[client] Preserve routed allowed IPs across lazy connection idle transitions

When a peer went idle under lazy connections, the WireGuard peer was
removed and the wake endpoint re-armed with only the overlay allowed
IPs, dropping routed prefixes installed by the route manager. The
asynchronous route-watcher re-add uses update_only, which is a silent
no-op while the peer is absent, so routed subnets stayed black-holed
until the peer was woken by other means.

Split the idle transition from the full close: Conn.Idle tears down
transports, cancels pending delayed endpoint updates and updates the
status without touching the WireGuard peer. The activity listener then
arms the wake endpoint via the new IdlePeerEndpoint operation, which
removes and re-creates the peer in a single transaction: handshake
state is dropped (keeping the handshake-first wake semantics of packet
staging and first-packet capture/reinjection) while the currently
installed allowed IPs are preserved. The read-modify-write runs under
the interface mutex, serializing it against concurrent allowed IP
updates from the route manager.

Conn.Close no longer takes signalToRemote: the idle transition is the
only path that signals GOAWAY to the remote peer.

client/iface/configurer/common.go

@@ -3,6 +3,7 @@ package configurer
 import (
 	"net"
 	"net/netip"
+	"time"
 
 	"golang.zx2c4.com/wireguard/wgctrl/wgtypes"
 )
@@ -19,6 +20,43 @@ func buildPresharedKeyConfig(peerKey wgtypes.Key, psk wgtypes.Key, updateOnly bo
 	}
 }
 
+// buildIdlePeerEndpointConfig creates a config that removes and re-creates a peer in a
+// single transaction with the given allowed IPs, endpoint and disabled keepalive.
+func buildIdlePeerEndpointConfig(peerKey wgtypes.Key, allowedIPs []netip.Prefix, endpoint *net.UDPAddr) wgtypes.Config {
+	keepAlive := time.Duration(0)
+	return wgtypes.Config{
+		Peers: []wgtypes.PeerConfig{
+			{
+				PublicKey: peerKey,
+				Remove:    true,
+			},
+			{
+				PublicKey:                   peerKey,
+				AllowedIPs:                  prefixesToIPNets(allowedIPs),
+				Endpoint:                    endpoint,
+				PersistentKeepaliveInterval: &keepAlive,
+			},
+		},
+	}
+}
+
+// mergePrefixes returns the union of the two prefix lists, keeping the original order and
+// dropping duplicates.
+func mergePrefixes(current, base []netip.Prefix) []netip.Prefix {
+	merged := make([]netip.Prefix, 0, len(current)+len(base))
+	seen := make(map[netip.Prefix]struct{}, len(current)+len(base))
+	for _, group := range [][]netip.Prefix{current, base} {
+		for _, prefix := range group {
+			if _, ok := seen[prefix]; ok {
+				continue
+			}
+			seen[prefix] = struct{}{}
+			merged = append(merged, prefix)
+		}
+	}
+	return merged
+}
+
 func prefixesToIPNets(prefixes []netip.Prefix) []net.IPNet {
 	ipNets := make([]net.IPNet, len(prefixes))
 	for i, prefix := range prefixes {

client/iface/configurer/kernel_unix.go

@@ -3,6 +3,7 @@
 package configurer
 
 import (
+	"errors"
 	"fmt"
 	"net"
 	"net/netip"
@@ -145,6 +146,39 @@ func (c *KernelConfigurer) RemovePeer(peerKey string) error {
 	return nil
 }
 
