Develop simple net_device in the linux kernel - linux

Question

I am trying to implement a netdevice (net_device) in linux kernel. This is simple net_device which pass the command/data from user space to kernel space and vice versa this is the goal of this simple net_device. I am using socket for passing command/data from user space to kernel space . After googling i successed in registering net_device and able to see my device in /sys/class/net/abc0 (device name)
when coming to file operation there is no clear idea of the flow
struct net_device_ops
{
.ndo_open =open,
.ndo_close = close,
.ndo_start_xmit = start_xmit
}
if i issue write in socket will it call start_xmit in data link layer.
If i want to call open method, how to call it using socket
How to call start_xmit using socket
How will i find , there is data packet in the receive buffer and pass it to user space.
There is no clear flow/information about simple net_device (except ethernet) can any suggest a link/pdf.
I tried writing simple socket program to test open,close,start_xmit. where socket read/write is not calling open,close,star_xmit .
Is there any way to test the developed net_device ?
Thank you

Answer 1

I found how to test the open,close function .
type : ifconfig abc0(Device name) up will call open method
type : ifconfig abc0(Device name) down will call close method
Can some one help me how to test these methods with sockets.

Answer 2

SIOCSIFFLAGS, -> IFF_UP you can actually set or unset it while doing an ioctl to the netdevice abc0.
first off you have to create a dgram socket,
then use ifreq structure defined in net/if.h
and fill interface and iff_flags
iff_flags can be set with IFF_UP or can be negated with the same IFF_UP to make interface down
and then close the socket.
#include <net/if.h>
....
sock = socket(AF_INET, SOCK_DGRAM, 0);
if (sock < 0) {
goto fail;
}
struct ifreq ifreq;
strcpy(ifreq.ifr_name, "abcd0");
ifreq.iff_flags |= IFF_UP;
if (ioctl(sock, &ifreq, sizeof(ifreq) < 0) {
perror("ioctl setting interface up");
}
ifreq.iff_flags ~= IFF_UP;
if (ioctl(sock, &ifreq, sizeof(ifreq) < 0) {
perror("ioctl setting interface down");
}
close(sock);
offtopic:
will you please share your code? we can understand too about your network device :)