Define wrap-safe snapshot sequencing

server/transport_policy.py

@@ -26,3 +26,13 @@ def delivery_for_packet_type(packet_type: str) -> Delivery:
 
 def is_snapshot_packet(packet_type: str) -> bool:
     return delivery_for_packet_type(packet_type) is Delivery.UNRELIABLE_SEQUENCED
+
+
+def requires_application_sequence(packet_type: str) -> bool:
+    """Return whether the protocol must reject stale copies after reordering.
+
+    GameNetworkingSockets can deliver unreliable messages without retransmit,
+    but the application still owns latest-wins snapshot semantics. Sequence
+    numbers are therefore required for every unreliable snapshot family.
+    """
+    return is_snapshot_packet(packet_type)