RX depacketizer =============== This component takes a QUIC packet and parses the frames contained therein, to be forwarded to appropriate other components for further processing. In the [overview], this is called the "RX Frame Handler". The name "RX depacketizer" was chosen to reflect the kinship with the [TX packetizer]. Main structures --------------- ### Connection Represented by an `QUIC_CONNECTION` object, defined in [`include/internal/quic_ssl.h`](../../../include/internal/quic_ssl.h). ### Stream Represented by an `QUIC_STREAM` object (yet to be defined). ### Packets Represented by the `OSSL_QRX_PKT` structure, defined in `include/internal/quic_record_rx.h` in [QUIC Demuxer and Record Layer (RX+TX)]. Interactions ------------ The RX depacketizer receives a packet from the QUIC Read Record Layer, and then processes frames in two phases: 1. [Collect information for the ACK Manager](#collect-information-for-the-ack-manager) 2. [Pass frame data](#pass-frame-data) ### Other components There are a number of other components that the RX depacketizer wants to interact with: - [ACK manager] - Handshake manager, which is currently unspecified. It's assumed that this will wrap around what is called the "TLS Handshake Record Layer", in the [overview] - Session manager, which is currently unspecified for QUIC, but may very well be the existing `SSL_SESSION` functionality, extended to fit QUIC purposes. - Flow control, which is currently unspecified. In the [overview], it's called the "Flow Controller And Statistics Collector" - Connection manager, which is currently unspecified. In the [overview], there's a "Connection State Machine" that the "RX Frame Handler" isn't talking directly with, so it's possible that the Connection manager will turn out to be the Handshake manager. - Stream SSL objects, to pass the stream data to. ### Read and process a packet Following how things are designed elsewhere, the depacketizer is assumed to be called "from above" using the following function: ``` C __owur int ossl_quic_depacketize(QUIC_CONNECTION *connection); ``` This function would create an `OSSL_QRX_PKT` and call the QUIC Read Record Layer with a pointer to it, leaving it to the QUIC Read Record Layer to fill in the data. This uses the `ossl_qrx_read_pkt()` packet reading function from [QUIC Demuxer and Record Layer (RX+TX)]. (the `OSSL_QRX_PKT` structure / sub-structure needs to be extended to take an `OSSL_TIME`, possibly by reference, which should be filled in with the packet reception time) ### Collect information for the [ACK manager] This collects appropriate data into a `QUIC_ACKM_RX_PKT` structure: - The packet number (`packet->packet_number`) - The packet receive time (`received`) - The packet space, which is always: - `QUIC_PN_SPACE_INITIAL` when `packet->packet_type == pkt_initial` - `QUIC_PN_SPACE_HANDSHAKE` when `packet->packet_type == pkt_handshake` - `QUIC_PN_SPACE_APP` for all other packet types - The ACK eliciting flag. This is calculated by looping through all frames and noting those that are ACK eliciting, as determined from [Table 1](#table-1) below) ### Passing frame data This loops through all the frames, extracts data where there is any and calls diverse other components as shown in the Passed to column in [Table 1](#table-1) below. #### Table 1 Taken from [RFC 9000 12.4 Frames and Frame Types] | Type | Name | Passed to | ACK eliciting | I | H | 0 | 1 | |------|-------------------------|--------------------------|---------------|----------|----------|----------|----------| | 0x00 | [padding] | - | | ✔ | ✔ | ✔ | ✔ | | 0x01 | [ping] | - | ✔ | ✔ | ✔ | ✔ | ✔ | | 0x02 | [ack 0x02] | [ACK manager] [^1] | | ✔ | ✔ | | ✔ | | 0x03 | [ack 0x03] | [ACK manager] [^1] | | ✔ | ✔ | | ✔ | | 0x04 | [reset_stream] | - [^2] | ✔ | | | ✔ | ✔ | | 0x05 | [stop_sending] | - [^3] | ✔ | | | ✔ | ✔ | | 0x06 | [crypto] | Handshake manager | ✔ | ✔ | ✔ | | ✔ | | 0x07 | [new_token] | Session manager | ✔ | | | | ✔ | | 0x08 | [stream 0x08] | Apprioriate stream [^4] | ✔ | | | ✔ | ✔ | | 0x09 | [stream 0x09] | Apprioriate stream [^4] | ✔ | | | ✔ | ✔ | | 0x0A | [stream 0x0A] | Apprioriate stream [^4] | ✔ | | | ✔ | ✔ | | 0x0B | [stream 0x0B] | Apprioriate stream [^4] | ✔ | | | ✔ | ✔ | | 0x0C | [stream 0x0C] | Apprioriate stream [^4] | ✔ | | | ✔ | ✔ | | 0x0D | [stream 0x0D] | Apprioriate stream [^4] | ✔ | | | ✔ | ✔ | | 0x0E | [stream 0x0E] | Apprioriate stream [^4] | ✔ | | | ✔ | ✔ | | 0x0F | [stream 0x0F] | Apprioriate stream [^4] | ✔ | | | ✔ | ✔ | | 0x10 | [max_data] | Flow control [^5] | ✔ | | | ✔ | ✔ | | 0x11 | [max_stream_data] | Flow control [^5] | ✔ | | | ✔ | ✔ | | 0x12 | [max_streams 0x12] | Connection manager? [^6] | ✔ | | | ✔ | ✔ | | 0x13 | [max_streams 0x13] | Connection manager? [^6] | ✔ | | | ✔ | ✔ | | 0x14 | [data_blocked] | Flow control [^5] | ✔ | | | ✔ | ✔ | | 0x15 | [stream_data_blocked] | Flow control [^5] | ✔ | | | ✔ | ✔ | | 0x16 | [streams_blocked 0x16] | Connection manager? [^6] | ✔ | | | ✔ | ✔ | | 0x17 | [streams_blocked 0x17] | Connection manager? [^6] | ✔ | | | ✔ | ✔ | | 0x18 | [new_connection_id] | Connection manager | ✔ | | | ✔ | ✔ | | 0x19 | [retire_connection_id] | Connection manager | ✔ | | | ✔ | ✔ | | 0x1A | [path_challenge] | Connection manager? [^7] | ✔ | | | ✔ | ✔ | | 0x1B | [path_response] | Connection manager? [^7] | ✔ | | | | ✔ | | 0x1C | [connection_close 0x1C] | Connection manager | | ✔ | ✔ | ✔ | ✔ | | 0x1D | [connection_close 0x1D] | Connection manager | | | | ✔ | ✔ | | 0x1E | [handshake_done] | Handshake manager | ✔ | | | | ✔ | | ???? | *[Extension Frames]* | - [^8] | ✔ | | | | | The I, H, 0, and 1 columns are validity in different packet types, with this meaning: | Pkts | Description | |:----:|----------------------------| | I | Valid in Initial packets | | H | Valid in Handshake packets | | 0 | Valid in 0-RTT packets | | 1 | Valid in 1-RTT packets | Notes: [^1]: This creates and populates an `QUIC_ACKM_ACK` structure, then calls `QUIC_ACKM_on_rx_ack_frame()`, with the appropriate context (`QUIC_ACKM`, the created `QUIC_ACKM_ACK`, `pkt_space` and `rx_time`) [^2]: Immediately terminates the appropriate receiving stream `QUIC_STREAM` object. This includes discarding any buffered application data. For a stream that's send-only, the error `STREAM_STATE_ERROR` is raised, and the `QUIC_CONNECTION` object is terminated. [^3]: Immediately terminates the appropriate sending stream `QUIC_STREAM` object. For a stream that's receive-only, the error `STREAM_STATE_ERROR` is raised, and the `QUIC_CONNECTION` object is terminated. [^4]: The frame payload (Stream Data) is passed as is to the `QUIC_STREAM` object, along with available metadata (offset and length, as determined to be available from the lower 3 bits of the frame type). [^5]: