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Newsgroups: comp.lang.python
Date: Tue, 21 Aug 2012 10:00:28 -0700 (PDT)
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Subject: Re: How to set the socket type and the protocol of a socket using create_connection?
From: Guillaume Comte <guillaume.comte10@gmail.com>
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Unfortunatly, my_socket.bind((src_addr, 1)) doesn't work. I get the error message: "socket.error: [Errno 49] Can't assign requested address"...

I've tried to change the protocol to IPPROTO_RAW. Here is a simple example of the code:



import socket
import os
import struct
import time
import select

ICMP_ECHO_REQUEST = 8
PACKET_SIZE = 64 # Bytes
TIMEOUT = 0.5 # Seconds

def do_one(src_addr, dest_addr):
    my_socket = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_RAW)

    if src_addr != None:
        src_addr = socket.gethostbyname(src_addr)
        my_socket.bind((src_addr, 1))

    my_id = os.getpid() & 0xFFFF

    print "id: " + str(my_id)

    print "sending..."
    send_one(dest_addr, my_socket, my_id)

    print "receiving..."
    id = receive_one(my_socket)
    if id == None:
        print "nothing received !"
    else:
        print "received id: " + str(id)

    my_socket.close()

def checksum(source_string):
    ...

def send_one(addr, my_socket, id):
    # Header: type (8), code (8), checksum (16), id (16), sequence number (16)
    cs = 0
    header = struct.pack("bbHHh", ICMP_ECHO_REQUEST, 0, cs, socket.htons(id), 0)
    data = PACKET_SIZE * "G"

    cs = checksum(header + data)

    header = struct.pack("bbHHh", ICMP_ECHO_REQUEST, 0, socket.htons(cs), socket.htons(id), 0)
    packet = header + data

    my_socket.sendto(packet, (socket.gethostbyname(addr), 1))

def receive_one(my_socket):
    while True:
        what_ready = select.select([my_socket], [], [], TIMEOUT)
        if what_ready[0] == []:
            return None

        received_packet = my_socket.recvfrom(1024)[0]
        header = received_packet[20:28]
        id = struct.unpack("bbHHh", header)[3]
        return socket.ntohs(id)

if __name__ == "__main__":

    import sys
    dst = sys.argv[1]
    print "dst: " + dst
    try:
        src = sys.argv[2]
        print "src: " + src
    except IndexError:
        src = None
    do_one(src, dst)


But when I try to set a source address, I still get the same error message...

Does anyone know how I could build the IP header (I don't even know if it can be the solution but it's worth a try...)?