Getting netlink socket creation returns NULL in the kernel

[Irfan Ullah (울라 이르판)]

Still, I am stuck in the same problem, I have also used share memory, and
while(!nl_sk) but nothing work:(.
Can you please tell me what's the mistake I am doing?

On Thu, Oct 17, 2019 at 3:23 PM Irfan Ullah (울라 이르판) <irfan at dke.khu.ac.kr>
wrote:

> My actual goal is to develop kernel space and user space programs to
> establish communication in which kernel should initiate the communication.
> The kernel will send information (e.g., guest physical address from
> handle_ept_violation() in vmx.c, finding the corresponding page of that
> address, owner process (or if possible the application, i.e., VLC, open
> office) of the page, process/application releasing the page) at run time to
> the user space application.
> I have written code  consists of three file i.e., netlink_kernel_module.c,
> netlink_kernel_space.h, netlink_user_module.c.  "netlink_kernel_module.c"
> contains just kernel loading/ unloading module functions i.e., __init
> hello_init(), and _exit hello_exit().  "netlink_kernel_space.h" contains
> all the rest of the kernel space code for sending/ receiving data while
>  "netlink_user_module.c" contains the user space application code for
> sending/receiving data.
>
> *During development and testing* I use  "netlink_kernel_module.c" to load
> and unload kernel module, in which the "__init hello_init()" just call the
> "create_socket(int data)" defined in  "netlink_kernel_space.h" with the
> data which I want to pass to the user space program. And my code works
> perfectly in this way.
>
> *But, To get the required data from the kernel in real time*, I include
> " netlink_kernel_space.h " in kernel file i.e., vmx.c and call the
> "create_socket(int data)"  from the handle_ept_voilation() defined in
> vmx.c
> <https://elixir.bootlin.com/linux/latest/source/arch/x86/kvm/vmx/vmx.c#L5079> after
> line#5098. I compile, and install the kernel, and reboot the system (and
> thus I don't need  "netlink_kernel_module.c"  because I don't load/unload
> the kernel module but include  "netlink_kernel_space.h"  in the vmx.c by
> using #include "netlink_kernel_space.h").  But, I am getting “NULL” while
> creating socket (nl_sk = NULL in nl_sk = netlink_kernel_create(&init_net,
> NETLINK_USER, &cfg);). Here code also shows weird behaviour. If I put 1-3
> seconds sleep just before the socket creating statement, then it works just
> during booting of the virtual machine, after successful boot I get the same
> socket NULL error. Please find the code in the attachment..
> Thank you very much.
>
> On Wed, Oct 16, 2019 at 11:29 PM Valdis Klētnieks <valdis.kletnieks at vt.edu>
> wrote:
>
>> On Wed, 16 Oct 2019 13:54:08 +0900, Irfan Ullah said:
>>
>> > developed kernel space, and user space programs.  Kernel and user space
>> > programs working perfectly when I load and run these modules from the
>> > terminal using “sudo insmod kernelmodule.ko”, and “./userspaceApp”
>> > respectively.  But, when I try to use kernel program  (directly as a
>> header
>> > file #include "kernelmodule.h") with the kernel original file that is
>> > “vmx.c” then it returns “NULL” while creating socket (nl_sk = NULL in
>> nl_sk
>>
>> You're going to have to explain in more detail what you're doing, and
>> possibly
>> share your code.  "when I try to use kernel program directly" doesn't
>> make sense....
>>
>>
>
> --
> *Best Regards,*
>
>
> *Mr. Irfan Ullah*
> PhD Candidate
> Data and Knowledge Engineering(DKE) Lab
> Department of Computer Science and Engineering
> Kyung Hee University, South Korea.
>  +82-010-591-51651 <+82%2010-3877-8867>
>   sahibzada.iu at gmail.com
>  sahibzada_irfanullah
>


-- 
*Best Regards,*


*Mr. Irfan Ullah*
PhD Candidate
Data and Knowledge Engineering(DKE) Lab
Department of Computer Science and Engineering
Kyung Hee University, South Korea.
 +82-010-591-51651 <+82%2010-3877-8867>
  sahibzada.iu at gmail.com
 sahibzada_irfanullah
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