protocol coverage

Each protocol is a parser / assembler pair over a frozen header dataclass, with integrity + sanity validation and typed wire enums.

Family	Governing RFC(s)
Ethernet II	RFC 894 / 7042 (EtherType)
IEEE 802.3 + LLC / SNAP	IEEE 802.3 / 802.2 / RFC 1042
ARP	RFC 826
IPv4 (+ options: LSRR/SSRR, RR, Timestamp, Router-Alert, CIPSO)	RFC 791 / 1108 / 2113
IPv6	RFC 8200
IPv6 Hop-by-Hop / Destination Options (PadN, Jumbo, RouterAlert, Tunnel-Limit, CALIPSO)	RFC 8200 / 2675 / 2711
IPv6 Routing / Fragment extension headers	RFC 8200 / 5095
ICMPv4	RFC 792 / 1122
ICMPv6	RFC 4443
ICMPv6 Neighbor Discovery (+ options)	RFC 4861 / 8106
ICMPv6 MLDv2 (+ MLDv1 compatibility)	RFC 3810 / 2710
IGMP (host membership: IGMPv1/v2/v3 + source-specific)	RFC 1112 / 2236 / 3376
TCP (+ options: MSS, WScale, SACK, Timestamps, AccECN, Fast-Open)	RFC 9293 / 2018 / 7323 / 9768 / 7413
UDP	RFC 768
DHCPv4 (+ options)	RFC 2131 / 2132
DHCPv6 (+ options)	RFC 8415

The six-file pattern

Every protocol under protocols/<proto>/ follows the same layout (see .claude/rules/net_proto.md):

• <proto>__header.py — the frozen *Header dataclass (@dataclass(frozen=True, kw_only=True, slots=True)) + the *HeaderProperties read-mixin + the RFC ASCII diagram + struct constants.
• <proto>__base.py — * base composing header (+ options + payload) with the shared dunders (__len__ / __str__ / __repr__ / __buffer__).
• <proto>__parser.py — the three-phase RX pipeline: _validate_integrity() → _parse() → _validate_sanity().
• <proto>__assembler.py — the keyword-only TX constructor + assemble(buffers, /) with checksum injection.
• <proto>__errors.py — the *IntegrityError / *SanityError pair.
• <proto>__enums.py + options/ — protocol enums and TLV options where the protocol has them.

Validation-error model

One two-axis tree, rendered with a canonical category + protocol prefix so tests and logs match exactly:

PacketIntegrityError → "[INTEGRITY ERROR][<PROTO>] ..."   (structural / wire-shape)
PacketSanityError    → "[SANITY ERROR][<PROTO>] ..."      (logical invariant)

Integrity vs sanity: integrity checks run on the raw frame before fields are trusted (length bounds, checksum, header shape); sanity checks run on already-parsed fields (a port of 0, a reserved-bit violation). Both raise typed *Errors — never assert — so they survive python -O (assertions stripped), because they defend against hostile wire input. Conversely, *Header.__post_init__ and *Assembler.__init__ use assert (programmer-error guards, OK to strip under -O); any wire-reachable bound an assert guards is mirrored as a typed raise in _validate_integrity. This wire-input vs programmer-input discipline (rule §9.2) is AST-clean across the package.

Typed wire enums

Protocol codepoints are ProtoEnumByte / ProtoEnumWord subclasses (EtherType, IpProto, Icmp6Type, ArpOperation, …), never bare ints. Unknown wire codepoints are materialised natively via the stdlib enum.Enum._missing_ hook (an UNKNOWN_<value> identity-stable pseudo-member) — no third-party aenum dependency.

Install

pip install PyTCP-net_proto

Depends only on PyTCP-net_addr (the address value-type library) — no other runtime dependencies. Fully typed (ships py.typed, PEP 561); strict-mypy clean.

Requirements

Python 3.14+ (PEP 695 generics on the assembler stacking, modern typing throughout).

Current state (3.0.6)

• ~260 source modules; 5770 unit tests, ~99% source coverage (the remaining lines are protocol dunders, from_buffer unpacking, and a few integrity-rejection branches with no dedicated rejection test — test-completeness, not defects).
• Per-RFC adherence records live in docs/rfc/ (the wire-format header / parser / assembler / options rows are net_proto's surface). The parser RFC-adherence pass and the assembler audit pass are both CLOSED; follow-up audits A–L are complete (see docs/refactor/net_proto_remaining_audits.md).

License

GPL-3.0-or-later. Part of the PyTCP project by Sebastian Majewski.