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75 lines
4.2 KiB
Plaintext
75 lines
4.2 KiB
Plaintext
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2023-05-23 - closing states on the stream endpoint descriptor
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This document deals with the current flags on the SE desc:
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- SE_FL_ERR_PENDING: an error was met while sending, but some incoming data
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might still be pending. This flag will be promoted to SE_FL_ERROR when the
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SE_FL_EOI or SE_FL_EOS flags are set via the standard API (se_fl_set()).
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- SE_FL_ERROR ("ERR"): an error was met, last data were received if any, and no
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more progress will happen.
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- SE_FL_EOI ("EOI"): the end of the input message was seen, without implying
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an end of the connection nor the end of event reporting for this stream. For
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example and end of HTTP request or response will set EOI, after which it's
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still possible (in case of a request) to bring an abort or error. Said
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differently, the expected end of the message was seen.
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- SE_FL_EOS ("EOS"): the definitive end of the input data was detected. It may
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result from an error, an abort, a connection shutdown, and no more receive
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events will be reported.
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The different muxes (H1,H2,H3) can face slightly different situations due to
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the nature, properties, and limitations of their underlying protocols, and will
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set these 3 flags to best translate the lower layer's situation and report it
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to the upper layer:
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+-----------+-----------------------------------------------------------------
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|ERR EOS EOI| Description per mux
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+-----------+-----------------------------------------------------------------
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| 0 0 0 | all: transfer still in progress
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+-----------+-----------------------------------------------------------------
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| 0 0 1 | H1: end of message reached.
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| | H2: "ES" flag seen on a frame.
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| | H3: not set
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+-----------+-----------------------------------------------------------------
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| 0 1 0 | H1: not set (*1)
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| | H2: not set (*2)
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| | H3: RST received before FIN (client stops uploading)
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+-----------+-----------------------------------------------------------------
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| 0 1 1 | H1: end of message + read0, such as close response or aborted
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| | request
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| | H2: not set (*2)
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| | H3: end of message reached (any subsequent RSTs are ignored)
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+-----------+-----------------------------------------------------------------
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| 1 0 0 | all: could be used to report a protocol error (ex: invalid chunk
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| | encoding, forbidden response header seen from a server).
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+-----------+-----------------------------------------------------------------
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| 1 0 1 | all: could be used to report an internal error or a downstream
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| | protocol error, such as a forbidden header in an HTX block
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| | coming from the stream layer or the impossibility to encode
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| | a message. Seems unused right now.
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+-----------+-----------------------------------------------------------------
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| 1 1 0 | H1: truncated client input data before response, or truncated
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| | response from the server
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| | H2: RST or read0 received before end of input message
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| | H3: RST + STOP_SENDING before FIN
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+-----------+-----------------------------------------------------------------
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| 1 1 1 | H1: error face while sending after end of input message
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| | H2: RST or read0 received after end of input message
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| | H3: STOP_SENDING received after a frame with FIN
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+-----------+-----------------------------------------------------------------
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*1: EOS alone is currently not set by H1, however this situation could best
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describe an H1 upload that was interrupted by the client while receiving
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an early response, a reused persistent server connection that delivered a
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read0 immediately after the request was sent, or a truncated server
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response (or possibly one in close mode when no C-L was advertised). Right
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now these situations are always accompanied with an ERR flag in addition to
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the EOS one.
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*2: H2 doesn't set EOS without ERR because currently the only ways to close a
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stream in H2 are by resetting the stream (which conveys an error) or
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closing the connection (which renders it unusable in both directions and
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prevents from sending as well).
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