Fix bugs with _raw_packet_cache_field_value in cache of payloads

Author: gpotter2

scapy/packet.py

@@ -664,10 +664,10 @@ def _raw_packet_cache_field_value(self, fld, val, copy=False):
             # avoid copying whole packets (perf: #GH3894)
             if fld.islist:
                 return [
-                    _cpy(x.fields) for x in val
+                    (_cpy(x.fields), x.payload.raw_packet_cache) for x in val
                 ]
             else:
-                return _cpy(val.fields)
+                return (_cpy(val.fields), val.payload.raw_packet_cache)
         elif fld.islist or fld.ismutable:
             return _cpy(val)
         return None

test/fields.uts

@@ -863,6 +863,53 @@ while p.pl:
 
 assert i == 100
 
+= Test cache handling of payload modification in a PacketListField
+~ field
+
+# GH4414
+class SubPacket(Packet):
+    fields_desc = [
+        ByteField("b", 0),
+    ]
+
+class MyPacket(Packet):
+    fields_desc = [
+        PacketListField("a", [], SubPacket),
+    ]
+
+
+p = MyPacket(b"\x00extrapayload")
+p.a[0] = SubPacket(b=0) / b"test"
+
+assert bytes(p) == b"\x00test"
+
+= Test cache handling of payload modification in a PacketField
+~ field
+
+# also GH4414
+class PayloadPacket(Packet):
+    fields_desc = [
+        StrField("b", ""),
+    ]
+
+class SubPacket(Packet):
+    fields_desc = []
+
+bind_layers(SubPacket, PayloadPacket)
+
+class MyPacket(Packet):
+    fields_desc = [
+        PacketField("a", None, SubPacket),
+    ]
+
+
+s = b'test'
+p = MyPacket(s)
+
+p[PayloadPacket].b = b'new'
+assert p.build() != s
+
+
 ############
 ############
 + Tests on MultiFlagsField