Python ICMPv6 客户端

Question

我正在做一个简单的icmpv6客户端，但在计算校验和时遇到了一些问题。这里是我的代码，使用Wireshark抓包后发现校验和没有正确设置。错误信息显示类似于 pcs.FieldBoundsError: 'Value must be between 0 and 65535' 的内容。

import pcs, sys
from socket import *
from pcs.packets.ethernet import *
from pcs.packets.ipv6 import *
from pcs.packets.icmpv6 import *

class packet:
    def __init__(self, src, dst, mac):
        self.src = src
        self.dst = dst
        self.mac = mac

    def construct(self):
        e               = ethernet()
        e.src           = ether_atob("de:de:de:de:de:de")
        e.dst           = ether_atob(self.mac)
        e.type          = ETHERTYPE_IPV6

        ip6               = ipv6()
        ip6.version       = 6
        ip6.traffic_class = 0
        ip6.flow          = 0  
        ip6.length        = 8              # icmpv6 packet length
        ip6.next_header   = IPPROTO_ICMPV6
        ip6.hop           = 255
        ip6.src           = inet_pton(AF_INET6, self.src)
        ip6.dst           = inet_pton(AF_INET6, self.dst)

        icmp6           = icmpv6(ICMP6_ECHO_REQUEST)
        icmp6.code      = 0
        icmp6.id        = 0xf0
        icmp6.seq       = 1
        icmp6.mtu       = 1280
        icmp6.checksum  = 0

        ip6.length      = len(icmp6.getbytes())
        ip6.flow        = len(ip6.getbytes()) + ip6.length

        icmp6.checksum  = icmp6.cksum(ip6)
        pkt = pcs.Chain([e, ip6, icmp6])

        s = pcs.PcapConnector('eth0')
        s.write(pkt.bytes, len(pkt.bytes))

if __name__=='__main__':
    p = packet(sys.argv[1], sys.argv[2], sys.argv[3])
    p.construct()                     

Answer 1

这似乎和python-pcs中的一个错误有关，这个错误导致了校验和计算不正确。修剪掉那些错误的位应该能解决问题：

cs = icmp6.cksum(ip6) & 0xffff