Update dependencies

vendor/tailscale.com/net/netmon/defaultroute_darwin.go

@@ -0,0 +1,96 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build darwin || ios
+
+package netmon
+
+import (
+	"log"
+	"net"
+
+	"tailscale.com/syncs"
+)
+
+var (
+	lastKnownDefaultRouteIfName syncs.AtomicValue[string]
+)
+
+// UpdateLastKnownDefaultRouteInterface is called by ipn-go-bridge in the iOS app when
+// our NWPathMonitor instance detects a network path transition.
+func UpdateLastKnownDefaultRouteInterface(ifName string) {
+	if ifName == "" {
+		return
+	}
+	if old := lastKnownDefaultRouteIfName.Swap(ifName); old != ifName {
+		log.Printf("defaultroute_darwin: update from Swift, ifName = %s (was %s)", ifName, old)
+	}
+}
+
+func defaultRoute() (d DefaultRouteDetails, err error) {
+	// We cannot rely on the delegated interface data on darwin. The NetworkExtension framework
+	// seems to set the delegate interface only once, upon the *creation* of the VPN tunnel.
+	// If a network transition (e.g. from Wi-Fi to Cellular) happens while the tunnel is
+	// connected, it will be ignored and we will still try to set Wi-Fi as the default route
+	// because the delegated interface is not updated by the NetworkExtension framework.
+	//
+	// We work around this on the Swift side with a NWPathMonitor instance that observes
+	// the interface name of the first currently satisfied network path. Our Swift code will
+	// call into `UpdateLastKnownDefaultRouteInterface`, so we can rely on that when it is set.
+	//
+	// If for any reason the Swift machinery didn't work and we don't get any updates, we will
+	// fallback to the BSD logic.
+
+	// Start by getting all available interfaces.
+	interfaces, err := netInterfaces()
+	if err != nil {
+		log.Printf("defaultroute_darwin: could not get interfaces: %v", err)
+		return d, ErrNoGatewayIndexFound
+	}
+
+	getInterfaceByName := func(name string) *Interface {
+		for _, ifc := range interfaces {
+			if ifc.Name != name {
+				continue
+			}
+
+			if !ifc.IsUp() {
+				log.Printf("defaultroute_darwin: %s is down", name)
+				return nil
+			}
+
+			addrs, _ := ifc.Addrs()
+			if len(addrs) == 0 {
+				log.Printf("defaultroute_darwin: %s has no addresses", name)
+				return nil
+			}
+			return &ifc
+		}
+		return nil
+	}
+
+	// Did Swift set lastKnownDefaultRouteInterface? If so, we should use it and don't bother
+	// with anything else. However, for sanity, do check whether Swift gave us with an interface
+	// that exists, is up, and has an address.
+	if swiftIfName := lastKnownDefaultRouteIfName.Load(); swiftIfName != "" {
+		ifc := getInterfaceByName(swiftIfName)
+		if ifc != nil {
+			d.InterfaceName = ifc.Name
+			d.InterfaceIndex = ifc.Index
+			return d, nil
+		}
+	}
+
+	// Fallback to the BSD logic
+	idx, err := DefaultRouteInterfaceIndex()
+	if err != nil {
+		return d, err
+	}
+	iface, err := net.InterfaceByIndex(idx)
+	if err != nil {
+		return d, err
+	}
+	d.InterfaceName = iface.Name
+	d.InterfaceIndex = idx
+	return d, nil
+}