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Sending ECHO_REQUEST (pinging) with python

Hi, I've writing a python application in which I'd like to have a small
"ping label", to always tell the current ping time to the server.

It seems however that I have to be root to send those imcp packages, but
I guess there must be a workaround since I can easily use the "ping"
command as ordinary user.

Do anybody know how to do this in python?
Mar 26 '07 #1
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8 Replies
On Mar 26, 2007, at 1:30 AM, Thomas Dybdahl Ahle wrote:
Hi, I've writing a python application in which I'd like to have a
small
"ping label", to always tell the current ping time to the server.

It seems however that I have to be root to send those imcp
packages, but
I guess there must be a workaround since I can easily use the "ping"
command as ordinary user.

Do anybody know how to do this in python?
This won't solve your privileges issue, but this seems to get the
ping time to server:

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

# 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/>.
# Distributable under the terms of the GNU General Public License
# version 2. Provided with no warranties of any sort.

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

# Revision history:
#
# 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.
#

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

# 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
def checksum(str):
csum = 0
countTo = (len(str) / 2) * 2
count = 0
while count < countTo:
thisVal = ord(str[count+1]) * 256 + ord(str[count])
csum = csum + thisVal
csum = csum & 0xffffffffL # Necessary?
count = count + 2

if countTo < len(str):
csum = csum + ord(str[len(str) - 1])
csum = csum & 0xffffffffL # Necessary?

csum = (csum >16) + (csum & 0xffff)
csum = csum + (csum >16)
answer = ~csum
answer = answer & 0xffff

# Swap bytes. Bugger me if I know why.
answer = answer >8 | (answer << 8 & 0xff00)

return answer

def receiveOnePing(mySocket, ID, timeout):
timeLeft = timeout

while 1:
startedSelect = time.time()
whatReady = select.select([mySocket], [], [], timeLeft)
howLongInSelect = (time.time() - startedSelect)

if whatReady[0] == []: # Timeout
return -1

timeReceived = time.time()
recPacket, addr = mySocket.recvfrom(1024)
icmpHeader = recPacket[20:28]
typ, 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 -1

def sendOnePing(mySocket, destAddr, ID):
# Header is type (8), code (8), checksum (16), id (16), sequence
(16)
myChecksum = 0

# Make a dummy heder with a 0 checksum.
header = struct.pack("bbHHh", ICMP_ECHO_REQUEST, 0, myChecksum,
ID, 1)
bytesInDouble = struct.calcsize("d")
data = (192 - bytesInDouble) * "Q"
data = struct.pack("d", time.time()) + data

# Calculate the checksum on the data and the dummy header.
myChecksum = 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.
if sys.platform == 'darwin':
myChecksum = socket.htons(myChecksum) & 0xffff
else:
myChecksum = socket.htons(myChecksum)

header = struct.pack("bbHHh", ICMP_ECHO_REQUEST, 0,
myChecksum, ID, 1)

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

def doOne(destAddr, timeout=10):
# Returns either the delay (in seconds) or none on timeout.
icmp = socket.getprotobyname("icmp")
mySocket = socket.socket(socket.AF_INET,socket.SOCK_RAW,icmp)
myID = os.getpid() & 0xFFFF
sendOnePing(mySocket, destAddr, myID)
delay = receiveOnePing(mySocket, myID, timeout)
mySocket.close()

return delay
def ping(host, timeout=1):
dest = socket.gethostbyname(host)
delay = doOne(dest, timeout)
return delay
Hope this helps,
Michael

---
The Rules of Optimization are simple.
Rule 1: Don't do it.
Rule 2 (for experts only): Don't do it yet.
-- Michael A. Jackson , "Principles of
Program Design", 1975.
Mar 26 '07 #2

On Mar 26, 2007, at 1:30 AM, Thomas Dybdahl Ahle wrote:
>
It seems however that I have to be root to send those imcp
packages, but
I guess there must be a workaround since I can easily use the "ping"
command as ordinary user.
The workaround your ping command is using btw, is probably running
suid root.

hth,
Michael

---
Simplicity is the ultimate sophistication.
-Leonardo da Vinci

Mar 26 '07 #3
On Mon, Mar 26, 2007 at 08:30:16AM +0200, Thomas Dybdahl Ahle wrote:
Hi, I've writing a python application in which I'd like to have a small
"ping label", to always tell the current ping time to the server.

