net/tsdial: move macOS/iOS peerapi sockopt logic from LocalBackend

Change-Id: I812cae027c40c70cdc701427b1a1850cd9bcd60c
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

cmd/tailscaled/tailscaled.go

@@ -308,8 +308,6 @@ func run() error {
 	socksListener, httpProxyListener := mustStartProxyListeners(args.socksAddr, args.httpProxyAddr)
 
 	dialer := new(tsdial.Dialer) // mutated below (before used)
-	dialer.SetLinkMonitor(linkMon)
-
 	e, useNetstack, err := createEngine(logf, linkMon, dialer)
 	if err != nil {
 		logf("wgengine.New: %v", err)

ipn/ipnlocal/local.go

@@ -22,7 +22,6 @@
 	"strings"
 	"sync"
 	"sync/atomic"
-	"syscall"
 	"time"
 
 	"inet.af/netaddr"
@@ -192,7 +191,6 @@ func NewLocalBackend(logf logger.Logf, logid string, store ipn.StateStore, diale
 		portpoll:       portpoll,
 		gotPortPollRes: make(chan struct{}),
 	}
-	dialer.SetPeerDialControlFuncGetter(b.peerDialControlFunc)
 
 	// Default filter blocks everything and logs nothing, until Start() is called.
 	b.setFilter(filter.NewAllowNone(logf, &netaddr.IPSet{}))
@@ -3041,19 +3039,6 @@ func disabledSysctls(sysctls ...string) (disabled []string, err error) {
 	return disabled, nil
 }
 
-// peerDialControlFunc is non-nil on platforms that require a way to
-// bind to dial out to other peers.
-var peerDialControlFunc func(*LocalBackend) func(network, address string, c syscall.RawConn) error
-
-// peerDialControlFunc returns a net.Dialer.Control func (possibly nil) to use to
-// dial other Tailscale peers from the current environment.
-func (b *LocalBackend) peerDialControlFunc() func(network, address string, c syscall.RawConn) error {
-	if peerDialControlFunc != nil {
-		return peerDialControlFunc(b)
-	}
-	return nil
-}
-
 // DERPMap returns the current DERPMap in use, or nil if not connected.
 func (b *LocalBackend) DERPMap() *tailcfg.DERPMap {
 	b.mu.Lock()

ipn/ipnlocal/peerapi_macios_ext.go

@@ -9,10 +9,8 @@
 package ipnlocal
 
 import (
-	"errors"
 	"fmt"
 	"net"
-	"syscall"
 
 	"inet.af/netaddr"
 	"tailscale.com/net/interfaces"
@@ -21,7 +19,6 @@
 
 func init() {
 	initListenConfig = initListenConfigNetworkExtension
-	peerDialControlFunc = peerDialControlFuncNetworkExtension
 }
 
 // initListenConfigNetworkExtension configures nc for listening on IP
@@ -34,24 +31,3 @@ func initListenConfigNetworkExtension(nc *net.ListenConfig, ip netaddr.IP, st *i
 	}
 	return netns.SetListenConfigInterfaceIndex(nc, tunIf.Index)
 }
-
-func peerDialControlFuncNetworkExtension(b *LocalBackend) func(network, address string, c syscall.RawConn) error {
-	b.mu.Lock()
-	defer b.mu.Unlock()
-	st := b.prevIfState
-	pas := b.peerAPIServer
-	index := -1
-	if st != nil && pas != nil && pas.tunName != "" {
-		if tunIf, ok := st.Interface[pas.tunName]; ok {
-			index = tunIf.Index
-		}
-	}
-	var lc net.ListenConfig
-	netns.SetListenConfigInterfaceIndex(&lc, index)
-	return func(network, address string, c syscall.RawConn) error {
-		if index == -1 {
-			return errors.New("failed to find TUN interface to bind to")
-		}
-		return lc.Control(network, address, c)
-	}
-}

ipn/ipnserver/server.go

@@ -739,12 +739,11 @@ func Run(ctx context.Context, logf logger.Logf, ln net.Listener, store ipn.State
 	}
 
 	dialer := new(tsdial.Dialer)
-	dialer.SetLinkMonitor(linkMon)
 	eng.AddNetworkMapCallback(func(nm *netmap.NetworkMap) {
 		dialer.SetDNSMap(tsdial.DNSMapFromNetworkMap(nm))
 	})
 
