网络链路套接字使用3.X linux内核

Question

您好，我一直在努力试图让网络链路插座为3.2 Linux内核工作，但我似乎无法弄清楚如何做到这一点。我已经找遍了Netlink套接字的基础示例，但似乎我找到的所有示例都是针对内核的。

我在试图找到的是如何使用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，并且遇到同样的问题。

使用this previous stack overflow answer作为基础，我设法使它工作。在3.5和3.6之间，“netlink_kernel_create”函数改变了...而我在3.8上。下面的代码应该适合你。

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); 
} 

的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 

只要运行 “make”，然后“GCC netlinkUser.c -o netlinkUser“，然后”sudo insmod netlinkKernel.ko“，然后当你运行”./netlinkUser“你应该看到一条消息被发送到t他的内核模块和答复是由用户空间应用程序接收的。在看到内核模块打印的调试消息后，在终端中运行“dmesg”。

如果您还有其他问题，请告诉我，我现在正在用我自己的项目深深陷入困境。