Module h3 

Available on crate features http-backend and http and std only.

HTTP/3 client/server engine and connection-scoped codecs (RFC 9114, RFC 9204).

This module holds the stateful pieces that sit above the pure wire vocabulary in rama_http_types::proto::h3: the bounded incremental frame reader and the stateful QPACK encoder/decoder with their dynamic tables and blocked-section accounting.

client and server expose Rama requests, responses and the common crate::body::Incoming body. Run their accompanying connection::Driver concurrently to drive control and QPACK streams independently of application bodies. The underlying frame and compression codecs also remain usable synchronously.

Received field lines retain their order, duplicates, values and sensitivity in the common header map; encoders use its ordered iterator. Names must be lowercase on the H3 wire. The shared rama_http_types::proto::h3::PseudoHeaderOrder and rama_http_types::proto::h3::PseudoHeaderSensitivity extensions retain pseudo-field ordering and never-index requirements across forwarding and message edits. Split Cookie lines stay separate in this H3 API, as in H2. Before passing them to a non-H2/H3 context (including a generic server application), coalesce them using rama_http::layer::remove_header::coalesce_cookie_headers; the HTTP/1 version adapter does this automatically.

Ordinary CONNECT and Extended CONNECT (RFC 9220, when connection::Config::extended_connect is set on a server) expose their tunnels through Rama’s upgrade API after a 2xx response. Extended CONNECT tunnels declared with HttpDatagrams (client request, server 2xx response) publish a rama_http::datagram::NativeDatagrams carrier (RFC 9297 §2.1). The driver alone reads QUIC DATAGRAM frames and files them per request within DatagramConfig; datagrams for other requests follow its violation policy. Use rama_http::datagram::HttpDatagramSession on the tunnel.

This is HTTP message forwarding, not a wire capture/replay API: URI serialization can normalize pseudo-field values, and connection settings, unknown frames, frame boundaries and QPACK representations are not reproduced on another connection.

The frame decoder accepts owned rama_core::bytes::Bytes through frame::FrameDecoder::feed_bytes. Drain poll until it needs more input before feeding the next chunk; rejected input stays with the caller. Contiguous payloads share their input storage, and only fragmented known payloads are coalesced. Input chunk and frame limits are independent.

QPACK encoders accept ordinary name/value tuples or qpack::EncodeField inputs preserving sensitivity. qpack::EncodeField::from_header carries Rama header sensitivity across the boundary, and decoded qpack::FieldPair values can be forwarded directly. Optional dynamic compression falls back to literals when reference or encoder-output budgets are exhausted.

Drain both QPACK instruction outputs regularly. qpack::QpackError::OutputBlocked is local backpressure with no wire error code; retry after draining (or split an oversized input batch). Other errors expose their wire code and stream/connection scope. A driver abandoning a field section must also arrange stream cancellation so the remote encoder can release references. Plain decoded literals share section storage. Blocked sections and dynamic-table literals use compact owned storage instead, so small retained slices cannot pin unrelated large buffers.

Modules

client

Rama-native HTTP/3 request sender.

connection

Connection-owned compression and critical-stream state.

frame

A bounded, incremental HTTP/3 frame decoder (RFC 9114 §7.1).

push

Bounded, opt-in server push. Pushes are delivered to an application, never cached implicitly.

qpack

Connection-scoped QPACK (RFC 9204): the dynamic table plus the stateful encoder and decoder.

server

HTTP/3 server stream admission and response sending.

Structs

DatagramConfig

HTTP/3 datagram support of a connection.

DatagramDrops

Received HTTP/3 datagrams a connection discarded, by reason.

DatagramLimits

Buffering budgets for received HTTP/3 datagrams. A zero queue_len, pending_len or max_buffered_bytes drops (and counts) every datagram it would hold. The request semantics are enforced regardless.

Error

A terminal HTTP/3 protocol error.

PriorityHandle

Update the peer’s response scheduling through RFC 9218 PRIORITY_UPDATE. Available in client response extensions, including informational responses. This weak handle does not keep the connection or response body alive.

Constants

MIN_DATAGRAM_CHARGE

The smallest packet every QUIC path carries (RFC 9000 §14): what a buffered datagram is charged at least, so tiny datagrams cannot fill the budget’s queues for free.