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net/interfaces: use windows API to get the default route instead of parsing route print output

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Fixes: #1470

Signed-off-by: Aleksandar Pesic <peske.nis@gmail.com>
This commit is contained in:
Aleksandar Pesic 2021-03-16 15:52:26 +01:00
parent 439d70dce2
commit 7b57310966
3 changed files with 68 additions and 48 deletions
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2
cmd/tailscale/depaware.txt
View File

@ -50,7 +50,7 @@ tailscale.com/cmd/tailscale dependencies: (generated by github.com/tailscale/dep
tailscale.com/types/wgkey from tailscale.com/types/netmap+
tailscale.com/util/dnsname from tailscale.com/cmd/tailscale/cli+
W tailscale.com/util/endian from tailscale.com/net/netns
LW tailscale.com/util/lineread from tailscale.com/net/interfaces
L tailscale.com/util/lineread from tailscale.com/net/interfaces
tailscale.com/version from tailscale.com/cmd/tailscale/cli+
tailscale.com/version/distro from tailscale.com/cmd/tailscale/cli
tailscale.com/wgengine/filter from tailscale.com/types/netmap

2
cmd/tailscaled/depaware.txt
View File

@ -126,7 +126,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
tailscale.com/types/wgkey from tailscale.com/control/controlclient+
tailscale.com/util/dnsname from tailscale.com/wgengine/tsdns+
LW tailscale.com/util/endian from tailscale.com/net/netns+
LW tailscale.com/util/lineread from tailscale.com/control/controlclient+
L tailscale.com/util/lineread from tailscale.com/control/controlclient+
tailscale.com/util/pidowner from tailscale.com/ipn/ipnserver
tailscale.com/util/racebuild from tailscale.com/logpolicy
tailscale.com/util/systemd from tailscale.com/control/controlclient+

112
net/interfaces/interfaces_windows.go
View File

@ -7,17 +7,19 @@ package interfaces
import (
"fmt"
"log"
"net"
"net/url"
"os/exec"
"syscall"
"unsafe"
"go4.org/mem"
"golang.org/x/sys/windows"
"golang.zx2c4.com/wireguard/windows/tunnel/winipcfg"
"inet.af/netaddr"
"tailscale.com/tsconst"
"tailscale.com/util/lineread"
)
const (
fallbackInterfaceMetric = uint32(0) // Used if we cannot get the actual interface metric
)
func init() {
@ -25,58 +27,76 @@ func init() {
getPAC = getPACWindows
}
/*
Parse out 10.0.0.1 from:
Z:\>route print -4
===========================================================================
Interface List
15...aa 15 48 ff 1c 72 ......Red Hat VirtIO Ethernet Adapter
5...........................Tailscale Tunnel
1...........................Software Loopback Interface 1
===========================================================================
IPv4 Route Table
===========================================================================
Active Routes:
Network Destination Netmask Gateway Interface Metric
0.0.0.0 0.0.0.0 10.0.0.1 10.0.28.63 5
10.0.0.0 255.255.0.0 On-link 10.0.28.63 261
10.0.28.63 255.255.255.255 On-link 10.0.28.63 261
10.0.42.0 255.255.255.0 100.103.42.106 100.103.42.106 5
10.0.255.255 255.255.255.255 On-link 10.0.28.63 261
34.193.248.174 255.255.255.255 100.103.42.106 100.103.42.106 5
*/
func likelyHomeRouterIPWindows() (ret netaddr.IP, ok bool) {
cmd := exec.Command("route", "print", "-4")
cmd.SysProcAttr = &syscall.SysProcAttr{HideWindow: true}
stdout, err := cmd.StdoutPipe()
rs, err := winipcfg.GetIPForwardTable2(windows.AF_INET)
if err != nil {
log.Printf("routerIP/GetIPForwardTable2 error: %v", err)
return
}
if err := cmd.Start(); err != nil {
return
}
defer cmd.Wait()
var f []mem.RO
lineread.Reader(stdout, func(lineb []byte) error {
line := mem.B(lineb)
if !mem.Contains(line, mem.S("0.0.0.0")) {
return nil
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
}
f = mem.AppendFields(f[:0], line)
if len(f) < 3 || !f[0].EqualString("0.0.0.0") || !f[1].EqualString("0.0.0.0") {
return nil
if iface, err := luid.IPInterface(windows.AF_INET); err == nil {
metric = iface.Metric
} else {
log.Printf("routerIP/luid.IPInterface error: %v", err)
metric = fallbackInterfaceMetric
}
ipm := f[2]
ip, err := netaddr.ParseIP(string(mem.Append(nil, ipm)))
if err == nil && isPrivateIP(ip) {
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
}
return nil
})
}
if !ret.IsZero() && !isPrivateIP(ret) {
// Default route has a non-private gateway
return netaddr.IP{}, false
}
return ret, !ret.IsZero()
}