如何确定用户空间进程是否已连接到netlink内核模块？

Question

I'm currently writing a little linux kernel module (> 3.10) which should communicate with a userspace process through a netlink socket. Receiving and sending data on both sides is working fine. But how is it possible, inside the kernel module, to find out if there is any userspace process connected?

At the moment I just wait for the process to send data to the module, and save the process pid for the answer. But what if my module should send data periodically from kernel- to userspace, without any requests from the userspace process? Is it possible to find out if there are any sockets open?

I found some interesting callback pointers in struct proto , but they seem not to be used (for netlink sockets?).

Answer 1

Kernel space <> User space communicate through kernel's netlink sockets. They have hotplug [ udev , modprob , etc] events [add, change, remove, etc] which fire when major state changes happens.

If you listen to those events in your system, you could be able to dig further.

If you have a udev hotplug, you can use below command, or there are some older commands for the same:

udevadm monitor