wireguard-go/receive.go

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/* SPDX-License-Identifier: GPL-2.0
*
* Copyright (C) 2017-2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
*/
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package main
import (
"bytes"
"encoding/binary"
"golang.org/x/crypto/chacha20poly1305"
"golang.org/x/net/ipv4"
"golang.org/x/net/ipv6"
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"net"
"strconv"
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"sync"
"sync/atomic"
"time"
)
type QueueHandshakeElement struct {
msgType uint32
packet []byte
endpoint Endpoint
buffer *[MaxMessageSize]byte
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}
type QueueInboundElement struct {
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dropped int32
mutex sync.Mutex
buffer *[MaxMessageSize]byte
packet []byte
counter uint64
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keypair *Keypair
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endpoint Endpoint
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}
func (elem *QueueInboundElement) Drop() {
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atomic.StoreInt32(&elem.dropped, AtomicTrue)
}
func (elem *QueueInboundElement) IsDropped() bool {
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return atomic.LoadInt32(&elem.dropped) == AtomicTrue
}
func (device *Device) addToInboundQueue(
queue chan *QueueInboundElement,
element *QueueInboundElement,
) {
for {
select {
case queue <- element:
return
default:
select {
case old := <-queue:
old.Drop()
default:
}
}
}
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}
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func (device *Device) addToDecryptionQueue(
queue chan *QueueInboundElement,
element *QueueInboundElement,
) {
for {
select {
case queue <- element:
return
default:
select {
case old := <-queue:
// drop & release to potential consumer
old.Drop()
old.mutex.Unlock()
default:
}
}
}
}
func (device *Device) addToHandshakeQueue(
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queue chan QueueHandshakeElement,
element QueueHandshakeElement,
) {
for {
select {
case queue <- element:
return
default:
select {
case elem := <-queue:
device.PutMessageBuffer(elem.buffer)
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default:
}
}
}
}
/* Called when a new authenticated message has been received
*
* NOTE: Not thread safe, but called by sequential receiver!
*/
func (peer *Peer) keepKeyFreshReceiving() {
if peer.timers.sentLastMinuteHandshake {
return
}
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keypair := peer.keypairs.Current()
if keypair != nil && keypair.isInitiator && time.Now().Sub(keypair.created) > (RejectAfterTime-KeepaliveTimeout-RekeyTimeout) {
peer.timers.sentLastMinuteHandshake = true
peer.SendHandshakeInitiation(false)
}
}
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/* Receives incoming datagrams for the device
*
* Every time the bind is updated a new routine is started for
* IPv4 and IPv6 (separately)
*/
func (device *Device) RoutineReceiveIncoming(IP int, bind Bind) {
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logDebug := device.log.Debug
defer func() {
logDebug.Println("Routine: receive incoming IPv" + strconv.Itoa(IP) + " - stopped")
}()
logDebug.Println("Routine: receive incoming IPv" + strconv.Itoa(IP) + " - starting")
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// receive datagrams until conn is closed
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buffer := device.GetMessageBuffer()
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var (
err error
size int
endpoint Endpoint
)
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for {
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// read next datagram
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switch IP {
case ipv4.Version:
size, endpoint, err = bind.ReceiveIPv4(buffer[:])
case ipv6.Version:
size, endpoint, err = bind.ReceiveIPv6(buffer[:])
default:
panic("invalid IP version")
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}
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if err != nil {
return
}
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if size < MinMessageSize {
continue
}
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// check size of packet
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packet := buffer[:size]
msgType := binary.LittleEndian.Uint32(packet[:4])
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var okay bool
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switch msgType {
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// check if transport
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case MessageTransportType:
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// check size
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if len(packet) < MessageTransportType {
continue
}
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// lookup key pair
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receiver := binary.LittleEndian.Uint32(
packet[MessageTransportOffsetReceiver:MessageTransportOffsetCounter],
)
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value := device.indexTable.Lookup(receiver)
keypair := value.keypair
if keypair == nil {
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continue
}
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// check keypair expiry
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if keypair.created.Add(RejectAfterTime).Before(time.Now()) {
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continue
}
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// create work element
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peer := value.peer
elem := &QueueInboundElement{
packet: packet,
buffer: buffer,
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keypair: keypair,
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dropped: AtomicFalse,
endpoint: endpoint,
}
elem.mutex.Lock()
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// add to decryption queues
if peer.isRunning.Get() {
device.addToDecryptionQueue(device.queue.decryption, elem)
device.addToInboundQueue(peer.queue.inbound, elem)
buffer = device.GetMessageBuffer()
}
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continue
