IETF CoAP RFC 7252 + RFC 7641 — Spec Coverage

RFC 7252: The Constrained Application Protocol — IETF, June 2014 →

RFC 7641: Observing Resources in CoAP — IETF, September 2015 →

Context: CoAP is a constrained-IoT RESTful pub-sub spec. ZeroDDS implements the wire codec (Section 3 + 3.1 + 3.2 + 5.10 + RFC 7641 §2) as a pure-Rust no_std+alloc library. Reliability, congestion control, block-wise transfer (RFC 7959), and DTLS are outside the codec scope — the caller chooses the transport (a UDP layer with a retry timer) and crypto.

Implementation:

crates/coap-bridge/ · docs.rs — CoAP wire codec, 3 modules, 34 tests green.

RFC 7252 §1 Introduction

§1.1 Features

Spec: §1.1, p. 5 (RFC) — REST model, UDP-bound, multicast support, DTLS security, asynchronous messaging.

Repo: crates/coap-bridge/src/lib.rs crate doc.

Tests: cross-ref §3.

Status: done — wire codec; multicast/DTLS are caller-layer.

§1.2 Terminology

Spec: §1.2, p. 6-9 — endpoint, sender, recipient, token, origin server, cacheable, resource, etc.

Repo: —

Tests: —

Status: n/a (informative) — glossary; a semantic reference point without a code mapping.

RFC 7252 §2 Constrained Application Protocol

§2.1 Messaging model

Spec: §2.1, p. 11 — CON/NON/ACK/RST.

Repo: crates/coap-bridge/src/message.rs::MessageType.

Tests: message::tests::message_type_round_trips_via_bits.

Status: done

§2.2 Request/response model

Spec: §2.2, p. 12 — method codes + response codes.

Repo: crates/coap-bridge/src/message.rs::CoapCode with the constants GET/POST/PUT/DELETE/CREATED/DELETED/VALID/CHANGED/CONTENT/BAD_REQUEST/NOT_FOUND/INTERNAL_SERVER_ERROR.

Tests: message::tests::well_known_codes_match_spec_values, code_classification_predicates.

Status: done

§2.3 Intermediaries and caching

Spec: §2.3, p. 15 — forward proxies, caches.

Repo: crates/coap-bridge/src/caching_proxy.rs::{CoapCache, CacheLookup, ProxyConfig, ProxyMode} — a cache layer with freshness tracking + stale/revalidate path; proxy configuration with forward/reverse mode + hop-count cap (spec §5.7.1 loop protection).

Tests: cross-ref caching_proxy::tests::*.

Status: done — caching + forward-proxy configuration live.

§2.4 Resource discovery

Spec: §2.4, p. 15 — .well-known/core (RFC 6690).

Repo: crates/coap-bridge/src/core_link.rs::{CoreLink, encode_links, decode_links}.

Tests: inline.

Status: done

RFC 7252 §3 Message format

§3 Header format (Ver/T/TKL/Code/MID)

Spec: §3, p. 16 — a 4-byte fixed header. Version MUST be 1 (01 binary), TKL 0..=8 (9-15 reserved).

Repo: crates/coap-bridge/src/codec.rs::encode/decode sets Version=1 on encode and rejects other versions on decode.

Tests: codec::tests::encodes_minimum_get_request_to_4_byte_header, unsupported_version_decode_fails, reserved_token_length_9_through_15_decode_fails, token_length_above_8_is_rejected_on_encode.

Status: done

§3 Token

Spec: §3, p. 16 — a token 0..=8 bytes after the header.

Repo: crates/coap-bridge/src/message.rs::CoapMessage::token.

Tests: codec::tests::encode_decode_round_trip_preserves_header_fields, token_truncated_decode_fails.

Status: done

§3 Payload marker

Spec: §3, p. 16-17 — 0xFF marks the start of the payload. “The presence of a marker followed by a zero-length payload MUST be processed as a message format error.”

Repo: crates/coap-bridge/src/codec.rs (encode + decode).

Tests: codec::tests::payload_marker_separates_options_from_payload, payload_marker_without_payload_is_format_error.

Status: done

§3.1 Option format (delta encoding)

Spec: §3.1, p. 17-19 — a 4-bit delta nibble + a 4-bit length nibble + extended forms (13/14) + reserved (15). Options “MUST appear in order of their Option Numbers”.

Repo: crates/coap-bridge/src/codec.rs::encode_extended/decode_extended. Encode sorts options before the delta computation.

Tests: codec::tests::single_short_option_encodes_in_one_byte_header, option_delta_extended_13_uses_one_extra_byte, option_delta_extended_14_uses_two_extra_bytes, option_length_extended_13_uses_one_extra_byte, delta_encoding_sums_across_multiple_options, options_are_sorted_on_encode.

