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