97 lines
2.8 KiB
Go
97 lines
2.8 KiB
Go
// Copyright (c) Tailscale Inc & AUTHORS
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// SPDX-License-Identifier: BSD-3-Clause
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//go:build darwin || ios
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package netmon
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import (
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"log"
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"net"
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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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if old := lastKnownDefaultRouteIfName.Swap(ifName); old != ifName {
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log.Printf("defaultroute_darwin: update from Swift, ifName = %s (was %s)", ifName, old)
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}
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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 darwin. 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, we will
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// fallback to the BSD logic.
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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_darwin: 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.Printf("defaultroute_darwin: %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.Printf("defaultroute_darwin: %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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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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// Fallback to the BSD logic
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idx, err := DefaultRouteInterfaceIndex()
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if err != nil {
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return d, err
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}
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iface, err := net.InterfaceByIndex(idx)
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if err != nil {
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return d, err
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}
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d.InterfaceName = iface.Name
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d.InterfaceIndex = idx
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return d, nil
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}
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