Revert "cmd/tailscaled, ipn/{ipnlocal,ipnserver}: let netstack get access to LocalBackend"

This reverts commit 2bc518dcb2.

@namansood didn't end up needing it in his 770aa71ffb.

cmd/tailscaled/tailscaled.go

@@ -29,7 +29,6 @@ import (
 	"time"
 
 	"github.com/go-multierror/multierror"
-	"tailscale.com/ipn/ipnlocal"
 	"tailscale.com/ipn/ipnserver"
 	"tailscale.com/logpolicy"
 	"tailscale.com/net/socks5"
@@ -228,8 +227,6 @@ func run() error {
 		return err
 	}
 
-	localBEFuture := ipnlocal.NewLocalBackendFuture()
-
 	var ns *netstack.Impl
 	if useNetstack {
 		tunDev, magicConn := e.(wgengine.InternalsGetter).GetInternals()
@@ -301,7 +298,6 @@ func run() error {
 		LegacyConfigPath:   paths.LegacyConfigPath(),
 		SurviveDisconnects: true,
 		DebugMux:           debugMux,
-		OnBackendCreated:   localBEFuture.Set,
 	}
 	err = ipnserver.Run(ctx, logf, pol.PublicID.String(), ipnserver.FixedEngine(e), opts)
 	// Cancelation is not an error: it is the only way to stop ipnserver.

ipn/ipnlocal/future.go

@@ -1,28 +0,0 @@
-// Copyright (c) 2021 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 ipnlocal
-
-import "sync"
-
-// LocalBackendFuture is a Future that returns a *LocalBackend.
-type LocalBackendFuture struct {
-	getOnce sync.Once
-	ch      chan *LocalBackend
-	v       *LocalBackend
-}
-
-func (f *LocalBackendFuture) Get() *LocalBackend {
-	f.getOnce.Do(f.get)
-	return f.v
-}
-
-func (f *LocalBackendFuture) get()                { f.v = <-f.ch }
-func (f *LocalBackendFuture) Set(v *LocalBackend) { f.ch <- v }
-
-func NewLocalBackendFuture() *LocalBackendFuture {
-	return &LocalBackendFuture{
-		ch: make(chan *LocalBackend, 1),
-	}
-}

ipn/ipnserver/server.go

@@ -92,10 +92,6 @@ type Options struct {
 	// DebugMux, if non-nil, specifies an HTTP ServeMux in which
 	// to register a debug handler.
 	DebugMux *http.ServeMux
-
-	// OnBackendCreated, if non-nil, is called once when the LocalBackend
-	// is created.
-	OnBackendCreated func(*ipnlocal.LocalBackend)
 }
 
 // server is an IPN backend and its set of 0 or more active connections
@@ -743,10 +739,6 @@ func Run(ctx context.Context, logf logger.Logf, logid string, getEngine func() (
 		return smallzstd.NewDecoder(nil)
 	})
 
-	if opts.OnBackendCreated != nil {
-		opts.OnBackendCreated(b)
-	}
-
 	if opts.DebugMux != nil {
 		opts.DebugMux.HandleFunc("/debug/ipn", func(w http.ResponseWriter, r *http.Request) {
 			serveHTMLStatus(w, b)