fix: improve event loop handling and code organization in network sniffer

backend/src/network_sniffer.py

@@ -6,9 +6,13 @@ import threading
 
 DB_DSN = "postgresql://mitm_user:mitm_password@localhost:5432/mitm_db"
 
-sniffer_tasks = {}
 sniffer_threads = {}
+event_loop = None     # <-- we store FastAPI's main loop here
 
+
+# -----------------------------
+#  DB INSERT
+# -----------------------------
 async def db_insert_packet(pkt_info: dict):
     conn = await asyncpg.connect(DB_DSN)
     try:
@@ -40,13 +44,15 @@ async def db_insert_packet(pkt_info: dict):
         await conn.close()
 
 
+# -----------------------------
+#  PACKET HANDLER (Thread)
+# -----------------------------
 def handle_packet(pkt, iface):
-    """
-    Scapy callback → run in thread.
-    """
+    global event_loop
+
     pkt_info = {
         "iface": iface,
-        "direction": "unknown",  # You can set eth0=ingress, eth1=egress
+        "direction": "unknown",
         "src_mac": pkt[Ether].src if Ether in pkt else None,
         "dst_mac": pkt[Ether].dst if Ether in pkt else None,
         "eth_type": pkt[Ether].type if Ether in pkt else None,
@@ -54,26 +60,39 @@ def handle_packet(pkt, iface):
         "dst_ip": pkt[IP].dst if IP in pkt else None,
         "protocol": pkt[IP].proto if IP in pkt else None,
         "length": len(pkt),
-        "ebpf_verdict": None,  # will integrate later
+        "ebpf_verdict": None,
         "ebpf_chain": None,
-        "raw": bytes(pkt)
+        "raw": bytes(pkt),
     }
 
-    # push to asyncio loop
-    loop = asyncio.get_event_loop()
-    loop.create_task(db_insert_packet(pkt_info))
+    # Schedule coroutine in main event loop from thread
+    asyncio.run_coroutine_threadsafe(
+        db_insert_packet(pkt_info),
+        event_loop
+    )
 
 
+# -----------------------------
+#  SNIFFER THREAD
+# -----------------------------
 def start_sniffer_thread(iface: str):
     def sniff_blocking():
-        sniff(prn=lambda x: handle_packet(x, iface), iface=iface, store=False)
+        sniff(prn=lambda x: handle_packet(x, iface),
+              iface=iface,
+              store=False)
 
     thread = threading.Thread(target=sniff_blocking, daemon=True)
     thread.start()
     return thread
 
 
+# -----------------------------
+#  PUBLIC API
+# -----------------------------
 async def start_sniffing(interfaces: List[str]):
+    global event_loop
+    event_loop = asyncio.get_running_loop()   # <-- IMPORTANT FIX
+
     for iface in interfaces:
         if iface in sniffer_threads:
             continue
@@ -81,6 +100,6 @@ async def start_sniffing(interfaces: List[str]):
 
 
 async def stop_sniffing():
-    # Scapy cannot easily stop sniff(), so we simply kill threads
+    # Scapy cannot stop sniff(), but threads die on shutdown
     sniffer_threads.clear()
     return True