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" ) /* Handles outbound flow * * 1. TUN queue * 2. Routing (sequential) * 3. Nonce assignment (sequential) * 4. Encryption (parallel) * 5. Transmission (sequential) * * The order of packets (per peer) is maintained. * The functions in this file occure (roughly) in the order packets are processed. */ /* 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 preceeded 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 "data" (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: 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(tun TUNDevice) { if tun == nil { return } elem := device.NewOutboundElement() logDebug := device.log.Debug logError := device.log.Error logDebug.Println("Routine, TUN Reader: started") for { // read packet if elem == nil { elem = device.NewOutboundElement() } elem.packet = elem.buffer[MessageTransportHeaderSize:] size, err := tun.Read(elem.packet) if err != nil { // stop process logError.Println("Failed to read packet from TUN device:", err) device.Close() return } elem.packet = elem.packet[:size] if len(elem.packet) < ipv4.HeaderLen { logError.Println("Packet too short, length:", size) continue } // lookup peer var peer *Peer switch elem.packet[0] >> 4 { case ipv4.Version: dst := elem.packet[IPv4offsetDst : IPv4offsetDst+net.IPv4len] peer = device.routingTable.LookupIPv4(dst) case ipv6.Version: dst := elem.packet[IPv6offsetDst : IPv6offsetDst+net.IPv6len] peer = device.routingTable.LookupIPv6(dst) default: logDebug.Println("Receieved packet with unknown IP version") } if peer == nil { continue } if peer.endpoint == nil { logDebug.Println("No known endpoint for peer", peer.String()) continue } // insert into nonce/pre-handshake queue addToOutboundQueue(peer.queue.nonce, elem) elem = nil } } /* Queues packets when there is no handshake. * Then assigns nonces to packets sequentially * and creates "work" structs for workers * * TODO: Avoid dynamic allocation of work queue elements * * Obs. A single instance per peer */ func (peer *Peer) RoutineNonce() { var keyPair *KeyPair var elem *QueueOutboundElement device := peer.device logDebug := device.log.Debug logDebug.Println("Routine, nonce worker, started for peer", peer.String()) func() { for { NextPacket: // wait for packet if elem == nil { select { case elem = <-peer.queue.nonce: case <-peer.signal.stop: return } } // wait for key pair for { select { case <-peer.signal.newKeyPair: default: } keyPair = peer.keyPairs.Current() if keyPair != nil && keyPair.sendNonce < RejectAfterMessages { if time.Now().Sub(keyPair.created) < RejectAfterTime { break } } signalSend(peer.signal.handshakeBegin) logDebug.Println("Awaiting key-pair for", peer.String()) select { case <-peer.signal.newKeyPair: logDebug.Println("Key-pair negotiated for", peer.String()) goto NextPacket case <-peer.signal.flushNonceQueue: logDebug.Println("Clearing queue for", peer.String()) peer.FlushNonceQueue() elem = nil goto NextPacket case <-peer.signal.stop: return } } // process current packet if elem != nil { // create work element elem.keyPair = keyPair elem.nonce = atomic.AddUint64(&keyPair.sendNonce, 1) - 1 elem.dropped = AtomicFalse elem.peer = peer elem.mutex.Lock() // add to parallel and sequential queue addToEncryptionQueue(device.queue.encryption, elem) addToOutboundQueue(peer.queue.outbound, elem) elem = nil } } }() } /* 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 for work := range device.queue.encryption { // check if dropped if work.IsDropped() { continue } // populate header fields header := work.buffer[:MessageTransportHeaderSize] fieldType := header[0:4] fieldReceiver := header[4:8] fieldNonce := header[8:16] binary.LittleEndian.PutUint32(fieldType, MessageTransportType) binary.LittleEndian.PutUint32(fieldReceiver, work.keyPair.remoteIndex) binary.LittleEndian.PutUint64(fieldNonce, work.nonce) // pad content to MTU size mtu := int(atomic.LoadInt32(&device.mtu)) for i := len(work.packet); i < mtu; i++ { work.packet = append(work.packet, 0) } // encrypt content binary.LittleEndian.PutUint64(nonce[4:], work.nonce) work.packet = work.keyPair.send.Seal( work.packet[:0], nonce[:], work.packet, nil, ) length := MessageTransportHeaderSize + len(work.packet) work.packet = work.buffer[:length] work.mutex.Unlock() // refresh key if necessary work.peer.KeepKeyFreshSending() } } /* 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 logDebug := device.log.Debug logDebug.Println("Routine, sequential sender, started for", peer.String()) for { select { case <-peer.signal.stop: logDebug.Println("Routine, sequential sender, stopped for", peer.String()) return case work := <-peer.queue.outbound: work.mutex.Lock() func() { // return buffer to pool after processing defer device.PutMessageBuffer(work.buffer) if work.IsDropped() { return } // send to endpoint peer.mutex.RLock() defer peer.mutex.RUnlock() if peer.endpoint == nil { logDebug.Println("No endpoint for", peer.String()) return } device.net.mutex.RLock() defer device.net.mutex.RUnlock() if device.net.conn == nil { logDebug.Println("No source for device") return } // send message and return buffer to pool _, err := device.net.conn.WriteToUDP(work.packet, peer.endpoint) if err != nil { return } atomic.AddUint64(&peer.txBytes, uint64(len(work.packet))) // reset keep-alive peer.TimerResetKeepalive() }() } } }