Linux 内核态 Socket TCP 编程

标签: linux
c++ socket编程 c++ sock linux下socket
c++
转自: /article/9012996.html

1.内核态 socket API

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中可以看到如下导出符号：

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EXPORT_SYMBOL(kernel_sendmsg);

EXPORT_SYMBOL(kernel_recvmsg);

EXPORT_SYMBOL(sock_create_kern);

EXPORT_SYMBOL(sock_release);

EXPORT_SYMBOL(kernel_bind);

EXPORT_SYMBOL(kernel_listen);

EXPORT_SYMBOL(kernel_accept);

EXPORT_SYMBOL(kernel_connect);

EXPORT_SYMBOL(kernel_getsockname);

EXPORT_SYMBOL(kernel_getpeername);

EXPORT_SYMBOL(kernel_getsockopt);

EXPORT_SYMBOL(kernel_setsockopt);

EXPORT_SYMBOL(kernel_sendpage);

EXPORT_SYMBOL(kernel_sock_ioctl);

EXPORT_SYMBOL(kernel_sock_shutdown);

下面以两个内核模块间利用socket进行通信为例来讲述内核态下socket编程。

server内核模块功能是：建立套接字，绑定端口，监听端口，等待client的连接，并接收client发来的数据。

client内核模块功能是：建立套接字，和server建立连接，并向server发送数据。

2. server模块

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/*server.c*/

#include<linux/in.h>

#include<linux/inet.h>

#include<linux/socket.h>

#include<net/sock.h>

#include<linux/init.h>

#include<linux/module.h>

int myserver(void){

struct socket *sock,*client_sock;

struct sockaddr_in s_addr;

unsigned short portnum=0x8888;

int ret=0;

memset(&s_addr,0,sizeof(s_addr));

s_addr.sin_family=AF_INET;

s_addr.sin_port=htons(portnum);

s_addr.sin_addr.s_addr=htonl(INADDR_ANY);

sock=(struct socket *)kmalloc(sizeof(struct socket),GFP_KERNEL);

client_sock=(struct socket *)kmalloc(sizeof(struct socket),GFP_KERNEL);

/*create a socket*/

ret=sock_create_kern(AF_INET, SOCK_STREAM,0,&sock);

if(ret){

printk("server:socket_create error!\n");

}

printk("server:socket_create ok!\n");

/*bind the socket*/

ret=sock->ops->bind(sock,(struct sockaddr *)&s_addr,sizeof(struct sockaddr_in));

if(ret<0){

printk("server: bind error\n");

return ret;

}

printk("server:bind ok!\n");

/*listen*/

ret=sock->ops->listen(sock,10);

if(ret<0){

printk("server: listen error\n");

return ret;

}

printk("server:listen ok!\n");

ret=sock->ops->accept(sock,client_sock,10);if(ret<0){

printk("server:accept error!\n");

return ret;

}

printk("server: accept ok, Connection Established\n");

/*kmalloc a receive buffer*/

char *recvbuf=NULL;

recvbuf=kmalloc(1024,GFP_KERNEL);

if(recvbuf==NULL){

printk("server: recvbuf kmalloc error!\n");

return -1;

}

memset(recvbuf, 0, sizeof(recvbuf));

/*receive message from client*/

struct kvec vec;

struct msghdr msg;

memset(&vec,0,sizeof(vec));

memset(&msg,0,sizeof(msg));

vec.iov_base=recvbuf;

vec.iov_len=1024;

ret=kernel_recvmsg(client_sock,&msg,&vec,1,1024,0); /*receive message*/

printk("receive message:\n %s\n",recvbuf);

/*release socket*/

sock_release(sock);

sock_release(client_sock);

return ret;

}

static int server_init(void){

printk("server init:\n");

return (myserver());

}

static void server_exit(void){

printk("good bye\n");

}

module_init(server_init);

module_exit(server_exit);

MODULE_LICENSE("GPL");

3.client模块

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/*client.c*/

#include<linux/in.h>

#include<linux/inet.h>

#include<linux/socket.h>

#include<net/sock.h>

#include<linux/init.h>

#include<linux/module.h>

int myclient(void){

struct socket *sock;

struct sockaddr_in s_addr;

unsigned short portnum=0x8888;

int ret=0;

memset(&s_addr,0,sizeof(s_addr));

s_addr.sin_family=AF_INET;

s_addr.sin_port=htons(portnum);

s_addr.sin_addr.s_addr=in_aton("192.168.209.134"); /*server ip is 192.168.209.134*/

sock=(struct socket *)kmalloc(sizeof(struct socket),GFP_KERNEL);

/*create a socket*/

ret=sock_create_kern(AF_INET, SOCK_STREAM,0,&sock);

if(ret<0){

printk("client:socket create error!\n");

return ret;

}

printk("client: socket create ok!\n");

/*connect server*/

ret=sock->ops->connect(sock,(struct sockaddr *)&s_addr, sizeof(s_addr),0);

if(ret!=0){

printk("client:connect error!\n");

return ret;

}

printk("client:connect ok!\n");

/*kmalloc sendbuf*/

char *sendbuf=NULL;

sendbuf=kmalloc(1024,GFP_KERNEL);

if(sendbuf==NULL){

printk("client: sendbuf kmalloc error!\n");

return -1;

}

memset(sendbuf,1,1024);

struct kvec vec;

struct msghdr msg;

vec.iov_base=sendbuf;

vec.iov_len=1024;

memset(&msg,0,sizeof(msg));

ret=kernel_sendmsg(sock,&msg,&vec,1,1024); /*send message */

if(ret<0){

printk("client: kernel_sendmsg error!\n");

return ret;

}else if(ret!=1024){

printk("client: ret!=1024");

}

printk("client:send ok!\n");

return ret;

}

static int client_init(void){

printk("client:init\n");

return (myclient());

}

static void client_exit(void){

printk("client exit!\n");

}

module_init(client_init);

module_exit(client_exit);

MODULE_LICENSE("GPL");