sockets - 服务器不接受UDP数据包？

Question

包#1：

0000   08 00 27 7f 25 ae 08 00 27 2d 93 13 08 00 45 00   ..'.%®..'-....E.
0010   00 22 ab cd 40 00 40 11 00 00 0a 00 00 e8 0a 00   ."«Í@.@......è..
0020   00 87 22 b8 22 b8 00 0e 00 00 48 65 6c 6c 6f 0a   .."¸"¸....Hello.


Frame 1692: 48 bytes on wire (384 bits), 48 bytes captured (384 bits) on     interface 0
    Interface id: 0 (eth0)
    Encapsulation type: Ethernet (1)
    Arrival Time: Aug 18, 2020 22:47:52.475803259 EDT
    [Time shift for this packet: 0.000000000 seconds]
    Epoch Time: 1597805272.475803259 seconds
    [Time delta from previous captured frame: 0.198748689 seconds]
    [Time delta from previous displayed frame: 35.744487538 seconds]
    [Time since reference or first frame: 507.094545999 seconds]
    Frame Number: 1692
    Frame Length: 48 bytes (384 bits)
    Capture Length: 48 bytes (384 bits)
    [Frame is marked: False]
    [Frame is ignored: False]
    [Protocols in frame: eth:ethertype:ip:udp:data]
    [Coloring Rule Name: UDP]
    [Coloring Rule String: udp]
Ethernet II, Src: PcsCompu_2d:93:13 (08:00:27:2d:93:13), Dst:     PcsCompu_7f:25:ae (08:00:27:7f:25:ae)
    Destination: PcsCompu_7f:25:ae (08:00:27:7f:25:ae)
        Address: PcsCompu_7f:25:ae (08:00:27:7f:25:ae)
        .... ..0. .... .... .... .... = LG bit: Globally unique address  (factory default)
        .... ...0 .... .... .... .... = IG bit: Individual address (unicast)
        Source: PcsCompu_2d:93:13 (08:00:27:2d:93:13)
        Address: PcsCompu_2d:93:13 (08:00:27:2d:93:13)
        .... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
        .... ...0 .... .... .... .... = IG bit: Individual address (unicast)
    Type: IPv4 (0x0800)
Internet Protocol Version 4, Src: 10.0.0.232, Dst: 10.0.0.135
    0100 .... = Version: 4
    .... 0101 = Header Length: 20 bytes (5)
    Differentiated Services Field: 0x00 (DSCP: CS0, ECN: Not-ECT)
    Total Length: 34
    Identification: 0xabcd (43981)
    Flags: 0x4000, Don't fragment
    Time to live: 64
    Protocol: UDP (17)
    Header checksum: 0x0000 [validation disabled]
    [Header checksum status: Unverified]
    Source: 10.0.0.232
    Destination: 10.0.0.135
User Datagram Protocol, Src Port: 8888, Dst Port: 8888
Data (6 bytes)
    Data: 48656c6c6f0a
    [Length: 6]

包#2：

0000   08 00 27 7f 25 ae 08 00 27 2d 93 13 08 00 45 00   ..'.%®..'-....E.
0010   00 22 fa 39 40 00 40 11 2b 23 0a 00 00 e8 0a 00   ."ú9@.@.+#...è..
0020   00 87 cd 36 22 b8 00 0e 15 8e 48 65 6c 6c 6f 0a   ..Í6"¸....Hello.


    Frame 2078: 48 bytes on wire (384 bits), 48 bytes captured (384 bits) on interface 0
    Interface id: 0 (eth0)
    Encapsulation type: Ethernet (1)
    Arrival Time: Aug 18, 2020 22:50:12.624196163 EDT
    [Time shift for this packet: 0.000000000 seconds]
    Epoch Time: 1597805412.624196163 seconds
    [Time delta from previous captured frame: 0.804243424 seconds]
    [Time delta from previous displayed frame: 140.148392904 seconds]
    [Time since reference or first frame: 647.242938903 seconds]
    Frame Number: 2078
    Frame Length: 48 bytes (384 bits)
    Capture Length: 48 bytes (384 bits)
    [Frame is marked: False]
    [Frame is ignored: False]
    [Protocols in frame: eth:ethertype:ip:udp:data]
    [Coloring Rule Name: UDP]
    [Coloring Rule String: udp]
Ethernet II, Src: PcsCompu_2d:93:13 (08:00:27:2d:93:13), Dst:     PcsCompu_7f:25:ae (08:00:27:7f:25:ae)
    Destination: PcsCompu_7f:25:ae (08:00:27:7f:25:ae)
        Address: PcsCompu_7f:25:ae (08:00:27:7f:25:ae)
        .... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
        .... ...0 .... .... .... .... = IG bit: Individual address (unicast)
    Source: PcsCompu_2d:93:13 (08:00:27:2d:93:13)
        Address: PcsCompu_2d:93:13 (08:00:27:2d:93:13)
        .... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
        .... ...0 .... .... .... .... = IG bit: Individual address (unicast)
    Type: IPv4 (0x0800)
Internet Protocol Version 4, Src: 10.0.0.232, Dst: 10.0.0.135
    0100 .... = Version: 4
    .... 0101 = Header Length: 20 bytes (5)
    Differentiated Services Field: 0x00 (DSCP: CS0, ECN: Not-ECT)
    Total Length: 34
    Identification: 0xfa39 (64057)
    Flags: 0x4000, Don't fragment
    Time to live: 64
    Protocol: UDP (17)
    Header checksum: 0x2b23 [validation disabled]
    [Header checksum status: Unverified]
    Source: 10.0.0.232
    Destination: 10.0.0.135
User Datagram Protocol, Src Port: 52534, Dst Port: 8888

数据（6 字节） 数据：48656c6c6f0a [长度：6]

注意：数据包是由wireshark捕获的。

工具源代码：https ://github.com/MrMindKeeper/tcpf/blob/master/crafty.py

我用来生成数据包的参数： python3 packetP.py -s="10.0.0.232" -d="10.0.0.135" -dmac="08:00:27:7f:25:ae" -smac="08:00:27:2d:93:13" -sp="8888" -dp="8888" -ch="0" -tl="34" -flag="4" -hc="0"

如果您没有注意到两个数据包之间的唯一区别是 IP 标头校验和和 IP 标头标识字节或（字节 19-20 和 25-26）。

包 #1 是由我个人开发的工具生成的，包 #2 是由netcat两者在同一台 linux 机器上生成的。

服务器正在侦听端口 8888。服务器接收到两个数据包，但仅响应数据包 #2 或由 生成的数据包netcat。

我还尝试了一堆其他随机IP Header Identification值，将 Header Checksum 设置为00 00，但它仍然不起作用。有人能告诉我这里有什么问题吗？为什么我的工具生成的数据包不被接受？

我想，你不需要我的工具代码来解决这个问题，因为数据包是发送和接收的。因此，该工具不会有问题。

标签： sockets