使用3.X linux内核的C中的Netlink套接字

Question

嗨,我一直在努力让Netlink套接字适用于3.2 linux内核,但我似乎无法弄清楚如何做到这一点.我查看了Netlink套接字基础知识的示例,但似乎我找到的所有示例都是针对2.6内核的.

我想要找到的是如何使用Netlink套接字将信息从内核模块发送到用户模式应用程序,反之亦然？

任何帮助将不胜感激.谢谢!

Answer 1

我一直在努力在内核中使用Netlink套接字,并遇到与您相同的问题.

使用此先前的堆栈溢出答案作为基础,我设法使其工作.在3.5到3.6之间,"netlink_kernel_create"功能改变了......我在3.8.以下代码应该适合您.

netlinkKernel.c

#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__);
/* This is for 3.6 kernels and above.
struct netlink_kernel_cfg cfg = {
    .input = hello_nl_recv_msg,
};

nl_sk = netlink_kernel_create(&init_net, NETLINK_USER, &cfg);*/
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");

netlinkUser.c

#include <sys/socket.h>
#include <linux/netlink.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.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;

int 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 */

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", (char *)NLMSG_DATA(nlh));
close(sock_fd);
}

Makefile(用于netlinkKernel.c)

KBUILD_CFLAGS += -w

obj-m += netlinkKernel.o

all:
    make -w -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules
// Make sure the indentations before these "make" lines is a tab
clean:
    make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean

只需运行"make",然后运行"gcc netlinkUser.c -o netlinkUser",然后运行"sudo insmod netlinkKernel.ko",然后当你运行"./netlinkUser"时,你会看到一条消息被发送到内核模块并回复用户空间应用程序收到了.在您看到内核模块打印的调试消息后,在终端中运行"dmesg".

如果你有任何问题,请告诉我,我现在正用自己的项目深入研究这个问题.