What Is Raw Socket in Socket Programming

Connect function in raw socket?

Yes, IPPROTO_TCP creates TCP socket. To use raw socket, you need to pass SOCK_RAW as second argument to the socket function.

is raw socket datagram socket or not?

That depends on the kind of IP header you will include in your packets (TCP or UDP). Actually it's more easier to include the UDP header since the kernel will manage some TCP mechanism.

So you have to add the UDP header in your packets, then it will be a datagram socket.

How Do I Use Raw Socket in Python?

You do it like this:

First you disable your network card's automatic checksumming:

sudo ethtool -K eth1 tx off

And then send your dodgy frame from python 2 (You'll have to convert to Python 3 yourself):

#!/usr/bin/env python
from socket import socket, AF_PACKET, SOCK_RAW
s = socket(AF_PACKET, SOCK_RAW)
s.bind(("eth1", 0))

# We're putting together an ethernet frame here, 
# but you could have anything you want instead
# Have a look at the 'struct' module for more 
# flexible packing/unpacking of binary data
# and 'binascii' for 32 bit CRC
src_addr = "\x01\x02\x03\x04\x05\x06"
dst_addr = "\x01\x02\x03\x04\x05\x06"
payload = ("["*30)+"PAYLOAD"+("]"*30)
checksum = "\x1a\x2b\x3c\x4d"
ethertype = "\x08\x01"

s.send(dst_addr+src_addr+ethertype+payload+checksum)

Done.

Using raw socket in Python

Reading from a raw socket and parsing out the IP_ID is trivial:

response, addr = s.recvfrom(65535)
response_id = struct.unpack('!H', response[4:6])
print response_id

The hard part is getting someone to send you a packet in the first place. I'm pretty sure you can't use the same socket in raw mode and stream mode at the same time, so you're going to need to replace that connect and send with a bunch of much more complicated code that constructs and sends the appropriate TCP packets to initiate the connection. There are libraries like scapy that will do all that hard stuff for you, but if you want to do it manually, you just need to read RFC 791 and RFC 793 carefully, do all the tedious stuff (making sure you get all the endianness right), and you're on your way.

On *BSD (including OS X), the kernel will fill in the IP length, TCP length, and, best of all, the TCP checksum. It gets much more painful if you have to handle those yourself. (If this doesn't work on your platform, you probably do… either that, or I screwed up something else that OS X fixes for me automagically and your platform doesn't.)

import socket
import struct

def make_ip(proto, srcip, dstip, ident=54321):
    saddr = socket.inet_aton(srcip)
    daddr = socket.inet_aton(dstip)
    ihl_ver = (4 << 4) | 5
    return struct.pack('!BBHHHBBH4s4s' , 
                       ihl_ver, 0, 0, ident, 0, 255, proto, 0, saddr, daddr)

def make_tcp(srcport, dstport, payload, seq=123, ackseq=0,
             fin=False, syn=True, rst=False, psh=False, ack=False, urg=False,
             window=5840):
    offset_res = (5 << 4) | 0
    flags = (fin | (syn << 1) | (rst << 2) | 
             (psh <<3) | (ack << 4) | (urg << 5))
    return struct.pack('!HHLLBBHHH', 
                       srcport, dstport, seq, ackseq, offset_res, 
                       flags, window, 0, 0)

srcip = dstip = '127.0.0.1'
srcport, dstport = 11001, 11000
payload = '[TESTING]\n'

ip = make_ip(socket.IPPROTO_TCP, srcip, dstip)
tcp = make_tcp(srcport, dstport, payload)
packet = ip + tcp + payload

s = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_RAW)
s.sendto(packet, (dstip, 0))
response, addr = s.recvfrom(65535)
response_id = struct.unpack('!H', response[4:6])
print response_id

Each time I run this, I get a nak (if no one's listening on port 11000) or ack packet with a randomized IP_ID, just as you'd expect.

How do I use raw sockets in Perl?

Looks like Net::RawIP was what I was looking for:

use Net::RawIP;
$a = new Net::RawIP;
$a->set({ip => {saddr => 'my.target.lan',daddr => 'my.target.lan'},
         tcp => {source => 139,dest => 139,psh => 1, syn => 1}});
$a->send;

$a->ethnew("eth0");
$a->ethset(source => 'my.target.lan',dest =>'my.target.lan');      
$a->ethsend;

$p = $a->pcapinit("eth0","dst port 21",1500,30);
$f = dump_open($p,"/my/home/log");
loop $p,10,\&dump,$f;