glm-5.3-flash
bd7d1ad8ec
The Phase 0 OQ ledger (OQ-TN-01..10) promoted into
docs/architecture/open-questions.md (now OQ-TN-01..14, with four
new Phase 1 residues). Six ADRs and four spec docs, all Draft, all
decision-shaped per the SDD process (ADRs carry the WHY; specs carry
the WHAT and reference by number):
ADRs:
- 001 open-params-layout: params = {resource, substrate} — the
producer's stable name, not an address; wire-stable from the first
consumer; unknown substrates fail loudly at schema time
- 002 alpn-strategy: single alk/tunnel ALPN (option A); substrate in
params selects the framing; prior art (SSH/SOCKS5/udpgw) gives no
reason for the split
- 003 codec-and-udp-framing: raw pass-through (stream) / mandatory
[len: u16 BE] (UDP) — F-2 mandate recorded (the codec is mandatory
for correctness, not cosmetics); len=0 = legal empty datagram;
OQ-TN-13 resolved fail-loud (truncation)
- 004 no-backend-trait: halves functions at the assembly layer;
listen is an establisher shape; hub re-produce deferred(OQ-TN-12);
trait re-evaluated at the alknet ADR-078 convergence threshold
- 005 consumer-session-owns-teardown: TunnelSession with
open/adopt/stream_halves/take_halves/pump_against/close/join/Drop —
the W3 adopter gap closes structurally; Drop is the best-effort
fallback
- 006 access-control-posture: the open gate is the boundary;
TUNNEL_OPEN_SCOPE = tunnel:open (stable once published); op-level
ACL; ownership seam; no allowlists in v1; identity = 0.7.0's
precedence chain
Spec docs:
- overview.md: purpose, resource model, deps (alkcall 0.7.0,
wasm-clean default, local feature), module map
- wire.md: the open op (params/reply/typed errors), the data plane
by substrate, sentinels + half-close, byte diagrams
- producer.md: spec, establisher (dial + listen shapes), pump
handler (pump_bidi inline, R-02), registration API, ACL posture
- consumer.md: TunnelSession (forward open + reverse adopt
construction), data plane, teardown API (close/join/Drop incl.
pump-less join semantics)
- bast.md: the BAST doc for the UDP codec (convention 12's trigger
fired — the framing IS binary beyond pass-through)
- open-questions.md: OQ-TN-01..14; 01..10 promoted (faithful to the
phase-0 ledger's final states), 11 partially resolved (collision
domain = per-producer registry per ADR-001; lifecycle open),
12 deferred(scope), 13 resolved fail-loud (ADR-003), 14 open
Verified by an architecture-reviewer pass (2 criticals, 6 majors,
10 minors — all fixed: ADR-001/003-vs-OQ decision-state contradictions
resolved; the Layer-2 mislabel corrected to the ADR-047 §4 per-session
fork; alktty/alknet ADR misattributions fixed; codec placement pinned
to the establisher (pump stays substrate-agnostic); reverse-path
construction named (TunnelSession::adopt + pump_against); security
posture promoted to ADR-006; BAST doc written; F-2 rationale deduped;
README tables completed; channel_id > 0; MTU wording fixed; ADR-047 §5
attributions corrected; impacts lines added to unresolved OQs; review/
ledger pointer paths added to README references).
Verification: doc set internal cross-refs all resolve; cargo test,
fmt --check, doc --no-deps clean
status, last_updated
| status | last_updated |
|---|---|
| draft | 2026-09-07 |
alktunnels — Architecture
Arbitrary bidirectional tunnels over alkcall channels: the
alk/tunnel-family producer/consumer protocol crate. This directory
holds the architecture spec docs and the ADRs. It is the sibling of
alktty's architecture (/workspace/@alkdev/alktty/docs/architecture/)
— same substrate (alkcall channels), same shape (a producer
open-handler + a typed consumer session), different service (tunnels:
raw byte/datagram transport, not terminal sessions).
Documents
| Document | Status | Description |
|---|---|---|
| overview.md | draft | Crate purpose, the resource model in brief, dependencies, ALPN, feature gates, module map |
| wire.md | draft | The wire format: open-op params JSON (ADR-001), the data-plane codec (raw pass-through for stream substrates; mandatory [len: u16 BE] framing for UDP — ADR-003), sentinels, half-close semantics |
| producer.md | draft | The producer half: the channels/tunnel/sub open op, the establisher (dial + listen variants), the pump handler, registration, scope gating |
| consumer.md | draft | The consumer half: TunnelSession (stream + datagram variants), the reverse-flow initiator, teardown ownership (ADR-005) |
| bast.md | draft | The BAST (Binary Abstract Syntax Tree) document for the data-plane's binary framing (the UDP [len: u16 BE] codec — ADR-003); the stream pass-through has no binary framing to describe |
| open-questions.md | draft | Centralized OQ tracker (OQ-TN-01..14; the Phase 0 ledger promoted) |
Applicable ADRs
alktunnels-native ADRs (001..005). Upstream ADRs (alkcall/alknet) are
referenced by their own numbers and are NOT ported — the alkcall
originals at /workspace/@alkdev/alkcall/docs/architecture/decisions/
remain authoritative for the shared surfaces (establishment, channels
wire format, pump_bidi, identity seam).
