[client] refactor lazy detection (#4050)

This PR introduces a new inactivity package responsible for monitoring peer activity and notifying when peers become inactive.
Introduces a new Signal message type to close the peer connection after the idle timeout is reached.
Periodically checks the last activity of registered peers via a Bind interface.
Notifies via a channel when peers exceed a configurable inactivity threshold.
Default settings
DefaultInactivityThreshold is set to 15 minutes, with a minimum allowed threshold of 1 minute.

Limitations
This inactivity check does not support kernel WireGuard integration. In kernel–user space communication, the user space side will always be responsible for closing the connection.

client/internal/lazyconn/inactivity/manager.go

@@ -0,0 +1,152 @@
+package inactivity
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	log "github.com/sirupsen/logrus"
+
+	"github.com/netbirdio/netbird/client/internal/lazyconn"
+)
+
+const (
+	checkInterval = 1 * time.Minute
+
+	DefaultInactivityThreshold = 15 * time.Minute
+	MinimumInactivityThreshold = 1 * time.Minute
+)
+
+type WgInterface interface {
+	LastActivities() map[string]time.Time
+}
+
+type Manager struct {
+	inactivePeersChan chan map[string]struct{}
+
+	iface               WgInterface
+	interestedPeers     map[string]*lazyconn.PeerConfig
+	inactivityThreshold time.Duration
+}
+
+func NewManager(iface WgInterface, configuredThreshold *time.Duration) *Manager {
+	inactivityThreshold, err := validateInactivityThreshold(configuredThreshold)
+	if err != nil {
+		inactivityThreshold = DefaultInactivityThreshold
+		log.Warnf("invalid inactivity threshold configured: %v, using default: %v", err, DefaultInactivityThreshold)
+	}
+
+	log.Infof("inactivity threshold configured: %v", inactivityThreshold)
+	return &Manager{
+		inactivePeersChan:   make(chan map[string]struct{}, 1),
+		iface:               iface,
+		interestedPeers:     make(map[string]*lazyconn.PeerConfig),
+		inactivityThreshold: inactivityThreshold,
+	}
+}
+
+func (m *Manager) InactivePeersChan() chan map[string]struct{} {
+	if m == nil {
+		// return a nil channel that blocks forever
+		return nil
+	}
+
+	return m.inactivePeersChan
+}
+
+func (m *Manager) AddPeer(peerCfg *lazyconn.PeerConfig) {
+	if m == nil {
+		return
+	}
+
+	if _, exists := m.interestedPeers[peerCfg.PublicKey]; exists {
+		return
+	}
+
+	peerCfg.Log.Infof("adding peer to inactivity manager")
+	m.interestedPeers[peerCfg.PublicKey] = peerCfg
+}
+
+func (m *Manager) RemovePeer(peer string) {
+	if m == nil {
+		return
+	}
+
+	pi, ok := m.interestedPeers[peer]
+	if !ok {
+		return
+	}
+
+	pi.Log.Debugf("remove peer from inactivity manager")
+	delete(m.interestedPeers, peer)
+}
+
+func (m *Manager) Start(ctx context.Context) {
+	if m == nil {
+		return
+	}
+
+	ticker := newTicker(checkInterval)
+	defer ticker.Stop()
+
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case <-ticker.C():
+			idlePeers, err := m.checkStats()
+			if err != nil {
+				log.Errorf("error checking stats: %v", err)
+				return
+			}
+
+			if len(idlePeers) == 0 {
+				continue
+			}
+
+			m.notifyInactivePeers(ctx, idlePeers)
+		}
+	}
+}
+
+func (m *Manager) notifyInactivePeers(ctx context.Context, inactivePeers map[string]struct{}) {
+	select {
+	case m.inactivePeersChan <- inactivePeers:
+	case <-ctx.Done():
+		return
+	default:
+		return
+	}
+}
+
+func (m *Manager) checkStats() (map[string]struct{}, error) {
+	lastActivities := m.iface.LastActivities()
+
+	idlePeers := make(map[string]struct{})
+
+	for peerID, peerCfg := range m.interestedPeers {
+		lastActive, ok := lastActivities[peerID]
+		if !ok {
+			// when peer is in connecting state
+			peerCfg.Log.Warnf("peer not found in wg stats")
+			continue
+		}
+
+		if time.Since(lastActive) > m.inactivityThreshold {
+			peerCfg.Log.Infof("peer is inactive since: %v", lastActive)
+			idlePeers[peerID] = struct{}{}
+		}
+	}
+
+	return idlePeers, nil
+}
+
+func validateInactivityThreshold(configuredThreshold *time.Duration) (time.Duration, error) {
+	if configuredThreshold == nil {
+		return DefaultInactivityThreshold, nil
+	}
+	if *configuredThreshold < MinimumInactivityThreshold {
+		return 0, fmt.Errorf("configured inactivity threshold %v is too low, using %v", *configuredThreshold, MinimumInactivityThreshold)
+	}
+	return *configuredThreshold, nil
+}