ipn,ipn/local: always accept routes for Tailscale Services (cgnat range) (#18173)

Updates #18198

Signed-off-by: chaosinthecrd <tom@tmlabs.co.uk>
Co-authored-by: James Tucker <raggi@tailscale.com>

types/netmap/netmap.go

@@ -13,6 +13,7 @@ import (
 	"strings"
 	"time"
 
+	"tailscale.com/net/tsaddr"
 	"tailscale.com/tailcfg"
 	"tailscale.com/tka"
 	"tailscale.com/types/key"
@@ -154,8 +155,11 @@ func (nm *NetworkMap) SelfNodeOrZero() tailcfg.NodeView {
 // AnyPeersAdvertiseRoutes reports whether any peer is advertising non-exit node routes.
 func (nm *NetworkMap) AnyPeersAdvertiseRoutes() bool {
 	for _, p := range nm.Peers {
-		if p.PrimaryRoutes().Len() > 0 {
-			return true
+		// NOTE: (ChaosInTheCRD) if the peer being advertised is a tailscale ip, we ignore it in this check
+		for _, r := range p.PrimaryRoutes().All() {
+			if !tsaddr.IsTailscaleIP(r.Addr()) || !r.IsSingleIP() {
+				return true
+			}
 		}
 	}
 	return false