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// otherwise it is a fixed size & handshake related packet
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case MessageInitiationType:
okay = len(packet) == MessageInitiationSize
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case MessageResponseType:
okay = len(packet) == MessageResponseSize
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case MessageCookieReplyType:
okay = len(packet) == MessageCookieReplySize
default:
logDebug.Println("Received message with unknown type")
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}
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if okay {
device.addToHandshakeQueue(
device.queue.handshake,
QueueHandshakeElement{
msgType: msgType,
buffer: buffer,
packet: packet,
endpoint: endpoint,
},
)
buffer = device.GetMessageBuffer()
}
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}
}
func (device *Device) RoutineDecryption() {
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var nonce [chacha20poly1305.NonceSize]byte
logDebug := device.log.Debug
defer func() {
logDebug.Println("Routine: decryption worker - stopped")
device.state.stopping.Done()
}()
logDebug.Println("Routine: decryption worker - started")
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for {
select {
case <-device.signals.stop:
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return
case elem, ok := <-device.queue.decryption:
if !ok {
return
}
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// check if dropped
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if elem.IsDropped() {
continue
}
// split message into fields
counter := elem.packet[MessageTransportOffsetCounter:MessageTransportOffsetContent]
content := elem.packet[MessageTransportOffsetContent:]
// expand nonce
nonce[0x4] = counter[0x0]
nonce[0x5] = counter[0x1]
nonce[0x6] = counter[0x2]
nonce[0x7] = counter[0x3]
nonce[0x8] = counter[0x4]
nonce[0x9] = counter[0x5]
nonce[0xa] = counter[0x6]
nonce[0xb] = counter[0x7]
// decrypt and release to consumer
var err error
elem.counter = binary.LittleEndian.Uint64(counter)
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elem.packet, err = elem.keypair.receive.Open(
content[:0],
nonce[:],
content,
nil,
)
if err != nil {
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elem.Drop()
}
elem.mutex.Unlock()
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}
}
}
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/* Handles incoming packets related to handshake
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*/
func (device *Device) RoutineHandshake() {
logInfo := device.log.Info
logError := device.log.Error
logDebug := device.log.Debug
defer func() {
logDebug.Println("Routine: handshake worker - stopped")
device.state.stopping.Done()
}()
logDebug.Println("Routine: handshake worker - started")
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var elem QueueHandshakeElement
var ok bool
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for {
select {
case elem, ok = <-device.queue.handshake:
case <-device.signals.stop:
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return
}
if !ok {
return
}
// handle cookie fields and ratelimiting
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switch elem.msgType {
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case MessageCookieReplyType:
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// unmarshal packet
var reply MessageCookieReply
reader := bytes.NewReader(elem.packet)
err := binary.Read(reader, binary.LittleEndian, &reply)
if err != nil {
logDebug.Println("Failed to decode cookie reply")
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return
}
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// lookup peer from index
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entry := device.indexTable.Lookup(reply.Receiver)
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if entry.peer == nil {
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continue
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}
// consume reply
if peer := entry.peer; peer.isRunning.Get() {
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peer.cookieGenerator.ConsumeReply(&reply)
}
continue
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case MessageInitiationType, MessageResponseType:
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// check mac fields and maybe ratelimit
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if !device.cookieChecker.CheckMAC1(elem.packet) {
logDebug.Println("Received packet with invalid mac1")
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continue
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}
// endpoints destination address is the source of the datagram
if device.IsUnderLoad() {
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// verify MAC2 field
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if !device.cookieChecker.CheckMAC2(elem.packet, elem.endpoint.DstToBytes()) {
device.SendHandshakeCookie(&elem)
continue
}
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// check ratelimiter
if !device.rate.limiter.Allow(elem.endpoint.DstIP()) {
continue
}
}
default:
logError.Println("Invalid packet ended up in the handshake queue")
continue
}
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// handle handshake initiation/response content
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switch elem.msgType {
case MessageInitiationType:
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// unmarshal
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var msg MessageInitiation
reader := bytes.NewReader(elem.packet)
err := binary.Read(reader, binary.LittleEndian, &msg)
if err != nil {
logError.Println("Failed to decode initiation message")
continue
}
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// consume initiation
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peer := device.ConsumeMessageInitiation(&msg)
if peer == nil {
logInfo.Println(
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"Received invalid initiation message from",
elem.endpoint.DstToString(),
)
continue
}
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// update timers
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peer.timersAnyAuthenticatedPacketTraversal()
