使用Python

Question

我有一个Python项目，我需要将简单的TCP SYN消息发送到IPv6地址并使用原始套接字。我的脚本可以无误地执行，但没有发送syn包。我在我的脚本中不确定IPv6标头，TCP标头或IPv6原始套接字出错了。网络配置为IPv6，因此可以排除网络问题。

这是我的脚本，我在RHEL 5上使用Python 2.4：

import socket, sys
from struct import *

# checksum functions needed for calculation checksum
def checksum(msg):
    s = 0
    # loop taking 2 characters at a time
    for i in range(0, len(msg), 2):
        w = (ord(msg[i]) << 8) + (ord(msg[i+1]) )
        s = s + w

    s = (s>>16) + (s & 0xffff);
    s = ~s & 0xffff

    return s

def init_tcp_syn_packet_v6(source_port,dest_port, source_ip, dest_ip):
    packet = '';
    # ip header fields
    version     = 6                       #4 bit
    traffic_class = 0                     #8 bit
    flow_level  = 1                       #20 bit
    payload_len = 20 #not true lenght, I just selected a random value        #16 bit
    next_header = socket.IPPROTO_TCP      #8 bit
    hop_limit   = 255                     #8 bit
    saddr = socket.inet_pton ( socket.AF_INET6, source_ip )  #128 bit
    daddr = socket.inet_pton ( socket.AF_INET6, dest_ip   )  #128 bit

    ver_traff_flow = (version << 8) + traffic_class
    ver_traff_flow = (ver_traff_flow << 20) + flow_level

    ip_header = pack( '!IHBB', ver_traff_flow, payload_len, next_header, hop_limit)
    ip_header = ip_header + saddr + daddr

    # tcp header fields
    seq = 0
    ack_seq = 0
    doff = 5    #4 bit field, size of tcp header, 5*4 = 20 bytes
    #tcp flags
    fin = 0
    syn = 1
    rst = 0
    psh = 0
    ack = 0
    urg = 0
    window = socket.htons (5840)    #maximum allowed window size
    check = 0
    urg_ptr = 0

    offset_res = (doff << 4) + 0
    tcp_flags  = fin + (syn << 1) + (rst << 2) + (psh <<3) + (ack << 4) + (urg << 5)

    tcp_header = pack('!HHLLBBHHH' , source_port, dest_port, seq, ack_seq, offset_res, tcp_flags,  window, check, urg_ptr)

    source_address = socket.inet_pton( socket.AF_INET6, source_ip )
    dest_address = socket.inet_pton( socket.AF_INET6, dest_ip )

    placeholder = 0
    protocol = socket.IPPROTO_TCP
    tcp_length = len(tcp_header)
    psh = source_address + dest_address + pack('!BBH' , placeholder , protocol , tcp_length);
    psh = psh + tcp_header;

    tcp_checksum = checksum(psh)
    # make the tcp header again and fill the correct checksum
    tcp_header = pack('!HHLLBBHHH' , source_port, dest_port, seq, ack_seq, offset_res, tcp_flags,  window, tcp_checksum , urg_ptr)

    packet = ip_header + tcp_header

    return packet

#main 
#create raw socket v6
s = socket.socket(socket.AF_INET6, socket.SOCK_RAW, socket.IPPROTO_TCP)
s.setsockopt(socket.IPPROTO_IPV6, socket.IP_HDRINCL, 1)
#send syn packet
packet = init_tcp_syn_packet_v6( 1235, 80,  '2001:172:22:5::31','2014:2008:0:c::284a:78a4')