Sending a payload with scapy

Question

from scapy.all import *

ip = IP(dst = "192.168.1.1")

tcp = TCP (dport = 80, flags = "S")


raw = Raw(b"Olaa")

pkt = ip/tcp/raw

sr(pkt)

ans,unans = sr(pkt)

I’m learning to use Python Scapy. I couldn’t figure out what raw is. Why to send a payload I need to do raw = Raw(b"Olaa") ? I also didn’t understand why to pass a tuple on ans,unans = sr(pkt) Could someone please clarify?

Answer 1

Raw is a file class packet.py of Scapy. You can see the source code here.

class Raw(Packet):
     name = "Raw"
     fields_desc = [ StrField("load", "") ]
     def answers(self, other):
         return 1
         #s = str(other)
         #t = self.load
         #l = min(len(s), len(t))
         #return  s[:l] == t[:l]
     def mysummary(self):
         cs = conf.raw_summary
         if cs:
             if callable(cs):
                 return "Raw %s" % cs(self.load)
             else:
                 return "Raw %r" % self.load
         return Packet.mysummary(self)

The letter b or B prior to string in Python 2 is ignored:

A prefix b or B is ignored in Python 2; this indicates that literal should become a byte literal in Python 3. The prefix u or b can be followed by a prefix r.

In Python 3, according to documentation:

(In free translation)

Bytes literals are always prefixed with b or B; they produce an instance of the bytes instead of the kind str. They can only contain ASCII characters; bytes with a numerical value of 128 or greater must be expressed with escapes.

You must pass the variables ans and unans because the function sr returns a tuple returning unanswered packages and responses and packages.