Don't rotate PQ keys if data path is idle for ~90s (less than a WG handhshake time

client/internal/peer/conn.go

@@ -3,6 +3,7 @@ package peer
 import (
 	"context"
 	"fmt"
+	"math"
 	"net"
 	"net/netip"
 	"runtime"
@@ -26,6 +27,7 @@ import (
 	"github.com/netbirdio/netbird/client/internal/portforward"
 	"github.com/netbirdio/netbird/client/internal/rosenpass"
 	"github.com/netbirdio/netbird/client/internal/stdnet"
+	"github.com/netbirdio/netbird/monotime"
 	"github.com/netbirdio/netbird/route"
 	relayClient "github.com/netbirdio/netbird/shared/relay/client"
 )
@@ -94,8 +96,10 @@ type PQHandshaker interface {
 	// its WG overlay IP with the advertised pq UDP port.
 	SetRemoteAddr(remoteKey string, addr netip.AddrPort)
 	// OnDataPathRekeyed signals a fresh WireGuard handshake for the peer; it clocks the
-	// next chained PSK rotation pushed over the data path.
-	OnDataPathRekeyed(remoteKey string)
+	// next chained PSK rotation pushed over the data path. sinceActivity is how long
+	// ago the peer last exchanged real user data, so the rotation can be skipped for
+	// idle tunnels.
+	OnDataPathRekeyed(remoteKey string, sinceActivity time.Duration)
 	// OnDataPathDown signals the peer's tunnel went down.
 	OnDataPathDown(remoteKey string)
 }
@@ -980,12 +984,27 @@ func (conn *Conn) onWGCheckSuccess() {
 	conn.wgTimeouts = 0
 	conn.mu.Unlock()
 
-	// A fresh WireGuard handshake is the clock for the post-quantum PSK rotation.
+	// A fresh WireGuard handshake clocks the post-quantum PSK rotation. Pass how long
+	// ago the peer last exchanged real user data (keepalives excluded) so the pqkem
+	// manager can skip rotation on idle tunnels — rotating then would push data-path
+	// traffic that keeps the lazy connection artificially active.
 	if conn.config.PQ != nil {
-		conn.config.PQ.OnDataPathRekeyed(conn.config.Key)
+		conn.config.PQ.OnDataPathRekeyed(conn.config.Key, conn.dataActivityAge())
 	}
 }
 
+// dataActivityAge returns how long ago the peer last exchanged real user data
+// (WireGuard keepalives excluded), per the same LastActivities signal the
+// lazy-connection inactivity monitor uses. It reports a very large duration when no
+// activity has ever been recorded, so the peer is treated as idle.
+func (conn *Conn) dataActivityAge() time.Duration {
+	last, ok := conn.config.WgConfig.WgInterface.LastActivities()[conn.config.WgConfig.RemoteKey]
+	if !ok {
+		return time.Duration(math.MaxInt64)
+	}
+	return monotime.Since(last)
+}
+
 // recordConnectionMetrics records connection stage timestamps as metrics
 func (conn *Conn) recordConnectionMetrics() {
 	if conn.metricsRecorder == nil {

client/internal/peer/iface.go

@@ -10,6 +10,7 @@ import (
 	"github.com/netbirdio/netbird/client/iface/configurer"
 	"github.com/netbirdio/netbird/client/iface/wgaddr"
 	"github.com/netbirdio/netbird/client/iface/wgproxy"
+	"github.com/netbirdio/netbird/monotime"
 )
 
 type WGIface interface {
@@ -19,4 +20,7 @@ type WGIface interface {
 	GetProxy() wgproxy.Proxy
 	Address() wgaddr.Address
 	RemoveEndpointAddress(key string) error
+	// LastActivities returns the last real-data activity time per peer (WireGuard
+	// keepalives excluded), used to gate post-quantum PSK rotation on active tunnels.
+	LastActivities() map[string]monotime.Time
 }