- Rewrote em dash prose across the whole tree outside docs/reviews/ (the historical reviews stay verbatim, matching the alktunnels and alktty precedent): src doc comments and inline comments (587), docs/architecture (319), docs/research + sdd_process (484), tests (361), tasks (899), fuzz (28), README/CHANGELOG/Cargo.toml (77), AGENTS.md (85), and the .opencode/agents prompts (109) - Fenced content follows the precedent: comments, ASCII-diagram label separators, and template placeholders rewritten; wire data, JSON/BAST documents, byte diagrams, and transcripts survive verbatim; assert, expect, panic, error-display, and format message literals rewritten as prose; no code, fixture, or test data change - src/rfc1928/LICENSE: the two dashes in alksocks' own provenance header rewritten; the MIT legal text untouched - AGENTS.md adds Project Convention 18: no em dashes in prose; varied restructure, no spaced-hyphen substitutes, fenced prose rule, en dash numeric ranges exempt, docs/reviews/ exempt from the greps - tasks/*.md frontmatter: the name values rewritten by the sweep are now quoted (a raw colon inside an unquoted YAML scalar parsed as null); taskgraph validate reports 37 tasks, no issues Verification: cargo test; cargo clippy --all-targets -D warnings; cargo fmt --check; cargo doc --no-deps; fuzz corpus replay (cargo test --manifest-path fuzz/shared/Cargo.toml); wasm check and clippy for wasm32-unknown-unknown with -D warnings; em dash grep over the repo returns matches only in docs/reviews/ and the bast.md BAST JSON data fence
4.1 KiB
ADR-004: The Dial-Callback Shape: Function, not Trait, at Three Seams
Status
Accepted (2026-09-20, Phase 1; shape resolved empirically, with POC #1 (2026-09-13), POC #2 (2026-09-14), POC #5 (2026-09-15))
Context
The SOCKS5 protocol must be substrate-agnostic (AGENTS.md convention 7): the far side of a session may be a kernel socket, an alktunnels channel, or any other byte/datagram source. The question is the inversion point for the three I/O planes a SOCKS5 server touches: the CONNECT dial, the ASSOCIATE datagram egress, and the BIND accept. alktunnels resolved the same question for its establisher with the no-trait finding (OQ-TN-05 → alktunnels ADR-004): "produce boxed halves for a resource" is a function, not a trait; two real implementations existed as callbacks, and the trait added nothing.
The POCs extended that finding to all three SOCKS5 seams:
- CONNECT: the dial cannot live in the establisher; the target
is unknown at open time (it arrives in-stream at command read).
The injected
DialFn(target) -> TargetHandle {read, write}closure is called at the command-read interception point (poc-connect-wasm-findings.md§Structural findings). Per-target refusal is an RFC reply code; session-level refusal stays channels-level. - ASSOCIATE: the
EgressFactory, called once per association; the datagram stage owns the egress; stage exit drops it (poc-udp-associate-findings.md§The per-association egress instance). - BIND: the
BindAcceptFactory, one instance per session; its future owns the listener/tunnel and is dropped by the quiet wait'sselect!on the control-stream branch (the client-gone teardown;poc-bind-findings.md§The quiet wait is select!-single-shot).
Decision
- No dialer/egress/accept trait. All three seams are
function-shaped callbacks injected at registration/assembly:
DialFn(target) -> TargetHandle(boxed halves,+ Sync, satisfying theChannelPlanpayload bound; the bound binds handle/plan payloads downstream; the SOCKS5 establisher itself carries no plan,Establishment::default())EgressFactory() -> impl Egress(per-association instance;next_replyreadiness contract:Pendingwhen nothing is ready)BindAcceptFactory(per-session; the future owns its resources end-to-end, the ownership-rides-the-handle lesson)
- Ownership rides the handle structurally. Plan/handle payloads
own their channel sessions and socket halves inside the payload
(the third witness of the teardown-at-birth pattern: POC #2's
egress table, alktunnels ADR-005, POC #5's
BindTargetHandle). The compiler should enforce it: no_bindings of owning values. - The trait re-evaluation threshold is the same as alktunnels ADR-004's: revisit if three real implementations exist as trait impls in practice. Evidence so far: local-socket and composed providers are callbacks; the no-trait hunch is evidence-backed at all three seams.
Consequences
- The protocol layer never names a substrate type. Substrate-specific providers live in feature-gated backend modules and are wired at the assembly layer (see producer.md §Wiring and the module map in overview.md).
- The composed providers (alktunnels direct-op egress, bind-first listen accept) are assembly-layer compositions, not crate dependencies of the protocol layer; the protocol crate depends on alkcall only (see overview.md §Dependencies; the composed-provider helpers that reference alktunnels types live behind the composition feature, ADR-009).
- The seams' contracts (readiness, ownership, refusal mapping) are load-bearing API surface, pinned by the POC findings and re-pinned by the crate's test suite.
References
- OQ-SK-01 (the dial policy, the A/B/C options; this ADR closes the dialer-trait-vs-callback half), OQ-SK-03 (the egress seam), OQ-SK-08 (the accept seam)
- POC #1/#2/#5 findings (the three seams' empirical records)
- alktunnels ADR-004 (the no-trait precedent), alknet ADR-078 / alkcall ADR-050 (the two-pump contract the handles feed)