linux socket实现内核态和用户态通信

最近有一个的需求，需要将一些linux用户态的命令做成自动化。
比如在用户态执行lspci命令，判断获取的设备中是否有某个型号的pci卡，这就需要linux内核态和用户态交互。实现的方法是通过linux内核态编程。在内核驱动中通过socket发送一个用户态请求,server端接收到请求并执行，执行后将结果返回给内核驱动，驱动中判断结果。

内核态socket编程的过程和用户态下的socket编程流程一样，但是接口不同。Kernel提供了一组内核态的socket API，基本上在用户态的sockt API在内核中都有对应的API。

在net/socket.c中可以看到导出符号：
主要实现：
server端代码：

#include <stdio.h>#include <string.h>#include <unistd.h>#include <ctype.h>#include <sys/socket.h>#include <netinet/in.h>#include <arpa/inet.h>#include <stdlib.h>#include <errno.h>#include "public.h"#include <sys/time.h>#include <sys/ioctl.h>#include <fcntl.h>#include <netinet/in.h>#include <netinet/tcp.h>#include <errno.h>int server_listen_fd;int server_accept_fd;int port= 2002;int get_current_time(){    struct timeval stime;    gettimeofday( &stime, NULL);    return stime.tv_sec * 1000000 + stime.tv_usec;}int excute_cmd(char* cmd, char* result) {    char buffer[1024];                                                                                                 //定义缓冲区                                                                                                 FILE* pipe = popen(cmd, "r");      if (!pipe)        return 1;                                while (!feof(pipe)) {        if (fgets(buffer, 1024, pipe)){               strcat(result,buffer);        }    }    pclose(pipe);                                                                                                             //关闭管道        return 0;                                                                                                                       }int server_recv(int fd, cmd_request *request, int len_recv, int timeout){       int len;    unsigned int recved = 0;    unsigned long last_time = get_current_time();    int temp_time;    printf("server recv start %d time:%d!\n", len_recv, timeout);    while (1) {        temp_time =  get_current_time() - last_time;        if (get_current_time() - last_time > timeout * 1000) {            printf("server recv timeout!\n");            break;        }        len = recv(fd, request->reqbuf + recved, len_recv - recved, MSG_DONTWAIT);        printf("recv buf is %s:\n",request->reqbuf);        if (len <= 0) {            printf("server recv error!\n");            return  -1;        }        printf("server has recv %d\n",len);        recved += len;        if (recved >= len_recv) {            printf("recved %d bytes!\n", recved);            return recved;        }    }    return 0;}int server_accept(){       int size;    int opt = 1;    int flags;    struct sockaddr_in server_accept_addr;    bzero(&server_accept_addr, sizeof(server_accept_addr));    size = sizeof(server_accept_addr);    flags = fcntl(server_accept_fd, F_GETFL, 0);    fcntl(server_accept_fd, F_SETFL, flags | O_NONBLOCK);    setsockopt(server_accept_fd, IPPROTO_TCP, TCP_NODELAY, (char *)&opt,sizeof(int));Step1:    server_accept_fd = accept(server_listen_fd, (struct sockaddr*)&server_accept_addr, &size);    if (server_accept_fd < 0) {           if (errno == EAGAIN) {            goto Step1;        }        perror("error:socket accept1 exited!\n");                         exit(1);                     } }int server_init(char *ip){    int opt =1;    int flags;    struct sockaddr_in server_listen_addr;    bzero(&server_listen_addr, sizeof(server_listen_addr));    server_listen_addr.sin_family = AF_INET;         server_listen_addr.sin_addr.s_addr = inet_addr(ip);    server_listen_addr.sin_port = htons(port);    setsockopt(server_listen_fd, SOL_SOCKET, SO_REUSEADDR,(char *)&opt, sizeof(int));    if (bind(server_listen_fd, (struct sockaddr*)&server_listen_addr,        sizeof(server_listen_addr)) == -1) {        perror("can't to bind");        exit(1);    }    flags = fcntl(server_listen_fd, F_GETFL, 0);    fcntl(server_listen_fd, F_SETFL, flags | O_NONBLOCK);    if (listen(server_listen_fd, 10) == -1) {        perror("can't to bind");        exit(1);    }    return 0;}int main(int argc,char *argv[]){    int ret;    int flags;    int timeout = 1000;    struct sockaddr_in server_send_addr;    cmd_request  request;    cmd_response response;    //printf("argv is %s\n", argv[1]);    if (!argv[1]) {        printf("need ip!\n");        return -1;    }    bzero(&server_send_addr, sizeof(server_send_addr));    memset(&request, 0 ,sizeof(request));    memset(&response, 0 ,sizeof(response));    server_listen_fd = socket(AF_INET,SOCK_STREAM,0);    if (-1 == server_listen_fd) {        perror("fail to create socket!");        exit(1);    }    server_init(argv[1]);    while (1) {        printf("server socket begin accept:\n");        server_accept();        //recv        ret = server_recv(server_accept_fd, &request, sizeof(cmd_request), timeout);        if (ret <= 0) {            printf("server recv error!\n");        }         //ret = recv(server_accept_fd, request.reqbuf, 1024, 0);        printf("DATA:[%s]\n", request.reqbuf);        excute_cmd(request.reqbuf,response.rspbuf);        printf("the result is %s",response.rspbuf);         //send        ret = send(server_accept_fd, response.rspbuf, sizeof(response.rspbuf), 0);        if (ret <= 0){            printf("send %d failed!\n",ret);        }    }    close(server_accept_fd);    return 0;}

