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// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package interfaces
import (
"fmt"
"log"
"net"
"net/url"
"syscall"
"unsafe"
"golang.org/x/sys/windows"
"golang.zx2c4.com/wireguard/windows/tunnel/winipcfg"
"inet.af/netaddr"
"tailscale.com/tsconst"
)
const (
fallbackInterfaceMetric = uint32(0) // Used if we cannot get the actual interface metric
)
func init() {
likelyHomeRouterIP = likelyHomeRouterIPWindows
getPAC = getPACWindows
}
func likelyHomeRouterIPWindows() (ret netaddr.IP, ok bool) {
rs, err := winipcfg.GetIPForwardTable2(windows.AF_INET)
if err != nil {
log.Printf("routerIP/GetIPForwardTable2 error: %v", err)
return
}
var ifaceMetricCache map[winipcfg.LUID]uint32
getIfaceMetric := func(luid winipcfg.LUID) (metric uint32) {
if ifaceMetricCache == nil {
ifaceMetricCache = make(map[winipcfg.LUID]uint32)
} else if m, ok := ifaceMetricCache[luid]; ok {
return m
}
if iface, err := luid.IPInterface(windows.AF_INET); err == nil {
metric = iface.Metric
} else {
log.Printf("routerIP/luid.IPInterface error: %v", err)
metric = fallbackInterfaceMetric
}
ifaceMetricCache[luid] = metric
return
}
unspec := net.IPv4(0, 0, 0, 0)
var best *winipcfg.MibIPforwardRow2 // best (lowest metric) found so far, or nil
for i := range rs {
r := &rs[i]
if r.Loopback || r.DestinationPrefix.PrefixLength != 0 || !r.DestinationPrefix.Prefix.IP().Equal(unspec) {
// Not a default route, so skip
continue
}
ip, ok := netaddr.FromStdIP(r.NextHop.IP())
if !ok {
// Not a valid gateway, so skip (won't happen though)
continue
}
if best == nil {
best = r
ret = ip
continue
}
// We can get here only if there are multiple default gateways defined (rare case),
// in which case we need to calculate the effective metric.
// Effective metric is sum of interface metric and route metric offset
if ifaceMetricCache == nil {
// If we're here it means that previous route still isn't updated, so update it
best.Metric += getIfaceMetric(best.InterfaceLUID)
}
r.Metric += getIfaceMetric(r.InterfaceLUID)
if best.Metric > r.Metric || best.Metric == r.Metric && ret.Compare(ip) > 0 {
// Pick the route with lower metric, or lower IP if metrics are equal
best = r
ret = ip
}
}
if !ret.IsZero() && !isPrivateIP(ret) {
// Default route has a non-private gateway
return netaddr.IP{}, false
}
return ret, !ret.IsZero()
}
// NonTailscaleMTUs returns a map of interface LUID to interface MTU,
// for all interfaces except Tailscale tunnels.
func NonTailscaleMTUs() (map[winipcfg.LUID]uint32, error) {
mtus := map[winipcfg.LUID]uint32{}
ifs, err := NonTailscaleInterfaces()
for luid, iface := range ifs {
mtus[luid] = iface.MTU
}
return mtus, err
}
// NonTailscaleInterfaces returns a map of interface LUID to interface
// for all interfaces except Tailscale tunnels.
func NonTailscaleInterfaces() (map[winipcfg.LUID]*winipcfg.IPAdapterAddresses, error) {
ifs, err := winipcfg.GetAdaptersAddresses(windows.AF_UNSPEC, winipcfg.GAAFlagIncludeAllInterfaces)
if err != nil {
return nil, err
}
ret := map[winipcfg.LUID]*winipcfg.IPAdapterAddresses{}
for _, iface := range ifs {
if iface.Description() == tsconst.WintunInterfaceDesc {
continue
}
ret[iface.LUID] = iface
}
return ret, nil
}
// GetWindowsDefault returns the interface that has the non-Tailscale
// default route for the given address family.
//
// It returns (nil, nil) if no interface is found.
func GetWindowsDefault(family winipcfg.AddressFamily) (*winipcfg.IPAdapterAddresses, error) {
ifs, err := NonTailscaleInterfaces()
if err != nil {
return nil, err
}
routes, err := winipcfg.GetIPForwardTable2(family)
if err != nil {
return nil, err
}
bestMetric := ^uint32(0)
var bestIface *winipcfg.IPAdapterAddresses
for _, route := range routes {
iface := ifs[route.InterfaceLUID]
if route.DestinationPrefix.PrefixLength != 0 || iface == nil {
continue
}
if iface.OperStatus == winipcfg.IfOperStatusUp && route.Metric < bestMetric {
bestMetric = route.Metric
bestIface = iface
}
}
return bestIface, nil
}
func DefaultRouteInterface() (string, error) {
iface, err := GetWindowsDefault(windows.AF_INET)
if err != nil {
return "", err
}
if iface == nil {
return "(none)", nil
}
return fmt.Sprintf("%s (%s)", iface.FriendlyName(), iface.Description()), nil
}
var (
winHTTP = windows.NewLazySystemDLL("winhttp.dll")
detectAutoProxyConfigURL = winHTTP.NewProc("WinHttpDetectAutoProxyConfigUrl")
kernel32 = windows.NewLazySystemDLL("kernel32.dll")
globalFree = kernel32.NewProc("GlobalFree")
)
const (
winHTTP_AUTO_DETECT_TYPE_DHCP = 0x00000001
winHTTP_AUTO_DETECT_TYPE_DNS_A = 0x00000002
)
func getPACWindows() string {
var res *uint16
r, _, e := detectAutoProxyConfigURL.Call(
winHTTP_AUTO_DETECT_TYPE_DHCP|winHTTP_AUTO_DETECT_TYPE_DNS_A,
uintptr(unsafe.Pointer(&res)),
)
if r == 1 {
if res == nil {
log.Printf("getPACWindows: unexpected success with nil result")
return ""
}
defer globalFree.Call(uintptr(unsafe.Pointer(res)))
s := windows.UTF16PtrToString(res)
if _, err := url.Parse(s); err != nil {
log.Printf("getPACWindows: invalid URL %q from winhttp; ignoring", s)
return ""
}
return s
}
const (
ERROR_WINHTTP_AUTODETECTION_FAILED = 12180
)
if e == syscall.Errno(ERROR_WINHTTP_AUTODETECTION_FAILED) {
// Common case on networks without advertised PAC.
return ""
}
log.Printf("getPACWindows: %T=%v", e, e) // syscall.Errno=0x....
return ""
}
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