peer.timersAnyAuthenticatedPacketReceived()
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// update endpoint
peer.mutex.Lock()
peer.endpoint = elem.endpoint
peer.mutex.Unlock()
logDebug.Println(peer, ": Received handshake initiation")
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peer.SendHandshakeResponse()
case MessageResponseType:
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// unmarshal
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var msg MessageResponse
reader := bytes.NewReader(elem.packet)
err := binary.Read(reader, binary.LittleEndian, &msg)
if err != nil {
logError.Println("Failed to decode response message")
continue
}
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// consume response
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peer := device.ConsumeMessageResponse(&msg)
if peer == nil {
logInfo.Println(
"Recieved invalid response message from",
elem.endpoint.DstToString(),
)
continue
}
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// update endpoint
peer.mutex.Lock()
peer.endpoint = elem.endpoint
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peer.mutex.Unlock()
logDebug.Println(peer, ": Received handshake response")
// update timers
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peer.timersAnyAuthenticatedPacketTraversal()
peer.timersAnyAuthenticatedPacketReceived()
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// derive keypair
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err = peer.BeginSymmetricSession()
if err != nil {
logError.Println(peer, ": Failed to derive keypair:", err)
continue
}
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peer.timersSessionDerived()
peer.timersHandshakeComplete()
peer.SendKeepalive()
select {
case peer.signals.newKeypairArrived <- struct{}{}:
default:
}
}
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}
}
func (peer *Peer) RoutineSequentialReceiver() {
device := peer.device
logInfo := device.log.Info
logError := device.log.Error
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logDebug := device.log.Debug
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defer func() {
logDebug.Println(peer, ": Routine: sequential receiver - stopped")
peer.routines.stopping.Done()
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}()
logDebug.Println(peer, ": Routine: sequential receiver - started")
peer.routines.starting.Done()
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for {
select {
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case <-peer.routines.stop:
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return
case elem, ok := <-peer.queue.inbound:
if !ok {
return
}
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// wait for decryption
elem.mutex.Lock()
if elem.IsDropped() {
continue
}
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// check for replay
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if !elem.keypair.replayFilter.ValidateCounter(elem.counter) {
continue
}
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// update endpoint
peer.mutex.Lock()
peer.endpoint = elem.endpoint
peer.mutex.Unlock()
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// check if using new keypair
if peer.ReceivedWithKeypair(elem.keypair) {
peer.timersHandshakeComplete()
select {
case peer.signals.newKeypairArrived <- struct{}{}:
default:
}
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}
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peer.keepKeyFreshReceiving()
peer.timersAnyAuthenticatedPacketTraversal()
peer.timersAnyAuthenticatedPacketReceived()
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// check for keepalive
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if len(elem.packet) == 0 {
logDebug.Println(peer, ": Receiving keepalive packet")
continue
}
peer.timersDataReceived()
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// verify source and strip padding
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switch elem.packet[0] >> 4 {
case ipv4.Version:
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// strip padding
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if len(elem.packet) < ipv4.HeaderLen {
continue
}
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field := elem.packet[IPv4offsetTotalLength : IPv4offsetTotalLength+2]
length := binary.BigEndian.Uint16(field)
if int(length) > len(elem.packet) || int(length) < ipv4.HeaderLen {
continue
}
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elem.packet = elem.packet[:length]
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// verify IPv4 source
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src := elem.packet[IPv4offsetSrc : IPv4offsetSrc+net.IPv4len]
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if device.allowedips.LookupIPv4(src) != peer {
logInfo.Println(
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"IPv4 packet with disallowed source address from",
peer,
)
continue
}
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case ipv6.Version:
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// strip padding
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if len(elem.packet) < ipv6.HeaderLen {
continue
}
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field := elem.packet[IPv6offsetPayloadLength : IPv6offsetPayloadLength+2]
length := binary.BigEndian.Uint16(field)
length += ipv6.HeaderLen
if int(length) > len(elem.packet) {
continue
}
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elem.packet = elem.packet[:length]
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// verify IPv6 source
src := elem.packet[IPv6offsetSrc : IPv6offsetSrc+net.IPv6len]
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if device.allowedips.LookupIPv6(src) != peer {
logInfo.Println(
peer,
"sent packet with disallowed IPv6 source",
)
continue
}
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default:
logInfo.Println("Packet with invalid IP version from", peer)
continue
}
// write to tun device
offset := MessageTransportOffsetContent
atomic.AddUint64(&peer.stats.rxBytes, uint64(len(elem.packet)))
_, err := device.tun.device.Write(
elem.buffer[:offset+len(elem.packet)],
offset)
device.PutMessageBuffer(elem.buffer)
if err != nil {
logError.Println("Failed to write packet to TUN device:", err)
}
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}
}
}