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package main
/* Copyright (C) 2015-2017 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved. */
/* This file contains a port of the rate-limiter from the linux kernel version */
import (
"net"
"sync"
"time"
)
const (
packetsPerSecond = 20
packetsBurstable = 5
garbageCollectTime = time.Second
packetCost = 1000000000 / packetsPerSecond
maxTokens = packetCost * packetsBurstable
)
type RatelimiterEntry struct {
mutex sync.Mutex
lastTime time.Time
tokens int64
}
type Ratelimiter struct {
mutex sync.RWMutex
stop chan struct{}
tableIPv4 map[[net.IPv4len]byte]*RatelimiterEntry
tableIPv6 map[[net.IPv6len]byte]*RatelimiterEntry
}
func (rate *Ratelimiter) Close() {
rate.mutex.Lock()
defer rate.mutex.Unlock()
if rate.stop != nil {
close(rate.stop)
}
}
func (rate *Ratelimiter) Init() {
rate.mutex.Lock()
defer rate.mutex.Unlock()
// stop any ongoing garbage collection routine
if rate.stop != nil {
close(rate.stop)
}
rate.stop = make(chan struct{})
rate.tableIPv4 = make(map[[net.IPv4len]byte]*RatelimiterEntry)
rate.tableIPv6 = make(map[[net.IPv6len]byte]*RatelimiterEntry)
// start garbage collection routine
go func() {
timer := time.NewTimer(time.Second)
for {
select {
case <-rate.stop:
return
case <-timer.C:
func() {
rate.mutex.Lock()
defer rate.mutex.Unlock()
for key, entry := range rate.tableIPv4 {
entry.mutex.Lock()
if time.Now().Sub(entry.lastTime) > garbageCollectTime {
delete(rate.tableIPv4, key)
}
entry.mutex.Unlock()
}
for key, entry := range rate.tableIPv6 {
entry.mutex.Lock()
if time.Now().Sub(entry.lastTime) > garbageCollectTime {
delete(rate.tableIPv6, key)
}
entry.mutex.Unlock()
}
}()
timer.Reset(time.Second)
}
}
}()
}
func (rate *Ratelimiter) Allow(ip net.IP) bool {
var entry *RatelimiterEntry
var KeyIPv4 [net.IPv4len]byte
var KeyIPv6 [net.IPv6len]byte
// lookup entry
IPv4 := ip.To4()
IPv6 := ip.To16()
rate.mutex.RLock()
if IPv4 != nil {
copy(KeyIPv4[:], IPv4)
entry = rate.tableIPv4[KeyIPv4]
} else {
copy(KeyIPv6[:], IPv6)
entry = rate.tableIPv6[KeyIPv6]
}
rate.mutex.RUnlock()
// make new entry if not found
if entry == nil {
rate.mutex.Lock()
entry = new(RatelimiterEntry)
entry.tokens = maxTokens - packetCost
entry.lastTime = time.Now()
if IPv4 != nil {
rate.tableIPv4[KeyIPv4] = entry
} else {
rate.tableIPv6[KeyIPv6] = entry
}
rate.mutex.Unlock()
return true
}
// add tokens to entry
entry.mutex.Lock()
now := time.Now()
entry.tokens += now.Sub(entry.lastTime).Nanoseconds()
entry.lastTime = now
if entry.tokens > maxTokens {
entry.tokens = maxTokens
}
// subtract cost of packet
if entry.tokens > packetCost {
entry.tokens -= packetCost
entry.mutex.Unlock()
return true
}
entry.mutex.Unlock()
return false
}
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