Linux kernel socket programming

Hi,
I am trying to figure out how to write socket program in kernel mode.
From the kernel source of 2.4.20-8, I figured the following steps, but it
seems it does not work(the receiver is a user-space program, just listen and
recv udp packages. what happened is the receiver got nothing, while no error
msg at sender). I have tried to play with the same sender program in user
space, which works. So the problem seems to be incorrect use of socket
creation and msg send call. Could sb point a link for a working examples, or
nicely point out my mistake?

Thanks a lot!
Shuang,

struct socket * sock;
struct sockaddr_in serv_addr;

struct msghdr msg_header;
struct iovec msg_iov;

unsigned char send_buf[SIZE];

res.bytes[0] = 192;
res.bytes[1] = 168;
res.bytes[2] = 102;
res.bytes[3] = 1;

memset (send_buf, 255, SIZE);

memset (&serv_addr, 0, sizeof (serv_addr));
serv_addr.sin_family = AF_INET;
serv_addr.sin_addr.s_addr = res.word|htonl(0);
serv_addr.sin_port = htons (PORT);


printk ("<1>Hello, world\n");
printk ("The process is %s (pid %i)\n", (char *) current->comm,
current->pid);
printk ("s_addr = %u", serv_addr.sin_addr.s_addr);

if (sock_create(AF_INET, SOCK_DGRAM, 0,&sock)<0)
{
printk(" Error Creating socket\n");
return -1;
}

if (sock_map_fd(sock) < 0)
{
printk(" Error mapping socket\n");
return -1;
}


sock->sk->allocation = GFP_NOIO;
msg_iov.iov_base = send_buf;
msg_iov.iov_len = 8;
msg_header.msg_name = (struct sockaddr*) &serv_addr;
msg_header.msg_namelen = sizeof (serv_addr);
msg_header.msg_iov = &msg_iov;
msg_header.msg_iovlen = 1;
msg_header.msg_control = NULL;
msg_header.msg_controllen = 0;

if (sock_sendmsg(sock, &msg_header, 8) < 0){
printk("Request send Error, \n");
}
printk(" Message sent\n");

return 0;

Shuang Liang wrote:
> Hi,
> I am trying to figure out how to write socket program in kernel mode.
> From the kernel source of 2.4.20-8, I figured the following steps, but it
> seems it does not work(the receiver is a user-space program, just listen and
> recv udp packages. what happened is the receiver got nothing, while no error
> msg at sender). I have tried to play with the same sender program in user
> space, which works. So the problem seems to be incorrect use of socket
> creation and msg send call. Could sb point a link for a working examples, or
> nicely point out my mistake?
>

Why are you trying to use sockets in kernel mode?

They are intended to be used from user mode.

You should not use kernel mode for something that
can be handled in user mode - maybe using a
suitable daemon.

--

Tauno Voipio
tauno voipio (at) iki fi

"Tauno Voipio" <(E-Mail Removed)> wrote in message
news:u9M4e.63$(E-Mail Removed)...
> Shuang Liang wrote:
>> Hi,
>> I am trying to figure out how to write socket program in kernel mode.
>> From the kernel source of 2.4.20-8, I figured the following steps, but it
>> seems it does not work(the receiver is a user-space program, just listen
>> and recv udp packages. what happened is the receiver got nothing, while
>> no error msg at sender). I have tried to play with the same sender
>> program in user space, which works. So the problem seems to be incorrect
>> use of socket creation and msg send call. Could sb point a link for a
>> working examples, or nicely point out my mistake?
>>
>
> Why are you trying to use sockets in kernel mode?
>
Since I am trying to write a driver which needs network access. So I need to
figure out how to do that.

> They are intended to be used from user mode.
>
> You should not use kernel mode for something that
> can be handled in user mode - maybe using a
> suitable daemon.
>
I can do it in user space, but I will need to move data in and out of kernel
space. So I appreciate somebody can give me a hand.
> --
>
> Tauno Voipio
> tauno voipio (at) iki fi
>