Netlink套接字内核广播

Netlink套接字内核广播原理程序 调试需改动

multicast_app
---------------------------
#include <asm/types.h>
#include <sys/socket.h>
#include <linux/netlink.h>

#define MAX_PAYLOAD 1024 /* maximum payload size*/
#define NETLINK_TEST 17

struct sockaddr_nl src_addr, dest_addr;
struct nlmsghdr *nlh = NULL;
struct iovec iov;
struct msghdr msg;
int sock_fd;

void main() {
sock_fd=socket(PF_NETLINK, SOCK_RAW, NETLINK_TEST);
memset(&src_addr, 0, sizeof(src_addr));
src_addr.nl_family = AF_NETLINK;
src_addr.nl_pid = getpid(); /* self pid */
/* interested in group 1<<0 */
src_addr.nl_groups = 1;
bind(sock_fd, (struct sockaddr*)&src_addr,
sizeof(src_addr));
memset(&dest_addr, 0, sizeof(dest_addr));
nlh = (struct nlmsghdr *)malloc(
NLMSG_SPACE(MAX_PAYLOAD));
memset(nlh, 0, NLMSG_SPACE(MAX_PAYLOAD));

iov.iov_base = (void *)nlh;
iov.iov_len = NLMSG_SPACE(MAX_PAYLOAD);
msg.msg_name = (void *)&dest_addr;
msg.msg_namelen = sizeof(dest_addr);
msg.msg_iov = &iov;
msg.msg_iovlen = 1;
printf("Waiting for message from kernel\n");
/* Read message from kernel */
recvmsg(sock_fd, &msg, 0);
printf(" Received message payload: %s\n",
NLMSG_DATA(nlh));
close(sock_fd);
}

multicast_knl.c
--------------------------
#ifndef __KERNEL__
#define __KERNEL__
#endif

#ifndef MODULE
#define MODULE
#endif

#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>

#define NETLINK_TEST 17
#define MAX_PAYLOAD 1024

struct sock *nl_sk = NULL;

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

void netlink_test()
{
struct sk_buff *skb = NULL;
struct nlmsghdr *nlh;
int err;
nl_sk = netlink_kernel_create(NETLINK_TEST,
nl_data_ready);
skb=alloc_skb(NLMSG_SPACE(MAX_PAYLOAD),GFP_KERNEL);
memset(skb->data,0,NLMSG_SPACE(MAX_PAYLOAD));
nlh = (struct nlmsghdr *)skb->data;
skb_put(skb,sizeof(struct nlmsghdr));
nlh->nlmsg_len = NLMSG_SPACE(MAX_PAYLOAD);
nlh->nlmsg_pid = 0; /* from kernel */
nlh->nlmsg_flags = 0;

skb_put(skb,strlen("Greeting from kernel!"));
strcpy(NLMSG_DATA(nlh), "Greeting from kernel!");
nlh->nlmsg_len = skb->len;
/* sender is in group 1<<0 */
NETLINK_CB(skb).groups = 1;
NETLINK_CB(skb).pid = 0; /* from kernel */
NETLINK_CB(skb).dst_pid = 0; /* multicast */
/* to mcast group 1<<0 */
NETLINK_CB(skb).dst_groups = 1;
/*multicast the message to all listening processes*/
netlink_broadcast(nl_sk, skb, 0, 1, GFP_KERNEL);
sock_release(nl_sk->socket);
}

static int __init my_module_init(void)
{
printk(KERN_INFO "Initializing Netlink Socket");
netlink_test();
return 0;
}

static void __exit my_module_exit(void)
{
printk(KERN_INFO "Goodbye");
}

module_init(my_module_init);
module_exit(my_module_exit);