1 files changed, 227 insertions, 0 deletions
diff --git a/device/timers.go b/device/timers.go
new file mode 100644
index 0000000..5f28fcc
--- /dev/null
+++ b/device/timers.go
@@ -0,0 +1,227 @@
+/* SPDX-License-Identifier: MIT
+ *
+ * Copyright (C) 2017-2019 WireGuard LLC. All Rights Reserved.
+ *
+ * This is based heavily on timers.c from the kernel implementation.
+ */
+
+package device
+
+import (
+	"math/rand"
+	"sync"
+	"sync/atomic"
+	"time"
+)
+
+/* This Timer structure and related functions should roughly copy the interface of
+ * the Linux kernel's struct timer_list.
+ */
+
+type Timer struct {
+	*time.Timer
+	modifyingLock sync.RWMutex
+	runningLock   sync.Mutex
+	isPending     bool
+}
+
+func (peer *Peer) NewTimer(expirationFunction func(*Peer)) *Timer {
+	timer := &Timer{}
+	timer.Timer = time.AfterFunc(time.Hour, func() {
+		timer.runningLock.Lock()
+
+		timer.modifyingLock.Lock()
+		if !timer.isPending {
+			timer.modifyingLock.Unlock()
+			timer.runningLock.Unlock()
+			return
+		}
+		timer.isPending = false
+		timer.modifyingLock.Unlock()
+
+		expirationFunction(peer)
+		timer.runningLock.Unlock()
+	})
+	timer.Stop()
+	return timer
+}
+
+func (timer *Timer) Mod(d time.Duration) {
+	timer.modifyingLock.Lock()
+	timer.isPending = true
+	timer.Reset(d)
+	timer.modifyingLock.Unlock()
+}
+
+func (timer *Timer) Del() {
+	timer.modifyingLock.Lock()
+	timer.isPending = false
+	timer.Stop()
+	timer.modifyingLock.Unlock()
+}
+
+func (timer *Timer) DelSync() {
+	timer.Del()
+	timer.runningLock.Lock()
+	timer.Del()
+	timer.runningLock.Unlock()
+}
+
+func (timer *Timer) IsPending() bool {
+	timer.modifyingLock.RLock()
+	defer timer.modifyingLock.RUnlock()
+	return timer.isPending
+}
+
+func (peer *Peer) timersActive() bool {
+	return peer.isRunning.Get() && peer.device != nil && peer.device.isUp.Get() && len(peer.device.peers.keyMap) > 0
+}
+
+func expiredRetransmitHandshake(peer *Peer) {
+	if atomic.LoadUint32(&peer.timers.handshakeAttempts) > MaxTimerHandshakes {
+		peer.device.log.Debug.Printf("%s - Handshake did not complete after %d attempts, giving up\n", peer, MaxTimerHandshakes+2)
+
+		if peer.timersActive() {
+			peer.timers.sendKeepalive.Del()
+		}
+
+		/* We drop all packets without a keypair and don't try again,
+		 * if we try unsuccessfully for too long to make a handshake.
+		 */
+		peer.FlushNonceQueue()
+
+		/* We set a timer for destroying any residue that might be left
+		 * of a partial exchange.
+		 */
+		if peer.timersActive() && !peer.timers.zeroKeyMaterial.IsPending() {
+			peer.timers.zeroKeyMaterial.Mod(RejectAfterTime * 3)
+		}
+	} else {
+		atomic.AddUint32(&peer.timers.handshakeAttempts, 1)
+		peer.device.log.Debug.Printf("%s - Handshake did not complete after %d seconds, retrying (try %d)\n", peer, int(RekeyTimeout.Seconds()), atomic.LoadUint32(&peer.timers.handshakeAttempts)+1)
+
+		/* We clear the endpoint address src address, in case this is the cause of trouble. */
+		peer.Lock()
+		if peer.endpoint != nil {
+			peer.endpoint.ClearSrc()
+		}
+		peer.Unlock()
+
+		peer.SendHandshakeInitiation(true)
+	}
+}
+
+func expiredSendKeepalive(peer *Peer) {
+	peer.SendKeepalive()
+	if peer.timers.needAnotherKeepalive.Get() {
+		peer.timers.needAnotherKeepalive.Set(false)
+		if peer.timersActive() {
+			peer.timers.sendKeepalive.Mod(KeepaliveTimeout)
+		}
+	}
+}
+
+func expiredNewHandshake(peer *Peer) {
+	peer.device.log.Debug.Printf("%s - Retrying handshake because we stopped hearing back after %d seconds\n", peer, int((KeepaliveTimeout + RekeyTimeout).Seconds()))
+	/* We clear the endpoint address src address, in case this is the cause of trouble. */
+	peer.Lock()