| ADR | Title | Status |
|---|---|---|
| 001 | Open-Op Params Layout: Resource + Substrate | Accepted |
| 002 | Single alk/tunnel ALPN (Option A) |
Accepted |
| 003 | Data-Plane Codec: Raw Pass-Through (Stream) / Mandatory Length Framing (UDP) | Accepted |
| 004 | No TunnelBackend Trait — Halves Functions at the Assembly Layer | Accepted |
| 005 | The Consumer Session Type Owns Teardown | Accepted |
| 006 | Access-Control Posture — the Open Gate Is the Security Boundary | Accepted |
Key Design Principles
-
A tunnel is a resource, not an address.
paramsidentify a produced resource + substrate discriminator; the producer owns the backing (local port, docker container, in-process service, unix socket). No URL-style general addressing in the wire — rich addressing enters only through-D/dynamic composition, which speaks its protocol inside the tunnel payload. See ADR-001 and wire.md. -
Role follows the resource; connection direction is independent. Whoever can reach the target is the producer (registers openable channels); whoever wants the bytes is the consumer.
-Land-Rare the same open op with the entry point on different machines — no protocol-level direction (the hub-owns-the-connection model, OQ-TN-03). Validated by the reverse-flow POC: the worker serves on the connect side; the hub initiates per accept. See producer.md and consumer.md. -
Raw pass-through for stream substrates; mandatory length framing for UDP. A tunnel has one data stream per direction — no sub-demux key, no tunnel-level header on stream substrates (0 B tunnel overhead; the channels 8-byte header is the only cost). UDP rides
[len: u16 BE]framing — mandatory for correctness (F-2; the rationale and the executable pin live in ADR-003). See ADR-003 and wire.md. -
The two-pump shape is
alkcall::channels::pump_bidi— never hand-rolled. The producer's pump handler and the consumer-side pump both consume the upstream helper (ADR-050); each pump shuts down the opposite sink on completion (half-close semantics fall out). TheOpenHandler's returnedJoinHandletracks the data-plane lifetime (early return = teardown-at-birth, R-02). See producer.md. -
No backend trait. Stream substrates need "produce boxed halves for a resource" — a function, not a trait (the UDP POC's OQ-TN-05 finding). The inversion point is the assembly layer wiring substrate halves into the establisher/pump; substrate types stay in feature-gated backend modules. The listen variant (producer accepts instead of dialing) is an establisher shape, not a trait. See ADR-004.
-
The consumer session type owns teardown. One session = one channel = one tunnel (the channel ID is the flow key). The adopted side has no wrapper awaiting its pump (reverse POC W3) — the session must hold the pump handle and reap the channel on completion/close. See ADR-005 and consumer.md.
-
Backpressure and limits are inherited, not redefined. Bounded per-channel buffers, the 256-channel cap, monotonic IDs, and the zero-length-sentinel EOF convention are alkcall channels invariants; the tunnel crate consumes them and does not build a second demux/mux (AGENTS.md convention 10).
-
Security posture: the open gate is the boundary. Scope-gated opens (
TUNNEL_OPEN_SCOPE = "tunnel:open", stable once published — ADR-006), alkcall's op-level ACL viaregister_openable; caller identity resolves in the 0.7.0 precedence order (token >ServingConfig.identity> transport); the establisher/pump handler see the per-call opener identity. No target allowlists, no tunnel-specific policy machinery in v1. See ADR-006 and producer.md. -
Wasm-clean default crate. The default crate (protocol only) compiles to
wasm32-unknown-unknown; socket/platform I/O lives in feature-gated backend modules (AGENTS.md conventions 4/14), same as alktty.
Relevant Open Questions
All open questions are tracked in
open-questions.md. The Phase 0 OQ ledger
(OQ-TN-01..10, docs/research/phase-0-findings.md) is promoted there;
the questions affecting the spec set are summarized in each doc's Open
Questions section.
References
- Phase 0 research:
docs/research/phase-0-findings.md(OQ ledger),docs/research/poc-summary.md(UDP POC),docs/research/reverse-poc-summary.md(reverse-flow POC),docs/research/ssh-socks5-survey.md(SSH/SOCKS5/udpgw prior art) - Upstream: alkcall ADR-047 (openable ALPNs are operations), ADR-049
(establishment phase + amendment 2 plan payload), ADR-050
(
pump_bidi), ADR-022 §2 (both-sides serving), ADR-047 §5 (connection-owner allocation), ledger CF-005/CF-006 (identity seam); alknet ADR-078 (two-pump contract), ADR-071/093 (channels wire format); alkcall ADR-042 (hub relay) - Upstream reviews/ledger (the spec cites these IDs):
/workspace/@alkdev/alkcall/docs/reviews/007-establishment-follow-ups-review.md(R-01 = theEstablishmentplan payload, R-02 = theOpenHandlerlifetime contract, R-03 =pump_bidi) and/workspace/@alkdev/alkcall/docs/reviews/consumer-findings-ledger.md(CF-005/CF-006 = the identity seam, resolved in 0.7.0) - Sibling precedent: alktty (
/workspace/@alkdev/alktty) — the producer/consumer-on-channels shape, wasm-clean default, feature-gated local backend, BAST convention - POC code:
/workspace/alktunnels-udp-poc(forward),/workspace/alktunnels-reverse-poc(reverse)