int main(int argc, char *argv[])
{
    init_nl();

    while (1) {
        recvmsg(nl_sock, &msg, 0);
        printf("Received from kernel: %s\n", NLMSG_DATA(nlh));
    }

    close_nl();
}


int init_nl()
{
    nl_sock = socket(PF_NETLINK, SOCK_RAW, NETLINK_TEST);

    if (nl_sock < 0) {
        printf("Error: could not create socket\n");

        return -1;
    }
    
    memset(&src_addr, 0, sizeof(src_addr));
    src_addr.nl_family = AF_NETLINK;
    src_addr.nl_pid = getpid();     /* self pid */
    src_addr.nl_groups = 0;         /* not in mcast groups */

    bind(nl_sock, (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;               /* kernel pid */
    dest_addr.nl_groups = 0;            /* unicast */

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

    memset(nlh, 0, NLMSG_SPACE(MAX_PAYLOAD));

    nlh->nlmsg_len = NLMSG_SPACE(MAX_PAYLOAD);
    nlh->nlmsg_pid = getpid();
    nlh->nlmsg_flags = 0;

    /* fill the netlink msg payload */
    strcpy(NLMSG_DATA(nlh), "User Space to Kernel Space Message!");

    iov.iov_base = (void *) nlh;
    iov.iov_len = nlh->nlmsg_len; //NLMSG_SPACE(MAX_PAYLOAD);

    msg.msg_name = (void *) &dest_addr;
    msg.msg_namelen = sizeof(dest_addr);
    msg.msg_iov = &iov;
    msg.msg_iovlen = 1;

    printf("Waiting for msg from kernel\n");

    sendmsg(nl_sock, &msg, 0);

    memset(nlh, 0, NLMSG_SPACE(MAX_PAYLOAD));
}

static int __init my_init(void) {
    struct sk_buff *skb = NULL;
    struct nlmsghdr *nlh = NULL;
    u8 *payload = NULL;
    int err = 0;                                              
    int seq = 0;
    u32 pid = 0;

    printk(KERN_INFO "%s() called", __FUNCTION__);

    nl_sk = netlink_kernel_create(&init_net, NETLINK_TEST, 0, nl_data_ready,
        NULL, THIS_MODULE);

    if (nl_sk == NULL) {
        printk(KERN_DEBUG "Could not create socket\n");

        return -1;
    }

    size_t len = 0;

    skb = alloc_skb(NLMSG_LENGTH(MAX_PAYLOAD), GFP_KERNEL);

    if (skb) {
        strcpy(skb->data, "MY_INIT");

        len = strlen(skb->data);

        if (len > 0) {
            skb->data[len - 1] = '\0';
        }

        nlh = (struct nlmsghdr *) skb_put(skb, NLMSG_SPACE(MAX_PAYLOAD));
    }
    else {
        printk("skb doesn't exist!\n");
    }

    nlh = (struct nlmsghdr *) skb->data;
    nlh->nlmsg_len = len;
    nlh->nlmsg_pid = 0;
    nlh->nlmsg_flags = 0;
    nlh->nlmsg_type = 2;
    nlh->nlmsg_seq = seq++;

    NETLINK_CB(skb).pid = 0;
    NETLINK_CB(skb).dst_group = 0;

    payload = NLMSG_DATA(nlh);

    err = netlink_unicast(nl_sk, skb, pid, MSG_DONTWAIT);

    return 0;
}