+	if peer.endpoint != nil {
+		peer.endpoint.ClearSrc()
+	}
+	peer.Unlock()
+	peer.SendHandshakeInitiation(false)
+
+}
+
+func expiredZeroKeyMaterial(peer *Peer) {
+	peer.device.log.Debug.Printf("%s - Removing all keys, since we haven't received a new one in %d seconds\n", peer, int((RejectAfterTime * 3).Seconds()))
+	peer.ZeroAndFlushAll()
+}
+
+func expiredPersistentKeepalive(peer *Peer) {
+	if peer.persistentKeepaliveInterval > 0 {
+		peer.SendKeepalive()
+	}
+}
+
+/* Should be called after an authenticated data packet is sent. */
+func (peer *Peer) timersDataSent() {
+	if peer.timersActive() && !peer.timers.newHandshake.IsPending() {
+		peer.timers.newHandshake.Mod(KeepaliveTimeout + RekeyTimeout)
+	}
+}
+
+/* Should be called after an authenticated data packet is received. */
+func (peer *Peer) timersDataReceived() {
+	if peer.timersActive() {
+		if !peer.timers.sendKeepalive.IsPending() {
+			peer.timers.sendKeepalive.Mod(KeepaliveTimeout)
+		} else {
+			peer.timers.needAnotherKeepalive.Set(true)
+		}
+	}
+}
+
+/* Should be called after any type of authenticated packet is sent -- keepalive, data, or handshake. */
+func (peer *Peer) timersAnyAuthenticatedPacketSent() {
+	if peer.timersActive() {
+		peer.timers.sendKeepalive.Del()
+	}
+}
+
+/* Should be called after any type of authenticated packet is received -- keepalive, data, or handshake. */
+func (peer *Peer) timersAnyAuthenticatedPacketReceived() {
+	if peer.timersActive() {
+		peer.timers.newHandshake.Del()
+	}
+}
+
+/* Should be called after a handshake initiation message is sent. */
+func (peer *Peer) timersHandshakeInitiated() {
+	if peer.timersActive() {
+		peer.timers.retransmitHandshake.Mod(RekeyTimeout + time.Millisecond*time.Duration(rand.Int31n(RekeyTimeoutJitterMaxMs)))
+	}
+}
+
+/* Should be called after a handshake response message is received and processed or when getting key confirmation via the first data message. */
+func (peer *Peer) timersHandshakeComplete() {
+	if peer.timersActive() {
+		peer.timers.retransmitHandshake.Del()
+	}
+	atomic.StoreUint32(&peer.timers.handshakeAttempts, 0)
+	peer.timers.sentLastMinuteHandshake.Set(false)
+	atomic.StoreInt64(&peer.stats.lastHandshakeNano, time.Now().UnixNano())
+}
+
+/* Should be called after an ephemeral key is created, which is before sending a handshake response or after receiving a handshake response. */
+func (peer *Peer) timersSessionDerived() {
+	if peer.timersActive() {
+		peer.timers.zeroKeyMaterial.Mod(RejectAfterTime * 3)
+	}
+}
+
+/* Should be called before a packet with authentication -- keepalive, data, or handshake -- is sent, or after one is received. */
+func (peer *Peer) timersAnyAuthenticatedPacketTraversal() {
+	if peer.persistentKeepaliveInterval > 0 && peer.timersActive() {
+		peer.timers.persistentKeepalive.Mod(time.Duration(peer.persistentKeepaliveInterval) * time.Second)
+	}
+}
+
+func (peer *Peer) timersInit() {
+	peer.timers.retransmitHandshake = peer.NewTimer(expiredRetransmitHandshake)
+	peer.timers.sendKeepalive = peer.NewTimer(expiredSendKeepalive)
+	peer.timers.newHandshake = peer.NewTimer(expiredNewHandshake)
+	peer.timers.zeroKeyMaterial = peer.NewTimer(expiredZeroKeyMaterial)
+	peer.timers.persistentKeepalive = peer.NewTimer(expiredPersistentKeepalive)
+	atomic.StoreUint32(&peer.timers.handshakeAttempts, 0)
+	peer.timers.sentLastMinuteHandshake.Set(false)
+	peer.timers.needAnotherKeepalive.Set(false)
+}
+
+func (peer *Peer) timersStop() {
+	peer.timers.retransmitHandshake.DelSync()
+	peer.timers.sendKeepalive.DelSync()
+	peer.timers.newHandshake.DelSync()
+	peer.timers.zeroKeyMaterial.DelSync()
+	peer.timers.persistentKeepalive.DelSync()
+}