1/*	$NetBSD: ratelim-internal.h,v 1.4 2021/04/10 19:02:37 rillig Exp $	*/
2/*
3 * Copyright (c) 2009-2012 Niels Provos and Nick Mathewson
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 * 3. The name of the author may not be used to endorse or promote products
14 *    derived from this software without specific prior written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
19 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
21 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
25 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26 */
27#ifndef RATELIM_INTERNAL_H_INCLUDED_
28#define RATELIM_INTERNAL_H_INCLUDED_
29
30#ifdef __cplusplus
31extern "C" {
32#endif
33
34#include "event2/util.h"
35
36/** A token bucket is an internal structure that tracks how many bytes we are
37 * currently willing to read or write on a given bufferevent or group of
38 * bufferevents */
39struct ev_token_bucket {
40	/** How many bytes are we willing to read or write right now? These
41	 * values are signed so that we can do "defecit spending" */
42	ev_ssize_t read_limit, write_limit;
43	/** When was this bucket last updated?  Measured in abstract 'ticks'
44	 * relative to the token bucket configuration. */
45	ev_uint32_t last_updated;
46};
47
48/** Configuration info for a token bucket or set of token buckets. */
49struct ev_token_bucket_cfg {
50	/** How many bytes are we willing to read on average per tick? */
51	size_t read_rate;
52	/** How many bytes are we willing to read at most in any one tick? */
53	size_t read_maximum;
54	/** How many bytes are we willing to write on average per tick? */
55	size_t write_rate;
56	/** How many bytes are we willing to write at most in any one tick? */
57	size_t write_maximum;
58
59	/* How long is a tick?  Note that fractions of a millisecond are
60	 * ignored. */
61	struct timeval tick_timeout;
62
63	/* How long is a tick, in milliseconds?  Derived from tick_timeout. */
64	unsigned msec_per_tick;
65};
66
67/** The current tick is 'current_tick': add bytes to 'bucket' as specified in
68 * 'cfg'. */
69int ev_token_bucket_update_(struct ev_token_bucket *bucket,
70    const struct ev_token_bucket_cfg *cfg,
71    ev_uint32_t current_tick);
72
73/** In which tick does 'tv' fall according to 'cfg'?  Note that ticks can
74 * overflow easily; your code needs to handle this. */
75ev_uint32_t ev_token_bucket_get_tick_(const struct timeval *tv,
76    const struct ev_token_bucket_cfg *cfg);
77
78/** Adjust 'bucket' to respect 'cfg', and note that it was last updated in
79 * 'current_tick'.  If 'reinitialize' is true, we are changing the
80 * configuration of 'bucket'; otherwise, we are setting it up for the first
81 * time.
82 */
83int ev_token_bucket_init_(struct ev_token_bucket *bucket,
84    const struct ev_token_bucket_cfg *cfg,
85    ev_uint32_t current_tick,
86    int reinitialize);
87
88int bufferevent_remove_from_rate_limit_group_internal_(struct bufferevent *bev,
89    int unsuspend);
90
91/** Decrease the read limit of 'b' by 'n' bytes */
92#define ev_token_bucket_decrement_read(b,n)	\
93	do {					\
94		(b)->read_limit -= (n);		\
95	} while (0)
96/** Decrease the write limit of 'b' by 'n' bytes */
97#define ev_token_bucket_decrement_write(b,n)	\
98	do {					\
99		(b)->write_limit -= (n);	\
100	} while (0)
101
102#ifdef __cplusplus
103}
104#endif
105
106#endif
107