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tailscale/wgengine/router/ifconfig_windows.go

409 lines
10 KiB
Go

/* SPDX-License-Identifier: MIT
*
* Copyright (C) 2019 WireGuard LLC. All Rights Reserved.
*/
package router
import (
"bytes"
"errors"
"fmt"
"log"
"net"
"os"
"sort"
"time"
ole "github.com/go-ole/go-ole"
winipcfg "github.com/tailscale/winipcfg-go"
"github.com/tailscale/wireguard-go/tun"
"golang.org/x/sys/windows"
"tailscale.com/net/interfaces"
"tailscale.com/wgengine/winnet"
)
// monitorDefaultRoutes subscribes to route change events and updates
// the Tailscale tunnel interface's MTU to match that of the
// underlying default route.
//
// This is an attempt at making the MTU mostly correct, but in
// practice this entire piece of code ends up just using the 1280
// value passed in at device construction time. This code might make
// the MTU go lower due to very low-MTU IPv4 interfaces.
//
// TODO: this code is insufficient to control the MTU correctly. The
// correct way to do it is per-peer PMTU discovery, and synthesizing
// ICMP fragmentation-needed messages within tailscaled. This code may
// address a few rare corner cases, but is unlikely to significantly
// help with MTU issues compared to a static 1280B implementation.
func monitorDefaultRoutes(tun *tun.NativeTun) (*winipcfg.RouteChangeCallback, error) {
guid := tun.GUID()
ourLuid, err := winipcfg.InterfaceGuidToLuid(&guid)
lastMtu := uint32(0)
if err != nil {
return nil, err
}
doIt := func() error {
mtu, err := getDefaultRouteMTU()
if err != nil {
return err
}
if mtu > 0 && (lastMtu == 0 || lastMtu != mtu) {
iface, err := winipcfg.GetIpInterface(ourLuid, winipcfg.AF_INET)
if err != nil {
return err
}
iface.NlMtu = mtu - 80
// If the TUN device was created with a smaller MTU,
// though, such as 1280, we don't want to go bigger than
// configured. (See the comment on minimalMTU in the
// wgengine package.)
if min, err := tun.MTU(); err == nil && min < int(iface.NlMtu) {
iface.NlMtu = uint32(min)
}
if iface.NlMtu < 576 {
iface.NlMtu = 576
}
err = iface.Set()
if err != nil {
return err
}
tun.ForceMTU(int(iface.NlMtu))
iface, err = winipcfg.GetIpInterface(ourLuid, winipcfg.AF_INET6)
if err != nil {
if !isMissingIPv6Err(err) {
return err
}
} else {
iface.NlMtu = mtu - 80
if iface.NlMtu < 1280 {
iface.NlMtu = 1280
}
err = iface.Set()
if err != nil {
return err
}
}
lastMtu = mtu
}
return nil
}
err = doIt()
if err != nil {
return nil, err
}
cb, err := winipcfg.RegisterRouteChangeCallback(func(notificationType winipcfg.MibNotificationType, route *winipcfg.Route) {
//fmt.Printf("MonitorDefaultRoutes: changed: %v\n", route.DestinationPrefix)
if route.DestinationPrefix.PrefixLength == 0 {
_ = doIt()
}
})
if err != nil {
return nil, err
}
return cb, nil
}
func getDefaultRouteMTU() (uint32, error) {
mtus, err := interfaces.NonTailscaleMTUs()
if err != nil {
return 0, err
}
routes, err := winipcfg.GetRoutes(winipcfg.AF_INET)
if err != nil {
return 0, err
}
best := ^uint32(0)
mtu := uint32(0)
for _, route := range routes {
if route.DestinationPrefix.PrefixLength != 0 {
continue
}
routeMTU := mtus[route.InterfaceLuid]
if routeMTU == 0 {
continue
}
if route.Metric < best {
best = route.Metric
mtu = routeMTU
}
}
routes, err = winipcfg.GetRoutes(winipcfg.AF_INET6)
if err != nil {
return 0, err
}
best = ^uint32(0)
for _, route := range routes {
if route.DestinationPrefix.PrefixLength != 0 {
continue
}
routeMTU := mtus[route.InterfaceLuid]
if routeMTU == 0 {
continue
}
if route.Metric < best {
best = route.Metric
if routeMTU < mtu {
mtu = routeMTU
}
}
}
return mtu, nil
}
// setPrivateNetwork marks the provided network adapter's category to private.
