wireguard-go/send.go

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package main
import (
"encoding/binary"
"golang.org/x/crypto/chacha20poly1305"
"golang.org/x/net/ipv4"
"golang.org/x/net/ipv6"
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"net"
"sync"
"sync/atomic"
"time"
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)
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/* Outbound flow
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*
* 1. TUN queue
* 2. Routing (sequential)
* 3. Nonce assignment (sequential)
* 4. Encryption (parallel)
* 5. Transmission (sequential)
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*
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* The functions in this file occur (roughly) in the order in
* which the packets are processed.
*
* Locking, Producers and Consumers
*
* The order of packets (per peer) must be maintained,
* but encryption of packets happen out-of-order:
*
* The sequential consumers will attempt to take the lock,
* workers release lock when they have completed work (encryption) on the packet.
*
* If the element is inserted into the "encryption queue",
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* the content is preceded by enough "junk" to contain the transport header
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* (to allow the construction of transport messages in-place)
*/
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type QueueOutboundElement struct {
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dropped int32
mutex sync.Mutex
buffer *[MaxMessageSize]byte // slice holding the packet data
packet []byte // slice of "buffer" (always!)
nonce uint64 // nonce for encryption
keyPair *KeyPair // key-pair for encryption
peer *Peer // related peer
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}
func (peer *Peer) FlushNonceQueue() {
elems := len(peer.queue.nonce)
for i := 0; i < elems; i++ {
select {
case <-peer.queue.nonce:
default:
return
}
}
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}
func (device *Device) NewOutboundElement() *QueueOutboundElement {
return &QueueOutboundElement{
dropped: AtomicFalse,
buffer: device.pool.messageBuffers.Get().(*[MaxMessageSize]byte),
}
}
func (elem *QueueOutboundElement) Drop() {
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atomic.StoreInt32(&elem.dropped, AtomicTrue)
}
func (elem *QueueOutboundElement) IsDropped() bool {
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return atomic.LoadInt32(&elem.dropped) == AtomicTrue
}
func addToOutboundQueue(
queue chan *QueueOutboundElement,
element *QueueOutboundElement,
) {
for {
select {
case queue <- element:
return
default:
select {
case old := <-queue:
old.Drop()
default:
}
}
}
}
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func addToEncryptionQueue(
queue chan *QueueOutboundElement,
element *QueueOutboundElement,
) {
for {
select {
case queue <- element:
return
default:
select {
case old := <-queue:
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// drop & release to potential consumer
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old.Drop()
old.mutex.Unlock()
default:
}
}
}
}
/* Reads packets from the TUN and inserts
* into nonce queue for peer
*
* Obs. Single instance per TUN device
*/
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func (device *Device) RoutineReadFromTUN() {
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elem := device.NewOutboundElement()
logDebug := device.log.Debug
logError := device.log.Error
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logDebug.Println("Routine, TUN Reader started")
for {
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// read packet
offset := MessageTransportHeaderSize
size, err := device.tun.device.Read(elem.buffer[:], offset)
if err != nil {
logError.Println("Failed to read packet from TUN device:", err)
device.Close()
return
}
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if size == 0 || size > MaxContentSize {
continue
}
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elem.packet = elem.buffer[offset : offset+size]
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// lookup peer
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var peer *Peer
switch elem.packet[0] >> 4 {
case ipv4.Version:
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if len(elem.packet) < ipv4.HeaderLen {
continue
}
dst := elem.packet[IPv4offsetDst : IPv4offsetDst+net.IPv4len]
peer = device.routing.table.LookupIPv4(dst)
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case ipv6.Version:
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if len(elem.packet) < ipv6.HeaderLen {
continue
}
dst := elem.packet[IPv6offsetDst : IPv6offsetDst+net.IPv6len]
peer = device.routing.table.LookupIPv6(dst)
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default:
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logDebug.Println("Received packet with unknown IP version")
}
if peer == nil {
continue
}
// insert into nonce/pre-handshake queue
if peer.isRunning.Get() {
peer.timer.handshakeDeadline.Reset(RekeyAttemptTime)
addToOutboundQueue(peer.queue.nonce, elem)
elem = device.NewOutboundElement()
}
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}
}
/* Queues packets when there is no handshake.