+// IdlePeerEndpoint re-creates the peer pointing at the lazy wake endpoint, dropping
+// handshake state while preserving the peer's currently installed allowed IPs.
+func (c *KernelConfigurer) IdlePeerEndpoint(peerKey string, allowedIPs []netip.Prefix, endpoint *net.UDPAddr) error {
+	peerKeyParsed, err := wgtypes.ParseKey(peerKey)
+	if err != nil {
+		return err
+	}
+
+	var current []netip.Prefix
+	existing, err := c.getPeer(c.deviceName, peerKey)
+	switch {
+	case errors.Is(err, ErrPeerNotFound):
+	case err != nil:
+		return fmt.Errorf("get peer: %w", err)
+	default:
+		for _, ipNet := range existing.AllowedIPs {
+			addr, ok := netip.AddrFromSlice(ipNet.IP)
+			if !ok {
+				log.Warnf("failed to convert allowed IP %s of peer %s", ipNet.String(), peerKey)
+				continue
+			}
+			ones, _ := ipNet.Mask.Size()
+			current = append(current, netip.PrefixFrom(addr.Unmap(), ones))
+		}
+	}
+
+	config := buildIdlePeerEndpointConfig(peerKeyParsed, mergePrefixes(current, allowedIPs), endpoint)
+	if err := c.configure(config); err != nil {
+		return fmt.Errorf(`received error "%w" while setting idle endpoint for peer %s on interface %s`, err, peerKey, c.deviceName)
+	}
+	return nil
+}
+
 func (c *KernelConfigurer) AddAllowedIP(peerKey string, allowedIP netip.Prefix) error {
 	ipNet := net.IPNet{
 		IP:   allowedIP.Addr().AsSlice(),

client/iface/configurer/usp.go

@@ -210,6 +210,64 @@ func (c *WGUSPConfigurer) RemovePeer(peerKey string) error {
 	return ipcErr
 }
 
+// IdlePeerEndpoint re-creates the peer pointing at the lazy wake endpoint, dropping
+// handshake state while preserving the peer's currently installed allowed IPs.
+func (c *WGUSPConfigurer) IdlePeerEndpoint(peerKey string, allowedIPs []netip.Prefix, endpoint *net.UDPAddr) error {
+	peerKeyParsed, err := wgtypes.ParseKey(peerKey)
+	if err != nil {
+		return err
+	}
+
+	current, err := c.currentAllowedIPs(hex.EncodeToString(peerKeyParsed[:]))
+	if err != nil {
+		return fmt.Errorf("get current allowed IPs: %w", err)
+	}
+
+	config := buildIdlePeerEndpointConfig(peerKeyParsed, mergePrefixes(current, allowedIPs), endpoint)
+	if err := c.device.IpcSet(toWgUserspaceString(config)); err != nil {
+		return fmt.Errorf("set idle peer endpoint: %w", err)
+	}
+
+	if endpoint != nil {
+		addr, err := netip.ParseAddr(endpoint.IP.String())
+		if err != nil {
+			return fmt.Errorf("parse endpoint address: %w", err)
+		}
+		c.activityRecorder.UpsertAddress(peerKey, netip.AddrPortFrom(addr.Unmap(), uint16(endpoint.Port)))
+	}
+	return nil
+}
+
+// currentAllowedIPs returns the allowed IPs currently installed for the peer identified by
+// its hex-encoded public key. It returns an empty list when the peer does not exist.
+func (c *WGUSPConfigurer) currentAllowedIPs(hexKey string) ([]netip.Prefix, error) {
+	ipc, err := c.device.IpcGet()
+	if err != nil {
+		return nil, err
+	}
+
+	var prefixes []netip.Prefix
+	foundPeer := false
+	for _, line := range strings.Split(ipc, "\n") {
+		line = strings.TrimSpace(line)
+		if strings.HasPrefix(line, "public_key=") {
+			foundPeer = line == "public_key="+hexKey
+			continue
+		}
+		if !foundPeer || !strings.HasPrefix(line, "allowed_ip=") {
+			continue
+		}
+
+		prefix, err := netip.ParsePrefix(strings.TrimPrefix(line, "allowed_ip="))
+		if err != nil {
+			log.Warnf("failed to parse allowed IP %q: %v", line, err)
+			continue
+		}
+		prefixes = append(prefixes, prefix)
+	}
+	return prefixes, nil
+}
+
 func (c *WGUSPConfigurer) AddAllowedIP(peerKey string, allowedIP netip.Prefix) error {
 	ipNet := net.IPNet{
 		IP:   allowedIP.Addr().AsSlice(),