It seems however that I have to be root to send those imcp packages, but
I guess there must be a workaround since I can easily use the "ping"
command as ordinary user.

Do anybody know how to do this in python?
You need root for that and the ping command is allowed to have them by
suid bit. You can execute ping from inside python and use ping as is, if
you need.

--
This is a terroristic email. It will explode in 10 minutes,
if you do not close it in the meantime.

Michal "vorner" Vaner

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Version: GnuPG v2.0.3 (GNU/Linux)

iD8DBQBGB5FS7/oWwynB3bIRAoqwAJ43yY0CqUfwivEGQHItkpVLPvpYygCfUZ6W
haX6LC/gBtEUnS7Hc3CGUNk=
=jRXs
-----END PGP SIGNATURE-----

Mar 26 '07 #4
Michael Bentley <mi*****@jedimindworks.comwrote:
On Mar 26, 2007, at 1:30 AM, Thomas Dybdahl Ahle wrote:
It seems however that I have to be root to send those imcp
packages, but I guess there must be a workaround since I can
easily use the "ping" command as ordinary user.

The workaround your ping command is using btw, is probably running
suid root.
Under linux the only priviledge you need is CAP_NET_RAW. It is
possible to give this to a process - a bit of searching with google
will show you how!

--
Nick Craig-Wood <ni**@craig-wood.com-- http://www.craig-wood.com/nick
Mar 26 '07 #5
Den Mon, 26 Mar 2007 11:24:34 +0200 skrev Michal 'vorner' Vaner:
On Mon, Mar 26, 2007 at 08:30:16AM +0200, Thomas Dybdahl Ahle wrote:
>Do anybody know how to do this in python?
You need root for that and the ping command is allowed to have them by
suid bit. You can execute ping from inside python and use ping as is, if
you need.
Yeah, I could execute ping, but it would lock me harder to the platform.
Mar 26 '07 #6
Den Mon, 26 Mar 2007 06:30:04 -0500 skrev Nick Craig-Wood:
Michael Bentley <mi*****@jedimindworks.comwrote:
> On Mar 26, 2007, at 1:30 AM, Thomas Dybdahl Ahle wrote:
It seems however that I have to be root to send those imcp packages,
but I guess there must be a workaround since I can easily use the
"ping" command as ordinary user.

The workaround your ping command is using btw, is probably running
suid root.

Under linux the only priviledge you need is CAP_NET_RAW. It is possible
to give this to a process - a bit of searching with google will show you
how!
How, I did google, but I wasn't able to find any way to do this in
python..
Mar 26 '07 #7
Jean-Paul Calderone <ex*****@divmod.comwrote:
On Mon, 26 Mar 2007 16:50:33 +0200, Thomas Dybdahl Ahle <lo****@gmail.comwrote:
Den Mon, 26 Mar 2007 06:30:04 -0500 skrev Nick Craig-Wood:
Under linux the only priviledge you need is CAP_NET_RAW. It is possible
to give this to a process - a bit of searching with google will show you
how!
How, I did google, but I wasn't able to find any way to do this in
python..

You need a sendmsg wrapper (there are several, none in the stdlib), then
you need a privileged process which is willing to give you the privilege.

It's pretty inconvenient.
You start a user process with an extra capability using want using
libcap and the execcap and sucap tools.

--
Nick Craig-Wood <ni**@craig-wood.com-- http://www.craig-wood.com/nick
Mar 27 '07 #8
On Mon, 26 Mar 2007 16:50:09 +0200, Thomas Dybdahl Ahle <lo****@gmail.comwrote:
Den Mon, 26 Mar 2007 11:24:34 +0200 skrev Michal 'vorner' Vaner:
>On Mon, Mar 26, 2007 at 08:30:16AM +0200, Thomas Dybdahl Ahle wrote:
>>Do anybody know how to do this in python?
>You need root for that and the ping command is allowed to have them by
suid bit. You can execute ping from inside python and use ping as is, if
you need.

Yeah, I could execute ping, but it would lock me harder to the platform.
True; Linux ping and Solaris ping have incompatible flags and output.
I even believe several implementations are in use on Linux. Then add
Windows to the mix ...

-Jorgen

--
// Jorgen Grahn <grahn@ Ph'nglui mglw'nafh Cthulhu
\X/ snipabacken.dyndns.org R'lyeh wgah'nagl fhtagn!
Mar 27 '07 #9

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