The future client pump should exchange Ethernet frames with TAP through a narrow
API, not raw byte reads and writes. Add TAP frame validation at the adapter
boundary so malformed or jumbo frames are rejected before they enter the relay
path.
Expose `TAP_FRAME_BUFFER_LEN` and `validate_tap_ethernet_frame`, then add
Windows helpers that read a TAP frame and validate it, or validate and fully
write an Ethernet frame. Raw read/write methods remain available for lower-level
adapter work.
Test Plan:
- cargo fmt --check
- cargo test --workspace
- cargo clippy --workspace --all-targets -- -D warnings
- Windows-target cargo clippy for lanparty-client-tap with -D warnings
- git diff --check
Refs: PLAN.md one TAP Ethernet frame per datagram
The Windows client still needs a real Ethernet TAP boundary before it can pump
frames between the adapter and the relay session. Keep that OS-specific surface
separate from the QUIC client state by adding a `lanparty-client-tap` crate.
The new crate discovers TAP-Windows6 adapters through the Windows network
adapter registry class, validates `tap0901` component ids, constructs the
`\\.\Global\{NetCfgInstanceId}.tap` device path, opens the TAP device handle,
and exposes blocking Ethernet frame read/write helpers. It also wraps the
TAP-Windows IOCTLs for media status, driver MAC, and driver MTU.
This does not wire the TAP crate into `lanparty-client-win` yet and does not
attempt route protection. The value of this slice is the target-checkable OS
boundary that the next client pump can depend on.
Test Plan:
- cargo fmt --check
- cargo test --workspace
- cargo clippy --workspace --all-targets -- -D warnings
- Windows-target cargo check for lanparty-client-tap with clang-cl/lld-link
- Windows-target cargo clippy for lanparty-client-tap with -D warnings
- git diff --check
Refs: PLAN.md Windows TAP client
ddidderr
