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我使用 Netlink 套接字尝试了下面的程序，它就像一个魅力。

源：http ://binwaheed.blogspot.in/2010/08/after-reading-kernel-source-i-finally.html

内核模块

#include <linux/module.h>
#include <net/sock.h>
#include <linux/netlink.h>
#include <linux/skbuff.h>

#define NETLINK_USER 31

struct sock *nl_sk = NULL;

static void hello_nl_recv_msg(struct sk_buff *skb)
{
    struct nlmsghdr *nlh;
    int pid;
    struct sk_buff *skb_out;
    int msg_size;
    char *msg="Hello from kernel";
    int res;

    printk(KERN_INFO "Entering: %s\n", __FUNCTION__);

    msg_size=strlen(msg);

    nlh=(struct nlmsghdr*)skb->data;
    printk(KERN_INFO "Netlink received msg payload: %s\n",(char*)nlmsg_data(nlh));
pid = nlh->nlmsg_pid; /*pid of sending process */


skb_out = nlmsg_new(msg_size,0);


if(!skb_out)
{
    printk(KERN_ERR "Failed to allocate new skb\n");
    return;
} 
nlh=nlmsg_put(skb_out,0,0,NLMSG_DONE,msg_size,0);


NETLINK_CB(skb_out).dst_group = 0; /* not in mcast group */
strncpy(nlmsg_data(nlh),msg,msg_size);

res=nlmsg_unicast(nl_sk,skb_out,pid);

if(res<0)
    printk(KERN_INFO "Error while sending bak to user\n");
}


static int __init hello_init(void)
{
printk("Entering: %s\n",__FUNCTION__);
nl_sk=netlink_kernel_create(&init_net, NETLINK_USER, 0, hello_nl_recv_msg, NULL, THIS_MODULE);
if(!nl_sk)
{
    printk(KERN_ALERT "Error creating socket.\n");
    return -10;
}
return 0;
}


static void __exit hello_exit(void){
printk(KERN_INFO "exiting hello module\n");
netlink_kernel_release(nl_sk);
}


module_init(hello_init);
module_exit(hello_exit);


MODULE_LICENSE("GPL");

用户程序

#include <sys/socket.h>
#include <linux/netlink.h>

#define NETLINK_USER 31


#define MAX_PAYLOAD 1024  /* maximum payload size*/
struct sockaddr_nl src_addr, dest_addr;
struct nlmsghdr *nlh = NULL;
struct iovec iov;
int sock_fd;
struct msghdr msg;


void main() {
    sock_fd=socket(PF_NETLINK, SOCK_RAW, NETLINK_USER);
    if(sock_fd<0)
    return -1;


memset(&src_addr, 0, sizeof(src_addr));
src_addr.nl_family = AF_NETLINK;
src_addr.nl_pid = getpid();  /* self pid */
/* interested in group 1<<0 */
bind(sock_fd, (struct sockaddr*)&src_addr,
    sizeof(src_addr));


memset(&dest_addr, 0, sizeof(dest_addr));
memset(&dest_addr, 0, sizeof(dest_addr));
dest_addr.nl_family = AF_NETLINK;
dest_addr.nl_pid = 0;   /* For Linux Kernel */
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;
strcpy(NLMSG_DATA(nlh), "Hello");
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;


printf("Sending message to kernel\n");
sendmsg(sock_fd,&msg,0);
printf("Waiting for message from kernel\n");


/* Read message from kernel */
recvmsg(sock_fd, &msg, 0);
printf(" Received message payload: %s\n",
       NLMSG_DATA(nlh));
close(sock_fd);

}

但是，当我在第一次（在主程序内）sendmsg()之后立即执行时，内核崩溃并且系统重新启动。sendmsg

知道为什么会这样吗？

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0 回答 0