ipn/ipnlocal: use buildfeature consts in a few more places

Updates #12614

Change-Id: I561d434d9829172a3d7f6933399237924ff80490
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

ipn/ipnlocal/local.go

@@ -5416,7 +5416,9 @@ func (b *LocalBackend) applyPrefsToHostinfoLocked(hi *tailcfg.Hostinfo, prefs ip
 	hi.ShieldsUp = prefs.ShieldsUp()
 	hi.AllowsUpdate = buildfeatures.HasClientUpdate && (envknob.AllowsRemoteUpdate() || prefs.AutoUpdate().Apply.EqualBool(true))
 
+	if buildfeatures.HasAdvertiseRoutes {
 		b.metrics.advertisedRoutes.Set(float64(tsaddr.WithoutExitRoute(prefs.AdvertiseRoutes()).Len()))
+	}
 
 	var sshHostKeys []string
 	if buildfeatures.HasSSH && prefs.RunSSH() && envknob.CanSSHD() {
@@ -5445,7 +5447,10 @@ func (b *LocalBackend) applyPrefsToHostinfoLocked(hi *tailcfg.Hostinfo, prefs ip
 	// DNS records are needed, so we can save bandwidth and not send
 	// WireIngress.
 	hi.WireIngress = b.shouldWireInactiveIngressLocked()
+
+	if buildfeatures.HasAppConnectors {
 		hi.AppConnector.Set(prefs.AppConnector().Advertise)
+	}
 
 	// The [tailcfg.Hostinfo.ExitNodeID] field tells control which exit node
 	// was selected, if any.
@@ -5461,10 +5466,12 @@ func (b *LocalBackend) applyPrefsToHostinfoLocked(hi *tailcfg.Hostinfo, prefs ip
 	// ExitNodeID here; [LocalBackend.ResolveExitNode] will be called once
 	// the netmap and/or net report have been received to both pick the exit
 	// node and notify control of the change.
+	if buildfeatures.HasUseExitNode {
 		if sid := prefs.ExitNodeID(); sid != unresolvedExitNodeID {
 			hi.ExitNodeID = prefs.ExitNodeID()
 		}
 	}
+}
 
 // enterState transitions the backend into newState, updating internal
 // state and propagating events out as needed.

tailcfg/tailcfg.go

@@ -20,6 +20,7 @@ import (
 	"strings"
 	"time"
 
+	"tailscale.com/feature/buildfeatures"
 	"tailscale.com/types/dnstype"
 	"tailscale.com/types/key"
 	"tailscale.com/types/opt"
@@ -1088,6 +1089,9 @@ func (ni *NetInfo) String() string {
 }
 
 func (ni *NetInfo) portMapSummary() string {
+	if !buildfeatures.HasPortMapper {
+		return "x"
+	}
 	if !ni.HavePortMap && ni.UPnP == "" && ni.PMP == "" && ni.PCP == "" {
 		return "?"
 	}