scapy_server: skip uninitialized/unsupported field_desc._offset

Signed-off-by: Anton Kiselev <anton.kisel@gmail.com>

1 files changed, 6 insertions, 3 deletions

diff --git a/scripts/automation/trex_control_plane/stl/services/scapy_server/scapy_service.py b/scripts/automation/trex_control_plane/stl/services/scapy_server/scapy_service.py
index c0a753c7..35bcf1fe 100755
--- a/scripts/automation/trex_control_plane/stl/services/scapy_server/scapy_service.py
+++ b/scripts/automation/trex_control_plane/stl/services/scapy_server/scapy_service.py
@@ -644,8 +644,11 @@ class Scapy_service(Scapy_service_api):
             for field_desc in pkt.fields_desc:
                 field_id = field_desc.name
                 ignored = field_id not in layer_full.fields
-                offset = field_desc._offset
-                protocol_offset = pkt._offset
+                # scapy offset/length calculation doesn't support dynamic size structures
+                # since PktClass.fields_desc is a singletone,
+                # _offset/size can be missing, uninitialized or contain values from the previous runs
+                offset = getattr(field_desc, '_offset', None)
+                protocol_offset = getattr(pkt, '_offset', None)
                 field_sz = field_desc.get_size_bytes()
                 # some values are unavailable in pkt(original model)
                 # at the same time,
@@ -708,7 +711,7 @@ class Scapy_service(Scapy_service_api):
                 fields.append(field_data)
             layer_data = {
                     "id": layer_id,
-                    "offset": pkt._offset,
+                    "offset": protocol_offset,
                     "fields": fields,
                     "real_id": real_layer_id,
                     "valid_structure": valid_struct,