linux下的netlink编程

1.创建文件：net_link.c

#include <linux/string.h>
#include <linux/stat.h>
#include <linux/module.h>
#include <linux/version.h>
#include <linux/socket.h>
#include <linux/types.h>
#include <linux/capability.h>
#include <linux/errno.h>
#include <linux/stat.h>
#include <linux/skbuff.h>
#include <linux/netlink.h>
#include <net/sock.h>

struct sock *nl_sk = NULL;

static void nl_data_ready (struct sock *sk, int len)
{
    wake_up_interruptible(sk->sk_sleep);
}

int netlink_test()
{
    struct sk_buff *skb = NULL;
    struct nlmsghdr *nlh = NULL;
    int err;
    u32 pid;    
    nl_sk = netlink_kernel_create(28, 0, nl_data_ready, THIS_MODULE);
     
    if (!nl_sk)
    {
        printk("Fail to create lc user event netlink socket.\n");
        return 0;
    }
     /* wait for message coming down from user-space */
    skb = skb_recv_datagram(nl_sk, 0, 0, &err);
    nlh = (struct nlmsghdr *)skb->data;
    printk("%s: received netlink message payload:%s ",__FUNCTION__,NLMSG_DATA(nlh));
    pid = nlh->nlmsg_pid;

// skb_put(skb,strlen(" from kernet"));
// strcpy(NLMSG_DATA(nlh), "from kernet");
    nlh->nlmsg_len = skb->len;
    NETLINK_CB(skb).pid = 0;
    NETLINK_CB(skb).dst_pid = pid;
    NETLINK_CB(skb).dst_group = 1;
    netlink_broadcast(nl_sk, skb, 0, 1, GFP_KERNEL);
    return 1;

}

static int __init my_module_init(void)
{
    printk( "Initializing Netlink Socket\n");
    if( netlink_test())
    {
        printk( "Message has send\n");
    }
    else
    {
        printk("send error\n");
    }
    return 0;
}

static void __exit my_module_exit(void)
{
   
    if(nl_sk)
    {
       sock_release(nl_sk->sk_socket);
       printk( "Goodbye\n");
    }
    else
    {
        printk( "no sock,release error\n");
    }
}

module_init(my_module_init);
module_exit(my_module_exit);

2.创建 sender.c

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <stdarg.h>
#include <asm/types.h>
#include <sys/socket.h>
#include <linux/netlink.h>
#include <sys/select.h>

#define MAX_PAYLOAD 1024 /* maximum payload size*/
struct sockaddr_nl saddr, daddr;
struct msghdr msg;
struct nlmsghdr *nlh = NULL;
struct iovec iov;
int sd;
int main()
{
    sd = socket(PF_NETLINK, SOCK_RAW,28);
    if (sd == -1)
    {
        perror("socket error\n");
        exit(1);
    }

    memset(&saddr, 0, sizeof(saddr));
    memset(&daddr, 0, sizeof(daddr));

    saddr.nl_family = AF_NETLINK;     
    saddr.nl_pid = getpid();
    saddr.nl_groups = 1;//
    bind(sd, (struct sockaddr*)&saddr, sizeof(saddr));

    daddr.nl_family = AF_NETLINK;
    daddr.nl_pid = 0;  
    daddr.nl_groups = 1;

    nlh=(struct nlmsghdr *)malloc(NLMSG_SPACE(MAX_PAYLOAD));

     /* Fill the netlink message header */
    nlh->nlmsg_len = NLMSG_SPACE(MAX_PAYLOAD);
    nlh->nlmsg_pid = getpid(); /* self pid */
    nlh->nlmsg_flags = 0;

     /* Fill in the netlink message payload */
    strcpy(NLMSG_DATA(nlh), "crazysummers call kerbel!\n");
    iov.iov_base = (void *)nlh;
    iov.iov_len = nlh->nlmsg_len;
    msg.msg_name = (void *)&daddr;
    msg.msg_namelen = sizeof(daddr);
    msg.msg_iov = &iov;
    msg.msg_iovlen = 1;

    printf("Sent message to kernel\n");
    sendmsg(sd, &msg, 0);

    printf("Waiting for message from kernel\n");
    memset(nlh, 0, NLMSG_SPACE(MAX_PAYLOAD));
    recvmsg(sd, &msg, 0);
    printf(" Received message from kernel that send to it: %s \n", NLMSG_DATA(nlh));
   
     /* Close Netlink Socket */
     close(sd);
}   

3.创建Makefile

MODULE_NAME :=net_link
obj-m+=$(MODULE_NAME).o
KERNELDIR ?= /lib/modules/$(shell uname -r)/build
PWD := $(shell pwd)
all:
$(MAKE) -C $(KERNELDIR) M=$(PWD)
gcc -g -o sender sender.c
clean:
rm -f *.ko *.o *.cmd sender $(MODULE_NAME).mod.c Module.symvers
in:
insmod net_link.ko
rm:
rmmod net_link
sp:
cat /proc/net/netlink
ru:
./sender
sm:
dmesg -c

4.这几个文件都放到一个文件夹中，执行：

    （1）make

    （2）make sm (清理内核打印信息)

      (3) make in (这步将内核模块加载到内核)

    （4）打开一个终端 ctrl+shift+n， 运行 make rn

    （5）通讯完毕，运行 make sm 查看内核的打印信息

    （6）运行完毕 执行 make rm 和 make clean 进行清理

更多的例子请看http://blog.csdn.net/dipperkun/archive/2007/12/19/1953526.aspx 不过需要该其中的错误