Invalidate stale wirelen after packet edits

scapy/packet.py

@@ -593,9 +593,12 @@ def setfieldval(self, attr, val):
             self.raw_packet_cache = None
             self.raw_packet_cache_fields = None
             self.wirelen = None
+            self.firstlayer().wirelen = None
         elif attr == "payload":
             self.remove_payload()
             self.add_payload(val)
+            self.wirelen = None
+            self.firstlayer().wirelen = None
         else:
             self.payload.setfieldval(attr, val)
 
@@ -617,6 +620,7 @@ def delfieldval(self, attr):
             self.raw_packet_cache = None
             self.raw_packet_cache_fields = None
             self.wirelen = None
+            self.firstlayer().wirelen = None
         elif attr in self.default_fields:
             pass
         elif attr == "payload":
@@ -781,6 +785,8 @@ def clear_cache(self):
         # type: () -> None
         """Clear the raw packet cache for the field and all its subfields"""
         self.raw_packet_cache = None
+        self.wirelen = None
+        self.firstlayer().wirelen = None
         for fname, fval in self.fields.items():
             fld = self.get_field(fname)
             if fld.holds_packets:

test/regression.uts

@@ -2629,6 +2629,18 @@ assert newpktpcapwirelen[0].wirelen is not None
 assert len(newpktpcapwirelen[0]) < newpktpcapwirelen[0].wirelen
 assert newpktpcapwirelen[0].wirelen == pktpcapwirelen[0].wirelen
 
+= Check wrpcap() resets wirelen after a nested length change
+filename1 = get_temp_file(autoext=".pcap")
+filename2 = get_temp_file(autoext=".pcap")
+wrpcap(filename1, [Ether()/Raw(b"a")])
+pkt = rdpcap(filename1)[0]
+assert pkt.wirelen == len(pkt)
+pkt[Raw].load = b"abcdef"
+wrpcap(filename2, [pkt])
+newpkt = rdpcap(filename2)[0]
+assert newpkt[Raw].load == b"abcdef"
+assert newpkt.wirelen == len(newpkt)
+
 = Check wrpcap() then rdpcap() with sent_time on SndRcvList
 f = get_temp_file()
 s = Ether()/IP()