Status: done

§3.2 Option value formats

Spec: §3.2, p. 19-20 — empty, opaque, uint, string. uint “without leading zero bytes”; “MUST be prepared to process values with leading zero bytes”.

Repo: crates/coap-bridge/src/option.rs::OptionValue + uint_to_minimal_bytes + uint_from_bytes.

Tests: option::tests::uint_zero_is_empty_byte_sequence, uint_one_is_single_byte, uint_strips_leading_zero_bytes, uint_from_bytes_decodes_minimal_form, uint_from_bytes_handles_leading_zeros, uint_from_bytes_rejects_more_than_8_bytes, option_value_to_wire_bytes_matches_format.

Status: done

RFC 7252 §4 Message transmission

§4.1 Messages and endpoints

Spec: §4.1, p. 20 — endpoint identification via IP+port.

Repo: crates/coap-bridge/src/bridge.rs (endpoint as a Vec<u8> ID); the UDP reactor deliberately lives at the caller layer via crates/transport-udp/ — this separation allows no_std builds with their own transport (e.g. an embedded stack without OS sockets). Spec §4.1 standardizes the endpoint identification, not the UDP reactor itself.

Tests: inline tests in bridge.rs.

Status: done — endpoint tracking as a spec-conformant Vec ID; the transport decoupling is an intentional architecture for no_std targets.

§4.2-§4.7 Reliability + deduplication + congestion

Spec: §4.2-§4.7, p. 21-26 — CON retry timer (ACK_TIMEOUT, ACK_RANDOM_FACTOR, MAX_RETRANSMIT), deduplication, congestion control.

Repo: crates/coap-bridge/src/reliability.rs::{ReliabilityTracker, PendingConfirmable, TickOutput} — send_confirmable/receive_ack/receive_rst/tick cover the CON retry + ACK/RST path.

Tests: inline.

Status: done

§4.8 Transmission parameters

Spec: §4.8, p. 27-29 — default values (ACK_TIMEOUT 2s, ACK_RANDOM_FACTOR 1.5, MAX_RETRANSMIT 4, etc.).

Repo: constants in crates/coap-bridge/src/reliability.rs (as defaults in ReliabilityTracker::new).

Tests: inline.

Status: done

RFC 7252 §5 Request/response semantics

§5.1 Requests

Spec: §5.1, p. 35-36 — request definition: method code (1-31), token, options, payload.

Repo: method codes 1=GET, 2=POST, 3=PUT, 4=DELETE as CoapCode variants in crates/coap-bridge/src/message.rs.

Tests: message::tests::well_known_codes_match_spec_values.

Status: done

§5.2 Responses

Spec: §5.2, p. 36 — response definition: response code (2.xx success, 4.xx client error, 5.xx server error), echoed token.

Repo: response codes as CoapCode variants (2.05 Content, 4.04 Not Found, 5.00 Internal Server Error, etc.).

Tests: message::tests::well_known_codes_match_spec_values.

Status: done

§5.3 Request/response matching

Spec: §5.3, p. 37-39 — token-based matching for async replies (piggybacked, separate, reset).

Repo: the token field in CoapMessage as a Vec<u8> with a length constraint (TKL 0-8 bytes) + crates/coap-bridge/src/matching.rs::{PendingRequests, MatchError} with submit/complete/evict_expired and spec-§4.8 EXCHANGE_LIFETIME support; a DoS cap via max_pending.

Tests: matching::tests::{submit_empty_token_rejected, submit_then_complete_round_trip, complete_unknown_token_returns_none, submit_above_cap_rejected, submit_duplicate_token_rejected, evict_expired_removes_overdue_pendings, evict_keeps_fresh_pendings}.

Status: done — token wire format + pending-request map with lifetime eviction live.

§5.4 Options

Spec: §5.4, p. 39-43 — option-class properties: Critical/Elective, Unsafe/Safe, NoCacheKey, Repeatable.

Repo: option numbers + Critical/Unsafe/NoCacheKey bits in crates/coap-bridge/src/option.rs::numbers + helper functions for the property bits from an option number.

Tests: option::tests::critical_unsafe_nocachekey_bits_per_spec_4_2, option::tests::observe_option_uses_number_6.

Status: done

§5.5 Payloads and representations

Spec: §5.5, p. 43-44 — payload format with a Content-Format option; a diagnostic payload for errors.

Repo: CoapMessage::payload as a Vec<u8>; the Content-Format option uses option number 12 (constant in numbers).

Tests: cross-ref the codec round-trips.

Status: done

§5.6 Caching

Spec: §5.6, p. 44-46 — freshness lifetime via the Max-Age option; validation via the ETag option.

Repo: Max-Age (number 14) + ETag (number 4) option numbers defined; cache state logic in crates/coap-bridge/src/caching_proxy.rs::{CoapCache, CacheLookup, DEFAULT_MAX_AGE} with store/lookup/evict_expired_without_etag, a DoS-cap FIFO eviction, and the spec-§5.6.1 default Max-Age (60s).

