Python实现ping命令

#!/usr/bin/env python
# -*- coding: iso-8859-1 -*-
"""ping.py
 
 ping.py uses the ICMP protocol's mandatory ECHO_REQUEST
 datagram to elicit an ICMP ECHO_RESPONSE from a
 host or gateway.
 Copyright (C) 2004 - Lars Strand <lars strand at gnist org>;
 
 This program is free software; you can redistribute it and/or
 modify it under the terms of the GNU General Public License
 as published by the Free Software Foundation; either version 2
 of the License, or (at your option) any later version.
 
 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.
 
 You should have received a copy of the GNU General Public License
 along with this program; if not, write to the Free Software
 Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 Must be running as root, or write a suid-wrapper. Since newer *nix
 variants, the kernel ignores the set[ug]id flags on #! scripts for
 security reasons
 RFC792, echo/reply message:
  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |     Type      |     Code      |          Checksum             |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |           Identifier          |        Sequence Number        |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |     Data ...
 +-+-+-+-+-

TODO:
 - do not create socket inside 'while' (but if not: ipv6 won't work)
 - add support for broadcast/multicast
 - add support for own payload string
CHANGELOG:
 DONE -->; bugfix from Filip Van Raemdonck mechanix debian org
 DONE -->; add more support for modules (raise instead of sys.exit)
 DONE -->; locale func names
 DONE -->; package def
 DONE -->; some code cleanup
 
"""
import sys
import os
import struct
import array
import time
import select
import binascii
import math
import getopt
import string
import socket
# total size of data (payload)
ICMP_DATA_STR = 56  
# initial values of header variables
ICMP_TYPE = 8
ICMP_TYPE_IP6 = 128
ICMP_CODE = 0
ICMP_CHECKSUM = 0
ICMP_ID = 0
ICMP_SEQ_NR = 0
# Package definitions.
__program__   = 'ping'
__version__   = '0.5a'
__date__      = '2004/15/12'
__author__    = 'Lars Strand <lars at unik no>;'
__licence__   = 'GPL'
__copyright__ = 'Copyright (C) 2004 Lars Strand'
def _construct(id, size, ipv6):
    """Constructs a ICMP echo packet of variable size
    """
    # size must be big enough to contain time sent
    if size < int(struct.calcsize("d")):
        _error("packetsize to small, must be at least %d" % int(struct.calcsize("d")))
    
    # construct header
    if ipv6:
        header = struct.pack('BbHHh', ICMP_TYPE_IP6, ICMP_CODE, ICMP_CHECKSUM, \
                             ICMP_ID, ICMP_SEQ_NR+id)
    else:
        header = struct.pack('bbHHh', ICMP_TYPE, ICMP_CODE, ICMP_CHECKSUM, \
                             ICMP_ID, ICMP_SEQ_NR+id)
    # if size big enough, embed this payload
    load = "-- IF YOU ARE READING THIS YOU ARE A NERD! --"
    
    # space for time
    size -= struct.calcsize("d")
    # construct payload based on size, may be omitted :)
    rest = ""
    if size > len(load):
        rest = load
        size -= len(load)
    # pad the rest of payload
    rest += size * "X"
    # pack
    data = struct.pack("d", time.time()) + rest
    packet = header + data          # ping packet without checksum
    checksum = _in_cksum(packet)    # make checksum
    # construct header with correct checksum
    if ipv6:
        header = struct.pack('BbHHh', ICMP_TYPE_IP6, ICMP_CODE, checksum, \
                             ICMP_ID, ICMP_SEQ_NR+id)
    else:
        header = struct.pack('bbHHh', ICMP_TYPE, ICMP_CODE, checksum, ICMP_ID, \
                             ICMP_SEQ_NR+id)
    # ping packet *with* checksum
    packet = header + data 
    # a perfectly formatted ICMP echo packet
    return packet
def _in_cksum(packet):
    """THE RFC792 states: 'The 16 bit one's complement of
    the one's complement sum of all 16 bit words in the header.'
    Generates a checksum of a (ICMP) packet. Based on in_chksum found
    in ping.c on FreeBSD.
    """
    # add byte if not dividable by 2
    if len(packet) & 1:              
        packet = packet + '\0'
    # split into 16-bit word and insert into a binary array
    words = array.array('h', packet) 
    sum = 0
    # perform ones complement arithmetic on 16-bit words
    for word in words:
        sum += (word & 0xffff) 
    hi = sum >> 16 
    lo = sum & 0xffff 
    sum = hi + lo
    sum = sum + (sum >> 16)
    
