[tun_pkt]: Wait for AsyncSniffer to init fully (#10346)

Fix for Tunnel packet handler can crash at system startup 
Signed-off-by: Lawrence Lee <lawlee@microsoft.com>

dockers/docker-orchagent/tunnel_packet_handler.py

@@ -51,6 +51,10 @@ class TunnelPacketHandler(object):
         self._portchannel_intfs = None
         self.up_portchannels = None
         self.netlink_api = IPRoute()
+        self.sniffer = None
+        self.self_ip = ''
+        self.packet_filter = ''
+        self.sniff_intfs = []
 
     @property
     def portchannel_intfs(self):
@@ -270,6 +274,39 @@ class TunnelPacketHandler(object):
                     return True
         return False
 
+    def start_sniffer(self):
+        """
+        Starts an AsyncSniffer and waits for it to inititalize fully
+        """
+        self.sniffer = AsyncSniffer(
+            iface=self.sniff_intfs,
+            filter=self.packet_filter,
+            prn=self.ping_inner_dst,
+            store=0
+        )
+        self.sniffer.start()
+
+        while not hasattr(self.sniffer, 'stop_cb'):
+            time.sleep(0.1)
+
+    def ping_inner_dst(self, packet):
+        """
+        Pings the inner destination IP for an encapsulated packet
+
+        Args:
+            packet: The encapsulated packet received
+        """
+        inner_packet_type = self.get_inner_pkt_type(packet)
+        if inner_packet_type and packet[IP].dst == self.self_ip:
+            cmds = ['timeout', '0.2', 'ping', '-c1',
+                    '-W1', '-i0', '-n', '-q']
+            if inner_packet_type == IPv6:
+                cmds.append('-6')
+            dst_ip = packet[IP].payload[inner_packet_type].dst
+            cmds.append(dst_ip)
+            logger.log_info("Running command '{}'".format(' '.join(cmds)))
+            subprocess.run(cmds, stdout=subprocess.DEVNULL)
+
     def listen_for_tunnel_pkts(self):
         """
         Listens for tunnel packets that are trapped to CPU
@@ -277,59 +314,28 @@ class TunnelPacketHandler(object):
         These packets may be trapped if there is no neighbor info for the
         inner packet destination IP in the hardware.
         """
-
+        self.self_ip, peer_ip = self.get_ipinip_tunnel_addrs()
-        def _ping_inner_dst(packet):
+        if self.self_ip is None or peer_ip is None:
-            """
-            Pings the inner destination IP for an encapsulated packet
-
-            Args:
-                packet: The encapsulated packet received
-            """
-            inner_packet_type = self.get_inner_pkt_type(packet)
-            if inner_packet_type and packet[IP].dst == self_ip:
-                cmds = ['timeout', '0.2', 'ping', '-c1',
-                        '-W1', '-i0', '-n', '-q']
-                if inner_packet_type == IPv6:
-                    cmds.append('-6')
-                dst_ip = packet[IP].payload[inner_packet_type].dst
-                cmds.append(dst_ip)
-                logger.log_info("Running command '{}'".format(' '.join(cmds)))
-                subprocess.run(cmds, stdout=subprocess.DEVNULL)
-
-        self_ip, peer_ip = self.get_ipinip_tunnel_addrs()
-        if self_ip is None or peer_ip is None:
             logger.log_notice('Could not get tunnel addresses from '
                               'config DB, exiting...')
             return None
 
-        packet_filter = 'host {} and host {}'.format(self_ip, peer_ip)
+        self.packet_filter = 'host {} and host {}'.format(self.self_ip, peer_ip)
         logger.log_notice('Starting tunnel packet handler for {}'
-                          .format(packet_filter))
+                          .format(self.packet_filter))
 
-        sniff_intfs = self.get_up_portchannels()
+        self.sniff_intfs = self.get_up_portchannels()
-        logger.log_info("Listening on interfaces {}".format(sniff_intfs))
+        logger.log_info("Listening on interfaces {}".format(self.sniff_intfs))
 
-        sniffer = AsyncSniffer(
+        self.start_sniffer()
-            iface=sniff_intfs,
-            filter=packet_filter,
-            prn=_ping_inner_dst,
-            store=0
-        )
-        sniffer.start()
         while True:
             msgs = self.wait_for_netlink_msgs()
             if self.sniffer_restart_required(msgs):
-                sniffer.stop()
+                self.sniffer.stop()
                 sniff_intfs = self.get_up_portchannels()
                 logger.log_notice('Restarting tunnel packet handler on '
                                   'interfaces {}'.format(sniff_intfs))
-                sniffer = AsyncSniffer(
+                self.start_sniffer()
-                    iface=sniff_intfs,
-                    filter=packet_filter,
-                    prn=_ping_inner_dst,
-                    store=0
-                )
-                sniffer.start()
 
     def run(self):
         """