52 lines
1.4 KiB
Go
52 lines
1.4 KiB
Go
// Copyright (c) 2016-2017 Daniel Oaks <daniel@danieloaks.net>
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// released under the MIT license
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package connection_limits
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import (
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"time"
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)
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// ThrottleDetails holds the connection-throttling details for a subnet/IP.
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type ThrottleDetails struct {
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Start time.Time
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Count int
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}
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// GenericThrottle allows enforcing limits of the form
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// "at most X events per time window of duration Y"
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type GenericThrottle struct {
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ThrottleDetails // variable state: what events have been seen
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// these are constant after creation:
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Duration time.Duration // window length to consider
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Limit int // number of events allowed per window
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}
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// Touch checks whether an additional event is allowed:
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// it either denies it (by returning false) or allows it (by returning true)
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// and records it
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func (g *GenericThrottle) Touch() (throttled bool, remainingTime time.Duration) {
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return g.touch(time.Now().UTC())
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}
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func (g *GenericThrottle) touch(now time.Time) (throttled bool, remainingTime time.Duration) {
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if g.Limit == 0 {
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return // limit of 0 disables throttling
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}
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elapsed := now.Sub(g.Start)
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if elapsed > g.Duration {
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// reset window, record the operation
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g.Start = now
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g.Count = 1
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return false, 0
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} else if g.Count >= g.Limit {
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// we are throttled
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return true, g.Start.Add(g.Duration).Sub(now)
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} else {
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// we are not throttled, record the operation
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g.Count += 1
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return false, 0
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}
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}
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