PLAN.md keeps MVP traffic to one Ethernet frame per QUIC datagram with no
fragmentation. The relay already negotiates a datagram budget, but the client
and gateway send paths still relied on Quinn to reject oversized encoded
Ethernet datagrams.
Add a shared protocol validation helper for encoded datagram length versus the
negotiated QUIC budget. Thread the negotiated budget into client and gateway
send boundaries, reject oversized datagrams before send, and count those valid
but unsent frames as local drops.
Document the budget check in the workspace decomposition and gateway behavior.
Test Plan:
- cargo fmt --check
- cargo test -p lanparty-proto -p lanparty-client-core -p lanparty-gateway
- cargo test --workspace
- cargo clippy --workspace --all-targets -- -D warnings
- git diff --check
Refs: PLAN.md
Build the shared protocol contract that the client, gateway, and relay will use
for Ethernet datagrams. The MVP needs these pieces agreed on before socket or
TAP work can be reasoned about safely.
This adds strict MAC parsing and client identity validation, Ethernet header
inspection, fixed overlay datagram encoding and decoding, and MTU helpers for
the no-fragmentation QUIC datagram design. The protocol crate stays
transport-agnostic so platform and network code can depend on it without
pulling in OS-specific behavior.
Remaining work is to put these primitives behind the control-plane handshake,
relay forwarding loop, Windows TAP client, and Linux AF_PACKET gateway.
Test Plan:
- cargo fmt --check
- cargo test --workspace
- cargo clippy --workspace --all-targets -- -D warnings
Refs: PLAN.md Phase 1: prove the illusion
ddidderr