    return (~sum) & 0xffff # return ones complement
def pingNode(alive=0, timeout=1.0, ipv6=0, number=sys.maxint, node=None, \
             flood=0, size=ICMP_DATA_STR):
    """Pings a node based on input given to the function.
    """
    # if no node, exit
    if not node:
        _error("")
    # if not a valid host, exit
    if ipv6:
        if socket.has_ipv6:
            try:
                info, port = socket.getaddrinfo(node, None)
                host = info[4][0]
                # do not print ipv6 twice if ipv6 address given as node
                if host == node: 
                    noPrintIPv6adr = 1
            except:
                _error("cannot resolve %s: Unknow host" % node)
        else:
            _error("No support for IPv6 on this plattform")
    else:    # IPv4
        try:
            host = socket.gethostbyname(node)
        except:
            _error("cannot resolve %s: Unknow host" % node)
    # trying to ping a network?
    if not ipv6:
        if int(string.split(host, ".")[-1]) == 0:
            _error("no support for network ping")
    # do some sanity check
    if number == 0:
        _error("invalid count of packets to transmit: '%s'" % str(a))
    if alive:
        number = 1
    # Send the ping(s)
    start = 1; mint = 999; maxt = 0.0; avg = 0.0
    lost = 0; tsum = 0.0; tsumsq = 0.0
    # tell the user what we do
    if not alive:
        if ipv6:
            # do not print the ipv6 twice if ip adress given as node
            # (it can be to long in term window)
            if noPrintIPv6adr == 1:
                # add 40 (header) + 8 (icmp header) + payload
                print "PING %s : %d data bytes (40+8+%d)" % (str(node), \
                                                             40+8+size, size)
            else:
                # add 40 (header) + 8 (icmp header) + payload
                print "PING %s (%s): %d data bytes (40+8+%d)" % (str(node), \
                                                                 str(host), 40+8+size, size)
        else:
            # add 20 (header) + 8 (icmp header) + payload
            print "PING %s (%s): %d data bytes (20+8+%d)" % (str(node), str(host), \
                                                             20+8+size, size)
        
    # trap ctrl-d and ctrl-c
    try:
        
        # send the number of ping packets as given
        while start <= number:
            lost += 1 # in case user hit ctrl-c
            
            # create the IPv6/IPv4 socket
            if ipv6:
                # can not create a raw socket if not root or setuid to root
                try:
                    pingSocket = socket.socket(socket.AF_INET6, socket.SOCK_RAW, \
                                               socket.getprotobyname("ipv6-icmp"))
                except socket.error, e:
                    print "socket error: %s" % e
                    _error("You must be root (uses raw sockets)" % os.path.basename(sys.argv[0]))
                    
            # IPv4
            else:
                # can not create a raw socket if not root or setuid to root
                try:
                    pingSocket = socket.socket(socket.AF_INET, socket.SOCK_RAW, \
                                               socket.getprotobyname("icmp"))
                except socket.error, e:
                    print "socket error: %s" % e
                    _error("You must be root (%s uses raw sockets)" % os.path.basename(sys.argv[0]))
                
