LinuxQuestions.org - Netlink (Kernel 2.6.10) on ARM

Hi, everybody.

While developing a driver which has to run on an ARM platform I used the following very simple netlink example code :

Sender in userspace

Code:

#include <sys/socket.h>

#include >linux/netlink.h>

#define NETLINK_TEST 17

#define MAX_PAYLOAD 1024



struct sockaddr_nl src_addr, dest_addr;

struct msghdr msg;

struct nlmsghdr *nlh = NULL;

struct iovec iov;

int sock_fd;

int sent;





int main() 

{

        sock_fd = socket(PF_NETLINK, SOCK_RAW,NETLINK_TEST);

        memset(&src_addr, 0, sizeof(src_addr));

        src_addr.nl_family = AF_NETLINK;      

        src_addr.nl_pid = getpid();  

        src_addr.nl_groups = 0;  

        bind(sock_fd, (struct sockaddr*)&src_addr, sizeof(src_addr));

        memset(&dest_addr, 0, sizeof(dest_addr));

        dest_addr.nl_family = AF_NETLINK;

        dest_addr.nl_pid = 0;  

        dest_addr.nl_groups = 0; 

        nlh=(struct nlmsghdr *)malloc(NLMSG_SPACE(MAX_PAYLOAD));



        nlh->nlmsg_len = NLMSG_SPACE(MAX_PAYLOAD);

        nlh->nlmsg_pid = getpid();  

        nlh->nlmsg_flags = 0;

        strcpy(NLMSG_DATA(nlh), "Hello from userspace!\n\0");

        iov.iov_base = (void *)nlh;

        iov.iov_len = nlh->nlmsg_len;

        msg.msg_name = (void *)&dest_addr;

        msg.msg_namelen = sizeof(dest_addr);

        msg.msg_iov = &iov;

        msg.msg_iovlen = 1;

        if ((sent = sendmsg(sock_fd, &msg, 0)) >= 0)

        {

                printf("%d characters sent.\n", sent);

        }

        else

        {

                perror("Send error");

        }

        close(sock_fd);

        return 0;

}

Receiver as kernel module

Code:

#include <linux/config.h>

#include <linux/socket.h>

#include <linux/kernel.h>

#include <linux/module.h>

#include <linux/netlink.h>

#include <net/sock.h>



#define NETLINK_TEST 17

#define MAX_PAYLOAD 1024



static struct sock *nl_sk;



void input(struct sock *sk, int len)

{

        struct sk_buff *skb = NULL;

        struct nlmsghdr *nlh = NULL;

        u8 *payload = NULL;

        u32 pid = 0;

        while ((skb = skb_dequeue(&sk->sk_receive_queue)) != NULL) 

        {

                nlh = (struct nlmsghdr *)skb->data;

                payload = NLMSG_DATA(nlh);

                printk("%s: received netlink message payload:%s\n", __FUNCTION__, payload);

        }

}



static int __init my_module_init(void)

{

        int err;

        struct sk_buff *skb;

        struct nlmsghdr *nlh = NULL;

        nl_sk = netlink_kernel_create(NETLINK_TEST, input);

        return (nl_sk !=0);

}



static void __exit my_module_exit(void)

{

        sock_release(nl_sk->sk_socket);

}



module_init(my_module_init);

module_exit(my_module_exit);

The code works perfectly on my x86 platform but fails on the ARM platform : The callback function is called but the skb->data contains just senseless data. Are there some basic kernel settings or something else which I could have forgotten ? I'm thankful for any solution hint!