Update to enable offline sniff() to use a PacketList (#3026)

Author: piersoh

scapy/sendrecv.py

@@ -887,7 +887,7 @@ def _write_to_pcap(packets_list):
 
                 if isinstance(offline, Packet):
                     tempfile_written, offline = _write_to_pcap([offline])
-                elif isinstance(offline, list) and \
+                elif isinstance(offline, (list, PacketList)) and \
                         all(isinstance(elt, Packet) for elt in offline):
                     tempfile_written, offline = _write_to_pcap(offline)
 

test/regression.uts

@@ -1864,6 +1864,11 @@ fdesc = os.fdopen(fdesc, "wb")
 wrpcap(fdesc, pktpcap)
 fdesc.close()
 
+= Check offline sniff() (by PacketList)
+l=sniff(offline=PacketList([IP()/TCP(),IP()/TCP()]))
+assert len(l) == 2
+assert(all(TCP in p for p in l))
+
 = Check offline sniff() (by filename)
 assert list(pktpcap) == list(sniff(offline=filename))