mirror of
https://github.com/tailscale/tailscale.git
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109 lines
3.6 KiB
Go
109 lines
3.6 KiB
Go
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// Copyright (c) Tailscale Inc & AUTHORS
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// SPDX-License-Identifier: BSD-3-Clause
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//go:build ios
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package interfaces
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import (
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"log"
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"tailscale.com/syncs"
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)
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var (
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lastKnownDefaultRouteIfName syncs.AtomicValue[string]
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)
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// UpdateLastKnownDefaultRouteInterface is called by ipn-go-bridge in the iOS app when
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// our NWPathMonitor instance detects a network path transition.
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func UpdateLastKnownDefaultRouteInterface(ifName string) {
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if ifName == "" {
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return
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}
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lastKnownDefaultRouteIfName.Store(ifName)
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log.Printf("defaultroute_ios: update from Swift, ifName = %s", ifName)
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}
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func defaultRoute() (d DefaultRouteDetails, err error) {
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// We cannot rely on the delegated interface data on iOS. The NetworkExtension framework
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// seems to set the delegate interface only once, upon the *creation* of the VPN tunnel.
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// If a network transition (e.g. from Wi-Fi to Cellular) happens while the tunnel is
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// connected, it will be ignored and we will still try to set Wi-Fi as the default route
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// because the delegated interface is not updated by the NetworkExtension framework.
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//
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// We work around this on the Swift side with a NWPathMonitor instance that observes
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// the interface name of the first currently satisfied network path. Our Swift code will
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// call into `UpdateLastKnownDefaultRouteInterface`, so we can rely on that when it is set.
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//
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// If for any reason the Swift machinery didn't work and we don't get any updates, here
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// we also have some fallback logic: we try finding a hardcoded Wi-Fi interface called en0.
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// If en0 is down, we fall back to cellular (pdp_ip0) as a last resort. This doesn't handle
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// all edge cases like USB-Ethernet adapters or multiple Ethernet interfaces, but is good
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// enough to ensure connectivity isn't broken.
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// Start by getting all available interfaces.
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interfaces, err := netInterfaces()
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if err != nil {
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log.Printf("defaultroute_ios: could not get interfaces: %v", err)
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return d, ErrNoGatewayIndexFound
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}
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getInterfaceByName := func(name string) *Interface {
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for _, ifc := range interfaces {
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if ifc.Name != name {
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continue
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}
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if !ifc.IsUp() {
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log.Println("defaultroute_ios: %s is down", name)
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return nil
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}
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addrs, _ := ifc.Addrs()
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if len(addrs) == 0 {
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log.Println("defaultroute_ios: %s has no addresses", name)
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return nil
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}
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return &ifc
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}
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return nil
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}
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// Did Swift set lastKnownDefaultRouteInterface? If so, we should use it and don't bother
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// with anything else. However, for sanity, do check whether Swift gave us with an interface
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// that exists, is up, and has an address.
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if swiftIfName := lastKnownDefaultRouteIfName.Load(); swiftIfName != "" {
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ifc := getInterfaceByName(swiftIfName)
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if ifc != nil {
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log.Printf("defaultroute_ios: using %s (provided by Swift)", ifc.Name)
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d.InterfaceName = ifc.Name
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d.InterfaceIndex = ifc.Index
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return d, nil
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}
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}
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// Start of our fallback logic if Swift didn't give us an interface name, or gave us an invalid
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// one.
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// We start by attempting to use the Wi-Fi interface, which on iPhone is always called en0.
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enZeroIf := getInterfaceByName("en0")
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if enZeroIf != nil {
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log.Println("defaultroute_ios: using en0 (fallback)")
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d.InterfaceName = enZeroIf.Name
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d.InterfaceIndex = enZeroIf.Index
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return d, nil
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}
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// Did it not work? Let's try with Cellular (pdp_ip0).
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cellIf := getInterfaceByName("pdp_ip0")
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if cellIf != nil {
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log.Println("defaultroute_ios: using pdp_ip0 (fallback)")
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d.InterfaceName = cellIf.Name
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d.InterfaceIndex = cellIf.Index
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return d, nil
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}
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log.Println("defaultroute_ios: no running interfaces available")
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return d, ErrNoGatewayIndexFound
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}
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