// It returns (false, nil) if the adapter was not found.
func setPrivateNetwork(ifcGUID *windows.GUID) (bool, error) {
// NLM_NETWORK_CATEGORY values.
const (
categoryPublic = 0
categoryPrivate = 1
categoryDomain = 2
)
var c ole.Connection
if err := c.Initialize(); err != nil {
return false, fmt.Errorf("c.Initialize: %v", err)
}
defer c.Uninitialize()
m, err := winnet.NewNetworkListManager(&c)
if err != nil {
return false, fmt.Errorf("winnet.NewNetworkListManager: %v", err)
}
defer m.Release()
cl, err := m.GetNetworkConnections()
if err != nil {
return false, fmt.Errorf("m.GetNetworkConnections: %v", err)
}
defer cl.Release()
for _, nco := range cl {
aid, err := nco.GetAdapterId()
if err != nil {
return false, fmt.Errorf("nco.GetAdapterId: %v", err)
}
if aid != ifcGUID.String() {
continue
}
n, err := nco.GetNetwork()
if err != nil {
return false, fmt.Errorf("GetNetwork: %v", err)
}
defer n.Release()
cat, err := n.GetCategory()
if err != nil {
return false, fmt.Errorf("GetCategory: %v", err)
}
if cat != categoryPrivate {
if err := n.SetCategory(categoryPrivate); err != nil {
return false, fmt.Errorf("SetCategory: %v", err)
}
}
return true, nil
}
return false, nil
}
func configureInterface(cfg *Config, tun *tun.NativeTun) error {
const mtu = 0
guid := tun.GUID()
iface, err := winipcfg.InterfaceFromGUID(&guid)
if err != nil {
return err
}
go func() {
// It takes a weirdly long time for Windows to notice the
// new interface has come up. Poll periodically until it
// does.
const tries = 20
for i := 0; i < tries; i++ {
found, err := setPrivateNetwork(&guid)
if err != nil {
log.Printf("setPrivateNetwork(try=%d): %v", i, err)
} else {
if found {
return
}
log.Printf("setPrivateNetwork(try=%d): not found", i)
}
time.Sleep(1 * time.Second)
}
log.Printf("setPrivateNetwork: adapter %v not found after %d tries, giving up", guid, tries)
}()
var firstGateway4 *net.IP
var firstGateway6 *net.IP
addresses := make([]*net.IPNet, len(cfg.LocalAddrs))
for i, addr := range cfg.LocalAddrs {
ipnet := addr.IPNet()
addresses[i] = ipnet
gateway := ipnet.IP
if addr.IP.Is4() && firstGateway4 == nil {
firstGateway4 = &gateway
} else if addr.IP.Is6() && firstGateway6 == nil {
firstGateway6 = &gateway
}
}
var routes []winipcfg.RouteData
foundDefault4 := false
foundDefault6 := false
for _, route := range cfg.Routes {
if (route.IP.Is4() && firstGateway4 == nil) || (route.IP.Is6() && firstGateway6 == nil) {
return errors.New("Due to a Windows limitation, one cannot have interface routes without an interface address")
}
ipn := route.IPNet()
var gateway net.IP
if route.IP.Is4() {
gateway = *firstGateway4
} else if route.IP.Is6() {
gateway = *firstGateway6
}
r := winipcfg.RouteData{
Destination: net.IPNet{
IP: ipn.IP.Mask(ipn.Mask),
Mask: ipn.Mask,
},
NextHop: gateway,
Metric: 0,
}
if bytes.Compare(r.Destination.IP, gateway) == 0 {
// no need to add a route for the interface's
// own IP. The kernel does that for us.