            packet = _construct(start, size, ipv6) # make a ping packet
            # send the ping
            try:
                pingSocket.sendto(packet,(node,1))
            except socket.error, e:
                _error("socket error: %s" % e)
            # reset values
            pong = ""; iwtd = []
            # wait until there is data in the socket
            while 1:
                # input, output, exceptional conditions
                iwtd, owtd, ewtd = select.select([pingSocket], [], [], timeout)
                break # no data and timout occurred 
            # data on socket - this means we have an answer
            if iwtd:  # ok, data on socket
                endtime = time.time()  # time packet received
                # read data (we only need the header)
                pong, address = pingSocket.recvfrom(size+48)
                lost -= 1 # in case user hit ctrl-c
                # examine packet
                # fetch TTL from IP header
                if ipv6:
                    # since IPv6 header and any extension header are never passed
                    # to a raw socket, we can *not* get hoplimit field..
                    # I hoped that a socket option would help, but it's not
                    # supported:
                    #   pingSocket.setsockopt(IPPROTO_IPV6, IPV6_RECVHOPLIMIT, 1)
                    # so we can't fetch hoplimit..
                    # fetch hoplimit
                    #rawPongHop = struct.unpack("c", pong[7])[0]
                    # fetch pong header
                    pongHeader = pong[0:8]
                    pongType, pongCode, pongChksum, pongID, pongSeqnr = \
                              struct.unpack("bbHHh", pongHeader)
                    # fetch starttime from pong
                    starttime = struct.unpack("d", pong[8:16])[0]
                # IPv4
                else:
                    # time to live
                    rawPongHop = struct.unpack("s", pong[8])[0]
                    # convert TTL from 8 bit to 16 bit integer
                    pongHop = int(binascii.hexlify(str(rawPongHop)), 16)
                    # fetch pong header
                    pongHeader = pong[20:28]
                    pongType, pongCode, pongChksum, pongID, pongSeqnr = \
                              struct.unpack("bbHHh", pongHeader)
                    # fetch starttime from pong
                    starttime = struct.unpack("d", pong[28:36])[0]
                # valid ping packet received?
                if not pongSeqnr == start:
                    pong = None
            # NO data on socket - timeout waiting for answer
            if not pong:
                if alive:
                    print "no reply from %s (%s)" % (str(node), str(host))
                else:
                    print "ping timeout: %s (icmp_seq=%d) " % (host, start)
                # do not wait if just sending one packet
                if number != 1 and start < number:
                    time.sleep(flood ^ 1)
                start += 1
                continue  # lost a packet - try again
            triptime  = endtime - starttime # compute RRT
            tsum     += triptime            # triptime for all packets (stddev)
            tsumsq   += triptime * triptime # triptime^2  for all packets (stddev)
            # compute statistic
            maxt = max ((triptime, maxt))
            mint = min ((triptime, mint))
            if alive:
                print str(node) + " (" + str(host) +") is alive"
            else:
                if ipv6:
                    # size + 8 = payload + header
                    print "%d bytes from %s: icmp_seq=%d time=%.5f ms" % \
                          (size+8, host, pongSeqnr, triptime*1000)
                else:
                    print "%d bytes from %s: icmp_seq=%d ttl=%s time=%.5f ms" % \
                          (size+8, host, pongSeqnr, pongHop, triptime*1000)
            # do not wait if just sending one packet
            if number != 1 and start < number:
                # if flood = 1; do not sleep - just ping                
                time.sleep(flood ^ 1) # wait before send new packet
            # the last thing to do is update the counter - else the value
            # (can) get wrong when computing summary at the end (if user
            # hit ctrl-c when pinging)
            start += 1
            # end ping send/recv while
    # if user ctrl-d or ctrl-c
    except (EOFError, KeyboardInterrupt):
        # if user disrupts ping, it is most likly done before
        # the counter get updates - if do not update it here, the
        # summary get all wrong.
        start += 1
        pass
    # compute and print som stats
    # stddev computation based on ping.c from FreeBSD
    if start != 0 or lost > 0:  # do not print stats if 0 packet sent
        start -= 1              # since while is '<='
        avg = tsum / start      # avg round trip
        vari = tsumsq / start - avg * avg 
        # %-packet lost
        if start == lost:
            plost = 100
        else:
            plost = (lost/start)*100
        if not alive:
            print "\n--- %s ping statistics ---" % node
            print "%d packets transmitted, %d packets received, %d%% packet loss" % \
                  (start, start-lost, plost)
            # don't display summary if 100% packet-loss
            if plost != 100:
                print "round-trip min/avg/max/stddev = %.3f/%.3f/%.3f/%.3f ms" % \
                      (mint*1000, (tsum/start)*1000, maxt*1000, math.sqrt(vari)*1000)
    pingSocket.close()
    