client/iface/configurer/usp_idle_test.go

@@ -0,0 +1,158 @@
+package configurer
+
+import (
+	"encoding/hex"
+	"net"
+	"net/netip"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	wgconn "golang.zx2c4.com/wireguard/conn"
+	"golang.zx2c4.com/wireguard/device"
+	"golang.zx2c4.com/wireguard/tun/netstack"
+	"golang.zx2c4.com/wireguard/wgctrl/wgtypes"
+
+	"github.com/netbirdio/netbird/client/iface/bind"
+)
+
+// newTestConfigurer creates a configurer backed by an in-memory wireguard-go device.
+func newTestConfigurer(t *testing.T) *WGUSPConfigurer {
+	t.Helper()
+
+	tunDev, _, err := netstack.CreateNetTUN([]netip.Addr{netip.MustParseAddr("100.64.0.1")}, []netip.Addr{}, 1280)
+	require.NoError(t, err)
+
+	wgDev := device.NewDevice(tunDev, wgconn.NewDefaultBind(), device.NewLogger(device.LogLevelSilent, "[test] "))
+	t.Cleanup(wgDev.Close)
+
+	c := NewUSPConfigurerNoUAPI(wgDev, "utun-test", bind.NewActivityRecorder())
+
+	key, err := wgtypes.GeneratePrivateKey()
+	require.NoError(t, err)
+	require.NoError(t, c.ConfigureInterface(key.String(), 0))
+
+	return c
+}
+
+// peerAllowedIPs returns the allowed IPs currently installed for the given peer.
+func peerAllowedIPs(t *testing.T, c *WGUSPConfigurer, pubKey string) []string {
+	t.Helper()
+
+	var ips []string
+	for _, line := range peerIpcLines(t, c, pubKey) {
+		if strings.HasPrefix(line, "allowed_ip=") {
+			ips = append(ips, strings.TrimPrefix(line, "allowed_ip="))
+		}
+	}
+	return ips
+}
+
+// peerEndpoint returns the endpoint currently installed for the given peer.
+func peerEndpoint(t *testing.T, c *WGUSPConfigurer, pubKey string) string {
+	t.Helper()
+
+	for _, line := range peerIpcLines(t, c, pubKey) {
+		if strings.HasPrefix(line, "endpoint=") {
+			return strings.TrimPrefix(line, "endpoint=")
+		}
+	}
+	return ""
+}
+
+// peerIpcLines returns the uapi config lines belonging to the given peer.
+func peerIpcLines(t *testing.T, c *WGUSPConfigurer, pubKey string) []string {
+	t.Helper()
+
+	key, err := wgtypes.ParseKey(pubKey)
+	require.NoError(t, err)
+	hexKey := hex.EncodeToString(key[:])
+
+	ipc, err := c.device.IpcGet()
+	require.NoError(t, err)
+
+	var lines []string
+	inPeer := false
+	for _, line := range strings.Split(ipc, "\n") {
+		line = strings.TrimSpace(line)
+		if strings.HasPrefix(line, "public_key=") {
+			inPeer = line == "public_key="+hexKey
+			continue
+		}
+		if inPeer && line != "" {
+			lines = append(lines, line)
+		}
+	}
+	return lines
+}
+
+// TestUSPConfigurer_IdlePeerEndpointPreservesAllowedIPs verifies the invariant the lazy idle
+// transition relies on: IdlePeerEndpoint re-creates the peer (dropping handshake state via the
+// remove+add transaction) while keeping every installed allowed IP, including routed
+// prefixes added later by the route manager, and points the endpoint at the wake listener.
+func TestUSPConfigurer_IdlePeerEndpointPreservesAllowedIPs(t *testing.T) {
+	c := newTestConfigurer(t)
+
+	peerKey, err := wgtypes.GeneratePrivateKey()