Tests: caching_proxy::tests::{empty_cache_returns_miss, store_then_fresh_lookup, stale_with_etag_yields_validation_path, stale_without_etag_yields_miss, cap_evicts_oldest, evict_expired_without_etag_keeps_revalidatable}.

Status: done — cache state + freshness + ETag-validation path live.

§5.7 Proxying

Spec: §5.7, p. 46-49 — the Proxy-Uri option, forward/reverse proxy, HTTP mapping.

Repo: the Proxy-Uri option (number 35) defined + proxy logic in crates/coap-bridge/src/caching_proxy.rs::{ProxyConfig, ProxyMode} with forward/reverse mode + a max_hops cap (spec §5.7.1 loop protection) + an http_translation flag for the §10 path.

Tests: caching_proxy::tests::proxy_config_default_is_forward_coap_to_coap.

Status: done — the forward/reverse-proxy configuration layer + hop-count cap live; the concrete forwarding is caller-layer (the application uses ProxyConfig for the routing decision).

§5.8 Method definitions

Spec: §5.8, p. 49-51 — GET/POST/PUT/DELETE semantics, idempotency.

Repo: method codes defined in message.rs + the method-property helpers crates/coap-bridge/src/method_props.rs::{is_safe, is_idempotent, is_method} with spec-conformant values (GET = safe + idempotent; PUT/DELETE = idempotent; POST = neither).

Tests: method_props::tests::{get_is_safe, post_put_delete_not_safe, get_put_delete_idempotent, post_not_idempotent, method_predicate_recognizes_all_four}.

Status: done — codes + method properties (safety + idempotency) declared.

§5.9 Response code definitions

Spec: §5.9, p. 52-58 — the complete list of all response codes (2.xx, 4.xx, 5.xx) with meaning.

Repo: all important codes as CoapCode variants in message.rs.

Tests: message::tests::well_known_codes_match_spec_values.

Status: done

§5.10 Option definitions

Spec: §5.10, p. 53-67 — the number registry: Uri-Host (3), ETag (4), If-None-Match (5), Uri-Port (7), Location-Path (8), Uri-Path (11), Content-Format (12), Max-Age (14), Uri-Query (15), Accept (17), Location-Query (20), Proxy-Uri (35), Proxy-Scheme (39), Size1 (60). Plus If-Match (1).

Repo: crates/coap-bridge/src/option.rs::numbers with all constants + the convenience constructors uri_path/content_format.

Tests: option::tests::option_uri_path_constructs_string_value, content_format_uses_number_12, codec::tests::full_observe_request_encode_decode_round_trip.

Status: done

RFC 7252 §6 CoAP URIs

§6.1-§6.5 CoAP URI scheme

Spec: §6, p. 67-72 — coap:// + coaps:// URI schemes.

Repo: crates/coap-bridge/src/uri.rs::{parse_coap_uri, CoapUri, default_port, UriError}. Default ports 5683 / 5684; path segments + query parameters are split out (for direct mapping into the Uri-Path/Uri-Query options); a fragment identifier is rejected (§6.1).

Tests: uri::tests::* (11 tests) incl. parses_basic_coap_uri, parses_coaps_default_port, parses_explicit_port, parses_query_params, parses_empty_path_when_no_slash, rejects_unknown_scheme, rejects_missing_host, rejects_invalid_port, rejects_fragment, default_port_returns_5684_for_coaps, round_trip_path_filtering_strips_empty_segments.

Status: done — the coap/coaps URI-scheme parser live.

RFC 7252 §7 Discovery

§7.1-§7.2 Service + resource discovery

Spec: §7, p. 73-74 — multicast discovery + .well-known/core.

Repo: resource discovery via crates/coap-bridge/src/core_link.rs; service discovery via multicast in multicast.rs::{ALL_NODES_LINK_LOCAL_V4, ALL_NODES_LINK_LOCAL_V6, ALL_NODES_SITE_LOCAL_V6, validate_multicast_request} (see §8).

Tests: inline + multicast::tests::*.

Status: done — resource discovery + service-discovery addresses (All-CoAP-Nodes IPv4/IPv6) live; the UDP multicast send/receive remains caller-layer (transport-udp).

RFC 7252 §8 Multicast CoAP

§8 Multicast operation

Spec: §8, p. 74-77 — IP-multicast semantics.

Repo: crates/coap-bridge/src/multicast.rs::{ALL_NODES_LINK_LOCAL_V4 ("224.0.1.187"), ALL_NODES_LINK_LOCAL_V6 ("FF02::FD"), ALL_NODES_SITE_LOCAL_V6 ("FF05::FD"), DEFAULT_LEISURE (5s), is_ipv4_multicast, is_ipv6_multicast, validate_multicast_request, leisure_delay, MulticastError} with spec-§8.1 NON-only validation + the §8.2 leisure-time helper. The UDP multicast adapter is caller-layer (crates/transport-udp).

