[Tutor] Python ICMP

[chris hallman]

I need to create a class that sends ICMP packets from either a Windows or
Linux host. I found a few, but I like this one the best:


#!/usr/bin/env python


"""
    A pure python ping implementation using raw socket.



    Note that ICMP messages can only be sent from processes running as root.


    Derived from ping.c distributed in Linux's netkit. That code is
    copyright (c) 1989 by The Regents of the University of California.


    That code is in turn derived from code written by Mike Muuss of the
    US Army Ballistic Research Laboratory in December, 1983 and
    placed in the public domain. They have my thanks.

    Bugs are naturally mine. I'd be glad to hear about them. There are


    certainly word - size dependenceies here.

    Copyright (c) Matthew Dixon Cowles, <http://www.visi.com/~mdc/
<http://www.visi.com/%7Emdc/>>.
    Distributable under the terms of the GNU General Public License


    version 2. Provided with no warranties of any sort.

    Original Version from Matthew Dixon Cowles:
      -> ftp://ftp.visi.com/users/mdc/ping.py



    Rewrite by Jens Diemer:
      -> http://www.python-forum.de/post-69122.html#69122


    Revision history
    ~~~~~~~~~~~~~~~~



    May 30, 2007
    little rewrite by Jens Diemer:
     -  change socket asterisk import to a normal import
     -  replace time.time() with time.clock()
     -  delete "return None" (or change to "return" only)


     -  in checksum() rename "str" to "source_string"

    November 22, 1997
    Initial hack. Doesn't do much, but rather than try to guess
    what features I (or others) will want in the future, I've only


    put in what I need now.

    December 16, 1997
    For some reason, the checksum bytes are in the wrong order when
    this is run under Solaris 2.X for SPARC but it works right under
    Linux x86. Since I don't know just what's wrong, I'll swap the


    bytes always and then do an htons().

    December 4, 2000
    Changed the struct.pack() calls to pack the checksum and ID as
    unsigned. My thanks to Jerome Poincheval for the fix.


    Last commit info:


    ~~~~~~~~~~~~~~~~~
    $LastChangedDate: $
    $Rev: $
    $Author: $
"""


import os, sys, socket, struct, select, time



# From /usr/include/linux/icmp.h; your milage may vary.
ICMP_ECHO_REQUEST = 8 # Seems to be the same on Solaris.




def checksum(source_string):
    """


    I'm not too confident that this is right but testing seems
    to suggest that it gives the same answers as in_cksum in ping.c
    """
    sum = 0


    countTo = (len(source_string)/2)*2


    count = 0
    while count<countTo:
        thisVal = ord(source_string[count + 1])*256 + ord(source_string[count])


        sum = sum + thisVal
        sum = sum & 0xffffffff # Necessary?


        count = count + 2

    if countTo<len(source_string):


        sum = sum + ord(source_string[len(source_string) - 1])


        sum = sum & 0xffffffff # Necessary?



    sum = (sum >> 16)  +  (sum & 0xffff)


    sum = sum + (sum >> 16)


    answer = ~sum
    answer = answer & 0xffff

    # Swap bytes. Bugger me if I know why.


    answer = answer >> 8 | (answer << 8 & 0xff00)



    return answer


def receive_one_ping(my_socket, ID, timeout):


    """
    receive the ping from the socket.
    """
    timeLeft = timeout
    while True:


        startedSelect = time.clock()
        whatReady = select.select([my_socket], [], [], timeLeft)


        howLongInSelect = (time.clock() - startedSelect)


        if whatReady[0] == []: # Timeout


            return

        timeReceived = time.clock()


        recPacket, addr = my_socket.recvfrom(1024)
        icmpHeader = recPacket[20:28]


        type, code, checksum, packetID, sequence = struct.unpack(


            "bbHHh", icmpHeader
        )
        if packetID == ID:


            bytesInDouble = struct.calcsize("d")


            timeSent = struct.unpack("d", recPacket[28:28 + bytesInDouble])[0]


            return timeReceived - timeSent

        timeLeft = timeLeft - howLongInSelect
        if timeLeft <= 0:


            return


def send_one_ping(my_socket, dest_addr, ID):


    """
    Send one ping to the given >dest_addr<.
    """
    dest_addr  =  socket.gethostbyname(dest_addr)



    # Header is type (8), code (8), checksum (16), id (16), sequence (16)
    my_checksum = 0



    # Make a dummy heder with a 0 checksum.
    header = struct.pack("bbHHh", ICMP_ECHO_REQUEST, 0, my_checksum, ID, 1)


    bytesInDouble = struct.calcsize("d")


    data = (192 - bytesInDouble) * "Q"


    data = struct.pack("d", time.clock()) + data



    # Calculate the checksum on the data and the dummy header.
    my_checksum = checksum(header + data)



    # Now that we have the right checksum, we put that in. It's just easier
    # to make up a new header than to stuff it into the dummy.


    header = struct.pack(
        "bbHHh", ICMP_ECHO_REQUEST, 0, socket.htons(my_checksum), ID, 1


    )
    packet = header + data
    my_socket.sendto(packet, (dest_addr, 1)) # Don't know about the 1




def do_one(dest_addr, timeout):
    """


    Returns either the delay (in seconds) or none on timeout.
    """
    icmp = socket.getprotobyname("icmp")


    try:
        my_socket = socket.socket(socket.AF_INET, socket.SOCK_RAW, icmp)


    except socket.error, (errno, msg):


        if errno == 1:
            # Operation not permitted


            msg = msg + (
                " - Note that ICMP messages can only be sent from processes"
                " running as root."


            )
            raise socket.error(msg)


        raise # raise the original error

    my_ID = os.getpid() & 0xFFFF



    send_one_ping(my_socket, dest_addr, my_ID)
    delay = receive_one_ping(my_socket, my_ID, timeout)



    my_socket.close()
    return delay




def verbose_ping(dest_addr, timeout = 2, count = 4):


    """
    Send >count< ping to >dest_addr< with the given >timeout< and display
    the result.
    """
    for i in xrange(count):


        print "ping %s..." % dest_addr,
        try:


            delay  =  do_one(dest_addr, timeout)
        except socket.gaierror, e:


            print "failed. (socket error: '%s')" % e[1]


            break

        if delay  ==  None:


            print "failed. (timeout within %ssec.)" % timeout


        else:
            delay  =  delay * 1000
            print "get ping in %0.4fms" % delay


    print


if __name__ == '__main__':


    verbose_ping("heise.de")
    verbose_ping("google.com")


    verbose_ping("a-test-url-taht-is-not-available.com")


    verbose_ping("192.168.1.1")


However, there is one small problem. It works on Windows, but not on Linux.
When I run this on Linux, the host sends the requests but never gets a
response. Not one. I've compared the output from both hosts in Wireshark and
the only difference I see is the identification field in the IP header.
Packets frmo Linux show 0 but packets from Windows have an incrementing
number.

I'd like to have this working on both. I prefer this code since it's pure
Python, doesn't shell out (popen) and I can call/import it into another
program.

Any ideas?
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