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/* Copyright (c) 2001 Matej Pfajfar.
* Copyright (c) 2001-2004, Roger Dingledine.
* Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
* Copyright (c) 2007-2019, The Tor Project, Inc. */
/* See LICENSE for licensing information */
#ifndef DOWNLOAD_STATUS_ST_H
#define DOWNLOAD_STATUS_ST_H
/** Information about our plans for retrying downloads for a downloadable
* directory object.
* Each type of downloadable directory object has a corresponding retry
* <b>schedule</b>, which can be different depending on whether the object is
* being downloaded from an authority or a mirror (<b>want_authority</b>).
* <b>next_attempt_at</b> contains the next time we will attempt to download
* the object.
* For schedules that <b>increment_on</b> failure, <b>n_download_failures</b>
* is used to determine the position in the schedule. (Each schedule is a
* smartlist of integer delays, parsed from a CSV option.) Every time a
* connection attempt fails, <b>n_download_failures</b> is incremented,
* the new delay value is looked up from the schedule, and
* <b>next_attempt_at</b> is set delay seconds from the time the previous
* connection failed. Therefore, at most one failure-based connection can be
* in progress for each download_status_t.
* For schedules that <b>increment_on</b> attempt, <b>n_download_attempts</b>
* is used to determine the position in the schedule. Every time a
* connection attempt is made, <b>n_download_attempts</b> is incremented,
* the new delay value is looked up from the schedule, and
* <b>next_attempt_at</b> is set delay seconds from the time the previous
* connection was attempted. Therefore, multiple concurrent attempted-based
* connections can be in progress for each download_status_t.
* After an object is successfully downloaded, any other concurrent connections
* are terminated. A new schedule which starts at position 0 is used for
* subsequent downloads of the same object.
*/
struct download_status_t {
time_t next_attempt_at; /**< When should we try downloading this object
* again? */
uint8_t n_download_failures; /**< Number of failed downloads of the most
* recent object, since the last success. */
uint8_t n_download_attempts; /**< Number of (potentially concurrent) attempts
* to download the most recent object, since
* the last success. */
download_schedule_bitfield_t schedule : 8; /**< What kind of object is being
* downloaded? This determines the
* schedule used for the download.
*/
download_want_authority_bitfield_t want_authority : 1; /**< Is the download
* happening from an authority
* or a mirror? This determines
* the schedule used for the
* download. */
download_schedule_increment_bitfield_t increment_on : 1; /**< does this
* schedule increment on each attempt,
* or after each failure? */
uint8_t last_backoff_position; /**< number of attempts/failures, depending
* on increment_on, when we last recalculated
* the delay. Only updated if backoff
* == 1. */
int last_delay_used; /**< last delay used for random exponential backoff;
* only updated if backoff == 1 */
};
#endif
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