2.6.27内核 netlink socket实现内核和用户的通信

三天的努力，终于搞定了自己需要的这种通信机制：由内核态向用户态反馈信息；

先看代码，内核的：

#include <linux/init.h> #include <linux/module.h> #include <linux/timer.h> #include <linux/time.h> #include <linux/types.h>#include <net/sock.h>#include <net/netlink.h> //it include linux/netlink.h#define NETLINK_TEST 17#define MAX_MSGSIZE 1024struct sock *nl_sk = NULL;// Get string's lengthint stringlength(char *s){int slen = 0;for(; *s; s++){ slen++; }return slen;}// Send message by netlinkvoid sendnlmsg(char *message) {struct sk_buff *skb;struct nlmsghdr *nlh;int len = NLMSG_SPACE(MAX_MSGSIZE);int slen = 0;if(!message || !nl_sk){ return; }// Allocate a new sk_bufferskb = alloc_skb(len, GFP_KERNEL);if(!skb){printk(KERN_ERR "my_net_link: alloc_skb Error./n");return;}slen = stringlength(message); //Initialize the header of netlink messagenlh = nlmsg_put(skb, 0, 0, 0, MAX_MSGSIZE, 0);NETLINK_CB(skb).pid = 0; // from kernel NETLINK_CB(skb).dst_group = 1; // multi castmessage[slen] = '/0';memcpy(NLMSG_DATA(nlh), message, slen+1); printk("my_net_link: send message '%s'./n", (char *)NLMSG_DATA(nlh));//send message by multi cast netlink_broadcast(nl_sk, skb, 0, 1, GFP_KERNEL); return;}// Initialize netlinkint netlink_init(void){ int i = 10; struct completion cmpl; nl_sk = netlink_kernel_create(&init_net, NETLINK_TEST, 1, NULL, NULL, THIS_MODULE);if(!nl_sk){printk(KERN_ERR "my_net_link: create netlink socket error./n");return 1;}printk("my_net_link: create netlink socket ok./n"); while(i--){ init_completion(&cmpl); wait_for_completion_timeout(&cmpl, 3 * HZ); sendnlmsg("I am from kernel!"); }return 0;}static void netlink_exit(void) { if(nl_sk != NULL){ sock_release(nl_sk->sk_socket); }printk("my_net_link: self module exited/n"); }module_init(netlink_init); module_exit(netlink_exit); MODULE_AUTHOR("donglp"); MODULE_LICENSE("GPL");

 

用户的：

#include <sys/stat.h>#include <unistd.h>#include <stdio.h>#include <stdlib.h>#include <sys/socket.h>#include <sys/types.h>#include <string.h>#include <asm/types.h>#include <linux/netlink.h>#include <linux/socket.h>#include <errno.h>#define NETLINK_TEST 17#define MAX_PAYLOAD 1024 // maximum payload sizeint main(int argc, char* argv[]){ struct sockaddr_nl src_addr, dest_addr; struct nlmsghdr *nlh = NULL; struct iovec iov; struct msghdr msg; int sock_fd, retval; // Create a socket sock_fd = socket(PF_NETLINK, SOCK_RAW, NETLINK_TEST); if(sock_fd == -1){ printf("error getting socket: %s", strerror(errno)); return -1; } // To prepare binding memset(&src_addr, 0, sizeof(src_addr)); src_addr.nl_family = PF_NETLINK; src_addr.nl_pid = getpid(); // self pid src_addr.nl_groups = 1; // multi cast retval = bind(sock_fd, (struct sockaddr*)&src_addr, sizeof(src_addr)); if(retval < 0){ printf("bind failed: %s", strerror(errno)); close(sock_fd); return -1; } // To prepare recvmsg nlh = (struct nlmsghdr *)malloc(NLMSG_SPACE(MAX_PAYLOAD)); if(!nlh){ printf("malloc nlmsghdr error!/n"); close(sock_fd); return -1; } memset(nlh, 0, NLMSG_SPACE(MAX_PAYLOAD)); iov.iov_base = (void *)nlh; iov.iov_len = NLMSG_SPACE(MAX_PAYLOAD); memset(&msg, 0, sizeof(msg)); memset(&dest_addr, 0, sizeof(dest_addr)); msg.msg_name = (void *)&dest_addr; msg.msg_namelen = sizeof(dest_addr); msg.msg_iov = &iov; msg.msg_iovlen = 1; // Read message from kernel while(1){ recvmsg(sock_fd, &msg, 0); printf("Received message: %s/n", NLMSG_DATA(nlh)); } close(sock_fd); return 0;}

 

Makefile文件：

obj-m := self.oKERNELBUILD := /lib/modules/`uname -r`/builddefault:@echo " BUILD kmod"@make -C $(KERNELBUILD) M=$(shell pwd) modulesgcc -o u u.cclean:@echo " CLEAN kmod"@rm -rf *.o@rm -rf .depend .*.cmd *.ko *.mod.c .tmp_versions *.symvers .*.d

 

编译方法：直接make

 

如何看效果：

必须先运行insmod self.ko 

然后在另外一个终端运行./u

 

就能看到效果，关注dmesg信息和./u显示出来的信息；

 

 

这里有篇文章，实现了用户和内核之间的交互式通信：

http://prolqspace.spaces.live.com/blog/cns!7240DE3B63F5B841!939.entry