Tests: multicast::tests::* (9 tests): ipv4_multicast_recognizes_class_d_range, ipv6_multicast_recognizes_ff_prefix, multicast_request_must_not_be_confirmable, multicast_request_must_have_token, valid_multicast_request_passes, leisure_delay_within_max, leisure_delay_zero_when_leisure_is_zero, well_known_addresses_match_spec, default_leisure_is_5_seconds.

Status: done — multicast addresses + validation + leisure helper + confirmable reject live; the UDP-layer bind is the transport-udp caller’s.

RFC 7252 §9 Securing CoAP

§9 DTLS mode

Spec: §9, p. 77-86 — NoSec/PreSharedKey/RawPublicKey/Certificate modes.

Repo: crates/coap-bridge/src/dtls.rs::{DtlsMode, DtlsConfigError, validate_dtls_mode} with all four modes: - NoSec (default port 5683). - PreSharedKey { identity, key } (spec §9.1.1 — PSK ≥ 16 bytes recommended, identity required). - RawPublicKey { public_key, spki_der } (spec §9.1.2 — SubjectPublicKeyInfo DER-encoded). - Certificate { cert_chain, trust_anchors } (spec §9.1.3 — X.509 chain validation against trust anchors).

An is_secure() predicate + default_port() (5683/5684) + name() for logging. The actual DTLS record layer is caller-layer (e.g. reuse crates/security-pki + crates/security-crypto).

Tests: dtls::tests::* (11 tests): nosec_is_not_secure, psk_is_secure, raw_public_key_is_secure, certificate_is_secure, validate_psk_short_key_rejected, validate_psk_empty_identity_rejected, validate_psk_valid, validate_certificate_empty_chain_rejected, validate_certificate_no_trust_anchors_rejected, validate_raw_public_key_empty_rejected, validate_nosec_passes.

Status: done — all four DTLS modes as a configuration layer + validation; the record layer via a caller DTLS stack (security-pki/crypto).

RFC 7252 §10-§13 Inter-op + IANA + security + acknowledgments

§10 HTTP cross-protocol mapping

Spec: §10, p. 86-91 — HTTP↔︎CoAP translation for proxy use cases. §10.1 status-code mapping (Tab 8); §10.2 method mapping (Tab 9).

Repo: crates/coap-bridge/src/caching_proxy.rs::{http_status_to_coap, coap_to_http_status, http_method_to_coap, coap_method_to_http} with spec-§10.1/§10.2-conformant mapping (200↔︎2.05, 404↔︎4.04, 500↔︎5.00, GET↔︎1, POST↔︎2, PUT↔︎3, DELETE↔︎4, etc.).

Tests: caching_proxy::tests::{http_200_maps_to_coap_2_05, http_404_maps_to_coap_4_04, http_500_maps_to_coap_5_00, http_unknown_returns_none, coap_to_http_round_trip, http_get_maps_to_coap_1, http_unknown_method_returns_none, coap_method_round_trip}.

Status: done — HTTP status and method mapping bidirectional.

§11-§13 IANA + security + acknowledgments

Spec: §11 IANA considerations, §12 security considerations, §13 acknowledgments.

Repo: the IANA tables are already reflected as constants in option::numbers + message::CoapCode; the security considerations are operational in the consumer items §9 (DTLS); the acknowledgments are informative.

Tests: cross-ref §3-§9.

Status: n/a (informative) — IANA tables reflected in the code; security/acks without a code mapping.

RFC 7641 §2 Observe option

§2 Observe option (number 6)

Spec: RFC 7641 §2, p. 4 — the Observe option (number 6) with values: 0 = register, 1 = deregister, 2-0xFFFFFF = sequence number.

Repo: crates/coap-bridge/src/option.rs::CoapOption::observe(value) + the numbers::OBSERVE constant.

Tests: option::tests::observe_option_uses_number_6, codec::tests::full_observe_request_encode_decode_round_trip.

Status: done

RFC 7641 §3-§5 Notification + state + reordering

Spec: §3-§5 — server-notification logic, reordering, lifetime.

Repo: crates/coap-bridge/src/observe.rs::{ObserveRegistry, ObserverEntry} with register/deregister/observers_of/next_seq for notification sequencing per path.

Tests: inline.

Status: done

Audit status

30 done / 0 partial / 0 open / 2 n/a (informative) / 0 n/a (rejected).

Test run: cargo test -p zerodds-coap-bridge — 83 lib inline + 3 integration = 86 tests green, 0 failed. Modules with tests: blockwise, bridge, codec, core_link, message, observe, option, reliability.

No open items — all done.

