原始套接字编程 UDP Python

问题描述

如何在 Python 中以 SOCK_RAW 格式添加 IP 和 UDP 标头等自定义字段?我希望在数据包中有一个自定义字段并在计算中使用该字段.

解决方案

您没有指定自定义字段的位置.此示例允许您随意构建 UDP 标头(至少在 Linux 上 - 可能存在依赖于操作系统的行为):

从套接字导入 *导入结构s = 套接字(AF_INET，SOCK_RAW，IPPROTO_UDP)数据='字符串'sport = 4711 # 任意源端口dport = 45134 # 任意目的端口长度 = 8+len(数据)；校验和 = 0udp_header = struct.pack('!HHHH', 运动, dport, 长度, 校验和)s.sendto(udp_header+data, ('', 0));

测试:

<上一页># socat -u UDP:localhost:4711 - &# netstat -up活跃的互联网连接(无服务器)Proto Recv-Q Send-Q 本地地址 外部地址 状态 PID/程序名称udp 0 0 本地主机:45134 本地主机:4711 已建立 2663/socat# tcpdump -ilo -vv -x11:32:07.409163 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto UDP (17), length 34)localhost.4711 > localhost.45134:[无 cksum] UDP，长度 60x0000: 4500 0022 0000 4000 4011 3cc9 7f00 00010x0010: 7f00 0001 1267 b04e 000e 0000 7374 72690x0020: 6e67

How can I add custom fields like IP and UDP headers in python in the SOCK_RAW format?I want to have a custom field in the packet and use that field in computation.

解决方案

You didn't specify where you want that custom field. This example lets you build the UDP header at will (at least on Linux - there might be OS-dependent behaviour):

from socket import *
import struct
s = socket(AF_INET, SOCK_RAW, IPPROTO_UDP)
data = 'string'
sport = 4711    # arbitrary source port
dport = 45134   # arbitrary destination port
length = 8+len(data);
checksum = 0
udp_header = struct.pack('!HHHH', sport, dport, length, checksum)
s.sendto(udp_header+data, ('', 0));

Tested with:

# socat -u UDP:localhost:4711 - &
# netstat -up
Active Internet connections (w/o servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
udp        0      0 localhost:45134         localhost:4711          ESTABLISHED 2663/socat      
# tcpdump -ilo -vv -x
11:32:07.409163 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto UDP (17), length 34)
localhost.4711 > localhost.45134: [no cksum] UDP, length 6
    0x0000:  4500 0022 0000 4000 4011 3cc9 7f00 0001
    0x0010:  7f00 0001 1267 b04e 000e 0000 7374 7269
    0x0020:  6e67