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66 lines
3.7 KiB
C
66 lines
3.7 KiB
C
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/* Copyright (c) 2001 Matej Pfajfar.
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* Copyright (c) 2001-2004, Roger Dingledine.
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* Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
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* Copyright (c) 2007-2017, The Tor Project, Inc. */
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/* See LICENSE for licensing information */
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#ifndef DOWNLOAD_STATUS_ST_H
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#define DOWNLOAD_STATUS_ST_H
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/** Information about our plans for retrying downloads for a downloadable
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* directory object.
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* Each type of downloadable directory object has a corresponding retry
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* <b>schedule</b>, which can be different depending on whether the object is
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* being downloaded from an authority or a mirror (<b>want_authority</b>).
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* <b>next_attempt_at</b> contains the next time we will attempt to download
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* the object.
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* For schedules that <b>increment_on</b> failure, <b>n_download_failures</b>
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* is used to determine the position in the schedule. (Each schedule is a
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* smartlist of integer delays, parsed from a CSV option.) Every time a
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* connection attempt fails, <b>n_download_failures</b> is incremented,
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* the new delay value is looked up from the schedule, and
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* <b>next_attempt_at</b> is set delay seconds from the time the previous
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* connection failed. Therefore, at most one failure-based connection can be
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* in progress for each download_status_t.
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* For schedules that <b>increment_on</b> attempt, <b>n_download_attempts</b>
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* is used to determine the position in the schedule. Every time a
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* connection attempt is made, <b>n_download_attempts</b> is incremented,
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* the new delay value is looked up from the schedule, and
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* <b>next_attempt_at</b> is set delay seconds from the time the previous
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* connection was attempted. Therefore, multiple concurrent attempted-based
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* connections can be in progress for each download_status_t.
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* After an object is successfully downloaded, any other concurrent connections
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* are terminated. A new schedule which starts at position 0 is used for
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* subsequent downloads of the same object.
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*/
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struct download_status_t {
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time_t next_attempt_at; /**< When should we try downloading this object
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* again? */
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uint8_t n_download_failures; /**< Number of failed downloads of the most
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* recent object, since the last success. */
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uint8_t n_download_attempts; /**< Number of (potentially concurrent) attempts
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* to download the most recent object, since
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* the last success. */
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download_schedule_bitfield_t schedule : 8; /**< What kind of object is being
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* downloaded? This determines the
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* schedule used for the download.
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*/
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download_want_authority_bitfield_t want_authority : 1; /**< Is the download
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* happening from an authority
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* or a mirror? This determines
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* the schedule used for the
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* download. */
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download_schedule_increment_bitfield_t increment_on : 1; /**< does this
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* schedule increment on each attempt,
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* or after each failure? */
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uint8_t last_backoff_position; /**< number of attempts/failures, depending
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* on increment_on, when we last recalculated
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* the delay. Only updated if backoff
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* == 1. */
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int last_delay_used; /**< last delay used for random exponential backoff;
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* only updated if backoff == 1 */
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};
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#endif
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