def _error(err):
    """Exit if running standalone, else raise an exception
    """
    if __name__ == '__main__':
        print "%s: %s" % (os.path.basename(sys.argv[0]), str(err))
        print "Try `%s --help' for more information." % os.path.basename(sys.argv[0])
        sys.exit(1)
    else:
        raise Exception, str(err)
    
def _usage():
    """Print usage if run as a standalone program
    """
    print """usage: %s [OPTIONS] HOST
Send ICMP ECHO_REQUEST packets to network hosts.
Mandatory arguments to long options are mandatory for short options too.
  -c, --count=N    Stop after sending (and receiving) 'N' ECHO_RESPONSE
                   packets.
  -s, --size=S     Specify the number of data bytes to be sent. The default
                   is 56, which translates into 64 ICMP data bytes when
                   combined with the 8 bytes of ICMP header data.
  -f, --flood      Flood ping. Outputs packets as fast as they come back. Use
                   with caution!
  -6, --ipv6       Ping using IPv6.
  -t, --timeout=s  Specify a timeout, in seconds, before a ping packet is
                   considered 'lost'.
  -h, --help       Display this help and exit
Report bugs to lars [at] gnist org""" % os.path.basename(sys.argv[0])

if __name__ == '__main__':
    """Main loop
    """
    # version control
    version = string.split(string.split(sys.version)[0][:3], ".")
    if map(int, version) < [2, 3]:
        _error("You need Python ver 2.3 or higher to run!")
    try:
        # opts = arguments recognized,
        # args = arguments NOT recognized (leftovers)
        opts, args = getopt.getopt(sys.argv[1:-1], "hat:6c:fs:", \
                                   ["help", "alive", "timeout=", "ipv6", \
                                    "count=", "flood", "packetsize="])
    except getopt.GetoptError:
        # print help information and exit:
        _error("illegal option(s) -- " + str(sys.argv[1:]))
    # test whether any host given
    if len(sys.argv) >= 2:
        node = sys.argv[-1:][0]   # host to be pinged
        if node[0] == '-' or node == '-h' or node == '--help' :  
            _usage()
    else:
        _error("No arguments given")
    if args:
        _error("illegal option -- %s" % str(args))
        
    # default variables
    alive = 0; timeout = 1.0; ipv6 = 0; count = sys.maxint;
    flood = 0; size = ICMP_DATA_STR
    # run through arguments and set variables
    for o, a in opts:
        if o == "-h" or o == "--help":    # display help and exit
            _usage()
            sys.exit(0)
        if o == "-t" or o == "--timeout": # timeout before "lost"
            try:
                timeout = float(a)
            except:
                _error("invalid timout: '%s'" % str(a))
        if o == "-6" or o == "--ipv6":    # ping ipv6
            ipv6 = 1
        if o == "-c" or o == "--count":   # how many pings?
            try:
                count = int(a)
            except:
                _error("invalid count of packets to transmit: '%s'" % str(a))
        if o == "-f" or o == "--flood":   # no delay between ping send
            flood = 1
        if o == "-s" or o == "--packetsize":  # set the ping payload size
            try:
                size = int(a)
            except:
                _error("invalid packet size: '%s'" % str(a))
        # just send one packet and say "it's alive"
        if o == "-a" or o == "--alive":   
            alive = 1
    # here we send
    pingNode(alive=alive, timeout=timeout, ipv6=ipv6, number=count, \
             node=node, flood=flood, size=size)
    # if we made it this far, do a clean exit
    sys.exit(0)
### end