The details of what flow control will need are yet to be determined [^6]: I imagine that `max_streams` and `streams_blocked` concern a Connection manager before anything else. [^7]: I imagine that path challenge/response concerns a Connection manager before anything else. [^8]: We have no idea what extension frames there will be. However, we must at least acknowledge their presence, so much is clear from the RFC. [overview]: https://github.com/openssl/openssl/blob/master/doc/designs/quic-design/quic-overview.md [TX packetizer]: https://github.com/openssl/openssl/pull/18570 [SSL object refactoring using SSL_CONNECTION object]: https://github.com/openssl/openssl/pull/18612 [QUIC Demuxer and Record Layer (RX+TX)]: https://github.com/openssl/openssl/pull/18949 [ACK manager]: https://github.com/openssl/openssl/pull/18564 [RFC 9000 12.4 Frames and Frame Types]: https://datatracker.ietf.org/doc/html/rfc9000#section-12.4 [padding]: https://datatracker.ietf.org/doc/html/rfc9000#section-19.1 [ping]: https://datatracker.ietf.org/doc/html/rfc9000#section-19.2 [ack 0x02]: https://datatracker.ietf.org/doc/html/rfc9000#section-19.3 [ack 0x03]: https://datatracker.ietf.org/doc/html/rfc9000#section-19.3 [reset_stream]: https://datatracker.ietf.org/doc/html/rfc9000#section-19.4 [stop_sending]: https://datatracker.ietf.org/doc/html/rfc9000#section-19.5 [crypto]: https://datatracker.ietf.org/doc/html/rfc9000#section-19.6 [new_token]: https://datatracker.ietf.org/doc/html/rfc9000#section-19.7 [stream 0x08]: https://datatracker.ietf.org/doc/html/rfc9000#section-19.8 [stream 0x09]: https://datatracker.ietf.org/doc/html/rfc9000#section-19.8 [stream 0x0A]: https://datatracker.ietf.org/doc/html/rfc9000#section-19.8 [stream 0x0B]: https://datatracker.ietf.org/doc/html/rfc9000#section-19.8 [stream 0x0C]: https://datatracker.ietf.org/doc/html/rfc9000#section-19.8 [stream 0x0D]: https://datatracker.ietf.org/doc/html/rfc9000#section-19.8 [stream 0x0E]: https://datatracker.ietf.org/doc/html/rfc9000#section-19.8 [stream 0x0F]: https://datatracker.ietf.org/doc/html/rfc9000#section-19.8 [max_data]: https://datatracker.ietf.org/doc/html/rfc9000#section-19.9 [max_stream_data]: https://datatracker.ietf.org/doc/html/rfc9000#section-19.10 [max_streams 0x12]: https://datatracker.ietf.org/doc/html/rfc9000#section-19.11 [max_streams 0x13]: https://datatracker.ietf.org/doc/html/rfc9000#section-19.11 [data_blocked]: https://datatracker.ietf.org/doc/html/rfc9000#section-19.12 [stream_data_blocked]: https://datatracker.ietf.org/doc/html/rfc9000#section-19.13 [streams_blocked 0x16]: https://datatracker.ietf.org/doc/html/rfc9000#section-19.14 [streams_blocked 0x17]: https://datatracker.ietf.org/doc/html/rfc9000#section-19.14 [new_connection_id]: https://datatracker.ietf.org/doc/html/rfc9000#section-19.15 [retire_connection_id]: https://datatracker.ietf.org/doc/html/rfc9000#section-19.16 [path_challenge]: https://datatracker.ietf.org/doc/html/rfc9000#section-19.17 [path_response]: https://datatracker.ietf.org/doc/html/rfc9000#section-19.18 [connection_close 0x1C]: https://datatracker.ietf.org/doc/html/rfc9000#section-19.19 [connection_close 0x1D]: https://datatracker.ietf.org/doc/html/rfc9000#section-19.19 [handshake_done]: https://datatracker.ietf.org/doc/html/rfc9000#section-19.20 [Extension Frames]: https://datatracker.ietf.org/doc/html/rfc9000#section-19.21