Python中的ICMP Pinger

Question

我正在尝试编写一个使用ICMP协议和python raw套接字的简单pinger。我已经完成了代码，可以正确运行它，但是无论我设置了多长时间，我的请求都会超时。我怀疑校验和功能有问题，因此服务器只会丢弃数据。这是代码：

from socket import *
import os
import sys
import struct
import time
import select
import binascii

ICMP_ECHO_REQUEST = 8

def checksum(string):
    csum = 0
    countTo = (len(string) // 2) * 2
    count = 0

    while count < countTo:
        thisVal = ord(string[count+1]) * 256 + ord(string[count])
        csum = csum + thisVal
        csum = csum & 0xffffffff
        count = count + 2
    if countTo < len(string):
        csum = csum + ord(string[len(string) - 1])
        csum = csum & 0xffffffff
    csum = (csum >> 16) + (csum & 0xffff)
    csum = csum + (csum >> 16)
    answer = ~csum
    answer = answer & 0xffff
    answer = answer >> 8 | (answer << 8 & 0xff00)
    return answer

def receiveOnePing(mySocket, ID, timeout, destAddr):
    timeLeft = timeout
    while 1:
        startedSelect = time.time()
        whatReady = select.select([mySocket], [], [], timeLeft)
        howLongInSelect = (time.time() - startedSelect)
        if whatReady[0] == []: # Timeout
            return "Request timed out."
        timeReceived = time.time()
        recPacket, addr = mySocket.recvfrom(1024)

        type, code, checksum, recID, sequence = struct.unpack("bbHHh", recPacket[20:28])

        if code != 0:
             return 'expected code=0, but got {}'.format(code)
        if type != 0:
            return f'expected type 0 but got {code}'
        if recID != ID:
            return f'expected id={ID} but got {recID}'

        payload = struct.unpack('b', recPacket[28:])
        rtt = timeReceived - payload
        return rtt

        timeLeft = timeLeft - howLongInSelect
        if timeLeft <= 0:
            return "Request timed out."

def sendOnePing(mySocket, destAddr, ID):
     myChecksum = 0  # Make a dummy header with a 0 checksum
     header = struct.pack("bbHHh", ICMP_ECHO_REQUEST, 0, myChecksum, ID, 1)
     data = struct.pack("d", time.time())  # Calculate the checksum on the data and the dummy header.
     myChecksum = checksum(str(header + data))    # Get the right checksum, and put in the header
     if sys.platform == 'darwin':   # Convert 16-bit integers from host to network  byte order
        myChecksum = htons(myChecksum) & 0xffff
     else:
          myChecksum = htons(myChecksum)
     header = struct.pack("bbHHh", ICMP_ECHO_REQUEST, 0, myChecksum, ID, 1)
     packet = header + data
     mySocket.sendto(packet, (destAddr, 1))


def doOnePing(destAddr, timeout):
    icmp = getprotobyname("icmp")  
    mySocket = socket(AF_INET, SOCK_RAW, icmp)
    myID = os.getpid() & 0xFFFF  # Return the current process i
    sendOnePing(mySocket, destAddr, myID)
    delay = receiveOnePing(mySocket, myID, timeout, destAddr)
    mySocket.close()
    return delay


def ping(host, timeout=1):  # timeout=1 means: If one second goes by without a reply from the server,
# the client assumes that either the client's ping or the server's pong is lost
    dest = gethostbyname(host)
    print("Pinging " + dest + " using Python:")
    print("")  # Send ping requests to a server separated by approximately one second
    while 1 :
        delay = doOnePing(dest, timeout)
        print(delay)
        time.sleep(1)# one second  return delay

ping("google.com")