netlink组播的使用

 1 #include <linux/module.h>
 2 #include <linux/kernel.h>
 3 #include <linux/init.h>
 4 #include <net/sock.h>
 5 #include <linux/socket.h>
 6 #include <linux/net.h>
 7 #include <asm/types.h>
 8 #include <linux/netlink.h>
 9 #include <linux/rtnetlink.h>
10 #include <linux/skbuff.h>
11 #include <linux/delay.h>
12 
13 #define NETLINK_USER 29  //User defined group, consistent in both kernel prog and user prog
14 #define MYGRP 2 //User defined group, consistent in both kernel prog and user prog
15 
16 struct sock *nl_sk = NULL;
17 
18 static void send_to_user(void);
19 
20 static void send_to_user(void)
21 {
22     struct sk_buff *skb_out;
23     struct nlmsghdr *nlh;
24     int msg_size;
25     char msg[20] = "Hello from kernel";
26     int res;
27 
28     printk(KERN_INFO "Entering: %s\n", __FUNCTION__);
29     msg_size = strlen(msg);
30     printk(KERN_INFO "msg_size: %d\n", msg_size);
31     //msg[msg_size - 1] = ‘\0‘;
32     skb_out = nlmsg_new(msg_size, 0);
33 
34     if (!skb_out) {
35         printk(KERN_ERR "Failed to allocate new skb\n");
36         return;
37     }
38     nlh = nlmsg_put(skb_out, 0, 1, NLMSG_DONE, msg_size, 0);
39     //NETLINK_CB(skb_out).dst_group = 1; /* Multicast to group 1, 1<<0 */
40     strncpy(nlmsg_data(nlh), msg, msg_size);
41 
42     res = nlmsg_multicast(nl_sk, skb_out, 0, MYGRP, 0);
43     if (res < 0) {
44         printk(KERN_INFO "Error while sending bak to user, err id: %d\n", res);
45     }
46 }
47 
48 static int __init
49 hello_init(void) {
50 
51     struct netlink_kernel_cfg cfg = {
52         .groups = MYGRP,
53     };
54     printk("Entering: %s\n", __FUNCTION__);
55     nl_sk = netlink_kernel_create(&init_net, NETLINK_USER, &cfg);
56     if (!nl_sk) {
57         printk(KERN_ALERT "Error creating socket.\n");
58         return -10;
59     }
60 
61     msleep(10000);
62     send_to_user();
63 
64     return 0;
65 }
66 
67 static void __exit
68 hello_exit(void) {
69 
70     printk(KERN_INFO "exiting hello module\n");
71     netlink_kernel_release(nl_sk);
72 }
73 
74 module_init(hello_init);
75 module_exit(hello_exit);
76 MODULE_LICENSE("GPL");

 1 #include<stdio.h>
 2 #include<string.h>
 3 #include<stdlib.h>
 4 #include<sys/socket.h>
 5 #include<linux/netlink.h>
 6 #include<sys/types.h>
 7 #include<unistd.h>
 8 
 9 #define MYPROTO 29 //User defined group, consistent in both kernel prog and user prog
10 #define MYMGRP 2 //User defined group, consistent in both kernel prog and user prog
11 
12 int open_netlink()
13 {
14     int sock = socket(AF_NETLINK,SOCK_RAW,MYPROTO);
15     struct sockaddr_nl addr;
16 
17     memset((void *)&addr, 0, sizeof(addr));
18 
19     if (sock<0)
20         return sock;
21     addr.nl_family = AF_NETLINK;
22     addr.nl_pid = getpid();
23     addr.nl_groups = MYMGRP;
24     if (bind(sock,(struct sockaddr *)&addr,sizeof(addr))<0)
25         return -1;
26     return sock;
27 }
28 
29 int read_event(int sock)
30 {
31     struct sockaddr_nl nladdr;
32     struct msghdr msg;
33     struct iovec iov[2];
34     struct nlmsghdr nlh;
35     char buffer[65536];
36     int ret;
37     iov[0].iov_base = (void *)&nlh;
38     iov[0].iov_len = sizeof(nlh);
39     iov[1].iov_base = (void *)buffer;
40     iov[1].iov_len = sizeof(buffer);
41     msg.msg_name = (void *)&(nladdr);
42     msg.msg_namelen = sizeof(nladdr);
43     msg.msg_iov = iov;
44     msg.msg_iovlen = sizeof(iov)/sizeof(iov[0]);
45     ret=recvmsg(sock, &msg, 0);
46     if (ret<0) {
47         return ret;
48     }
49     printf("Received message payload: %s\n", NLMSG_DATA(&nlh));
50     char *a = NLMSG_DATA(&nlh);
51     int i;
52     printf("Recv Data:\n");
53     for(i = 0; i < 10; i++) {
54         printf("%c", a[i]);
55     }
56     printf("\n");
57 }
58 
59 int main(int argc, char *argv[])
60 {
61     int nls = open_netlink();
62     if (nls<0) {
63         err(1,"netlink");
64     }
65 
66     while (1)
67         read_event(nls);
68     return 0;
69 }