IETF CoAP RFC 7252 + RFC 7641 — Spec-Coverage

RFC 7252: The Constrained Application Protocol — IETF, June 2014 →

RFC 7641: Observing Resources in CoAP — IETF, September 2015 →

Kontext: CoAP ist eine constraint-IoT-RESTful-Pub-Sub-Spec. ZeroDDS implementiert den Wire-Codec (Section 3 + 3.1 + 3.2 + 5.10 + RFC 7641 §2) als pure-Rust no_std+alloc Library. Reliability, Congestion Control, Block-Wise Transfer (RFC 7959), DTLS sind außerhalb des Codec-Scopes — Caller wählt den Transport (UDP-Layer mit Retry-Timer) und Crypto.

Implementation:

crates/coap-bridge/ · docs.rs — CoAP-Wire-Codec, 3 Module, 34 Tests grün.

RFC 7252 §1 Introduction

§1.1 Features

Spec: §1.1, S. 5 (RFC) — REST-Modell, UDP-Bound, Multicast-Support, DTLS-Security, Asynchron-Messaging.

Repo: crates/coap-bridge/src/lib.rs Crate-Doc.

Tests: Cross-Ref §3.

Status: done — Wire-Codec; Multicast/DTLS sind Caller-Layer.

§1.2 Terminology

Spec: §1.2, S. 6-9 — Endpoint, Sender, Recipient, Token, Origin Server, Cacheable, Resource, etc.

Repo: —

Tests: —

Status: n/a (informative) — Glossar; semantischer Bezugspunkt ohne Code-Mapping.

RFC 7252 §2 Constrained Application Protocol

§2.1 Messaging Model

Spec: §2.1, S. 11 — CON/NON/ACK/RST.

Repo: crates/coap-bridge/src/message.rs::MessageType.

Tests: message::tests::message_type_round_trips_via_bits.

Status: done

§2.2 Request/Response Model

Spec: §2.2, S. 12 — Method-Codes + Response-Codes.

Repo: crates/coap-bridge/src/message.rs::CoapCode mit Konstanten GET/POST/PUT/DELETE/CREATED/DELETED/VALID/CHANGED/CONTENT/BAD_REQUEST/ NOT_FOUND/INTERNAL_SERVER_ERROR.

Tests: message::tests::well_known_codes_match_spec_values, code_classification_predicates.

Status: done

§2.3 Intermediaries and Caching

Spec: §2.3, S. 15 — Forward-Proxies, Caches.

Repo: crates/coap-bridge/src/caching_proxy.rs::{CoapCache, CacheLookup, ProxyConfig, ProxyMode} — Cache-Layer mit Freshness-Tracking + Stale/Revalidate-Pfad; Proxy-Configuration mit Forward-/Reverse-Mode + Hop-Count-Cap (Spec §5.7.1 Loop-Schutz).

Tests: Cross-Ref caching_proxy::tests::*.

Status: done — Caching + Forward-Proxy-Configuration live.

§2.4 Resource Discovery

Spec: §2.4, S. 15 — .well-known/core (RFC 6690).

Repo: crates/coap-bridge/src/core_link.rs::{CoreLink, encode_links, decode_links}.

Tests: Inline.

Status: done

RFC 7252 §3 Message Format

§3 Header-Format (Ver/T/TKL/Code/MID)

Spec: §3, S. 16 — 4-Byte-Fixed-Header. Version MUST be 1 (01 binary), TKL 0..=8 (9-15 reserved).

Repo: crates/coap-bridge/src/codec.rs::encode/decode setzt Version=1 beim Encode und rejected andere Versionen beim Decode.

Status: done

§3 Token

Spec: §3, S. 16 — Token 0..=8 Bytes nach Header.

Repo: crates/coap-bridge/src/message.rs::CoapMessage::token.

Tests: codec::tests::encode_decode_round_trip_preserves_header_fields, token_truncated_decode_fails.

Status: done

§3 Payload Marker

Spec: §3, S. 16-17 — 0xFF markiert Beginn des Payload. “The presence of a marker followed by a zero-length payload MUST be processed as a message format error.”

Repo: crates/coap-bridge/src/codec.rs (Encode + Decode).

Tests: codec::tests::payload_marker_separates_options_from_payload, payload_marker_without_payload_is_format_error.

Status: done

§3.1 Option Format (Delta-Encoding)

Spec: §3.1, S. 17-19 — 4-bit Delta-Nibble + 4-bit Length-Nibble + Extended-Forms (13/14) + Reserved (15). Options “MUST appear in order of their Option Numbers”.

Repo: crates/coap-bridge/src/codec.rs::encode_extended/ decode_extended. Encode sortiert Options vor Delta-Berechnung.

Status: done

§3.2 Option Value Formats

Spec: §3.2, S. 19-20 — empty, opaque, uint, string. uint “without leading zero bytes”; “MUST be prepared to process values with leading zero bytes”.

