user.c

Linux kernel - user space IPC - Netlink example

#include <unistd.h>
#include <stdio.h>
#include <linux/types.h>
#include <string.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <asm/types.h>
#include <linux/netlink.h>
#include <signal.h>

/* public define */
#define IMP_U_PID        0
#define IMP_K_MSG        1
#define IMP_CLOSE        2

#define NL_IMP            31

struct msg_to_kernel
{
	struct nlmsghdr hdr;
};

struct u_packet_info
{
	struct nlmsghdr hdr;
	char buf[32];
};

static int skfd;

static void sig_int(int signo)
{
	struct sockaddr_nl kpeer;
	struct msg_to_kernel message;


	memset(&kpeer,0,sizeof(kpeer));
	kpeer.nl_family    = AF_NETLINK;
	kpeer.nl_pid    = 0;
	kpeer.nl_groups    = 0;

	memset(&message,0,sizeof(message));
	message.hdr.nlmsg_len    = NLMSG_LENGTH(0);
	message.hdr.nlmsg_flags    = 0;
	message.hdr.nlmsg_type    = IMP_CLOSE;
	message.hdr.nlmsg_pid    = getpid();

	sendto(skfd,&message,message.hdr.nlmsg_len,0,(struct sockaddr*)(&kpeer),sizeof(kpeer));

	close(skfd);
	exit(0);
}

int main(void)
{
	struct sockaddr_nl local;
	struct sockaddr_nl kpeer;
	int kpeerlen;
	struct msg_to_kernel message;
	struct u_packet_info info;
	int sendlen = 0;
	int rcvlen    = 0;
	struct in_addr addr;

	skfd = socket(PF_NETLINK,SOCK_RAW,NL_IMP);
	if(skfd < 0)
	{
		printf("can't create a netlink socket \n");
		exit(0);
	}

	memset(&local,0,sizeof(local));
	local.nl_family    = AF_NETLINK;
	local.nl_pid    = getpid();
	local.nl_groups = 0;

	if(bind(skfd,(struct sockaddr *)&local,sizeof(local)) != 0)
	{
		printf("bind() error \n");
		return -1;
	}

	signal(SIGINT,sig_int);

	memset(&kpeer,0,sizeof(kpeer));
	kpeer.nl_family    = AF_NETLINK;
	kpeer.nl_pid    = 0;
	kpeer.nl_groups = 0;
	memset(&message,0,sizeof(message));
	message.hdr.nlmsg_len    = NLMSG_LENGTH(0);
	message.hdr.nlmsg_flags = 0;
	message.hdr.nlmsg_type     = IMP_U_PID;
	message.hdr.nlmsg_pid    = local.nl_pid;

	sendto(skfd,&message,message.hdr.nlmsg_len,0,(struct sockaddr*)&kpeer,sizeof(kpeer));

	while(1)
	{
		kpeerlen = sizeof(struct sockaddr_nl);
		//rcvlen = recvfrom(skfd, &info, sizeof(struct u_packet_info), 0, (struct sockaddr*)&kpeer, &kpeerlen);
		rcvlen = recvfrom(skfd, &info, 64, 0, (struct sockaddr*)&kpeer, &kpeerlen);

		printf("receive len:%d msg:%s\n", rcvlen, info.buf);
	}

	return 0;    
}