+	require.NoError(t, err)
+	pubKey := peerKey.PublicKey().String()
+
+	overlay := netip.MustParsePrefix("100.64.0.5/32")
+	routed := netip.MustParsePrefix("10.99.0.0/24")
+
+	realEndpoint := &net.UDPAddr{IP: net.ParseIP("127.0.0.1"), Port: 51821}
+	require.NoError(t, c.UpdatePeer(pubKey, []netip.Prefix{overlay}, 25*time.Second, realEndpoint, nil))
+	require.NoError(t, c.AddAllowedIP(pubKey, routed))
+
+	ips := peerAllowedIPs(t, c, pubKey)
+	require.Contains(t, ips, overlay.String(), "overlay prefix must be installed before the idle endpoint swap")
+	require.Contains(t, ips, routed.String(), "routed prefix must be installed before the idle endpoint swap")
+
+	wakeEndpoint := &net.UDPAddr{IP: net.ParseIP("127.2.0.5"), Port: 17473}
+	require.NoError(t, c.IdlePeerEndpoint(pubKey, []netip.Prefix{overlay}, wakeEndpoint))
+
+	ips = peerAllowedIPs(t, c, pubKey)
+	assert.Contains(t, ips, routed.String(), "routed prefix must survive the idle endpoint swap")
+	assert.Contains(t, ips, overlay.String(), "overlay prefix must survive the idle endpoint swap")
+	assert.Equal(t, "127.2.0.5:17473", peerEndpoint(t, c, pubKey), "endpoint must point at the wake listener after the idle endpoint swap")
+}
+
+// TestUSPConfigurer_IdlePeerEndpointCreatesMissingPeer verifies the cold-start arm path: when the
+// peer does not exist yet (never connected), IdlePeerEndpoint creates it with the given base
+// allowed IPs and the wake endpoint.
+func TestUSPConfigurer_IdlePeerEndpointCreatesMissingPeer(t *testing.T) {
+	c := newTestConfigurer(t)
+
+	peerKey, err := wgtypes.GeneratePrivateKey()
+	require.NoError(t, err)
+	pubKey := peerKey.PublicKey().String()
+
+	overlay := netip.MustParsePrefix("100.64.0.5/32")
+	wakeEndpoint := &net.UDPAddr{IP: net.ParseIP("127.2.0.5"), Port: 17473}
+
+	require.NoError(t, c.IdlePeerEndpoint(pubKey, []netip.Prefix{overlay}, wakeEndpoint))
+
+	assert.Equal(t, []string{overlay.String()}, peerAllowedIPs(t, c, pubKey), "missing peer must be created with the base allowed IPs")
+	assert.Equal(t, "127.2.0.5:17473", peerEndpoint(t, c, pubKey), "missing peer must be created with the wake endpoint")
+}
+
+// TestUSPConfigurer_AddAllowedIPOnMissingPeerIsSilentNoOp documents the wireguard-go
+// behavior the removed-peer idle flow raced against: AddAllowedIP uses update_only,
+// which is a silent no-op when the peer does not exist. The idle transition must
+// therefore keep the WireGuard peer (Conn.Idle + IdlePeerEndpoint) instead of leaving a
+// window where the peer is absent.
+func TestUSPConfigurer_AddAllowedIPOnMissingPeerIsSilentNoOp(t *testing.T) {
+	c := newTestConfigurer(t)
+
+	peerKey, err := wgtypes.GeneratePrivateKey()
+	require.NoError(t, err)
+	pubKey := peerKey.PublicKey().String()
+
+	routed := netip.MustParsePrefix("10.99.0.0/24")
+
+	require.NoError(t, c.AddAllowedIP(pubKey, routed), "update-only on a missing peer must not return an error")
+
+	assert.Empty(t, peerIpcLines(t, c, pubKey), "update-only call must not create the peer")
+}