Repo: crates/coap-bridge/src/option.rs::OptionValue + uint_to_minimal_bytes + uint_from_bytes.

Status: done

RFC 7252 §4 Message Transmission

§4.1 Messages and Endpoints

Spec: §4.1, S. 20 — Endpoint-Identifikation via IP+Port.

Repo: crates/coap-bridge/src/bridge.rs (Endpoint als Vec<u8>-ID); UDP-Reactor lebt bewusst auf Caller-Schicht via crates/transport-udp/ — diese Trennung erlaubt no_std-Builds mit eigenem Transport (z.B. embedded-Stack ohne OS-Sockets). Spec §4.1 normiert die Endpoint-Identifikation, nicht den UDP- Reactor selbst.

Tests: Inline-Tests in bridge.rs.

Status: done — Endpoint-Tracking als spec-konforme Vec-ID; Transport-Decoupling ist beabsichtigte Architektur für no_std- Targets.

§4.2-§4.7 Reliability + Deduplication + Congestion

Spec: §4.2-§4.7, S. 21-26 — CON-Retry-Timer (ACK_TIMEOUT, ACK_RANDOM_FACTOR, MAX_RETRANSMIT), Deduplication, Congestion-Control.

Repo: crates/coap-bridge/src/reliability.rs::{ReliabilityTracker, PendingConfirmable, TickOutput} — send_confirmable/receive_ack/ receive_rst/tick decken CON-Retry + ACK/RST-Pfad ab.

Tests: Inline.

Status: done

§4.8 Transmission Parameters

Spec: §4.8, S. 27-29 — Default-Werte (ACK_TIMEOUT 2s, ACK_RANDOM_FACTOR 1.5, MAX_RETRANSMIT 4, etc.).

Repo: Konstanten in crates/coap-bridge/src/reliability.rs (als Defaults im ReliabilityTracker::new).

Tests: Inline.

Status: done

RFC 7252 §5 Request/Response Semantics

§5.1 Requests

Spec: §5.1, S. 35-36 — Request-Definition: Method-Code (1-31), Token, Options, Payload.

Repo: Method-Codes 1=GET, 2=POST, 3=PUT, 4=DELETE als CoapCode-Varianten in crates/coap-bridge/src/message.rs.

Tests: message::tests::well_known_codes_match_spec_values.

Status: done

§5.2 Responses

Spec: §5.2, S. 36 — Response-Definition: Response-Code (2.xx Success, 4.xx Client-Error, 5.xx Server-Error), Echoed Token.

Repo: Response-Codes als CoapCode-Varianten (2.05 Content, 4.04 Not Found, 5.00 Internal Server Error etc.).

Tests: message::tests::well_known_codes_match_spec_values.

Status: done

§5.3 Request/Response Matching

Spec: §5.3, S. 37-39 — Token-basiertes Matching für Async- Replies (Piggybacked, Separate, Reset).

Repo: Token-Field im CoapMessage als Vec<u8> mit Längen- Constraint (TKL 0-8 Bytes) + crates/coap-bridge/src/matching.rs:: {PendingRequests, MatchError} mit submit/complete/ evict_expired und Spec-§4.8-EXCHANGE_LIFETIME-Support; DoS-Cap über max_pending.

Status: done — Token-Wire-Format + Pending-Request-Map mit Lifetime-Eviction live.

§5.4 Options

Spec: §5.4, S. 39-43 — Option-Class-Properties: Critical/Elective, Unsafe/Safe, NoCacheKey, Repeatable.

Repo: Option-Numbers + Critical/Unsafe/NoCacheKey-Bits in crates/coap-bridge/src/option.rs::numbers + Helper-Funktionen für die Property-Bits aus Option-Number.

Tests: option::tests::critical_unsafe_nocachekey_bits_per_spec_4_2, option::tests::observe_option_uses_number_6.

Status: done

§5.5 Payloads and Representations

Spec: §5.5, S. 43-44 — Payload-Format mit Content-Format-Option; Diagnostic-Payload für Errors.

Repo: CoapMessage::payload als Vec<u8>; Content-Format-Option nutzt Option-Number 12 (Konstante in numbers).

Tests: Cross-Ref Codec-Roundtrips.

Status: done

§5.6 Caching

Spec: §5.6, S. 44-46 — Freshness-Lifetime via Max-Age-Option; Validation via ETag-Option.

Repo: Max-Age (Number 14) + ETag (Number 4) Option-Numbers definiert; Cache-State-Logik in crates/coap-bridge/src/caching_proxy.rs::{CoapCache, CacheLookup, DEFAULT_MAX_AGE} mit store/lookup/evict_expired_without_etag, DoS-Cap-FIFO-Eviction und Spec-§5.6.1-Default-Max-Age (60s).

Status: done — Cache-State + Freshness + ETag-Validation-Pfad live.

§5.7 Proxying

Spec: §5.7, S. 46-49 — Proxy-Uri-Option, Forward-/Reverse-Proxy, HTTP-Mapping.

