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tailscale/net/dns/manager_windows.go

119 lines
3.1 KiB
Go

// 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 dns
import (
"fmt"
"os/exec"
"strings"
"syscall"
"time"
"golang.org/x/sys/windows/registry"
"tailscale.com/types/logger"
)
const (
ipv4RegBase = `SYSTEM\CurrentControlSet\Services\Tcpip\Parameters`
ipv6RegBase = `SYSTEM\CurrentControlSet\Services\Tcpip6\Parameters`
)
type windowsManager struct {
logf logger.Logf
guid string
}
func newManager(mconfig ManagerConfig) managerImpl {
return windowsManager{
logf: mconfig.Logf,
guid: mconfig.InterfaceName,
}
}
// keyOpenTimeout is how long we wait for a registry key to
// appear. For some reason, registry keys tied to ephemeral interfaces
// can take a long while to appear after interface creation, and we
// can end up racing with that.
const keyOpenTimeout = 20 * time.Second
func setRegistryString(path, name, value string) error {
key, err := openKeyWait(registry.LOCAL_MACHINE, path, registry.SET_VALUE, keyOpenTimeout)
if err != nil {
return fmt.Errorf("opening %s: %w", path, err)
}
defer key.Close()
err = key.SetStringValue(name, value)
if err != nil {
return fmt.Errorf("setting %s[%s]: %w", path, name, err)
}
return nil
}
func (m windowsManager) setNameservers(basePath string, nameservers []string) error {
path := fmt.Sprintf(`%s\Interfaces\%s`, basePath, m.guid)
value := strings.Join(nameservers, ",")
return setRegistryString(path, "NameServer", value)
}
func (m windowsManager) setDomains(basePath string, domains []string) error {
path := fmt.Sprintf(`%s\Interfaces\%s`, basePath, m.guid)
value := strings.Join(domains, ",")
return setRegistryString(path, "SearchList", value)
}
func (m windowsManager) Up(config Config) error {
var ipsv4 []string
var ipsv6 []string
for _, ip := range config.Nameservers {
if ip.Is4() {
ipsv4 = append(ipsv4, ip.String())
} else {
ipsv6 = append(ipsv6, ip.String())
}
}
if err := m.setNameservers(ipv4RegBase, ipsv4); err != nil {
return err
}
if err := m.setDomains(ipv4RegBase, config.Domains); err != nil {
return err
}
if err := m.setNameservers(ipv6RegBase, ipsv6); err != nil {
return err
}
if err := m.setDomains(ipv6RegBase, config.Domains); err != nil {
return err
}
// Force DNS re-registration in Active Directory. What we actually
// care about is that this command invokes the undocumented hidden
// function that forces Windows to notice that adapter settings
// have changed, which makes the DNS settings actually take
// effect.
//
// This command can take a few seconds to run, so run it async, best effort.
go func() {
t0 := time.Now()
m.logf("running ipconfig /registerdns ...")
cmd := exec.Command("ipconfig", "/registerdns")
cmd.SysProcAttr = &syscall.SysProcAttr{HideWindow: true}
d := time.Since(t0).Round(time.Millisecond)
if err := cmd.Run(); err != nil {
m.logf("error running ipconfig /registerdns after %v: %v", d, err)
} else {
m.logf("ran ipconfig /registerdns in %v", d)
}
}()
return nil
}
func (m windowsManager) Down() error {
return m.Up(Config{Nameservers: nil, Domains: nil})
}