Align with go library layout

1 files changed, 362 insertions, 0 deletions

diff --git a/send.go b/send.go
new file mode 100644
index 0000000..7488d3a
--- /dev/null
+++ b/send.go
@@ -0,0 +1,362 @@
+package main
+
+import (
+	"encoding/binary"
+	"golang.org/x/crypto/chacha20poly1305"
+	"golang.org/x/net/ipv4"
+	"golang.org/x/net/ipv6"
+	"net"
+	"sync"
+	"sync/atomic"
+	"time"
+)
+
+/* Outbound flow
+ *
+ * 1. TUN queue
+ * 2. Routing (sequential)
+ * 3. Nonce assignment (sequential)
+ * 4. Encryption (parallel)
+ * 5. Transmission (sequential)
+ *
+ * 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",
+ * the content is preceded by enough "junk" to contain the transport header
+ * (to allow the construction of transport messages in-place)
+ */
+
+type QueueOutboundElement struct {
+	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
+}
+
+func (peer *Peer) FlushNonceQueue() {
+	elems := len(peer.queue.nonce)
+	for i := 0; i < elems; i++ {
+		select {
+		case <-peer.queue.nonce:
+		default:
+			return
+		}
+	}
+}
+
+func (device *Device) NewOutboundElement() *QueueOutboundElement {
+	return &QueueOutboundElement{
+		dropped: AtomicFalse,
+		buffer:  device.pool.messageBuffers.Get().(*[MaxMessageSize]byte),
+	}
+}
+
+func (elem *QueueOutboundElement) Drop() {
+	atomic.StoreInt32(&elem.dropped, AtomicTrue)
+}
+
+func (elem *QueueOutboundElement) IsDropped() bool {
+	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:
+			}
+		}
+	}
+}
+
+func addToEncryptionQueue(
+	queue chan *QueueOutboundElement,
+	element *QueueOutboundElement,
+) {
+	for {
+		select {
+		case queue <- element:
+			return
+		default:
+			select {
+			case old := <-queue:
+				// drop & release to potential consumer
+				old.Drop()
+				old.mutex.Unlock()
+			default:
+			}
+		}
+	}
+}
+
+/* Reads packets from the TUN and inserts
+ * into nonce queue for peer
+ *
+ * Obs. Single instance per TUN device
+ */
+func (device *Device) RoutineReadFromTUN() {
+
+	elem := device.NewOutboundElement()
+
+	logDebug := device.log.Debug
+	logError := device.log.Error
+
+	logDebug.Println("Routine, TUN Reader started")
+
+	for {
+
+		// 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
+		}
+
+		if size == 0 || size > MaxContentSize {
+			continue
+		}
+
+		elem.packet = elem.buffer[offset : offset+size]
+
+		// lookup peer
+
+		var peer *Peer
+		switch elem.packet[0] >> 4 {
+		case ipv4.Version:
+			if len(elem.packet) < ipv4.HeaderLen {
+				continue
+			}
+			dst := elem.packet[IPv4offsetDst : IPv4offsetDst+net.IPv4len]
+			peer = device.routing.table.LookupIPv4(dst)
+
+		case ipv6.Version:
+			if len(elem.packet) < ipv6.HeaderLen {
+				continue
+			}
+			dst := elem.packet[IPv6offsetDst : IPv6offsetDst+net.IPv6len]
+			peer = device.routing.table.LookupIPv6(dst)
+
+		default:
+			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()
+		}
+	}
+}
+
+/* Queues packets when there is no handshake.
+ * Then assigns nonces to packets sequentially
+ * and creates "work" structs for workers
+ *
+ * Obs. A single instance per peer
+ */
+func (peer *Peer) RoutineNonce() {
+	var keyPair *KeyPair
+
+	defer peer.routines.stopping.Done()
+
+	device := peer.device
+	logDebug := device.log.Debug
+	logDebug.Println("Routine, nonce worker, started for peer", peer.String())
+
+	peer.routines.starting.Done()
+
+	for {
+	NextPacket:
+		select {
+		case <-peer.routines.stop.Wait():
+			return
+
+		case elem := <-peer.queue.nonce:
+
+			// wait for key pair
+
+			for {
+				keyPair = peer.keyPairs.Current()
+				if keyPair != nil && keyPair.sendNonce < RejectAfterMessages {
+					if time.Now().Sub(keyPair.created) < RejectAfterTime {
+						break
+					}
+				}
+
+				peer.signal.handshakeBegin.Send()
+
+				logDebug.Println("Awaiting key-pair for", peer.String())
+
+				select {
+				case <-peer.signal.newKeyPair.Wait():
+				case <-peer.signal.flushNonceQueue.Wait():
+					logDebug.Println("Clearing queue for", peer.String())
+					peer.FlushNonceQueue()
+					goto NextPacket
+				case <-peer.routines.stop.Wait():
+					return
+				}
+			}
+
+			// populate work element
+
+			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)
+		}
+	}
+}
+
+/* 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() {
+
+	var nonce [chacha20poly1305.NonceSize]byte
+
+	logDebug := device.log.Debug
+	logDebug.Println("Routine, encryption worker, started")
+
+	for {
+
+		// fetch next element
+
+		select {
+		case <-device.signal.stop.Wait():
+			logDebug.Println("Routine, encryption worker, stopped")
+			return
+
+		case elem := <-device.queue.encryption:
+
+			// check if dropped
+
+			if elem.IsDropped() {
+				continue
+			}
+
+			// populate header fields
+
+			header := elem.buffer[:MessageTransportHeaderSize]
+
+			fieldType := header[0:4]
+			fieldReceiver := header[4:8]
+			fieldNonce := header[8:16]
+
+			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)
+				}
+			}
+
+			// 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() {
+
+	defer peer.routines.stopping.Done()
+
+	device := peer.device
+
+	logDebug := device.log.Debug
+	logDebug.Println("Routine, sequential sender, started for", peer.String())
+
+	peer.routines.starting.Done()
+
+	for {
+		select {
+
+		case <-peer.routines.stop.Wait():
+			logDebug.Println(
+				"Routine, sequential sender, stopped for", peer.String())
+			return
+
+		case elem := <-peer.queue.outbound:
+			elem.mutex.Lock()
+			if elem.IsDropped() {
+				continue
+			}
+
+			// send message and return buffer to pool
+
+			length := uint64(len(elem.packet))
+			err := peer.SendBuffer(elem.packet)
+			device.PutMessageBuffer(elem.buffer)
+			if err != nil {
+				logDebug.Println("Failed to send authenticated packet to peer", peer.String())
+				continue
+			}
+			atomic.AddUint64(&peer.stats.txBytes, length)
+
+			// update timers
+
+			peer.TimerAnyAuthenticatedPacketTraversal()
+			if len(elem.packet) != MessageKeepaliveSize {
+				peer.TimerDataSent()
+			}
+			peer.KeepKeyFreshSending()
+		}
+	}
+}