I'm parsing a PCAP file and I need to extract TCP flags (SYN, ACK, PSH, URG, ...).
I'm using the packet['TCP'].flags
value to obtain all the flags at once.
pkts = PcapReader(infile)
for p in pkts:
F = bin(p['TCP'].flags)
print F, bin(F), p.summary()
# manual flags extraction from F
Is there a way to obtain a single TCP flag without manually extract it from packet['TCP'].flags
value?
Normally, the usual way to handle FLAGS is with a bitmap and bitwise operators. If your Packet
class doesn't have specific method to test for flags, the best thing you can do IMHO is to:
FIN = 0x01
SYN = 0x02
RST = 0x04
PSH = 0x08
ACK = 0x10
URG = 0x20
ECE = 0x40
CWR = 0x80
And test them like this:
F = p['TCP'].flags # this should give you an integer
if F & FIN:
# FIN flag activated
if F & SYN:
# SYN flag activated
# rest of the flags here
Sadly, python doesn't have a switch
statement to make this more elegant but it doesn't really matter much.
Hope this helps!