android: only reconfigure VPN when ready
This avoids reconfiguring the VPN both when routes changed and then again when DNS changed. Updates tailscale/corp#18928 Signed-off-by: Percy Wegmann <percy@tailscale.com>pull/300/head
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// Copyright (c) Tailscale Inc & AUTHORS
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// SPDX-License-Identifier: BSD-3-Clause
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package libtailscale
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import (
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"sync"
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"tailscale.com/net/dns"
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"tailscale.com/wgengine/router"
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)
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var (
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_ router.Router = (*VPNFacade)(nil)
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_ dns.OSConfigurator = (*VPNFacade)(nil)
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)
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// VPNFacade is an implementation of both wgengine.Router and
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// dns.OSConfigurator. When ReconfigureVPN is called by the backend, SetBoth
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// gets called.
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type VPNFacade struct {
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SetBoth func(rcfg *router.Config, dcfg *dns.OSConfig) error
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// GetBaseConfigFunc optionally specifies a function to return the current DNS
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// config in response to GetBaseConfig.
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//
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// If nil, reading the current config isn't supported and GetBaseConfig()
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// will return ErrGetBaseConfigNotSupported.
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GetBaseConfigFunc func() (dns.OSConfig, error)
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// InitialMTU is the MTU the tun should be initialized with.
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// Zero means don't change the MTU from the default. This MTU
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// is applied only once, shortly after the TUN is created, and
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// ignored thereaftef.
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InitialMTU uint32
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mu sync.Mutex // protects all the following
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didSetMTU bool // if we set the MTU already
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rcfg *router.Config // last applied router config
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dcfg *dns.OSConfig // last applied DNS config
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}
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// Up implements wgengine.router.
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func (vf *VPNFacade) Up() error {
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return nil // TODO: check that all callers have no need for initialization
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}
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// Set implements wgengine.router.
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func (vf *VPNFacade) Set(rcfg *router.Config) error {
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vf.mu.Lock()
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defer vf.mu.Unlock()
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if vf.rcfg.Equal(rcfg) {
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return nil
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}
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if vf.didSetMTU == false {
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vf.didSetMTU = true
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rcfg.NewMTU = int(vf.InitialMTU)
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}
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vf.rcfg = rcfg
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return nil
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}
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// UpdateMagicsockPort implements wgengine.Router. This implementation
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// does nothing and returns nil because this router does not currently need
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// to know what the magicsock UDP port is.
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func (vf *VPNFacade) UpdateMagicsockPort(_ uint16, _ string) error {
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return nil
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}
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// SetDNS implements dns.OSConfigurator.
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func (vf *VPNFacade) SetDNS(dcfg dns.OSConfig) error {
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vf.mu.Lock()
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defer vf.mu.Unlock()
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if vf.dcfg != nil && vf.dcfg.Equal(dcfg) {
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return nil
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}
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vf.dcfg = &dcfg
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return nil
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}
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// Implements dns.OSConfigurator.
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func (vf *VPNFacade) SupportsSplitDNS() bool {
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return false
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}
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// Implements dns.OSConfigurator.
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func (vf *VPNFacade) GetBaseConfig() (dns.OSConfig, error) {
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if vf.GetBaseConfigFunc == nil {
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return dns.OSConfig{}, dns.ErrGetBaseConfigNotSupported
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}
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return vf.GetBaseConfigFunc()
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}
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// Implements wgengine.router and dns.OSConfigurator.
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func (vf *VPNFacade) Close() error {
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return vf.SetBoth(nil, nil) // TODO: check if makes sense
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}
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// ReconfigureVPN is the method value passed to wgengine.Config.ReconfigureVPN.
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func (vf *VPNFacade) ReconfigureVPN() error {
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vf.mu.Lock()
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defer vf.mu.Unlock()
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return vf.SetBoth(vf.rcfg, vf.dcfg)
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}
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