只有hello包实现多跳，还没加入业务数据

具体的还要看opencode和gpt记录接着优化

sim/node/node.py

@@ -16,6 +16,7 @@ from sim.core.packet import Packet, PacketType
 from sim.routing.gradient_routing import GradientRouting
 from sim.mac.reliable_mac import ReliableMAC
 from sim.radio.channel import Channel, ReceivedPacket
+from sim.core.metrics import MetricsCollector
 from sim import config
 
 
@@ -51,6 +52,7 @@ class Node:
         y: float,
         channel: Channel,
         is_sink: bool = False,
+        metrics_collector: MetricsCollector = None,
     ):
         """
         Initialize node.
@@ -62,6 +64,7 @@ class Node:
             y: Y coordinate
             channel: Wireless channel
             is_sink: Whether this is the sink node
+            metrics_collector: Metrics collector for observability
         """
         self.env = env
         self.node_id = node_id
@@ -70,6 +73,9 @@ class Node:
         self.channel = channel
         self.is_sink = is_sink
 
+        # Metrics collector for hop tracking
+        self.metrics_collector = metrics_collector
+
         # Register position with channel
         self.channel.register_node(node_id, x, y)
 
@@ -199,18 +205,26 @@ class Node:
 
     def _process_data(self, packet: Packet):
         """Process received DATA packet."""
-        # If we're the destination (sink), receive it
-        if packet.dst == self.node_id:
+        # If we're the sink, receive the packet
+        if self.is_sink:
             self.stats.data_received += 1
 
-            # If sink, we're done
-            if self.is_sink:
-                return
+            # Record hop count for analysis
+            if self.metrics_collector:
+                # print(f"SINK received packet with hop={packet.hop}")
+                self.metrics_collector.record_hop_count(packet.hop)
+            return
 
-            # Otherwise forward to parent (for multi-hop)
-            next_hop = self.routing.get_next_hop()
-            if next_hop is not None and next_hop != self.node_id:
-                self._forward_data(packet)
+        # If not sink, check if we should forward
+        # Don't forward if we've already forwarded this packet (check path)
+        if self.node_id in packet.path:
+            # We've already seen and forwarded this packet, skip it
+            return
+
+        # Forward to parent
+        next_hop = self.routing.get_next_hop()
+        if next_hop is not None and next_hop != self.node_id:
+            self._forward_data(packet)
 
     def _process_ack(self, packet: Packet):
         """Process received ACK packet."""
@@ -224,7 +238,7 @@ class Node:
             src=self.node_id,
             dst=config.SINK_NODE_ID,
             seq=self.data_seq,
-            hop=0,
+            hop=1,  # Start at 1 hop (first link)
             payload=f"data_{self.data_seq}",
         )
         self.data_seq += 1
@@ -237,8 +251,8 @@ class Node:
 
     def _forward_data(self, packet: Packet):
         """Forward a data packet towards sink."""
-        # Increment hop count
-        packet.hop += 1
+        # Record this node in the path and increment hop count
+        packet.add_hop(self.node_id)
 
         # Send to parent
         next_hop = self.routing.get_next_hop()