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/* SPDX-License-Identifier: MIT
*
* Copyright (C) 2017-2019 WireGuard LLC. All Rights Reserved.
*/
package main
import (
"sync/atomic"
)
/* Atomic Boolean */
const (
AtomicFalse = int32(iota)
AtomicTrue
)
type AtomicBool struct {
int32
}
func (a *AtomicBool) Get() bool {
return atomic.LoadInt32(&a.int32) == AtomicTrue
}
func (a *AtomicBool) Swap(val bool) bool {
flag := AtomicFalse
if val {
flag = AtomicTrue
}
return atomic.SwapInt32(&a.int32, flag) == AtomicTrue
}
func (a *AtomicBool) Set(val bool) {
flag := AtomicFalse
if val {
flag = AtomicTrue
}
atomic.StoreInt32(&a.int32, flag)
}
func min(a, b uint) uint {
if a > b {
return b
}
return a
}
// called from receive
func ecn_rfc6040_egress(inner byte, outer byte) (byte, bool) {
/*
+---------+------------------------------------------------+
|Arriving | Arriving Outer Header |
| Inner +---------+------------+------------+------------+
| Header | Not-ECT | ECT(0) | ECT(1) | CE |
+---------+---------+------------+------------+------------+
| Not-ECT | Not-ECT |Not-ECT(!!!)|Not-ECT(!!!)| <drop>(!!!)|
| ECT(0) | ECT(0) | ECT(0) | ECT(1) | CE |
| ECT(1) | ECT(1) | ECT(1) (!) | ECT(1) | CE |
| CE | CE | CE | CE(!!!)| CE |
+---------+---------+------------+------------+------------+
*/
innerECN := CongestionExperienced & inner
outerECN := CongestionExperienced & outer
switch outerECN {
case CongestionExperienced:
switch innerECN {
case NotECNTransport:
return 0, true
}
return (inner & (CongestionExperienced ^ 255)) | CongestionExperienced, false
case ECNTransport1:
switch innerECN {
case ECNTransport0:
return (inner & (CongestionExperienced ^ 255)) | ECNTransport1, false
}
}
return inner, false
}
// called from send
func ecn_rfc6040_ingress(inner byte, useNormalMode bool) byte {
/*
+-----------------+-------------------------------+
| Incoming Header | Departing Outer Header |
| (also equal to +---------------+---------------+
| departing Inner | Compatibility | Normal |
| Header) | Mode | Mode |
+-----------------+---------------+---------------+
| Not-ECT | Not-ECT | Not-ECT |
| ECT(0) | Not-ECT | ECT(0) |
| ECT(1) | Not-ECT | ECT(1) |
| CE | Not-ECT | CE |
+-----------------+---------------+---------------+
*/
if !useNormalMode {
inner &= (CongestionExperienced ^ 255)
}
return inner
}
func ecn_rfc6040_enabled(tos byte) bool {
return (CongestionExperienced & tos) == ECNTransport0
}
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