Module parser 

H2 frame parser (nom-based).

Decodes every RFC 9113 §6 frame type plus RFC 9218 PRIORITY_UPDATE and unknown extension frames; rejects malformed framing with the matching H2Error so the connection can react with GOAWAY / RST_STREAM. Mostly zero-allocation, with bounded Vec<u8> allocations on priority_update and a SETTINGS-list cap (cf. priority_update_frame and the SETTINGS allocation cap test). Frame-size invariants are enforced via ensure_frame_size!.

Structs

Continuation

Continuation frames are handled inline during HEADERS parsing. The wire-level parser does not track connection state (whether the previous frame was HEADERS/PUSH_PROMISE with END_HEADERS=0), so standalone CONTINUATION is rejected at the h2 state-machine layer (handle_header_state): when a CONTINUATION frame header is observed while the state is H2State::Header (i.e. no header block is in progress) we emit GOAWAY(PROTOCOL_ERROR) per RFC 9113 §6.10.

Data

FrameHeader

GoAway

Headers

ParserError

Ping

Priority

PriorityUpdate

RFC 9218 §7.1 PRIORITY_UPDATE frame payload.

PushPromise

PushPromise is always rejected with PROTOCOL_ERROR at the wire layer. Sozu never announces SETTINGS_ENABLE_PUSH=1, and RFC 9113 §8.4 requires that a peer which has not enabled server push treat a received PUSH_PROMISE as a connection error of type PROTOCOL_ERROR. Rejecting in the parser is defence-in-depth: any future refactor of mux/h2.rs that forgets to call handle_push_promise_frame cannot silently accept push traffic. The struct is retained so the outer match in h2.rs still compiles, but push_promise_frame never constructs it.

RstStream

Setting

Settings

StreamDependency

WindowUpdate

Enums

Frame

FrameType

H2Error

ParserErrorKind

PriorityPart

Constants

FLAG_ACK

ACK flag on SETTINGS/PING (§6.5, §6.7)

FLAG_END_HEADERS

END_HEADERS flag — signals last header block fragment (§6.2, §6.10)

FLAG_END_STREAM

END_STREAM flag — signals last frame for this stream (§6.1, §6.2)

FLAG_PADDED

PADDED flag — indicates padding is present (§6.1, §6.2)

FLAG_PRIORITY

PRIORITY flag on HEADERS — stream dependency follows (§6.2)

FRAME_HEADER_SIZE

H2 frame header size in bytes (RFC 9113 §4.1)

GOAWAY_PAYLOAD_SIZE

MAX_SETTINGS_ENTRIES

Maximum SETTINGS entries accepted in a single SETTINGS frame.

PING_PAYLOAD_SIZE

PRIORITY_PAYLOAD_SIZE

PRIORITY_UPDATE_MAX_VALUE

Maximum length of the priority_field_value portion of a PRIORITY_UPDATE frame (RFC 9218 §7.1). The field is a Structured Field Item (RFC 8941): ASCII-only, intended for compact dictionary payloads such as u=3, i. 1024 bytes mirrors nghttp2’s NGHTTP2_MAX_PRIORITY_VALUE_LEN and the upper-bound the h2 Rust crate enforces, an order of magnitude tighter than SETTINGS_MAX_FRAME_SIZE — the attacker is denied a per-frame 16 KiB allocation primitive sized in single TCP segments.

PRIORITY_UPDATE_MIN_PAYLOAD

Minimum payload size for a PRIORITY_UPDATE frame (RFC 9218 §7.1): the 4-byte prioritized stream ID. The priority field value is allowed to be empty (defaults to the RFC 9218 §4 defaults).

RST_STREAM_PAYLOAD_SIZE

SETTINGS_COUNT

Number of settings entries we send in our SETTINGS frame

SETTINGS_ENABLE_CONNECT_PROTOCOL

SETTINGS_ENABLE_PUSH

SETTINGS_ENTRY_SIZE

SETTINGS_HEADER_TABLE_SIZE

SETTINGS_INITIAL_WINDOW_SIZE

SETTINGS_MAX_CONCURRENT_STREAMS

SETTINGS_MAX_FRAME_SIZE

SETTINGS_MAX_HEADER_LIST_SIZE

SETTINGS_NO_RFC7540_PRIORITIES

STREAM_ID_MASK

Mask to extract 31-bit stream ID, clearing the reserved MSB (RFC 9113 §4.1)

WINDOW_UPDATE_PAYLOAD_SIZE

Functions

continuation_frame

data_frame

frame_body

frame_header

goaway_frame

headers_frame

ping_frame

preface

priority_frame

priority_update_frame

RFC 9218 §7.1 PRIORITY_UPDATE frame parser. Payload layout:

push_promise_frame

rst_stream_frame

settings_frame

unknown_frame

Silently consume the payload of a frame whose type byte is not recognised, per RFC 9113 §5.5 (“Implementations MUST ignore and discard frames of unknown type”). Previously covered RFC 9218 PRIORITY_UPDATE (type 0x10); PRIORITY_UPDATE is now parsed through priority_update_frame.

window_update_frame