linux netlink详解3-netlink总结

1 netlink初始化

2 内核netlink创建

3 应用层netlink创建

4 应用层向内核发送消息

 

5 应用层接收内核消息

 

6 内核向应用层发送消息

7 内核和应用层netlink通信实例

7.1 应用层代码实例

 1 /*应用层代码*/
 2 #include <sys/stat.h>
 3 #include <unistd.h>
 4 #include <stdio.h>
 5 #include <stdlib.h>
 6 #include <sys/socket.h>
 7 #include <sys/types.h>
 8 #include <string.h>
 9 #include <asm/types.h>
10 #include <linux/netlink.h>
11 #include <linux/socket.h>
12  
13 #define MAX_PAYLOAD 1024 /* maximum payload size*/
14 struct sockaddr_nl src_addr, dest_addr;
15 struct nlmsghdr *nlh = NULL;
16 struct iovec iov;
17 int sock_fd;
18 struct msghdr msg;
19  
20 int main(int argc, char* argv[])
21 {
22    sock_fd = socket(PF_NETLINK, SOCK_RAW, 21);
23    memset(&msg, 0, sizeof(msg));
24    memset(&src_addr, 0, sizeof(src_addr));
25    src_addr.nl_family = AF_NETLINK;
26    src_addr.nl_pid = getpid(); /* self pid */
27    src_addr.nl_groups = 0; /* not in mcast groups */
28    bind(sock_fd, (struct sockaddr*)&src_addr, sizeof(src_addr));
29    memset(&dest_addr, 0, sizeof(dest_addr));
30    dest_addr.nl_family = AF_NETLINK;
31    dest_addr.nl_pid = 0; /* For Linux Kernel */
32    dest_addr.nl_groups = 0; /* unicast */
33  
34    nlh=(struct nlmsghdr *)malloc(NLMSG_SPACE(MAX_PAYLOAD));
35    /* Fill the netlink message header */
36    nlh->nlmsg_len = NLMSG_SPACE(MAX_PAYLOAD);
37    nlh->nlmsg_pid = getpid(); /* self pid */
38    nlh->nlmsg_flags = 0;
39    /* Fill in the netlink message payload */
40    strcpy(NLMSG_DATA(nlh), "Hello you!");
41  
42    iov.iov_base = (void *)nlh;
43    iov.iov_len = nlh->nlmsg_len;
44    msg.msg_name = (void *)&dest_addr;
45    msg.msg_namelen = sizeof(dest_addr);
46    msg.msg_iov = &iov;
47    msg.msg_iovlen = 1;
48  
49    printf(" Sending message. ...\n");
50    sendmsg(sock_fd, &msg, 0);//向内核发送消息
51  
52    /* Read message from kernel */
53    memset(nlh, 0, NLMSG_SPACE(MAX_PAYLOAD));
54    printf(" Waiting message. ...\n");
55    recvmsg(sock_fd, &msg, 0);//接收内核的消息
56    printf(" Received message payload: %s\n",NLMSG_DATA(nlh));
57  
58     /* Close Netlink Socket */
59    close(sock_fd);
60 }

 7.2 内核层代码实例

 1 /*内核层代码*/
 2  
 3 #include <linux/kernel.h>
 4 #include <linux/module.h>
 5 #include <linux/types.h>
 6 #include <linux/sched.h>
 7 #include <net/sock.h>
 8 #include <net/netlink.h>
 9  
10 #define NETLINK_TEST 21
11  
12 struct sock *nl_sk = NULL;
13 EXPORT_SYMBOL_GPL(nl_sk);
14  
15 void nl_send(struct sk_buff *__skb)
16 {
17   struct sk_buff *skb;
18   struct nlmsghdr *nlh;
19   u32 pid;
20   int rc;
21   int len = NLMSG_SPACE(1200);
22   char str[100];
23  
24   printk("net_link: data is ready to read.\n");
25   skb = skb_get(__skb);
26  
27   if (skb->len >= NLMSG_SPACE(0)) {
28     nlh = nlmsg_hdr(skb);//接收应用层的消息头
29     printk("nl_send: recv %s.\n", (char *)NLMSG_DATA(nlh));//NLMSG_DATA(nlh)接收应用层消息数据
30     memcpy(str,NLMSG_DATA(nlh), sizeof(str)); 
31     pid = nlh->nlmsg_pid; /*pid of sending process */
32     printk("nl_send: pid is %d\n", pid);
33     kfree_skb(skb);
34  
35     skb = alloc_skb(len, GFP_ATOMIC);
36     if (!skb){
37       printk(KERN_ERR "nl_send: allocate failed.\n");
38       return;
39     }
40     nlh = nlmsg_put(skb,0,0,0,1200,0);
41     NETLINK_CB(skb).pid = 0; /* from kernel */
42  
43     memcpy(NLMSG_DATA(nlh), str, sizeof(str));
44     printk("nl_send: going to send.\n");
45     rc = netlink_unicast(nl_sk, skb, pid, MSG_DONTWAIT);//向应用层发送消息
46     if (rc < 0) {
47       printk(KERN_ERR "nl_send: can not unicast skb (%d)\n", rc);
48     }
49     printk("nl_send: send is ok.\n");
50   }
51   return;
52 }
53  
54 static int kernel_netlink_test(void) {
55   nl_sk = netlink_kernel_create(&init_net, NETLINK_TEST, 0, nl_send, NULL, THIS_MODULE);//创建netlink socket
56  
57   if (!nl_sk) {
58     printk(KERN_ERR "kernel_netlink_test: Cannot create netlink socket.\n");
59     return -EIO;
60   }
61   printk("kernel_netlink_test: create socket ok.\n");
62   return 0;
63 }
64  
65 int init_module()
66 {
67   kernel_netlink_test();
68   return 0;
69 }
70 void cleanup_module( )
71 {
72   if (nl_sk != NULL){
73     sock_release(nl_sk->sk_socket);
74   }
75   printk("kernel_netlink_test: remove ok.\n");
76 }
77 MODULE_LICENSE("GPL");
78 MODULE_AUTHOR("action_er");

 待测试。。。

posted @ 2020-10-11 19:44  Action_er  阅读(1001)  评论(0)    收藏  举报