client/iface/device/interface.go

@@ -15,6 +15,7 @@ type WGConfigurer interface {
 	ConfigureInterface(privateKey string, port int) error
 	UpdatePeer(peerKey string, allowedIps []netip.Prefix, keepAlive time.Duration, endpoint *net.UDPAddr, preSharedKey *wgtypes.Key) error
 	RemovePeer(peerKey string) error
+	IdlePeerEndpoint(peerKey string, allowedIPs []netip.Prefix, endpoint *net.UDPAddr) error
 	AddAllowedIP(peerKey string, allowedIP netip.Prefix) error
 	RemoveAllowedIP(peerKey string, allowedIP netip.Prefix) error
 	SetPresharedKey(peerKey string, psk wgtypes.Key, updateOnly bool) error

client/iface/iface.go

@@ -184,6 +184,19 @@ func (w *WGIface) RemovePeer(peerKey string) error {
 	return w.configurer.RemovePeer(peerKey)
 }
 
+// IdlePeerEndpoint re-creates the peer pointing at the lazy wake endpoint, dropping
+// handshake state while preserving the peer's currently installed allowed IPs.
+func (w *WGIface) IdlePeerEndpoint(peerKey string, allowedIPs []netip.Prefix, endpoint *net.UDPAddr) error {
+	w.mu.Lock()
+	defer w.mu.Unlock()
+	if w.configurer == nil {
+		return ErrIfaceNotFound
+	}
+
+	log.Debugf("Resetting peer on interface %s: %s, endpoint %s", w.tun.DeviceName(), peerKey, endpoint)
+	return w.configurer.IdlePeerEndpoint(peerKey, allowedIPs, endpoint)
+}
+
 // AddAllowedIP adds a prefix to the allowed IPs list of peer
 func (w *WGIface) AddAllowedIP(peerKey string, allowedIP netip.Prefix) error {
 	w.mu.Lock()

client/internal/conn_mgr.go

@@ -228,7 +228,7 @@ func (e *ConnMgr) RemovePeerConn(peerKey string) {
 	if !ok {
 		return
 	}
-	defer conn.Close(false)
+	defer conn.Close()
 
 	if !e.isStartedWithLazyMgr() {
 		return

client/internal/engine.go

@@ -1778,7 +1778,7 @@ func (e *Engine) addNewPeer(peerConfig *mgmProto.RemotePeerConfig) error {
 	}
 
 	if exists := e.connMgr.AddPeerConn(e.ctx, peerKey, conn); exists {
-		conn.Close(false)
+		conn.Close()
 		return fmt.Errorf("peer already exists: %s", peerKey)
 	}
 

client/internal/engine_test.go

@@ -53,6 +53,7 @@ type MockWGIface struct {
 	UpdateAddrFunc             func(newAddr wgaddr.Address) error
 	UpdatePeerFunc             func(peerKey string, allowedIps []netip.Prefix, keepAlive time.Duration, endpoint *net.UDPAddr, preSharedKey *wgtypes.Key) error
 	RemovePeerFunc             func(peerKey string) error
+	IdlePeerEndpointFunc       func(peerKey string, allowedIPs []netip.Prefix, endpoint *net.UDPAddr) error
 	AddAllowedIPFunc           func(peerKey string, allowedIP netip.Prefix) error
 	RemoveAllowedIPFunc        func(peerKey string, allowedIP netip.Prefix) error
 	CloseFunc                  func() error
@@ -124,6 +125,13 @@ func (m *MockWGIface) RemovePeer(peerKey string) error {
 	return m.RemovePeerFunc(peerKey)
 }
 
+func (m *MockWGIface) IdlePeerEndpoint(peerKey string, allowedIPs []netip.Prefix, endpoint *net.UDPAddr) error {
+	if m.IdlePeerEndpointFunc == nil {
+		return nil
+	}
+	return m.IdlePeerEndpointFunc(peerKey, allowedIPs, endpoint)
+}
+
 func (m *MockWGIface) AddAllowedIP(peerKey string, allowedIP netip.Prefix) error {
 	return m.AddAllowedIPFunc(peerKey, allowedIP)
 }

client/internal/iface_common.go

@@ -32,6 +32,7 @@ type wgIfaceBase interface {
 	UpdatePeer(peerKey string, allowedIps []netip.Prefix, keepAlive time.Duration, endpoint *net.UDPAddr, preSharedKey *wgtypes.Key) error
 	RemoveEndpointAddress(key string) error
 	RemovePeer(peerKey string) error
+	IdlePeerEndpoint(peerKey string, allowedIPs []netip.Prefix, endpoint *net.UDPAddr) error
 	AddAllowedIP(peerKey string, allowedIP netip.Prefix) error
 	RemoveAllowedIP(peerKey string, allowedIP netip.Prefix) error
 	Close() error

client/internal/lazyconn/activity/listener_bind.go

@@ -106,7 +106,7 @@ func (d *BindListener) setupLazyConn() error {
 		IP:   d.fakeIP.AsSlice(),
 		Port: lazyBindPort,
 	}
-	return d.wgIface.UpdatePeer(d.peerCfg.PublicKey, d.peerCfg.AllowedIPs, 0, endpoint, nil)
+	return d.wgIface.IdlePeerEndpoint(d.peerCfg.PublicKey, d.peerCfg.AllowedIPs, endpoint)
 }
 
 // ReadPackets blocks until activity is detected on the LazyConn or the listener is closed.

client/internal/lazyconn/activity/listener_bind_test.go

@@ -9,7 +9,6 @@ import (
 	log "github.com/sirupsen/logrus"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
-	"golang.zx2c4.com/wireguard/wgctrl/wgtypes"
 
