netlink_broadcast调用出错，返回值-3

90阿呆 2015-02-18 02:47:53

我想通过netlink实现内核和用户空间交互的功能
下面是从网上找的例子，原来单播netlink_unicast是好用的；
我换成netlink_broadcast调用出错，返回值-3。错误码意思是No such process
请问这是怎么回事？



#include <linux/kernel.h>

#include <linux/module.h>

#include <linux/types.h>

#include <linux/sched.h>

#include <net/sock.h>

#include <linux/netlink.h>



#define NETLINK_TEST 17



struct {



    __u32 pid;



}user_process;



static struct sock *netlinkfd = NULL;



int send_to_user(char *info) //发送到用户空间



{



    int size;

    struct sk_buff *skb;

    unsigned char *old_tail;

    struct nlmsghdr *nlh; //报文头



    int retval;



    size = NLMSG_SPACE(strlen(info)); //报文大小

    skb = alloc_skb(size, GFP_ATOMIC); //分配一个新的套接字缓存,使用GFP_ATOMIC标志进程不>会被置为睡眠



    //初始化一个netlink消息首部



    nlh = nlmsg_put(skb, 0, 0, 0, NLMSG_SPACE(strlen(info))-sizeof(struct nlmsghdr), 0); 

    old_tail = skb->tail;

    memcpy(NLMSG_DATA(nlh), info, strlen(info)); //填充数据区

    nlh->nlmsg_len = skb->tail - old_tail; //设置消息长度



    //设置控制字段

    NETLINK_CB(skb).pid = 0;

    NETLINK_CB(skb).dst_group = 0;



    printk(KERN_DEBUG "[kernel space] skb->data:%s\n", (char *)NLMSG_DATA((struct nlmsghdr *)skb->data));



    //发送数据

    retval = netlink_unicast(netlinkfd, skb, user_process.pid, MSG_DONTWAIT);

//    retval = netlink_broadcast(netlinkfd, skb, 0, 0, GFP_KERNEL);

    printk(KERN_DEBUG "[kernel space] netlink_unicast return: %d\n", retval);



    return 0;

}







void kernel_receive(struct sk_buff *__skb) //内核从用户空间接收数据



{

    struct sk_buff *skb;

    struct nlmsghdr *nlh = NULL;



    char *data = "This is eric's test message from kernel";



    printk(KERN_DEBUG "[kernel space] begin kernel_receive\n");

    skb = skb_get(__skb);



    if(skb->len >= sizeof(struct nlmsghdr)){

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



        if((nlh->nlmsg_len >= sizeof(struct nlmsghdr))

            && (__skb->len >= nlh->nlmsg_len)){

            user_process.pid = nlh->nlmsg_pid;

            printk(KERN_DEBUG "[kernel space] data receive from user are:%s\n", (char *)NLMSG_DATA(nlh));

            printk(KERN_DEBUG "[kernel space] user_pid:%d\n", user_process.pid);



            send_to_user(data);

        }



    }else{

        printk(KERN_DEBUG "[kernel space] data receive from user are:%s\n",(char *)NLMSG_DATA(nlmsg_hdr(__skb)));

        send_to_user(data);

    }



    kfree_skb(skb);

}







int __init test_netlink_init(void)

{



    netlinkfd = netlink_kernel_create(&init_net, NETLINK_TEST, 0, kernel_receive, NULL, THIS_MODULE);



    if(!netlinkfd){

        printk(KERN_ERR "can not create a netlink socket\n");

        return -1;

    }



    return 0;

}



void __exit test_netlink_exit(void)

{

    sock_release(netlinkfd->sk_socket);

    printk(KERN_DEBUG "test_netlink_exit!!\n");

}



module_init(test_netlink_init);

module_exit(test_netlink_exit);

MODULE_LICENSE("GPL");

MODULE_AUTHOR("eric.hu");