From 2fe19ce54db258d8c47ff03d8335fd28c7c7ad0f Mon Sep 17 00:00:00 2001
From: Josh Bleecher Snyder <josh@tailscale.com>
Date: Mon, 11 Jan 2021 17:21:16 -0800
Subject: [PATCH] device: remove selects from encrypt/decrypt/inbound/outbound
 enqueuing

Block instead. Backpressure here is fine, probably preferable.
This reduces code complexity.

Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>
---
 device/receive.go | 23 +++--------------------
 device/send.go    | 20 ++------------------
 2 files changed, 5 insertions(+), 38 deletions(-)

diff --git a/device/receive.go b/device/receive.go
index 20e0c8f..972b342 100644
--- a/device/receive.go
+++ b/device/receive.go
@@ -58,23 +58,6 @@ func (elem *QueueInboundElement) IsDropped() bool {
 	return atomic.LoadInt32(&elem.dropped) == AtomicTrue
 }
 
-func (device *Device) addToInboundAndDecryptionQueues(inboundQueue chan *QueueInboundElement, decryptionQueue chan *QueueInboundElement, elem *QueueInboundElement) bool {
-	select {
-	case inboundQueue <- elem:
-		select {
-		case decryptionQueue <- elem:
-			return true
-		default:
-			elem.Drop()
-			elem.Unlock()
-			return false
-		}
-	default:
-		device.PutInboundElement(elem)
-		return false
-	}
-}
-
 func (device *Device) addToHandshakeQueue(queue chan QueueHandshakeElement, elem QueueHandshakeElement) bool {
 	select {
 	case queue <- elem:
@@ -207,9 +190,9 @@ func (device *Device) RoutineReceiveIncoming(IP int, bind conn.Bind) {
 
 			peer.queue.RLock()
 			if peer.isRunning.Get() {
-				if device.addToInboundAndDecryptionQueues(peer.queue.inbound, device.queue.decryption.c, elem) {
-					buffer = device.GetMessageBuffer()
-				}
+				peer.queue.inbound <- elem
+				device.queue.decryption.c <- elem
+				buffer = device.GetMessageBuffer()
 			} else {
 				device.PutInboundElement(elem)
 			}
diff --git a/device/send.go b/device/send.go
index 55df4b3..c9b62e6 100644
--- a/device/send.go
+++ b/device/send.go
@@ -97,23 +97,6 @@ func addToNonceQueue(queue chan *QueueOutboundElement, elem *QueueOutboundElemen
 	}
 }
 
-func addToOutboundAndEncryptionQueues(outboundQueue chan *QueueOutboundElement, encryptionQueue chan *QueueOutboundElement, elem *QueueOutboundElement) {
-	select {
-	case outboundQueue <- elem:
-		select {
-		case encryptionQueue <- elem:
-			return
-		default:
-			elem.Drop()
-			elem.peer.device.PutMessageBuffer(elem.buffer)
-			elem.Unlock()
-		}
-	default:
-		elem.peer.device.PutMessageBuffer(elem.buffer)
-		elem.peer.device.PutOutboundElement(elem)
-	}
-}
-
 /* Queues a keepalive if no packets are queued for peer
  */
 func (peer *Peer) SendKeepalive() bool {
@@ -457,7 +440,8 @@ NextPacket:
 			elem.Lock()
 
 			// add to parallel and sequential queue
-			addToOutboundAndEncryptionQueues(peer.queue.outbound, device.queue.encryption.c, elem)
+			peer.queue.outbound <- elem
+			device.queue.encryption.c <- elem
 		}
 	}
 }