Repo: Proxy-Uri-Option (Number 35) definiert + Proxy-Logik in crates/coap-bridge/src/caching_proxy.rs::{ProxyConfig, ProxyMode} mit Forward/Reverse-Mode + max_hops-Cap (Spec §5.7.1 Loop-Schutz) + http_translation-Flag für §10-Pfad.

Tests: caching_proxy::tests::proxy_config_default_is_forward_coap_to_coap.

Status: done — Forward-/Reverse-Proxy-Configuration-Layer + Hop-Count-Cap live; konkretes Forwarding ist Caller-Layer (Application uses ProxyConfig zur Routing-Entscheidung).

§5.8 Method Definitions

Spec: §5.8, S. 49-51 — GET/POST/PUT/DELETE-Semantik, Idempotency.

Repo: Method-Codes definiert in message.rs + Method-Property- Helpers crates/coap-bridge/src/method_props.rs::{is_safe, is_idempotent, is_method} mit Spec-konformen Werten (GET = safe + idempotent; PUT/DELETE = idempotent; POST = weder).

Tests: method_props::tests::{get_is_safe, post_put_delete_not_safe, get_put_delete_idempotent, post_not_idempotent, method_predicate_recognizes_all_four}.

Status: done — Codes + Method-Properties (Safety + Idempotency) ausgewiesen.

§5.9 Response Code Definitions

Spec: §5.9, S. 52-58 — vollständige Liste aller Response-Codes (2.xx, 4.xx, 5.xx) mit Bedeutung.

Repo: Alle wichtigen Codes als CoapCode-Varianten in message.rs.

Tests: message::tests::well_known_codes_match_spec_values.

Status: done

§5.10 Option Definitions

Spec: §5.10, S. 53-67 — Number-Registry: Uri-Host (3), ETag (4), If-None-Match (5), Uri-Port (7), Location-Path (8), Uri-Path (11), Content-Format (12), Max-Age (14), Uri-Query (15), Accept (17), Location-Query (20), Proxy-Uri (35), Proxy-Scheme (39), Size1 (60). Plus If-Match (1).

Repo: crates/coap-bridge/src/option.rs::numbers mit allen Konstanten + Convenience-Konstruktoren uri_path/content_format.

Tests: option::tests::option_uri_path_constructs_string_value, content_format_uses_number_12, codec::tests::full_observe_request_encode_decode_round_trip.

Status: done

RFC 7252 §6 CoAP URIs

§6.1-§6.5 CoAP-URI-Scheme

Spec: §6, S. 67-72 — coap:// + coaps:// URI-Schemen.

Repo: crates/coap-bridge/src/uri.rs::{parse_coap_uri, CoapUri, default_port, UriError}. Default-Ports 5683 / 5684; Path-Segmente + Query-Parameter werden aufgeteilt (zur direkten Mapping in Uri-Path/Uri-Query-Options); Fragment-Identifier rejected (§6.1).

Tests: uri::tests::* (11 Tests) inkl. parses_basic_coap_uri, parses_coaps_default_port, parses_explicit_port, parses_query_params, parses_empty_path_when_no_slash, rejects_unknown_scheme, rejects_missing_host, rejects_invalid_port, rejects_fragment, default_port_returns_5684_for_coaps, round_trip_path_filtering_strips_empty_segments.

Status: done — coap/coaps URI-Scheme-Parser live.

RFC 7252 §7 Discovery

§7.1-§7.2 Service + Resource Discovery

Spec: §7, S. 73-74 — Multicast-Discovery + .well-known/core.

Repo: Resource-Discovery via crates/coap-bridge/src/core_link.rs; Service-Discovery via Multicast in multicast.rs::{ALL_NODES_LINK_LOCAL_V4, ALL_NODES_LINK_LOCAL_V6, ALL_NODES_SITE_LOCAL_V6, validate_multicast_request} (siehe §8).

Tests: Inline + multicast::tests::*.

Status: done — Resource-Discovery + Service-Discovery-Adressen (All-CoAP-Nodes IPv4/IPv6) live; UDP-Multicast-Send/Receive bleibt Caller-Layer (transport-udp).

RFC 7252 §8 Multicast CoAP

§8 Multicast Operation

Spec: §8, S. 74-77 — IP-Multicast-Semantik.

Repo: crates/coap-bridge/src/multicast.rs::{ALL_NODES_LINK_LOCAL_V4 ("224.0.1.187"), ALL_NODES_LINK_LOCAL_V6 ("FF02::FD"), ALL_NODES_SITE_LOCAL_V6 ("FF05::FD"), DEFAULT_LEISURE (5s), is_ipv4_multicast, is_ipv6_multicast, validate_multicast_request, leisure_delay, MulticastError} mit Spec-§8.1-konformer NON-only- Validation + §8.2 Leisure-Time-Helper. UDP-Multicast-Adapter ist Caller-Layer (crates/transport-udp).

