alksocks/tasks/implementation/composed-accept.md

id, name, status, depends_on, scope, risk, impact, level

id	name	status	depends_on	scope	risk	impact	level
implementation/composed-accept	Composed — the bind-first accept (the listener on a listen resource)	pending	implementation/composed-egress	moderate	medium	component	implementation

Description

The composed feature's accept provider (ADR-008's composed variants; ADR-007 variant 2): the BIND accept whose listener lives on an alktunnels 0.2.0 bind-first listen resource (register_tunnel_bindfirst_openable + BindFirstInjections) — per-listener ACL for free, hub-relayable. Vanilla-fidelity with no stand-ins since the graduation (ADR-007): reply#1 advertises the real OS-chosen bound (the open-op reply's bound field, alkcall 0.8.0 reply projection); reply#2 carries the real peer (the forwarded op's peer param).

Deliverables:

1. src/composed/ additions (feature composed) — the composed accept, named per producer.md §Wiring:
   • bindfirst_accept(...) → BindAcceptFactory: the POC #5 composed_bind_accept shape updated to the graduation — the POC's pinned workaround (reply#1 first, the tunnel open rides the accept future; the factory carries an expected bind_addr) is retired (ADR-007 §Consequences). The landed shape: the factory opens the bind-first listen channel (TunnelListener::open — the reply projection surfaces bound), reply#1 advertises the real bound, and the accept future correlates the forwarded sessions (the listen token → the adopted forwarded sessions the assembly correlates; the forwarded op's peer param is reply#2's peer).
   • The correlation shape is the design center (the POC's upstream-ask ledger retired by the graduation): the factory returns BindAccept whose accept future waits for the ONE forwarded session matching the listener's token. The correlation registry is assembly-side bookkeeping (the alktunnels TunnelListener docs: "forwarded sessions arrive as ordinary adopted sessions on the manager; the listener does not own the receipt queue"). The provider owns: the register_tunnel_forwarded_openable serving side (the opener half — the SOCKS5 producer's connection must serve the forwarded op), the token→waiter map, and the per-forwarded pump. Design the wait shape against the landed alkcall 0.8.0 adopt surface (manager.adopt_channel) and record it in Notes.
   • The Sync-bound wrinkle (shared with composed-egress): the accepted halves must be Box<dyn AsyncRead + Send + Sync + Unpin> (BindTargetHandle's payloads); alktunnels' Taken Halves yields Send + Unpin only. The owner-wrapper rides inside the handle payloads (egress.rs's documented posture) — the wrapper owns the adopted channel session so dropping the handle drops everything (the teardown-at-birth discipline, compiler-enforced). This is the load-bearing wrapper: design it once (with composed-egress's needs), pin it with a test.
   • Peer-address fidelity: the forwarded op's peer param is reply#2's real peer (the graduation's win); the wrapper-aware sentinel (0.0.0.0:0) is the in-band default's shape, not this variant's.
   • The establishment bound covers only the open-op round trip (ADR-007): the accept wait lives in the teardown-governed pump phase — the quiet wait's select! drop of the accept future IS the client-gone teardown; the listener (inside the future) closes with it. The forwarded-op correlation must survive a client-gone drop without leaking the listener (the accept future owns it end-to-end — the seam contract).
   • Module doc: names the ADRs (007/008), the graduation's vanilla-fidelity win, the correlation shape, the owner-wrapper.
2. Tests (tests/composed-accept.rs): the full composed BIND story over channels — a bind-first tunnel producer (register_tunnel_bindfirst_openable + injections), the SOCKS5 producer with composed::bindfirst_accept(...), a consumer BIND session: reply#1 carries the real bound, an app server dials the far listener, reply#2 carries the real peer, the pass-through data plane round-trips; the client-gone teardown releases the listener (drop-witness); two concurrent BIND sessions get distinct tokens; a forwarded-open failure is per-accept isolated.

Acceptance Criteria

• cargo test passes; cargo test --all-features passes
• cargo check --features composed --target wasm32-unknown- unknown clean (hard gate)
• cargo clippy --all-targets --all-features -- -D warnings clean; cargo fmt --check clean
• The graduation's shape lands (reply#1 = the real bound; reply#2 = the forwarded op's real peer) — no expected-addr stand-in — pinned by test
• The owner-wrapper rides inside the handle payloads (Sync halves; teardown structural) — pinned by test
• The client-gone teardown releases the listener (the accept future owns it end-to-end) — pinned by drop-witness test
• The forwarded-op serving side + correlation land; per-accept isolation — pinned by tests

References

• docs/architecture/decisions/007-bind-in-base.md (variant 2 + the graduation), 008-provider-defaults.md, 004 (the accept seam's contracts), 006 (the command gate)
• docs/architecture/producer.md §Wiring (composed::bindfirst_accept), §The Three Seams
• POC reference: /workspace/alksocks-bind-poc/src/accept.rs (composed_bind_accept — the superseded-in-shape workaround, the owner-wrapper's first witness)
• Landed surfaces: src/egress.rs (BindAccept/BindTargetHandle — the contracts), alktunnels 0.2.0 (register_tunnel_bindfirst_ openable, BindFirstInjections, TunnelListener, register_tunnel_forwarded_openable, ForwardedHandler)

Notes

To be filled by implementation agent

Summary

To be filled on completion