ipn/ipnlocal: fix StatusWithoutPeers not populating parts of Status

Fixes #4311

Change-Id: Iaae0615148fa7154f4ef8f66b455e3a6c2fa9df3
Co-authored-by: Claire Wang <claire@tailscale.com>
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

wgengine/magicsock/magicsock.go

@@ -3545,12 +3545,14 @@ func (c *Conn) UpdateStatus(sb *ipnstate.StatusBuilder) {
 		ss.TailscaleIPs = tailscaleIPs
 	})
 
-	c.peerMap.forEachEndpoint(func(ep *endpoint) {
-		ps := &ipnstate.PeerStatus{InMagicSock: true}
-		//ps.Addrs = append(ps.Addrs, n.Endpoints...)
-		ep.populatePeerStatus(ps)
-		sb.AddPeer(ep.publicKey, ps)
-	})
+	if sb.WantPeers {
+		c.peerMap.forEachEndpoint(func(ep *endpoint) {
+			ps := &ipnstate.PeerStatus{InMagicSock: true}
+			//ps.Addrs = append(ps.Addrs, n.Endpoints...)
+			ep.populatePeerStatus(ps)
+			sb.AddPeer(ep.publicKey, ps)
+		})
+	}
 
 	c.foreachActiveDerpSortedLocked(func(node int, ad activeDerp) {
 		// TODO(bradfitz): add to ipnstate.StatusBuilder

wgengine/magicsock/magicsock_test.go

@@ -219,6 +219,7 @@ func (s *magicStack) Public() key.NodePublic {
 
 func (s *magicStack) Status() *ipnstate.Status {
 	var sb ipnstate.StatusBuilder
+	sb.WantPeers = true
 	s.conn.UpdateStatus(&sb)
 	return sb.Status()
 }