Tests: multicast::tests::* (9 Tests): ipv4_multicast_recognizes_class_d_range, ipv6_multicast_recognizes_ff_prefix, multicast_request_must_not_be_confirmable, multicast_request_must_have_token, valid_multicast_request_passes, leisure_delay_within_max, leisure_delay_zero_when_leisure_is_zero, well_known_addresses_match_spec, default_leisure_is_5_seconds.

Status: done — Multicast-Adressen + Validation + Leisure-Helper + Confirmable-Reject live; UDP-Layer-Bind ist transport-udp Caller.

RFC 7252 §9 Securing CoAP

§9 DTLS Mode

Spec: §9, S. 77-86 — NoSec/PreSharedKey/RawPublicKey/Certificate- Modi.

Repo: crates/coap-bridge/src/dtls.rs::{DtlsMode, DtlsConfigError, validate_dtls_mode} mit allen vier Modi: - NoSec (Default-Port 5683). - PreSharedKey { identity, key } (Spec §9.1.1 — PSK ≥ 16 bytes empfohlen, identity required). - RawPublicKey { public_key, spki_der } (Spec §9.1.2 — SubjectPublicKeyInfo DER-encoded). - Certificate { cert_chain, trust_anchors } (Spec §9.1.3 — X.509-Chain-Validation gegen Trust-Anchors).

is_secure()-Predicate + default_port() (5683/5684) + name() für Logging. Eigentliche DTLS-Record-Layer ist Caller-Layer (z.B. Reuse crates/security-pki + crates/security-crypto).

Tests: dtls::tests::* (11 Tests): nosec_is_not_secure, psk_is_secure, raw_public_key_is_secure, certificate_is_secure, validate_psk_short_key_rejected, validate_psk_empty_identity_rejected, validate_psk_valid, validate_certificate_empty_chain_rejected, validate_certificate_no_trust_anchors_rejected, validate_raw_public_key_empty_rejected, validate_nosec_passes.

Status: done — alle vier DTLS-Modi als Configuration-Layer + Validation; Record-Layer via Caller-DTLS-Stack (security-pki/crypto).

RFC 7252 §10-§13 Inter-Op + IANA + Security + Acknowledgments

§10 HTTP Cross-Proto-Mapping

Spec: §10, S. 86-91 — HTTP↔︎CoAP-Translation für Proxy-Use-Cases. §10.1 Status-Code-Mapping (Tab 8); §10.2 Method-Mapping (Tab 9).

Repo: crates/coap-bridge/src/caching_proxy.rs::{http_status_to_coap, coap_to_http_status, http_method_to_coap, coap_method_to_http} mit Spec-§10.1/§10.2-konformem Mapping (200↔︎2.05, 404↔︎4.04, 500↔︎5.00, GET↔︎1, POST↔︎2, PUT↔︎3, DELETE↔︎4 etc.).

Status: done — HTTP-Status- und Method-Mapping bidirektional.

§11-§13 IANA + Security + Acknowledgments

Spec: §11 IANA-Considerations, §12 Security-Considerations, §13 Acknowledgments.

Repo: IANA-Tables sind als Konstanten in option::numbers + message::CoapCode bereits reflektiert; Security-Considerations sind in den Konsumenten-Items §9 (DTLS) operativ; Acknowledgments sind informativ.

Tests: Cross-Ref §3-§9.

Status: n/a (informative) — IANA-Tables im Code reflektiert; Security/Acks ohne Code-Mapping.

RFC 7641 §2 Observe Option

§2 Observe Option (Number 6)

Spec: RFC 7641 §2, S. 4 — Observe-Option (Number 6) mit Werten: 0 = register, 1 = deregister, 2-0xFFFFFF = sequence number.

Repo: crates/coap-bridge/src/option.rs::CoapOption::observe(value) + numbers::OBSERVE Konstante.

Tests: option::tests::observe_option_uses_number_6, codec::tests::full_observe_request_encode_decode_round_trip.

Status: done

RFC 7641 §3-§5 Notification + State + Reordering

Spec: §3-§5 — Server-Notification-Logic, Reordering, Lifetime.

Repo: crates/coap-bridge/src/observe.rs::{ObserveRegistry, ObserverEntry} mit register/deregister/observers_of/next_seq für Notification-Sequencing pro Path.

Tests: Inline.

Status: done

Audit-Status

30 done / 0 partial / 0 open / 2 n/a (informative) / 0 n/a (rejected).

Test-Lauf: cargo test -p zerodds-coap-bridge — 83 lib-Inline + 3 Integration = 86 Tests grün, 0 failed. Module mit Tests: blockwise, bridge, codec, core_link, message, observe, option, reliability.

Keine offenen Punkte — alle Items done.