客户端实现：

#include <linux/module.h>#include <linux/init.h>#include <linux/socket.h>#include <net/sock.h>#include <linux/in.h>#include <linux/tcp.h>#include <linux/in.h>#include <linux/inet.h>#include <linux/time.h>#include "public.h"int port_id = 2002;char * dst_ip = "192.168.0.103";module_param(dst_ip, charp, S_IRUSR);cmd_request *prequest;cmd_response *presponse;int client_init(void);int plugin_get_current_time(){    struct timeval stime;    do_gettimeofday(&stime);    return (stime.tv_sec * 1000000 + stime.tv_usec) / 1000;}int client_send(struct socket *sock, unsigned char *pbufsend, int len_send){    int len;    int sended = 0;    unsigned long last_time = plugin_get_current_time();    struct kvec vec;    struct msghdr msg;    unsigned short timeout = 1000;    while (1) {        if (plugin_get_current_time() - last_time > timeout){            printk("kernel send msg timeout!\n");            break;        }        vec.iov_base = pbufsend + sended;        vec.iov_len = len_send - sended;        msg.msg_flags = 0;        len = kernel_sendmsg(sock, &msg, &vec, 1, len_send - sended);        if (len < 0){            if (len == -EWOULDBLOCK){                printk("kernel send msg would block!\n");                continue;            } else {                printk("kernel send msg failed with < 0!\n");                return -EINVAL;            }        } else if (len == 0){            printk("kernel send msg failed with = 0!\n");            return -EINVAL;        }        sended += len;        if (sended >= len_send) {            printk("kernel send %d bytes!\n", sended);            return sended;        }    }}int client_init(void){       struct socket *sock;    struct sockaddr_in s_addr;    int ret = 0;    sock = (struct socket*)kmalloc(sizeof(struct socket), GFP_KERNEL);    memset(&s_addr, 0, sizeof(s_addr));    s_addr.sin_family = AF_INET;    s_addr.sin_port = htons(port_id);    s_addr.sin_addr.s_addr = in_aton(dst_ip);    /*create socket*/    ret = sock_create_kern(AF_INET, SOCK_STREAM, 0, &sock);    if (ret) {        printk("socket create failed\n");        return ret;    }    printk("create socket ok!\n");    /*connect server*/    ret = sock->ops->connect(sock, (struct sockaddr*)&s_addr, sizeof(struct sockaddr_in), 0);    if (ret) {        printk("socket connect server failed!\n");        return ret;    }    printk("connect server ok!\n");     // set opt    int opt = 1;    int flags;    kernel_setsockopt(sock, IPPROTO_TCP, TCP_NODELAY, (char *)&opt, sizeof(int));    flags = kernel_sock_ioctl(sock, F_GETFL, 0);    kernel_sock_ioctl(sock, F_SETFL, flags | O_NONBLOCK);    /*kmalloc sendbuf*/    char *sendbuf = NULL;    sendbuf = kmalloc(1024, GFP_KERNEL);    memset(sendbuf, 0, 1024);    strcpy(sendbuf, "lspci");    printk("the request is %s, size is %d\n", sendbuf, sizeof(sendbuf));    ret = client_send(sock, sendbuf, 1024);    if (ret <= 0) {        printk("client send failed !\n");        return -EINVAL;    }    recvbuf = kmalloc(1024, GFP_KERNEL);    memset(recvbuf, 0, 1024);    memset(&msg, 0, sizeof(msg));    memset(&vec, 0, sizeof(vec));    vec.iov_base = recvbuf;     vec.iov_len=1024;    int count = 0;    while (count < 1000) {        ret = kernel_recvmsg(sock, &msg, &vec, 1, 1024, 0);        if(ret < 0){            printk("client:kernel_sendmsg error!\n");            return ret;        } else if (ret > 0) {            printk("recv message %s\n",recvbuf);            break;        }        count ++;    }    if (count >= 1000)        printk("kernel recv msg timeout!\n");    //判断结果是否符合预期    char *expect = "PCI";    if (strstr(recvbuf, expect) != NULL) {        printk("lspci test pass!\n");    }    return ret;}#if 0int tc_run(skip_tc *pskip_tc){    socket *psock;    pskip_tc->desc = psock;    client_init();    client_recv_and_send(pskip_tc,pskip_tc->request,sizeof(cmd_request),pskip_tc->response,sizeof(cmd_response));}#endifstatic int __init plugin_init(void){    printk("hello, plugin!\n");     client_init();    return 0;}static void __exit plugin_exit(void){    printk("goodbye,plugin!\n");}module_init(plugin_init);module_exit(plugin_exit);MODULE_LICENSE("GPL");

使用示例:
服务端：

客户端：