[client] Remove endpoint address on peer disconnect, retain status for activity recording (#4228)

* When a peer disconnects, remove the endpoint address to avoid sending traffic to a non-existent address, but retain the status for the activity recorder.

client/iface/configurer/kernel_unix.go

@@ -73,6 +73,44 @@ func (c *KernelConfigurer) UpdatePeer(peerKey string, allowedIps []netip.Prefix,
 	return nil
 }
 
+func (c *KernelConfigurer) RemoveEndpointAddress(peerKey string) error {
+	peerKeyParsed, err := wgtypes.ParseKey(peerKey)
+	if err != nil {
+		return err
+	}
+
+	// Get the existing peer to preserve its allowed IPs
+	existingPeer, err := c.getPeer(c.deviceName, peerKey)
+	if err != nil {
+		return fmt.Errorf("get peer: %w", err)
+	}
+
+	removePeerCfg := wgtypes.PeerConfig{
+		PublicKey: peerKeyParsed,
+		Remove:    true,
+	}
+
+	if err := c.configure(wgtypes.Config{Peers: []wgtypes.PeerConfig{removePeerCfg}}); err != nil {
+		return fmt.Errorf(`error removing peer %s from interface %s: %w`, peerKey, c.deviceName, err)
+	}
+
+	//Re-add the peer without the endpoint but same AllowedIPs
+	reAddPeerCfg := wgtypes.PeerConfig{
+		PublicKey:         peerKeyParsed,
+		AllowedIPs:        existingPeer.AllowedIPs,
+		ReplaceAllowedIPs: true,
+	}
+
+	if err := c.configure(wgtypes.Config{Peers: []wgtypes.PeerConfig{reAddPeerCfg}}); err != nil {
+		return fmt.Errorf(
+			`error re-adding peer %s to interface %s with allowed IPs %v: %w`,
+			peerKey, c.deviceName, existingPeer.AllowedIPs, err,
+		)
+	}
+
+	return nil
+}
+
 func (c *KernelConfigurer) RemovePeer(peerKey string) error {
 	peerKeyParsed, err := wgtypes.ParseKey(peerKey)
 	if err != nil {

client/iface/configurer/usp.go

@@ -106,6 +106,67 @@ func (c *WGUSPConfigurer) UpdatePeer(peerKey string, allowedIps []netip.Prefix,
 	return nil
 }
 
+func (c *WGUSPConfigurer) RemoveEndpointAddress(peerKey string) error {
+	peerKeyParsed, err := wgtypes.ParseKey(peerKey)
+	if err != nil {
+		return fmt.Errorf("parse peer key: %w", err)
+	}
+
+	ipcStr, err := c.device.IpcGet()
+	if err != nil {
+		return fmt.Errorf("get IPC config: %w", err)
+	}
+
+	// Parse current status to get allowed IPs for the peer
+	stats, err := parseStatus(c.deviceName, ipcStr)
+	if err != nil {
+		return fmt.Errorf("parse IPC config: %w", err)
+	}
+
+	var allowedIPs []net.IPNet
+	found := false
+	for _, peer := range stats.Peers {
+		if peer.PublicKey == peerKey {
+			allowedIPs = peer.AllowedIPs
+			found = true
+			break
+		}
+	}
+	if !found {
+		return fmt.Errorf("peer %s not found", peerKey)
+	}
+
+	// remove the peer from the WireGuard configuration
+	peer := wgtypes.PeerConfig{
+		PublicKey: peerKeyParsed,
+		Remove:    true,
+	}
+
+	config := wgtypes.Config{
+		Peers: []wgtypes.PeerConfig{peer},
+	}
+	if ipcErr := c.device.IpcSet(toWgUserspaceString(config)); ipcErr != nil {
+		return fmt.Errorf("failed to remove peer: %s", ipcErr)
+	}
+
+	// Build the peer config
+	peer = wgtypes.PeerConfig{
+		PublicKey:         peerKeyParsed,
+		ReplaceAllowedIPs: true,
+		AllowedIPs:        allowedIPs,
+	}
+
+	config = wgtypes.Config{
+		Peers: []wgtypes.PeerConfig{peer},
+	}
+
+	if err := c.device.IpcSet(toWgUserspaceString(config)); err != nil {
+		return fmt.Errorf("remove endpoint address: %w", err)
+	}
+
+	return nil
+}
+
 func (c *WGUSPConfigurer) RemovePeer(peerKey string) error {
 	peerKeyParsed, err := wgtypes.ParseKey(peerKey)
 	if err != nil {

client/iface/device/interface.go

@@ -21,4 +21,5 @@ type WGConfigurer interface {
 	GetStats() (map[string]configurer.WGStats, error)
 	FullStats() (*configurer.Stats, error)
 	LastActivities() map[string]monotime.Time
+	RemoveEndpointAddress(peerKey string) error
 }

client/iface/iface.go

@@ -148,6 +148,17 @@ func (w *WGIface) UpdatePeer(peerKey string, allowedIps []netip.Prefix, keepAliv
 	return w.configurer.UpdatePeer(peerKey, allowedIps, keepAlive, endpoint, preSharedKey)
 }
 
+func (w *WGIface) RemoveEndpointAddress(peerKey string) error {
+	w.mu.Lock()
+	defer w.mu.Unlock()
+	if w.configurer == nil {
+		return ErrIfaceNotFound
+	}
+
+	log.Debugf("Removing endpoint address: %s", peerKey)
+	return w.configurer.RemoveEndpointAddress(peerKey)
+}
+
 // RemovePeer removes a Wireguard Peer from the interface iface
 func (w *WGIface) RemovePeer(peerKey string) error {
 	w.mu.Lock()