Linux 内核态与用户态通信 netlink

参考资料：

https://blog.csdn.net/zqixiao_09/article/details/77131283

 

 

 

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/sched.h>
#include <net/sock.h>
#include <net/netlink.h>
#include <linux/netlink.h>


#define NETLINK_USER 22
#define USER_MSG (NETLINK_USER   1)
#define USER_PORT 50


MODULE_LICENSE("GPL");
MODULE_AUTHOR("arvik");
MODULE_DESCRIPTION("netlink_demo");

static void test_netlink_rcv(struct sk_buff *skb);

struct netlink_kernel_cfg cfg = {
    .input = test_netlink_rcv,
    /*...*/
};
static struct sock *test_netlink_sock = NULL;

int send_msg(int8_t *pbuf, uint16_t len)
{
    struct sk_buff *nl_skb;
    struct nlmsghdr *nlh;

    int ret;

    nl_skb = nlmsg_new(len, GFP_ATOMIC);
    if (!nl_skb) {
        printk("netlink_alloc_skb error\n");
        return -1;
    }
    /*将header填充到skb中*/
    nlh = nlmsg_put(nl_skb, 0, 0, USER_MSG, len, 0);
    if (nlh == NULL) {
        printk("put error\n");
        nlmsg_free(nl_skb);
        return -1;
    }
    /*拷贝data*/
    memcpy(nlmsg_data(nlh), pbuf, len);

    /*发送*/
    ret = netlink_unicast(test_netlink_sock, nl_skb, USER_PORT, MSG_DONTWAIT);

    return ret;
}

static void test_netlink_rcv(struct sk_buff *skb)
{
    struct nlmsghdr *nlh = NULL;

    void *data = NULL;

    printk("skb->len %u\n", skb->len);
    if (skb->len >= nlmsg_total_size(0))
    {
        nlh = nlmsg_hdr(skb);
        data = NLMSG_DATA(nlh);
        if (data) {
            printk("kernel receive date : %s\n", (int8_t *)data);
            send_msg(data, nlmsg_len(nlh));
        }
    }
}


static int __init test_netlink_init(void)
{
    printk("test netlink init\n");

    test_netlink_sock = netlink_kernel_create(&init_net, USER_MSG, &cfg);    
    if (test_netlink_sock == NULL) {
        printk("test netlink init error\n");
        return -1;
    }

    printk("test netlink init ok\n");
    
    return 0;
}
static void __exit test_netlink_exit(void)
{
    netlink_kernel_release(test_netlink_sock);
    test_netlink_sock = NULL;

    printk("test netlink exit\n");
}

module_init(test_netlink_init);
module_exit(test_netlink_exit);

 

 

#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <string.h>
#include <linux/netlink.h>
#include <stdint.h>
#include <unistd.h>
#include <errno.h>

#define NETLINK_USER 22
#define USER_MSG (NETLINK_USER   1)

#define MSG_LEN 100

#define MAX_PLOAD 100

struct _my_msg {
    struct nlmsghdr hdr;
    int8_t data[MSG_LEN];
};

int main()
{
    char *data = "hello kernel";
    socklen_t addr_len;
    struct sockaddr_nl local, dest_addr;

    int skfd;
    struct nlmsghdr *nlh = NULL;
    struct _my_msg info;
    int ret;

    //创建socket
    skfd = socket(AF_NETLINK, SOCK_RAW, USER_MSG);
    if (skfd == (-1)) {
        fprintf(stderr, "create socket error...%s\n", strerror(errno));
        return (-1);
    }

    /*绑定*/
    memset(&local, 0, sizeof(local));
    local.nl_family =  AF_NETLINK;
    local.nl_pid = 50;
    local.nl_groups = 0;
    if (bind(skfd, (struct sockaddr *)&local, sizeof(local)) != 0) {
        fprintf(stderr, "bind error\n");
        close(skfd);
        return (-1);
    }

    //初始化目的地址
    memset(&dest_addr, 0, sizeof(dest_addr));
    dest_addr.nl_family = AF_NETLINK; 
    dest_addr.nl_pid = 0;
    dest_addr.nl_groups = 0;
    /*填写data*/
    nlh = (struct nlmsghdr *)malloc(NLMSG_SPACE(MAX_PLOAD));
    memset(nlh, 0, sizeof(struct nlmsghdr));
    nlh->nlmsg_len = NLMSG_SPACE(MAX_PLOAD);
    nlh->nlmsg_flags = 0;
    nlh->nlmsg_type = 0;
    nlh->nlmsg_seq = 0;
    nlh->nlmsg_pid = local.nl_pid;
    
    memcpy(NLMSG_DATA(nlh), data, strlen(data));
    ret = sendto(skfd, nlh, nlh->nlmsg_len, 0, (struct sockaddr *)&dest_addr, sizeof(struct sockaddr_nl));
    if (ret < 0) {
//        fprintf(stderr, "sendto error\n");
        perror("sendto error: ");
        close(skfd);
        return (-1);
    }

    printf("wait kernel msg!\n");
    memset(&info, 0, sizeof(info));

    /*接受信息*/
    ret = recvfrom(skfd, &info, sizeof(struct _my_msg), 0, (struct sockaddr *)&dest_addr, &addr_len);
    if (ret <= 0) {
//        fprintf(stderr, "recv from kernel  error\n");
        perror("recv from kernel error: ");
        close(skfd);
        return (-1);
    }

    printf("msg receive from kernel : %s\n", info.data);
    close(skfd);

    free((void *)nlh);

    close(skfd);

    return 0;
}

 

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