* Then assigns nonces to packets sequentially
* and creates "work" structs for workers
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*
* Obs. A single instance per peer
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*/
func (peer *Peer) RoutineNonce() {
var keyPair *KeyPair
device := peer.device
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logDebug := device.log.Debug
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defer func() {
peer.routines.stopping.Done()
logDebug.Println(peer.String(), ": Routine, Nonce Worker, Stopped")
}()
peer.routines.starting.Done()
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logDebug.Println(peer.String(), ": Routine, Nonce Worker, Started")
for {
NextPacket:
select {
case <-peer.routines.stop.Wait():
return
case elem := <-peer.queue.nonce:
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// wait for key pair
for {
keyPair = peer.keyPairs.Current()
if keyPair != nil && keyPair.sendNonce < RejectAfterMessages {
if time.Now().Sub(keyPair.created) < RejectAfterTime {
break
}
}
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peer.signal.handshakeBegin.Send()
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logDebug.Println(peer.String(), ": Awaiting key-pair")
select {
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case <-peer.signal.newKeyPair.Wait():
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logDebug.Println(peer.String(), ": Obtained awaited key-pair")
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case <-peer.signal.flushNonceQueue.Wait():
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logDebug.Println(peer.String(), ": Flushing nonce queue")
peer.FlushNonceQueue()
goto NextPacket
case <-peer.routines.stop.Wait():
return
}
}
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// populate work element
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elem.peer = peer
elem.nonce = atomic.AddUint64(&keyPair.sendNonce, 1) - 1
elem.keyPair = keyPair
elem.dropped = AtomicFalse
elem.mutex.Lock()
// add to parallel and sequential queue
addToEncryptionQueue(device.queue.encryption, elem)
addToOutboundQueue(peer.queue.outbound, elem)
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}
}
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}
/* Encrypts the elements in the queue
* and marks them for sequential consumption (by releasing the mutex)
*
* Obs. One instance per core
*/
func (device *Device) RoutineEncryption() {
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var nonce [chacha20poly1305.NonceSize]byte
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logDebug := device.log.Debug
logDebug.Println("Routine, encryption worker, started")
for {
// fetch next element
select {
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case <-device.signal.stop.Wait():
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logDebug.Println("Routine, encryption worker, stopped")
return
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case elem := <-device.queue.encryption:
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// check if dropped
if elem.IsDropped() {
continue
}
// populate header fields
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header := elem.buffer[:MessageTransportHeaderSize]
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fieldType := header[0:4]
fieldReceiver := header[4:8]
fieldNonce := header[8:16]
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binary.LittleEndian.PutUint32(fieldType, MessageTransportType)
binary.LittleEndian.PutUint32(fieldReceiver, elem.keyPair.remoteIndex)
binary.LittleEndian.PutUint64(fieldNonce, elem.nonce)
// pad content to multiple of 16
mtu := int(atomic.LoadInt32(&device.tun.mtu))
rem := len(elem.packet) % PaddingMultiple
if rem > 0 {
for i := 0; i < PaddingMultiple-rem && len(elem.packet) < mtu; i++ {
elem.packet = append(elem.packet, 0)
}
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}
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// encrypt content and release to consumer
binary.LittleEndian.PutUint64(nonce[4:], elem.nonce)
elem.packet = elem.keyPair.send.Seal(
header,
nonce[:],
elem.packet,
nil,
)
elem.mutex.Unlock()
}
}
}
/* Sequentially reads packets from queue and sends to endpoint
*
* Obs. Single instance per peer.
* The routine terminates then the outbound queue is closed.
*/
func (peer *Peer) RoutineSequentialSender() {
device := peer.device
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logDebug := device.log.Debug
logDebug.Println("Routine, sequential sender, started for", peer.String())
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defer func() {
peer.routines.stopping.Done()
logDebug.Println(peer.String(), ": Routine, Sequential sender, Stopped")
}()
peer.routines.starting.Done()
for {
select {
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case <-peer.routines.stop.Wait():
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logDebug.Println(
"Routine, sequential sender, stopped for", peer.String())
return
case elem, ok := <-peer.queue.outbound:
if !ok {
return
}
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elem.mutex.Lock()
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if elem.IsDropped() {
continue
}
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// send message and return buffer to pool
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length := uint64(len(elem.packet))
err := peer.SendBuffer(elem.packet)
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device.PutMessageBuffer(elem.buffer)
if err != nil {
logDebug.Println("Failed to send authenticated packet to peer", peer.String())
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continue
}
atomic.AddUint64(&peer.stats.txBytes, length)
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// update timers
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peer.TimerAnyAuthenticatedPacketTraversal()
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if len(elem.packet) != MessageKeepaliveSize {
peer.TimerDataSent()
}
peer.KeepKeyFreshSending()
}
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}
}