-	server, err := New(logf, logid, store, eng, nil, serverModeUser, opts)
+	server, err := New(logf, logid, store, eng, dialer, serverModeUser, opts)
 	if err != nil {
 		return err
 	}

net/tsdial/peerapi_macios_ext.go

@@ -0,0 +1,43 @@
+// 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.
+
+// This file's built on iOS and on two of three macOS build variants:
+// the two GUI variants that both use Extensions (Network Extension
+// and System Extension). It's not used on tailscaled-on-macOS.
+
+//go:build ts_macext && (darwin || ios)
+// +build ts_macext
+// +build darwin ios
+
+package tsdial
+
+import (
+	"errors"
+	"net"
+	"syscall"
+
+	"tailscale.com/net/netns"
+)
+
+func init() {
+	peerDialControlFunc = peerDialControlFuncNetworkExtension
+}
+
+func peerDialControlFuncNetworkExtension(d *Dialer) func(network, address string, c syscall.RawConn) error {
+	d.mu.Lock()
+	defer d.mu.Unlock()
+
+	index := -1
+	if x, ok := d.interfaceIndexLocked(d.tunName); ok {
+		index = x
+	}
+	var lc net.ListenConfig
+	netns.SetListenConfigInterfaceIndex(&lc, index)
+	return func(network, address string, c syscall.RawConn) error {
+		if index == -1 {
+			return errors.New("failed to find TUN interface to bind to")
+		}
+		return lc.Control(network, address, c)
+	}
+}

net/tsdial/tsdial.go

@@ -67,6 +67,22 @@ func (d *Dialer) SetLinkMonitor(mon *monitor.Mon) {
 	d.linkMon = mon
 }
 
+func (d *Dialer) interfaceIndexLocked(ifName string) (index int, ok bool) {
+	if d.linkMon == nil {
+		return 0, false
+	}
+	st := d.linkMon.InterfaceState()
+	iface, ok := st.Interface[ifName]
+	if !ok {
+		return 0, false
+	}
+	return iface.Index, true
+}
+
+// peerDialControlFunc is non-nil on platforms that require a way to
+// bind to dial out to other peers.
+var peerDialControlFunc func(*Dialer) func(network, address string, c syscall.RawConn) error
+
 // PeerDialControlFunc returns a function
 // that can assigned to net.Dialer.Control to set sockopts or whatnot
 // to make a dial escape the current platform's network sandbox.
@@ -76,19 +92,10 @@ func (d *Dialer) SetLinkMonitor(mon *monitor.Mon) {
 // Notably, this is non-nil on iOS and macOS when run as a Network or
 // System Extension (the GUI variants).
 func (d *Dialer) PeerDialControlFunc() func(network, address string, c syscall.RawConn) error {
-	gf, _ := d.peerDialControlFuncAtomic.Load().(func() func(network, address string, c syscall.RawConn) error)
-	if gf == nil {
+	if peerDialControlFunc == nil {
 		return nil
 	}
-	return gf()
-}
-
-// SetPeerDialControlFuncGetter sets a function that returns, for the
-// current network configuration at the time it's called, a function
-// that can assigned to net.Dialer.Control to set sockopts or whatnot
-// to make a dial escape the current platform's network sandbox.
-func (d *Dialer) SetPeerDialControlFuncGetter(getFunc func() func(network, address string, c syscall.RawConn) error) {
-	d.peerDialControlFuncAtomic.Store(getFunc)
+	return peerDialControlFunc(d)
 }
 
 // SetDNSMap sets the current map of DNS names learned from the netmap.

wgengine/userspace.go

@@ -319,6 +319,7 @@ func NewUserspaceEngine(logf logger.Logf, conf Config) (_ Engine, reterr error)
 
 	tunName, _ := conf.Tun.Name()
 	conf.Dialer.SetTUNName(tunName)
+	conf.Dialer.SetLinkMonitor(e.linkMon)
 	e.dns = dns.NewManager(logf, conf.DNS, e.linkMon, conf.Dialer, fwdDNSLinkSelector{e, tunName})
 
 	logf("link state: %+v", e.linkMon.InterfaceState())