Question:
I'm testing a section of cable-fault finding software, and I'd like to reliably and reproducibly generate cable faults on a cat5 cable.
我正在测试一段电缆故障查找软件，我想在cat5电缆上可靠且可重复地产生电缆故障。
At the moment I'm using a meter length of untwisted cable, and wriggle the cable manually next to a power supply, but I cannot detect any faults in the application (I'm reading the Ethernet fault counters off the Ethernet ASIC.) Whether this is because no faults are generated, or because the software/hardware detection is faulty, I cannot tell.
目前我正在使用一米长的无线电缆，并在电源旁边手动蠕动电缆，但我无法检测到应用中的任何故障（我正在读取以太网ASIC上的以太网故障计数器。）是否这是因为没有产生故障，或者因为软件/硬件检测有问题，我无法分辨。
Is there a way to do this in software?
有没有办法在软件中执行此操作？
I'd settle for writing something in a higher level language, like Java or python, and as a last resort would be willing to put it together in C, but I'd really rather not re-write an Ethernet driver purely to fix a possible bug.
我决定用更高级别的语言编写一些东西，比如Java或python，并且作为最后的手段愿意将它放在C中，但我真的不想重写以太网驱动程序纯粹是为了修复可能的错误。
[EDIT]: I want to create cable faults - not detect them.
[编辑]：我想创建电缆故障 - 不检测它们。
[EDIT]: I've transferred large files through FTP and SCP without problems with the doctored cable, and I see no errors coming up while inspecting the traffic with wireshark
[编辑]：我通过FTP和SCP传输大文件而没有使用篡改电缆的问题，我发现在使用wireshark检查流量时没有出现错误
[EDIT]: See also a similar question in python.
[编辑]：请参阅python中的类似问题。
Solution:
Well, after spending over a day fighting with C, this is the python solution.
好吧，花了一天时间与C战斗后，这就是python解决方案。
First disable automatic checksumming of the ethernet card:
首先禁用以太网卡的自动校验和：
sudo ethtool -K eth1 tx off
Then, send your dodgy frame from python:
然后，从python发送你的狡猾的框架：
#!/usr/bin/env python
from socket import *
#
# Ethernet Frame:
# [
# [ Destination address, 6 bytes ]
# [ Source address, 6 bytes ]
# [ Ethertype, 2 bytes ]
# [ Payload, 40 to 1500 bytes ]
# [ 32 bit CRC chcksum, 4 bytes ]
# ]
#
s = socket(AF_PACKET, SOCK_RAW)
s.bind(("eth1", 0))
src_addr = "\x01\x02\x03\x04\x05\x06"
dst_addr = "\x01\x02\x03\x04\x05\x06"
payload = ("["*30)+"PAYLOAD"+("]"*30)
checksum = "\x00\x00\x00\x00"
ethertype = "\x08\x01"
s.send(dst_addr+src_addr+ethertype+payload+checksum)
Who said it had to be complicated...
谁说它必须复杂......
PS: I Love Python.
PS：我喜欢Python。
1 个解决方案
#1
6
If you're working in C, you can send a raw Ethernet frame using socket(AF_PACKET, SOCK_RAW, ...), and passing it a pointer to a raw buffer that you've generated yourself (e.g. by following the frame layout at wikipedia ).
如果您在C中工作，则可以使用套接字（AF_PACKET，SOCK_RAW，...）发送原始以太网帧，并将指针传递给您自己生成的原始缓冲区（例如，通过遵循以下框架布局：*）。
It's been a long time since I've done this, so I'm not going to attempt to write a representative code snippet...
我已经很久没有这样做了，所以我不会尝试编写代表性的代码片段......
#1
6
If you're working in C, you can send a raw Ethernet frame using socket(AF_PACKET, SOCK_RAW, ...), and passing it a pointer to a raw buffer that you've generated yourself (e.g. by following the frame layout at wikipedia ).
如果您在C中工作，则可以使用套接字（AF_PACKET，SOCK_RAW，...）发送原始以太网帧，并将指针传递给您自己生成的原始缓冲区（例如，通过遵循以下框架布局：*）。
It's been a long time since I've done this, so I'm not going to attempt to write a representative code snippet...
我已经很久没有这样做了，所以我不会尝试编写代表性的代码片段......