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