Fix test_bgp_update_timer failure caused by scapy upgrade in sonic-mg…

…mt docker image

The scapy package in sonic-mgmt docker image was upgraded in PR sonic-net/sonic-buildimage#8554.
The new version of scapy uses a different way to represent and dissect BGP messages. This caused the failure of
test_bgp_update_time.py.

This PR is to address the compatibility issue of scapy. The test_bgp_update_timer.py script was updated to be
be compatible with both old and new scapy versions.

Signed-off-by: Xin Wang <xiwang5@microsoft.com>

tests/bgp/test_bgp_update_timer.py

@@ -152,12 +152,41 @@ def match_bgp_update(packet, src_ip, dst_ip, action, route):
         if not (packet[IP].src == src_ip and packet[IP].dst == dst_ip):
             return False
         subnet = ipaddress.ip_network(route["prefix"].decode())
-        _route = (subnet.prefixlen, str(subnet.network_address))
+
+        # New scapy (version 2.4.5) uses a different way to represent and dissect BGP messages. Below logic is to
+        # address the compatibility issue of scapy versions.
+        if hasattr(bgp, 'BGPNLRI_IPv4'):
+            _route = bgp.BGPNLRI_IPv4(prefix=str(subnet))
+        else:
+            _route = (subnet.prefixlen, str(subnet.network_address))
         bgp_fields = packet[bgp.BGPUpdate].fields
         if action == "announce":
-            return bgp_fields["tp_len"] > 0 and _route in bgp_fields["nlri"]
+            # New scapy (version 2.4.5) uses a different way to represent and dissect BGP messages. Below logic is to
+            # address the compatibility issue of scapy versions.
+            path_attr_valid = False
+            if "tp_len" in bgp_fields:
+                path_attr_valid = bgp_fields['tp_len'] > 0
+            elif "path_attr_len" in bgp_fields:
+                path_attr_valid = bgp_fields["path_attr_len"] > 0
+            return path_attr_valid and _route in bgp_fields["nlri"]
         elif action == "withdraw":
-            return bgp_fields["withdrawn_len"] > 0 and _route in bgp_fields["withdrawn"]
+            # New scapy (version 2.4.5) uses a different way to represent and dissect BGP messages. Below logic is to
+            # address the compatibility issue of scapy versions.
+            withdrawn_len_valid = False
+            if "withdrawn_len" in bgp_fields:
+                withdrawn_len_valid = bgp_fields["withdrawn_len"] > 0
+            elif "withdrawn_routes_len" in bgp_fields:
+                withdrawn_len_valid = bgp_fields["withdrawn_routes_len"] > 0
+
+            # New scapy (version 2.4.5) uses a different way to represent and dissect BGP messages. Below logic is to
+            # address the compatibility issue of scapy versions.
+            withdrawn_route_valid = False
+            if "withdrawn" in bgp_fields:
+                withdrawn_route_valid = _route in bgp_fields["withdrawn"]
+            elif "withdrawn_routes" in bgp_fields:
+                withdrawn_route_valid = _route in bgp_fields["withdrawn_routes"]
+
+            return withdrawn_len_valid and withdrawn_route_valid
         else:
             return False