 	"github.com/netbirdio/netbird/client/iface/device"
 	"github.com/netbirdio/netbird/client/iface/wgaddr"
@@ -45,7 +44,7 @@ type MockWGIfaceBind struct {
 	endpointMgr *mockEndpointManager
 }
 
-func (m *MockWGIfaceBind) UpdatePeer(string, []netip.Prefix, time.Duration, *net.UDPAddr, *wgtypes.Key) error {
+func (m *MockWGIfaceBind) IdlePeerEndpoint(string, []netip.Prefix, *net.UDPAddr) error {
 	return nil
 }
 

client/internal/lazyconn/activity/listener_udp.go

@@ -101,7 +101,7 @@ func (d *UDPListener) Close() {
 
 func (d *UDPListener) createEndpoint() error {
 	d.peerCfg.Log.Debugf("creating lazy endpoint: %s", d.endpoint.String())
-	return d.wgIface.UpdatePeer(d.peerCfg.PublicKey, d.peerCfg.AllowedIPs, 0, d.endpoint, nil)
+	return d.wgIface.IdlePeerEndpoint(d.peerCfg.PublicKey, d.peerCfg.AllowedIPs, d.endpoint)
 }
 
 func (d *UDPListener) newConn() (*net.UDPConn, error) {

client/internal/lazyconn/activity/manager.go

@@ -5,10 +5,8 @@ import (
 	"net"
 	"net/netip"
 	"sync"
-	"time"
 
 	log "github.com/sirupsen/logrus"
-	"golang.zx2c4.com/wireguard/wgctrl/wgtypes"
 
 	"github.com/netbirdio/netbird/client/iface/wgaddr"
 	"github.com/netbirdio/netbird/client/internal/lazyconn"
@@ -30,7 +28,7 @@ type Event struct {
 }
 
 type WgInterface interface {
-	UpdatePeer(peerKey string, allowedIps []netip.Prefix, keepAlive time.Duration, endpoint *net.UDPAddr, preSharedKey *wgtypes.Key) error
+	IdlePeerEndpoint(peerKey string, allowedIPs []netip.Prefix, endpoint *net.UDPAddr) error
 	IsUserspaceBind() bool
 	Address() wgaddr.Address
 	MTU() uint16

client/internal/lazyconn/activity/manager_test.go

@@ -8,7 +8,6 @@ import (
 	"time"
 
 	log "github.com/sirupsen/logrus"
-	"golang.zx2c4.com/wireguard/wgctrl/wgtypes"
 
 	"github.com/netbirdio/netbird/client/iface/wgaddr"
 	"github.com/netbirdio/netbird/client/internal/lazyconn"
@@ -26,7 +25,7 @@ func (m *MocPeer) ConnID() peerid.ConnID {
 type MocWGIface struct {
 }
 
-func (m MocWGIface) UpdatePeer(string, []netip.Prefix, time.Duration, *net.UDPAddr, *wgtypes.Key) error {
+func (m MocWGIface) IdlePeerEndpoint(string, []netip.Prefix, *net.UDPAddr) error {
 	return nil
 }
 

client/internal/lazyconn/manager/manager.go

@@ -280,7 +280,7 @@ func (m *Manager) DeactivatePeer(peerID peerid.ConnID) {
 		return
 	}
 
-	m.peerStore.PeerConnClose(mp.peerCfg.PublicKey)
+	m.peerStore.PeerConnIdle(mp.peerCfg.PublicKey, false)
 
 	mp.peerCfg.Log.Infof("start activity monitor")
 
@@ -569,7 +569,7 @@ func (m *Manager) onPeerInactivityTimedOut(peerIDs map[string]struct{}) {
 		mp.peerCfg.Log.Infof("connection timed out")
 
 		// this is blocking operation, potentially can be optimized
-		m.peerStore.PeerConnIdle(mp.peerCfg.PublicKey)
+		m.peerStore.PeerConnIdle(mp.peerCfg.PublicKey, true)
 
 		mp.expectedWatcher = watcherActivity
 

client/internal/lazyconn/wgiface.go

@@ -3,9 +3,6 @@ package lazyconn
 import (
 	"net"
 	"net/netip"
-	"time"
-
-	"golang.zx2c4.com/wireguard/wgctrl/wgtypes"
 
