flare.quic.transport_params

Return a :class:TransportParameters with every field cleared (every Optional is None and every byte buffer is empty). Build up the carrier by populating the fields the caller wants on the wire, then pass to :func:encode_transport_parameters.

Project a decoded :class:TransportParameters onto the send-constraining :class:PeerSendLimits view, applying the RFC 9000 §18.2 defaults for any absent parameter.

The flow-control parameters default to 0 (absence means "no initial allowance"); max_udp_payload_size defaults to 65527; max_datagram_frame_size defaults to 0 (peer forbids DATAGRAM frames). Pure / sans-I/O so it is unit-testable against :func:encode_transport_parameters round-trips.

Serialise params to bytes.

Only fields that have been populated (Optional is Some or a byte list is non-empty) are emitted; absent parameters are silently dropped so the receiver picks up the RFC default. The one exception is :data:disable_active_migration, which is emitted as a zero-length parameter whenever params.disable_ active_migration is True.

Parse a transport-parameters extension payload.

Loops varint(id) || varint(length) || bytes[length] until the buffer is drained. Unknown ids are silently dropped per RFC 9000 §7.4.2. Duplicate parameter ids are rejected (the RFC requires each parameter to appear at most once).

Whether parameter id occurs in the TLV list buf.

:func:decode_transport_parameters stores a CID parameter as a list that is empty both when the parameter is absent and when it is present with length 0, so a check that must tell the two apart (RFC 9000 §7.3, §18.2) scans the raw bytes instead. A malformed list reports False: the caller has already run (or will run) the decoder, which raises on it.

Validate the transport parameters a server received from a client.

Raises TRANSPORT_PARAMETER_ERROR (RFC 9000 §18.2, §7.3, §7.4) when the blob does not decode (truncation, duplicates, invalid values), when it carries a server-only parameter (original_destination_connection_id, stateless_reset_token, preferred_address or retry_source_connection_id), or when initial_source_connection_id is absent or differs from client_scid, the Source Connection ID of the client's Initial packet (which may legitimately be zero-length).

Validate the transport parameters a client received from a server.

Raises TRANSPORT_PARAMETER_ERROR (RFC 9000 §7.3, §18.2) when the blob does not decode, when original_destination_connection_id is absent or is not the DCID of the client's first Initial, when initial_source_connection_id is absent or is not the Source Connection ID the server used (a zero-length one must still be present), when retry_source_connection_id is present without a Retry (or absent after one, or different from the Retry's Source Connection ID), or when the server used a zero-length connection ID and sent a preferred_address.

Presence is read from the raw bytes (:func:transport_parameter_present) because the decoded record stores an absent CID parameter and a zero-length one alike as an empty list.