// If we try to replace it, we'll fail to
// add the route unless NextHop is set, but
// then the interface's IP won't be pingable.
continue
}
if route.IP.Is4() {
if route.Bits == 0 {
foundDefault4 = true
}
r.NextHop = *firstGateway4
} else if route.IP.Is6() {
if route.Bits == 0 {
foundDefault6 = true
}
r.NextHop = *firstGateway6
}
routes = append(routes, r)
}
err = iface.SyncAddresses(addresses)
if err != nil {
return err
}
sort.Slice(routes, func(i, j int) bool { return routeLess(&routes[i], &routes[j]) })
deduplicatedRoutes := []*winipcfg.RouteData{}
for i := 0; i < len(routes); i++ {
// There's only one way to get to a given IP+Mask, so delete
// all matches after the first.
if i > 0 &&
bytes.Equal(routes[i].Destination.IP, routes[i-1].Destination.IP) &&
bytes.Equal(routes[i].Destination.Mask, routes[i-1].Destination.Mask) {
continue
}
deduplicatedRoutes = append(deduplicatedRoutes, &routes[i])
}
var errAcc error
err = iface.SyncRoutes(deduplicatedRoutes)
if err != nil && errAcc == nil {
log.Printf("setroutes: %v", err)
errAcc = err
}
ipif, err := iface.GetIpInterface(winipcfg.AF_INET)
if err != nil {
log.Printf("getipif: %v", err)
return err
}
if foundDefault4 {
ipif.UseAutomaticMetric = false
ipif.Metric = 0
}
if mtu > 0 {
ipif.NlMtu = uint32(mtu)
tun.ForceMTU(int(ipif.NlMtu))
}
err = ipif.Set()
if err != nil && errAcc == nil {
errAcc = err
}
ipif, err = iface.GetIpInterface(winipcfg.AF_INET6)
if err != nil {
if !isMissingIPv6Err(err) {
return err
}
} else {
if foundDefault6 {
ipif.UseAutomaticMetric = false
ipif.Metric = 0
}
if mtu > 0 {
ipif.NlMtu = uint32(mtu)
}
ipif.DadTransmits = 0
ipif.RouterDiscoveryBehavior = winipcfg.RouterDiscoveryDisabled
err = ipif.Set()
if err != nil && errAcc == nil {
errAcc = err
}
}
return errAcc
}
// isMissingIPv6Err reports whether err is due to IPv6 not being enabled on the machine.
//
// It only currently supports the errors returned by winipcfg.Interface.GetIpInterface.
func isMissingIPv6Err(err error) bool {
if se, ok := err.(*os.SyscallError); ok {
switch se.Syscall {
case "iphlpapi.GetIpInterfaceEntry":
// ERROR_NOT_FOUND from means the address family (IPv6) is not found.
// (ERROR_FILE_NOT_FOUND means that the interface doesn't exist.)
// https://docs.microsoft.com/en-us/windows/win32/api/netioapi/nf-netioapi-getipinterfaceentry
return se.Err == windows.ERROR_NOT_FOUND
}
}
return false
}
// routeLess reports whether ri should sort before rj.
// The actual sort order doesn't appear to matter. The caller just
// wants them sorted to be able to de-dup.
func routeLess(ri, rj *winipcfg.RouteData) bool {
if v := bytes.Compare(ri.Destination.IP, rj.Destination.IP); v != 0 {
return v == -1
}
if v := bytes.Compare(ri.Destination.Mask, rj.Destination.Mask); v != 0 {
// Narrower masks first
return v == 1
}
if ri.Metric != rj.Metric {
// Lower metrics first
return ri.Metric < rj.Metric
}
if v := bytes.Compare(ri.NextHop, rj.NextHop); v != 0 {
// No nexthop before non-empty nexthop.
return v == -1
}
return false
}