Python原始UDP数据包未到达UDP监听器

Question

我正在尝试从一个原始套接字（在Windows上，如果这有关系的话）发送一个自定义的UDP数据包到我VPS上的UDP监听器，但这个数据包从来没有到达目的地。

客户端代码：

import struct

import socket

def make_ipv4_header(srcip, dstip, datal, srcprt, dstprt):
    srcip = socket.inet_aton(srcip)
    dstip = socket.inet_aton(dstip)

    ver = 4     #Version 4 for IPv4
    ihl = 5     #Header length in 32 bit words. 5 words == 20 bytes
    dscp_ecn = 0#Optional fields, don't feel like implementing. Let's keep it at 0
    tlen = datal + 28 #Length of data + 20 bytes for ipv4 header + 8 bytes for udp     header
    ident = socket.htons(54321) #ID of packet
    flg_frgoff = 0 #Flags and fragment offset
    ttl = 64 #Time to live
    ptcl = 17 #Protocol, 17 (UDP)
    chksm = 0 #Will automatically fill in checksum    

    return struct.pack(
        "!"     #Network(Big endian)
        "2B"    #Version and IHL, DSCP and ECN
        "3H"    #Total Length, Identification, Flags and Fragment Offset
        "2B"    #Time to live, Protocol
        "H"     #Checksum
        "4s"    #Source ip
        "4s"    #Destination ip
        , (ver << 4) + ihl, dscp_ecn, tlen, ident, flg_frgoff, ttl, ptcl, chksm, srcip, dstip)

def make_udp_header(srcprt, dstprt, datal):
    return struct.pack(
        "!4H"   #Source port, Destination port, Length, Checksum
        , srcprt, dstprt, datal+16, 0)

def makepacket(src, dst, data):
    ph = make_ipv4_header(src[0], dst[0], len(data), src[1], dst[1])
    uh = make_udp_header(src[1], dst[1], len(data))
    return ph+uh+data

s = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_RAW)
packet = makepacket(("my ip", 1000), ("vps ip", 10101), "asdf")
s.sendto(packet, ("vps ip", 10101))

服务器代码：

import socket
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
s.bind(("", 10101))
while True:
    msg, addr = s.recvfrom(1024)
    print msg, addr

我可以发送一个普通的UDP数据包，它会成功到达，像这样：

import socket
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
s.sendto("asdf", ("vps ip", 10101))

谁能帮帮我？

Answer 1

把这几行改一下

s = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_RAW)
packet = makepacket(("my ip", 1000), ("vps ip", 10101), "asdf")
s.sendto(packet, ("vps ip", 10101))

通过

s=socket.socket(socket.AF_INET,socket.SOCK_DGRAM)
packet = makepacket(("my ip", 1000), ("vps ip", 10101), "asdf")
s.connect(('vps ip',10101))
s.send(packet)

希望这正是你想要的内容！！

Answer 2

在 make_udp_header 这个地方，把数据长度从 +16 改成 +8。这样做对我来说好像有效。