From f575ab3cb47c86224dc4d84512f38aa1390459e4 Mon Sep 17 00:00:00 2001
From: mykola2312 <49044616+mykola2312@users.noreply.github.com>
Date: Wed, 29 Jan 2025 04:46:03 +0200
Subject: [PATCH] FIX deadlock related to blocking channel sending

---
 node/lux_node.go            | 41 ++++++++++++++++++++++++++++++-------
 node/lux_node_subscriber.go |  5 +++++
 2 files changed, 39 insertions(+), 7 deletions(-)
 create mode 100644 node/lux_node_subscriber.go

diff --git a/node/lux_node.go b/node/lux_node.go
index 29cccca..8532005 100644
--- a/node/lux_node.go
+++ b/node/lux_node.go
@@ -24,6 +24,9 @@ type LuxNode struct {
 	state     LuxNodeState
 	stateLock deadlock.RWMutex
 
+	subscribers []LuxNodeSubscriber
+	stopChan    chan bool
+
 	genlist net.LuxNonceList
 
 	dns *LuxDnsServer
@@ -31,13 +34,15 @@ type LuxNode struct {
 
 func NewLuxNode(nodeKey crypto.LuxKey, ks crypto.LuxKeyStore) LuxNode {
 	return LuxNode{
-		nodeId:    &nodeKey.Id,
-		router:    net.NewLuxRouter(nodeKey, ks),
-		running:   false,
-		neighbors: make(map[proto.LuxID]*ipnet.UDPAddr),
-		state:     NewLuxNodeState(),
-		genlist:   net.NewLuxNonceList(),
-		dns:       nil,
+		nodeId:      &nodeKey.Id,
+		router:      net.NewLuxRouter(nodeKey, ks),
+		running:     false,
+		neighbors:   make(map[proto.LuxID]*ipnet.UDPAddr),
+		state:       NewLuxNodeState(),
+		subscribers: make([]LuxNodeSubscriber, 0),
+		stopChan:    make(chan bool),
+		genlist:     net.NewLuxNonceList(),
+		dns:         nil,
 	}
 }
 
@@ -85,6 +90,10 @@ func (node *LuxNode) AddNeighbor(id proto.LuxID, udpAddr string) error {
 	return nil
 }
 
+func (node *LuxNode) AddSubscriber(subscriber LuxNodeSubscriber) {
+	node.subscribers = append(node.subscribers, subscriber)
+}
+
 func (node *LuxNode) AddDnsFrontend(udpListen string) error {
 	if node.dns == nil {
 		node.dns = NewLuxDnsServer(node)
@@ -232,11 +241,27 @@ func nodeLoop(node *LuxNode) {
 	}
 }
 
+// we need to read state from stateChan, or otherwise sending to it
+// will block everything and cause deadlock
+func subscriberLoop(node *LuxNode) {
+	for node.running {
+		select {
+		case <-node.stopChan:
+			return
+		case state := <-node.state.stateChan:
+			for _, subscriber := range node.subscribers {
+				subscriber.HandleStateUpdate(state)
+			}
+		}
+	}
+}
+
 func (node *LuxNode) Start() {
 	node.router.Start()
 	node.running = true
 
 	go nodeLoop(node)
+	go subscriberLoop(node)
 }
 
 func (node *LuxNode) Stop() {
@@ -245,6 +270,8 @@ func (node *LuxNode) Stop() {
 	}
 
 	node.running = false
+	node.stopChan <- true
+
 	node.router.Stop()
 }
 
diff --git a/node/lux_node_subscriber.go b/node/lux_node_subscriber.go
new file mode 100644
index 0000000..ff28532
--- /dev/null
+++ b/node/lux_node_subscriber.go
@@ -0,0 +1,5 @@
+package node
+
+type LuxNodeSubscriber interface {
+	HandleStateUpdate(state LuxHostState)
+}