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Enforce cumulative per-tick movement budget on server

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This commit is contained in:
Jage9
2026-02-24 20:15:24 -05:00
parent 3003aaf742
commit fa65d7bd0d
3 changed files with 56 additions and 10 deletions
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35
server/app/server.py
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@@ -576,12 +576,23 @@ class SignalingServer:
return 0 <= x < self.grid_size and 0 <= y < self.grid_size
def _max_allowed_position_delta(self, client: ClientConnection, now_ms: int) -> int:
"""Compute max allowed movement delta using server-authoritative rate policy."""
def _movement_window_index(self, now_ms: int) -> int:
"""Return current movement rate-limit window index for a server timestamp."""
elapsed_ms = max(0, now_ms - max(0, client.last_position_update_ms))
windows = max(1, elapsed_ms // self.movement_tick_ms)
return max(1, windows * self.movement_max_steps_per_tick)
return max(0, now_ms // self.movement_tick_ms)
def _consume_movement_budget(self, client: ClientConnection, now_ms: int, requested_delta: int) -> bool:
"""Consume per-window movement budget; return whether the move is allowed."""
window_index = self._movement_window_index(now_ms)
if client.movement_window_index != window_index:
client.movement_window_index = window_index
client.movement_window_steps_used = 0
remaining = max(0, self.movement_max_steps_per_tick - client.movement_window_steps_used)
if requested_delta > remaining:
return False
client.movement_window_steps_used += requested_delta
return True
@staticmethod
def _normalize_clock_timezone(value: object) -> str:
@@ -699,7 +710,10 @@ class SignalingServer:
client = ClientConnection(websocket=websocket, id=str(uuid.uuid4()))
client.x = random.randrange(self.grid_size)
client.y = random.randrange(self.grid_size)
client.last_position_update_ms = self.item_service.now_ms()
now_ms = self.item_service.now_ms()
client.last_position_update_ms = now_ms
client.movement_window_index = self._movement_window_index(now_ms)
client.movement_window_steps_used = 0
self.clients[websocket] = client
LOGGER.info("client connected id=%s total=%d", client.id, len(self.clients))
@@ -827,17 +841,18 @@ class SignalingServer:
return
now_ms = self.item_service.now_ms()
requested_delta = max(abs(packet.x - client.x), abs(packet.y - client.y))
max_delta = self._max_allowed_position_delta(client, now_ms)
if requested_delta > max_delta:
if not self._consume_movement_budget(client, now_ms, requested_delta):
remaining = max(0, self.movement_max_steps_per_tick - client.movement_window_steps_used)
PACKET_LOGGER.warning(
"position rate limit ignored id=%s from=%d,%d to=%d,%d requested_delta=%d max_delta=%d",
"position rate limit ignored id=%s from=%d,%d to=%d,%d requested_delta=%d remaining_budget=%d window=%d",
client.id,
client.x,
client.y,
packet.x,
packet.y,
requested_delta,
max_delta,
remaining,
client.movement_window_index,
)
return
client.x = packet.x