ping multiple Ips with python
Andrew McGregor
andrew at indranet.co.nz
Fri Jan 3 23:24:00 EST 2003
Actually, your checksum isn't right.
Try something more like:
def fixULPChecksum(packet):
# evil assumptions: no IP options, IPv4
pseudopkt = ''.join([packet[:IPheader_len][-8:],
'\x00',
packet[:IPheader_len][-11],
struct.pack('!H', len(packet) - IPheader_len),
packet[IPheader_len:IPheader_len+16],
'\x00\x00',
packet[IPheader_len+18:]]
+ [x for x in ['\x00'] if len(packet) & 1])
csum = reduce(operator.add,
struct.unpack('!%dH' % (len(pseudopkt)>>1),
pseudopkt))
csum = (csum>>16) + (csum&0xffff)
csum += (csum>>16)
csum = (csum&0xffff)^0xffff
return ''.join([packet[:IPheader_len+16],
struct.pack('!H', csum),
packet[IPheader_len+18:]])
(note: this will need some modification, because it actually takes a whole
packet with a broken TCP or UDP checksum, and returns one with it fixed,
but you get the idea.)
This version is pretty fast in comparison, too.
Also, the byte swap at the end is a host-to-network byte order change, and
is not portable as written (unlike mine).
Andrew
Ps: Just for fun, here's the above function in Pyrex :-)
import struct
IP6Header = '!LHBB16s16s'
IP6Header_len = struct.calcsize(IP6Header)
cdef extern from "netinet/in.h":
unsigned int htonl(unsigned int hostlong)
unsigned short htons(unsigned short hostshort)
unsigned int ntohl(unsigned int netlong)
unsigned short ntohs(unsigned short netshort)
cdef extern from "Python.h":
object PyString_FromStringAndSize(char *s, int len)
int PyString_AsStringAndSize(object obj, char **buffer, int *length)
int PyString_Check(object o)
cdef extern from "stdlib.h":
void *calloc(unsigned int nmemb, unsigned int size)
void *malloc(unsigned int size)
void free(void *ptr)
cdef extern from "string.h":
void *memcpy(void *dest, void *src, int n)
def fixULPChecksum(packet):
cdef int plength, csum, i
cdef char *packetbuf
plength = len(packet)
packetbuf = packet
# evil assumptions: no IP options, IPv4
csum = 0
for i from 0 <= i < 4:
csum = csum + ntohs((<unsigned short *> (packetbuf + 12))[i])
csum = csum + packetbuf[9] + (plength - 20)
i=0
for i from 0 <= i < 8:
csum = csum + ntohs((<unsigned short *> (packetbuf + 20))[i])
i=0
for i from 10 <= i < ((plength - 20) >> 1):
csum = csum + ntohs((<unsigned short *> (packetbuf + 20))[i])
csum = (csum>>16) + (csum&0xffff)
csum = csum + (csum>>16)
csum = (csum&0xffff)^0xffff
r = PyString_FromStringAndSize(packetbuf, plength)
# move packetbuf to pointing into the new string's buffer
packetbuf = r
((<unsigned short *> (packetbuf + 20))[8]) = htons(<unsigned short>
csum)
return r
--On Saturday, January 04, 2003 03:07:38 +0000 darrell
<dgallion1 at yahoo.com> wrote:
> Multiple ping sounded like fun.
> So here's a quick mod to some ping code I found.
>
> --Darrell Gallion
>
>
># !/usr/bin/env python
>
># 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.
>#
># Jan 3, 2003
># Added Pinger class to handle multiple ping dest
># Darrell Gallion
>#
>
> import os
> from socket import *
> import struct
> import select
> import time
> import sys
>
># From /usr/include/linux/icmp.h; your milage may vary.
> ICMP_ECHO_REQUEST=8 # Seems to be the same on Solaris.
> myID=os.getpid() & 0xFFFF
>
># 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):
> sum=0
> countTo=(len(str)/2)*2
> count=0
> while count<countTo:
> thisVal=ord(str[count+1])*256+ord(str[count])
> sum=sum+thisVal
> sum=sum & 0xffffffff # Necessary?
> count=count+2
>
> if countTo<len(str):
> sum=sum+ord(str[len(str)-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
>
>
> class Pinger:
> def __init__(self, *dest):
> self.results={}
> icmp=getprotobyname("icmp")
> self.soc=socket(AF_INET,SOCK_RAW,icmp)
>
> def receivePings(self,timeout):
> timeLeft=timeout
> while 1:
> startedSelect=time.time()
> whatReady=select.select([self.soc],[],[],timeLeft)
> howLongInSelect=(time.time()-startedSelect)
> if whatReady[0]==[]: # Timeout
> return
> timeReceived=time.time()
> recPacket,addr= self.soc.recvfrom(1024)
> icmpHeader=recPacket[20:28]
>
> type,code,checksum,packetID,sequence=struct.unpack("bbHHh",icmpHeader)
> if self.destDict.has_key(packetID):
> bytesInDouble=struct.calcsize("d")
>
> timeSent=struct.unpack("d",recPacket[28:28+bytesInDouble])[0]
> dT = timeReceived-timeSent
> self.results[self.destDict[packetID]]=dT
># print self.destDict[packetID], dT
> del self.destDict[packetID]
> if len(self.destDict)==0:
> return
>
> timeLeft=timeLeft-howLongInSelect
> if timeLeft<=0:
> return
>
> def sendPings(self):
> for ID, dest in self.destDict.items():
> # 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.
>
> header=struct.pack("bbHHh",ICMP_ECHO_REQUEST,0,htons(myChecksum), ID,1)
> packet=header+data
> self.soc.sendto(packet,(dest,1)) # Don't know about the 1
>
> def ping(self, destAddr,timeout=10):
> # Returns either the delay (in seconds) or none on timeout.
> dest=[]
> for n in destAddr:
> dest.append(gethostbyname(n))
> self.destDict={}
> cnt=3 # Started at 3 for no good reason
> for d in destAddr:
> self.destDict[cnt]=d
> cnt+=1
>
> self.sendPings()
> self.receivePings(timeout)
> self.soc.close()
> return self
>
> def main():
> if len(sys.argv)<2:
> print "Usage: %s hostname" % os.path.basename(sys.argv[0])
> sys.exit(1)
>
> print Pinger().ping(sys.argv[1:]).results
> return None
>
> if __name__=='__main__':
> main()
> sys.exit(0)
>
> --
> http://mail.python.org/mailman/listinfo/python-list
>
>
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