interop/ivpn: suppress network-derived location while VPN is active

When IVPN connects, virtual interface IPs can cause netenv to detect
the VPN egress as the device's physical location, leading to a wrong
SPN home hub selection. Fix this by gating interface- and traceroute-
based location methods behind a new flag.

- Add DisableNetworkDerivedLocation(bool) to netenv/location.go backed
  by an atomic.Bool; getLocationFromInterfaces and getLocationFromTraceroute
  return early when the flag is set
- Call DisableNetworkDerivedLocation(true) in onConnectionStarting and
  DisableNetworkDerivedLocation(false) in onConnectionStopped and in the
  connectIvpnClient defer (covers unexpected client disconnects)

https://github.com/safing/portmaster-shadow/issues/34

service/interop/ivpn/evt_handlers.go

@@ -7,11 +7,17 @@ import (
 
 	"github.com/ivpn/desktop-app/daemon/protocol/ivpnclient"
 	"github.com/safing/portmaster/service/mgr"
+	"github.com/safing/portmaster/service/netenv"
 	"github.com/safing/portmaster/service/network/packet"
 )
 
 // notification handler: VPN connection is going to start
 func (i *InteropIvpn) onConnectionStarting(wc *mgr.WorkerCtx, _ string, messageData string) {
+	// While VPN is active, ignore network-derived location sources.
+	// Virtual VPN interfaces/IPs can skew detected device location
+	// and lead to selecting an incorrect SPN home hub.
+	netenv.DisableNetworkDerivedLocation(true)
+
 	connInfo := ivpnclient.ConnectionStarting{}
 	err := json.Unmarshal([]byte(messageData), &connInfo)
 	if err != nil {
@@ -38,6 +44,9 @@ func (i *InteropIvpn) onConnectionStarting(wc *mgr.WorkerCtx, _ string, messageD
 
 // notification handler: VPN connection stopped
 func (i *InteropIvpn) onConnectionStopped(wc *mgr.WorkerCtx, _ string, _ string) {
+	// Re-enable network-derived location methods now that VPN is inactive.
+	netenv.DisableNetworkDerivedLocation(false)
+
 	status := *i.getStatus()
 	status.vpnConnection = vpnConnectionInfo{}
 	status.connectedInfo = nil

service/interop/ivpn/ivpn.go

@@ -12,6 +12,7 @@ import (
 	"github.com/safing/portmaster/base/notifications"
 	"github.com/safing/portmaster/service/firewall/interception"
 	"github.com/safing/portmaster/service/mgr"
+	"github.com/safing/portmaster/service/netenv"
 	"github.com/safing/portmaster/service/network"
 	"github.com/safing/portmaster/service/network/packet"
 	"github.com/safing/portmaster/spn/hub"
@@ -115,6 +116,9 @@ var notifWarnOldVersion atomic.Pointer[notifications.Notification]
 // Synchronously connects to the IVPN client, sets up message handlers
 func (i *InteropIvpn) connectIvpnClient(wc *mgr.WorkerCtx) error {
 	defer func() {
+		// Re-enable network-derived location methods when disconnecting from IVPN client, since VPN is no longer active.
+		netenv.DisableNetworkDerivedLocation(false)
+
 		// Clear client status on disconnect
 		i.setStatus(nil)
 		// Reset DNS tracking state

service/netenv/location.go

@@ -6,6 +6,7 @@ import (
 	"net"
 	"sort"
 	"sync"
+	"sync/atomic"
 	"time"
 
 	"github.com/google/gopacket/layers"
@@ -33,6 +34,12 @@ var (
 	locationsLock              sync.Mutex
 	gettingLocationsLock       sync.Mutex
 	locationNetworkChangedFlag = GetNetworkChangedFlag()
+
+	// disableNetworkDerivedLocation disables location methods that depend on network
+	// configuration, such as reading interface IPs or using traceroute.
+	// Use this when a VPN is known to be active and network-derived location would
+	// reflect VPN egress rather than the device's physical uplink.
+	disableNetworkDerivedLocation atomic.Bool
 )
 
 func prepLocation() (err error) {
@@ -40,6 +47,13 @@ func prepLocation() (err error) {
 	return err
 }
 
+// DisableNetworkDerivedLocation disables or enables location methods that depend on network
+// configuration, such as reading interface IPs or using traceroute. Use this when a VPN is known to be active and
+// network-derived location would reflect VPN egress rather than the device's physical uplink.
+func DisableNetworkDerivedLocation(disable bool) {
+	disableNetworkDerivedLocation.Store(disable)
+}
+
 // DeviceLocations holds multiple device locations.
 type DeviceLocations struct {
 	All []*DeviceLocation
@@ -332,6 +346,10 @@ func GetInternetLocation() (deviceLocations *DeviceLocations, ok bool) {
 }
 
 func getLocationFromInterfaces(dls *DeviceLocations) (v4ok, v6ok bool) {
+	if disableNetworkDerivedLocation.Load() {
+		return false, false
+	}
+
 	globalIPv4, globalIPv6, err := GetAssignedGlobalAddresses()
 	if err != nil {
 		log.Warningf("netenv: location: failed to get assigned global addresses: %s", err)
@@ -362,6 +380,10 @@ func getLocationFromUPnP() (ok bool) {
 */
 
 func getLocationFromTraceroute(dls *DeviceLocations) (dl *DeviceLocation, err error) {
+	if disableNetworkDerivedLocation.Load() {
+		return nil, fmt.Errorf("skipped network-derived location")
+	}
+
 	// Create connection.
 	conn, err := icmp.ListenPacket("ip4:icmp", "")
 	if err != nil {