summaryrefslogtreecommitdiff
path: root/node/BandwidthAccount.hpp
blob: be180cfca9d2fcc024d31c390d1db4d3cf69d89d (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
/*
 * ZeroTier One - Global Peer to Peer Ethernet
 * Copyright (C) 2012-2013  ZeroTier Networks LLC
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 * --
 *
 * ZeroTier may be used and distributed under the terms of the GPLv3, which
 * are available at: http://www.gnu.org/licenses/gpl-3.0.html
 *
 * If you would like to embed ZeroTier into a commercial application or
 * redistribute it in a modified binary form, please contact ZeroTier Networks
 * LLC. Start here: http://www.zerotier.com/
 */

#ifndef _ZT_BWACCOUNT_HPP
#define _ZT_BWACCOUNT_HPP

#include <stdint.h>
#include <math.h>

#include "Constants.hpp"
#include "Utils.hpp"

namespace ZeroTier {

/**
 * Bandwidth account used for rate limiting multicast groups
 *
 * This is used to apply a bank account model to multicast groups. Each
 * multicast packet counts against a balance, which accrues at a given
 * rate in bytes per second. Debt is possible. These parameters are
 * configurable.
 *
 * A bank account model permits bursting behavior, which correctly models
 * how OSes and apps typically use multicast. It's common for things to
 * spew lots of multicast messages at once, wait a while, then do it
 * again. A consistent bandwidth limit model doesn't fit.
 */
class BandwidthAccount
{
public:
	/**
	 * Create an uninitialized account
	 *
	 * init() must be called before this is used.
	 */
	BandwidthAccount() throw() {}

	/**
	 * Create and initialize
	 *
	 * @param preload Initial balance to place in account
	 * @param maxb Maximum allowed balance (> 0)
	 * @param acc Rate of accrual in bytes per second
	 */
	BandwidthAccount(uint32_t preload,uint32_t maxb,uint32_t acc)
		throw()
	{
		init(preload,maxb,acc);
	}

	/**
	 * Initialize or re-initialize account
	 *
	 * @param preload Initial balance to place in account
	 * @param maxb Maximum allowed balance (> 0)
	 * @param acc Rate of accrual in bytes per second
	 */
	inline void init(uint32_t preload,uint32_t maxb,uint32_t acc)
		throw()
	{
		_lastTime = Utils::nowf();
		_balance = preload;
		_maxBalance = maxb;
		_accrual = acc;
	}

	/**
	 * Update and retrieve balance of this account
	 *
	 * @return New balance updated from current clock
	 */
	inline uint32_t update()
		throw()
	{
		double lt = _lastTime;
		double now = Utils::nowf();
		_lastTime = now;
		return (_balance = std::min(_maxBalance,(uint32_t)round((double)_balance + ((double)_accrual * (now - lt)))));
	}

	/**
	 * Update balance and conditionally deduct
	 *
	 * If the deduction amount fits, it is deducted after update. Otherwise
	 * balance is updated and false is returned.
	 *
	 * @param amt Amount to deduct
	 * @return True if amount fit within balance and was deducted
	 */
	inline bool deduct(uint32_t amt)
		throw()
	{
		if (update() >= amt) {
			_balance -= amt;
			return true;
		}
		return false;
	}

	/**
	 * @return Most recent balance without update
	 */
	inline uint32_t balance() const
		throw()
	{
		return _balance;
	}

private:
	double _lastTime;
	uint32_t _balance;
	uint32_t _maxBalance;
	uint32_t _accrual;
};

} // namespace ZeroTier

#endif