net/tsdial: also plumb TUN name and monitor into tsdial.Dialer

In prep for moving stuff out of LocalBackend.

Change-Id: I9725aa9c3ebc7275f8c40e040b326483c0340127
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

ipn/ipnlocal/local.go

@@ -2185,17 +2185,9 @@ func (b *LocalBackend) initPeerAPIListener() {
 		return
 	}
 
-	var tunName string
-	if ge, ok := b.e.(wgengine.InternalsGetter); ok {
-		if tunWrap, _, ok := ge.GetInternals(); ok {
-			tunName, _ = tunWrap.Name()
-		}
-	}
-
 	ps := &peerAPIServer{
 		b:              b,
 		rootDir:        fileRoot,
-		tunName:        tunName,
 		selfNode:       selfNode,
 		directFileMode: b.directFileRoot != "",
 	}

ipn/ipnlocal/peerapi.go

@@ -49,7 +49,6 @@ var initListenConfig func(*net.ListenConfig, netaddr.IP, *interfaces.State, stri
 type peerAPIServer struct {
 	b          *LocalBackend
 	rootDir    string
-	tunName    string
 	selfNode   *tailcfg.Node
 	knownEmpty syncs.AtomicBool
 	resolver   *resolver.Resolver
@@ -363,7 +362,7 @@ func (s *peerAPIServer) listen(ip netaddr.IP, ifState *interfaces.State) (ln net
 		// On iOS/macOS, this sets the lc.Control hook to
 		// setsockopt the interface index to bind to, to get
 		// out of the network sandbox.
-		if err := initListenConfig(&lc, ip, ifState, s.tunName); err != nil {
+		if err := initListenConfig(&lc, ip, ifState, s.b.dialer.TUNName()); err != nil {
 			return nil, err
 		}
 		if runtime.GOOS == "darwin" || runtime.GOOS == "ios" {