 	"github.com/netbirdio/netbird/client/iface/wgaddr"
 	"github.com/netbirdio/netbird/monotime"
@@ -13,7 +10,7 @@ import (
 
 type WGIface interface {
 	RemovePeer(peerKey string) error
-	UpdatePeer(peerKey string, allowedIps []netip.Prefix, keepAlive time.Duration, endpoint *net.UDPAddr, preSharedKey *wgtypes.Key) error
+	IdlePeerEndpoint(peerKey string, allowedIPs []netip.Prefix, endpoint *net.UDPAddr) error
 	IsUserspaceBind() bool
 	Address() wgaddr.Address
 	LastActivities() map[string]monotime.Time

client/internal/peer/conn.go

@@ -285,8 +285,20 @@ func (conn *Conn) open(engineCtx context.Context, firstPacket []byte) error {
 	return nil
 }
 
-// Close closes this peer Conn issuing a close event to the Conn closeCh
-func (conn *Conn) Close(signalToRemote bool) {
+// Close closes this peer Conn issuing a close event to the Conn closeCh and removes the WireGuard peer
+func (conn *Conn) Close() {
+	conn.close(false, true)
+}
+
+// Idle tears down the connection for the lazy idle state: transports and proxies are
+// closed but the WireGuard peer is kept, so its AllowedIPs (including routed prefixes
+// installed by the route manager) survive until the activity listener re-points the
+// endpoint at the wake listener.
+func (conn *Conn) Idle(signalToRemote bool) {
+	conn.close(signalToRemote, false)
+}
+
+func (conn *Conn) close(signalToRemote bool, removeWgPeer bool) {
 	conn.mu.Lock()
 	defer conn.wgWatcherWg.Wait()
 	defer conn.mu.Unlock()
@@ -329,8 +341,12 @@ func (conn *Conn) Close(signalToRemote bool) {
 		conn.wgProxyICE = nil
 	}
 
-	if err := conn.endpointUpdater.RemoveWgPeer(); err != nil {
-		conn.Log.Errorf("failed to remove wg endpoint: %v", err)
+	if removeWgPeer {
+		if err := conn.endpointUpdater.RemoveWgPeer(); err != nil {
+			conn.Log.Errorf("failed to remove wg endpoint: %v", err)
+		}
+	} else {
+		conn.endpointUpdater.CancelPendingUpdates()
 	}
 
 	if conn.evalStatus() == StatusConnected && conn.onDisconnected != nil {

client/internal/peer/endpoint.go

@@ -65,6 +65,16 @@ func (e *EndpointUpdater) RemoveWgPeer() error {
 	return e.wgConfig.WgInterface.RemovePeer(e.wgConfig.RemoteKey)
 }
 
+// CancelPendingUpdates stops a scheduled delayed endpoint update without touching the
+// WireGuard peer. Used on the idle transition where the peer is kept so a pending
+// responder-side update cannot overwrite the wake endpoint later.
+func (e *EndpointUpdater) CancelPendingUpdates() {
+	e.mu.Lock()
+	defer e.mu.Unlock()
+
+	e.waitForCloseTheDelayedUpdate()
+}
+
 func (e *EndpointUpdater) RemoveEndpointAddress() error {
 	e.mu.Lock()
 	defer e.mu.Unlock()

