在内核模块中发送 UDP 数据包 [英] Sending a UDP packet within a kernel module
问题描述
背景:我是 UCSB 计算机工程专业的四年级学生.我参加了网络和操作系统课程.我在用户空间中创建了一个程序，它将 UDP 数据包广播到子网并在自组织网络中接收 UDP 数据包.我想要完成的是将这个程序转换为一个内核模块，该模块将在带有 Angstrom Linux 的 ARM 嵌入式系统上运行，内核版本 2.6.39(x86 到 ARM 架构的交叉编译是另一天的问题).迁移到内核的原因是为了摆脱用户空间函数的一些开销，并使发送和接收部分尽可能快.
Background: I'm a fourth year computer engineering major at UCSB. I've taken networking and operating systems courses. I created a program in userspace that broadcasts UDP packets onto the subnet and receives UDP packets in an adhoc network. What I'm trying to accomplish is to convert this program into a kernel module that will work on an ARM embedded system with Angstrom Linux, kernel version 2.6.39 (the x86 to ARM architecture cross compilation is an issue for another day). The reason for this move to the kernel is to shed some of the overhead of userspace functions and to make the sending and receiving part as quick as possible.
在我参加的任何课程中，我从来没有做过这样的事情，所以如果我说的任何内容不正确、无用或效率低下，请告诉我！
I've never done anything like this before in any of the courses I've taken, so please tell me if anything I am saying is incorrect, useless or inefficient!
在与 Google 进行研究后，我得出的结论是，典型的方法是完全取消套接字并使用 sockbuf 结构并自己填写必要的标头.这会对在子网上广播数据包的能力产生影响吗?我目前正在尝试遵循此处的代码:UDP 数据包使用 linux-kernel 模块发送而不使用套接字
After research with Google, I've concluded the typical way is to do away with sockets entirely and work with the sockbuf structure and fill in the necessary headers myself. Would this have an effect on the ability to broadcast packets on the subnet?
I am currently trying to follow the code here:
UDP packet send with linux-kernel module without using sockets
我已经弄清楚了大部分代码背后的原因，但最后一部分让我感到困惑:
I've figured out the reasoning behind most of the code, but the last part is what confuses me:
eth = (struct ethhdr *) skb_push(skb, ETH_HLEN);
skb_reset_mac_header(skb);
skb->protocol = eth->h_proto = htons(ETH_P_IP);
memcpy(eth->h_source, dev->dev_addr, ETH_ALEN);
memcpy(eth->h_dest, remote_mac, ETH_ALEN);
skb->dev = dev;
dev_queue_xmit(skb);
- 除了源 MAC 地址之外，所有的以太网标头似乎都是完全由内核中定义的标头构成的，对吗?我将广播我的数据包，那么究竟应该在目标 MAC 地址字段中输入什么?
- 更重要的是，
skb->dev = dev;行中的 dev 是什么?根据我的调查，它是指向与其关联的设备驱动程序的指针.据我了解，当我使用 802.11 进行通信时，我希望它指向无线芯片设备驱动程序.我是否必须为无线驱动程序创建自己的dev结构?如果是这样，有关于如何完成此操作的任何指导吗?如果没有，我如何访问现有的设备驱动程序并在内核模块中使用它? - All of the ethernet header seems to be constructed purely out of headers defined in the kernel besides the source MAC address, is this correct? I am going to be broadcasting my packets, so what exactly should be put into the destination MAC address field?
- More importantly, what is dev in the
skb->dev = dev;line? From my investigation, it is a pointer to the device driver it is associated with. From my understanding, I would want this to point to the wireless chip device driver as I am using 802.11 to communicate. Do I have to create my owndevstruct for the wireless driver? If so, there any guidance on how to accomplish this? If not, how can I access the existing device driver and use this in a kernel module?
我尝试注释掉 dev 行并运行代码，但不出所料，一旦它执行 dev_queue_xmit(skb);，我就会出现内核崩溃.
I've tried commenting out the dev line and running the code but unsurprisingly I get a kernel panic once it executes dev_queue_xmit(skb);.
再说一次，我以前从未做过这样的事情，所以任何建议都会有所帮助，即使这意味着要完全改变我的方法！我也明白这可能是一个小问题，但任何形式的指导都是值得赞赏的！
Again, I've never done anything like this before, so any advice would be helpful, even if it means changing my approach entirely! I also understand that this could be a niche of a question, but any sort of guidance is appreciated!
提前谢谢你！
推荐答案
如果您不想修改协议，最好的方法是不要干扰协议.在更高的(套接字)层上工作.这个 API 可以在 net/socket.c 中找到
The best way is not to interfere with the protocol if you are not trying to modify one. Work on a higher (socket) layer. This API can be found in net/socket.c
这将有所帮助:(在新的浏览器标签/窗口中打开以进行缩放)
This will help: (open in new browser tab/window to zoom)
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