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/*
* Copyright (c) 2018 by Farsight Security, Inc.
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/.
*/
package nmsg
import (
"container/list"
"time"
)
type seqCacheEntry struct {
lastUsed time.Time
seqid uint64
nextSeq uint32
}
type seqCache struct {
expiry time.Duration
idmap map[uint64]*list.Element
lru *list.List
}
func newSequenceCache(expiry time.Duration) *seqCache {
return &seqCache{
expiry: expiry,
idmap: make(map[uint64]*list.Element),
lru: list.New(),
}
}
const maxDrop = 1048576
func (sc *seqCache) Update(n *Nmsg) (missed int) {
if n.Sequence == nil || n.SequenceId == nil {
return
}
seqid := n.GetSequenceId()
lruent, ok := sc.idmap[seqid]
if !ok {
sc.idmap[seqid] = sc.lru.PushBack(
&seqCacheEntry{
lastUsed: time.Now(),
seqid: seqid,
nextSeq: n.GetSequence() + 1,
})
return 0
}
seq := n.GetSequence()
ent := lruent.Value.(*seqCacheEntry)
ent.lastUsed = time.Now()
sc.lru.MoveToBack(lruent)
if seq == ent.nextSeq {
ent.nextSeq++
return 0
}
if seq > ent.nextSeq {
if seq-ent.nextSeq < maxDrop {
missed = int(seq - ent.nextSeq)
}
ent.nextSeq = seq + 1
return missed
}
delta := int64(int64(seq) + (1 << 32) - int64(ent.nextSeq))
if delta < maxDrop {
missed = int(delta)
}
ent.nextSeq = seq + 1
return missed
}
func (sc *seqCache) Expire() {
for sc.lru.Len() > 0 {
lruent := sc.lru.Front()
ent := lruent.Value.(*seqCacheEntry)
if time.Since(ent.lastUsed) <= sc.expiry {
break
}
sc.lru.Remove(lruent)
delete(sc.idmap, ent.seqid)
}
}
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