netlink(三)-用户态发起会话

200阅读　0评论2023-08-04　zpf1218
分类：LINUX

用户态程序


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  1. #include <stdio.h>
  2. #include <stdlib.h>
  3. #include <sys/socket.h>
  4. #include <string.h>
  5. #include <linux/netlink.h>
  6. #include <stdint.h>
  7. #include <unistd.h>
  8. #include <fcntl.h>
  9. #include <errno.h>


  12. #define NETLINK_TEST 30
  13. #define MSG_LEN 100
  14. #define MAX_PLOAD 100
  15. #define USER_PORT 66
  16. typedef struct _user_msg_info
  17. {
  18.     struct nlmsghdr hdr;
  19.     char msg[MSG_LEN];
  20. } user_msg_info;

  22. int main(int argc,char **argv)
  23. {
  24.     int sockfd;
  25.     struct sockaddr_nl saddr, daddr;
  26.     struct nlmsghdr *nlh;
  27.     user_msg_info u_info;
  28.     char *msg = "hello kernel, I am user process!";
  29.     socklen_t len;

  31.     //创建socket SOCK_RAW|SOCK_NONBLOCK
  32.     sockfd = socket(AF_NETLINK,SOCK_RAW, NETLINK_TEST);
  33.  
  34.     //初始化目的地址
  35.     memset(&daddr, 0, sizeof(daddr));
  36.     daddr.nl_family = AF_NETLINK;
  37.     daddr.nl_pid = 0; // to kernel
  38.     daddr.nl_groups = 0;
  39.     
  40.     //初始化消息头
  41.     nlh = (struct nlmsghdr *)malloc(NLMSG_SPACE(MAX_PLOAD));
  42.     memset(nlh, 0, sizeof(struct nlmsghdr));
  43.     nlh->nlmsg_len = NLMSG_SPACE(MAX_PLOAD);
  44.     nlh->nlmsg_flags = 0;
  45.     nlh->nlmsg_type = 0;
  46.     nlh->nlmsg_seq = 0;
  47.     //nlh->nlmsg_pid = USER_PORT; //self port
  48.     nlh->nlmsg_pid = getpid();//我们希望得到内核回应，所以得告诉内核我们ID号

  50.     //设置消息内容
  51.     memcpy(NLMSG_DATA(nlh),msg,strlen(msg));

  53.     do
  54.     {
  55.         //发送消息
  56.         int ret = sendto(sockfd,nlh,nlh->nlmsg_len,0,(struct sockaddr *)&daddr,sizeof(struct sockaddr_nl));
  57.         if(ret < 0){
  58.             printf("sendto error, errno:%d \n", errno);
  59.             break;
  60.         }
  61.         printf("send to kernel :%s ret:%d nlmsg_len:%d \n",msg,ret, nlh->nlmsg_len);
  62.         
  63.         memset(&u_info, 0, sizeof(u_info));
  64.         len = sizeof(struct sockaddr_nl);
  65.         //接收消息
  66.         ret = recvfrom(sockfd,&u_info,sizeof(user_msg_info),0,(struct sockaddr *)&daddr,&len);
  67.         if(ret < 0){
  68.             printf("recvfrom error, errno:%d \n",errno);
  69.             break;
  70.         }
  71.         
  72.         printf("recv from kernel:%s ret:%d\n",u_info.msg,ret);
  73.     }while(0);
  74.     
  75.     free(nlh);
  76.     close(sockfd);
  77.     return 0;
  78. }

编译命令：

Gcc -o netlink_user netlink_user.c



内核态程序


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  1. #include <linux/init.h>
  2. #include <linux/module.h>
  3. #include <linux/types.h>
  4. #include <net/sock.h>
  5. #include <linux/netlink.h>

  7. #define NETLINK_TEST 30
  8. #define MSG_LEN 100
  9. #define USER_PORT 66

  11. struct sock *nlsk;

  13. extern struct net init_net;

  15. int send_usrmsg(char *pbuf, uint16_t len, int pid)
  16. {
  17.     struct sk_buff *nl_skb;
  18.     struct nlmsghdr *nlh; //消息头部

  20.     int ret;
  21.     //创建sk_buff
  22.     nl_skb = nlmsg_new(len, GFP_ATOMIC);
  23.     if(!nl_skb)
  24.     {
  25.         printk("netlink alloc failure\n");
  26.         return -1;
  27.     }
  28.     
  29.     /* 设置netlink消息头部 */
  30.     nlh = nlmsg_put(nl_skb, 0, 0, NETLINK_TEST, len, 0);
  31.     if(nlh == NULL)
  32.     {
  33.         printk("nlmsg_put failaure \n");
  34.         nlmsg_free(nl_skb);
  35.         return -1;
  36.     }
  37.  
  38.     /* 拷贝数据发送 */
  39.     memcpy(nlmsg_data(nlh), pbuf, len);
  40. ret = netlink_unicast(nlsk, nl_skb, pid, 0); //阻塞模式
  41.     //ret = netlink_unicast(nlsk, nl_skb, USER_PORT, MSG_DONTWAIT);
  42.     return ret;
  43. }

  45. static void netlink_rcv_msg(struct sk_buff *skb)
  46. {
  47.     struct nlmsghdr *nlh;
  48.     char *umsg = NULL;
  49.     char *kmsg = "hello users";
  50.     //从skb中获取data字段，并转换成nlh进行读取
  51.     nlh = nlmsg_hdr(skb);
  52.     //读取nlh后面的数据部分
  53.     umsg = NLMSG_DATA(nlh);
  54.     if(umsg){
  55.         printk("kernel recv from user: %s\n", umsg);
  56.         printk("port id :%d\n",NETLINK_CB(skb).portid);
  57.         send_usrmsg(kmsg, strlen(kmsg), nlh->nlmsg_pid); //给用户态发消息
  58.     }
  59.     
  60. }
  61. struct netlink_kernel_cfg cfg = {
  62.     .input = netlink_rcv_msg,
  63. };

  65. static int __init test_netlink_init(void)
  66. {
  67.     nlsk = (struct sock *)netlink_kernel_create(&init_net,NETLINK_TEST,&cfg);
  68.     return 0;
  69. }

  71. static void __exit test_netlink_exit(void)
  72. {
  73.      // 注销netlink协议
  74.     if(nlsk)
  75.     {
  76.         netlink_kernel_release(nlsk);
  77.         nlsk = NULL;
  78.     }
  79.     printk("exit......\n");
  80. }
  81. MODULE_LICENSE("GPL");
  82. module_init(test_netlink_init);
  83. module_exit(test_netlink_exit);

makefile 文件：

obj-m:=netlink_kernel.o     

                                  

CURRENT_PATH:=$(shell pwd)   

LINUX_KERNEL:=$(shell uname -r) 

LINUX_KERNEL_PATH:=/usr/src/kernels/$(LINUX_KERNEL) 

#linux-headers-                    

all:

       make -C $(LINUX_KERNEL_PATH) M=$(CURRENT_PATH) modules

clean:

       make -C $(LINUX_KERNEL_PATH) M=$(CURRENT_PATH) clean



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