client/internal/peer/endpoint_test.go

@@ -0,0 +1,99 @@
+package peer
+
+import (
+	"net"
+	"net/netip"
+	"sync"
+	"testing"
+	"time"
+
+	log "github.com/sirupsen/logrus"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"golang.zx2c4.com/wireguard/wgctrl/wgtypes"
+
+	"github.com/netbirdio/netbird/client/iface/configurer"
+	"github.com/netbirdio/netbird/client/iface/wgaddr"
+	"github.com/netbirdio/netbird/client/iface/wgproxy"
+)
+
+type endpointTestWGIface struct {
+	mu          sync.Mutex
+	updateCalls int
+	removeCalls int
+}
+
+func (m *endpointTestWGIface) UpdatePeer(string, []netip.Prefix, time.Duration, *net.UDPAddr, *wgtypes.Key) error {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.updateCalls++
+	return nil
+}
+
+func (m *endpointTestWGIface) RemovePeer(string) error {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.removeCalls++
+	return nil
+}
+
+func (m *endpointTestWGIface) GetStats() (map[string]configurer.WGStats, error) { return nil, nil }
+
+func (m *endpointTestWGIface) GetProxy() wgproxy.Proxy { return nil }
+
+func (m *endpointTestWGIface) Address() wgaddr.Address { return wgaddr.Address{} }
+
+func (m *endpointTestWGIface) RemoveEndpointAddress(string) error { return nil }
+
+func (m *endpointTestWGIface) counts() (updates, removes int) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	return m.updateCalls, m.removeCalls
+}
+
+func newTestEndpointUpdater(iface *endpointTestWGIface, initiator bool) *EndpointUpdater {
+	cfg := WgConfig{
+		RemoteKey:   "remoteKey",
+		WgInterface: iface,
+		AllowedIps:  []netip.Prefix{netip.MustParsePrefix("100.64.0.5/32")},
+	}
+	return NewEndpointUpdater(log.WithField("peer", "test"), cfg, initiator)
+}
+
+// TestEndpointUpdater_CancelPendingUpdates ensures a scheduled responder-side delayed
+// update is stopped without removing the WireGuard peer, so an idle transition cannot
+// be overwritten later by a stale endpoint update.
+func TestEndpointUpdater_CancelPendingUpdates(t *testing.T) {
+	iface := &endpointTestWGIface{}
+	e := newTestEndpointUpdater(iface, false)
+
+	addr := &net.UDPAddr{IP: net.ParseIP("127.0.0.1"), Port: 51820}
+	require.NoError(t, e.ConfigureWGEndpoint(addr, nil))
+
+	updates, _ := iface.counts()
+	require.Equal(t, 1, updates, "responder must apply the immediate nil-endpoint update")
+
+	// CancelPendingUpdates waits for the delayed-update goroutine to exit, so the
+	// call counts below are final: the 5s fallback update can never fire anymore.
+	e.CancelPendingUpdates()
+
+	updates, removes := iface.counts()
+	assert.Equal(t, 1, updates, "delayed endpoint update must not fire after cancellation")
+	assert.Equal(t, 0, removes, "cancellation must not remove the WireGuard peer")
+}
+
+// TestEndpointUpdater_CancelPendingUpdatesNoPending ensures cancellation is a safe no-op
+// when no delayed update is scheduled (initiator path).
+func TestEndpointUpdater_CancelPendingUpdatesNoPending(t *testing.T) {
+	iface := &endpointTestWGIface{}
+	e := newTestEndpointUpdater(iface, true)
+
+	addr := &net.UDPAddr{IP: net.ParseIP("127.0.0.1"), Port: 51820}
+	require.NoError(t, e.ConfigureWGEndpoint(addr, nil))
+
+	e.CancelPendingUpdates()
+
+	updates, removes := iface.counts()
+	assert.Equal(t, 1, updates, "initiator applies exactly one direct update")
+	assert.Equal(t, 0, removes, "cancellation must not remove the WireGuard peer")
+}

client/internal/peerstore/store.go

@@ -108,7 +108,10 @@ func (s *Store) PeerConnOpenWithFirstPacket(ctx context.Context, pubKey string,
 	}
 }
 
-func (s *Store) PeerConnIdle(pubKey string) {
+// PeerConnIdle transitions the peer connection to the lazy idle state, keeping the
+// WireGuard peer and its AllowedIPs in place. signalToRemote indicates whether the
+// remote peer should be notified (false when the remote initiated the idle via GOAWAY).
+func (s *Store) PeerConnIdle(pubKey string, signalToRemote bool) {
 	s.peerConnsMu.RLock()
 	defer s.peerConnsMu.RUnlock()
 
@@ -116,18 +119,7 @@ func (s *Store) PeerConnIdle(pubKey string) {
 	if !ok {
 		return
 	}
-	p.Close(true)
-}
-
-func (s *Store) PeerConnClose(pubKey string) {
-	s.peerConnsMu.RLock()
-	defer s.peerConnsMu.RUnlock()
-
-	p, ok := s.peerConns[pubKey]
-	if !ok {
-		return
-	}
-	p.Close(false)
+	p.Idle(signalToRemote)
 }
 
 func (s *Store) PeersPubKey() []string {