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tailscale/net/dns/manager.go

97 lines
2.4 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 (
"time"
"tailscale.com/types/logger"
)
// We use file-ignore below instead of ignore because on some platforms,
// the lint exception is necessary and on others it is not,
// and plain ignore complains if the exception is unnecessary.
//lint:file-ignore U1000 reconfigTimeout is used on some platforms but not others
// reconfigTimeout is the time interval within which Manager.{Up,Down} should complete.
//
// This is particularly useful because certain conditions can cause indefinite hangs
// (such as improper dbus auth followed by contextless dbus.Object.Call).
// Such operations should be wrapped in a timeout context.
const reconfigTimeout = time.Second
type managerImpl interface {
// Up updates system DNS settings to match the given configuration.
Up(OSConfig) error
// Down undoes the effects of Up.
// It is idempotent and performs no action if Up has never been called.
Down() error
}
// Manager manages system DNS settings.
type Manager struct {
logf logger.Logf
impl managerImpl
config OSConfig
}
// NewManagers created a new manager from the given config.
func NewManager(logf logger.Logf, interfaceName string) *Manager {
logf = logger.WithPrefix(logf, "dns: ")
m := &Manager{
logf: logf,
impl: newManager(logf, interfaceName),
}
m.logf("using %T", m.impl)
return m
}
func (m *Manager) Set(config OSConfig) error {
if config.Equal(m.config) {
return nil
}
m.logf("Set: %+v", config)
if len(config.Nameservers) == 0 {
err := m.impl.Down()
// If we save the config, we will not retry next time. Only do this on success.
if err == nil {
m.config = config
}
return err
}
err := m.impl.Up(config)
// If we save the config, we will not retry next time. Only do this on success.
if err == nil {
m.config = config
}
return err
}
func (m *Manager) Up() error {
return m.impl.Up(m.config)
}
func (m *Manager) Down() error {
return m.impl.Down()
}
// Cleanup restores the system DNS configuration to its original state
// in case the Tailscale daemon terminated without closing the router.
// No other state needs to be instantiated before this runs.
func Cleanup(logf logger.Logf, interfaceName string) {
dns := NewManager(logf, interfaceName)
if err := dns.Down(); err != nil {
logf("dns down: %v", err)
}
}