LINUX 虚拟网卡tun例子

/**
 *  linux TUN 例子 代码来至
 *  http://hi.baidu.com/zkheartboy/blog/item/e96acf33508e4a40ad4b5f88.html和
 *  http://blog.csdn.net/Z_man/archive/2009/05/26/4216530.aspx
 *  建立一个tun0的虚拟网卡进行通信，程序关闭后将消失。
 *  ping 10.0.0.1
 *  Documentation/networking/tuntap.txt
 *  br_select.c bridge based on select system call.
 *  br_sigio.c  bridge based on async io and SIGIO signal.
 *  http://hi.baidu.com/zkheartboy/blog/item/e96acf33508e4a40ad4b5f88.html
 *  http://blogold.chinaunix.net/u3/114446/showart_2245279.html
 *  http://www.ibm.com/developerworks/cn/linux/l-tuntap/index.html
 */

#include   
#include   
#include   
#include   
#include   
#include   
#include   
#include   
#include   
#include 

#include 
#include 
#include 
  
/** 
 *  激活接口 
 */  
int interface_up(char *interface_name)  
{  
    int s;  
  
    if((s = socket(PF_INET,SOCK_STREAM,0)) < 0)  
    {  
        printf("Error create socket :%d\n", errno);  
        return -1;  
    }  
  
    struct ifreq ifr;  
    strcpy(ifr.ifr_name,interface_name);  
  
    short flag;  
    flag = IFF_UP;  
    if(ioctl(s, SIOCGIFFLAGS, &ifr) < 0)  
    {  
        printf("Error up %s :%d\n",interface_name, errno);  
        return -1;  
    }  
  
    ifr.ifr_ifru.ifru_flags |= flag;  
  
    if(ioctl(s, SIOCSIFFLAGS, &ifr) < 0)  
    {  
        printf("Error up %s :%d\n",interface_name, errno);  
        return -1;  
    }  
  
    return 0;  
  
}  

#if 0
/** 
 *  设置接口ip地址 
 */  
int set_ipaddr(char *interface_name, char *ip)  
{  
    int s;  
  
    if((s = socket(PF_INET, SOCK_STREAM, 0)) < 0)  
    {  
        printf("Error up %s :%d\n",interface_name, errno);  
        return -1;  
    }  
  
    struct ifreq ifr;  
    strcpy(ifr.ifr_name, interface_name);  
  
    struct sockaddr_in addr;  
    bzero(&addr, sizeof(struct sockaddr_in));  
    addr.sin_family = PF_INET;  
    inet_aton(ip, &addr.sin_addr);  
  
    memcpy(&ifr.ifr_ifru.ifru_addr, &addr, sizeof(struct sockaddr_in));  
  
    if(ioctl(s, SIOCSIFADDR, &ifr) < 0)  
    {  
        printf("Error set %s ip :%d\n",interface_name, errno);  
        return -1;  
    }  
  
    return 0;  
}
#endif
  
/** 
 *  创建接口 
 */  
int tun_create(char *dev, int flags)  
{  
    struct ifreq ifr;  
    int fd, err;  
  
    if ((fd = open("/dev/net/tun", O_RDWR)) < 0)  
    {  
        printf("Error :%d\n", errno);  
        return -1;  
    }  
  
    memset(&ifr, 0, sizeof(ifr));  
    ifr.ifr_flags |= flags;  
  
    if (*dev != '\0')  
    {  
        strncpy(ifr.ifr_name, dev, IFNAMSIZ);  
    }  
  
    if ((err = ioctl(fd, TUNSETIFF, (void *)&ifr)) < 0)   
    {  
        printf("Error :%d\n", errno);  
        close(fd);  
        return -1;  
    }  
  
    strcpy(dev, ifr.ifr_name);  
  
    return fd;  
}  
  
/** 
 *  增加到10.0.0.1的路由 
 *  同命令:route add 10.0.0.1 dev tun0 
 */  
int route_add(char * interface_name)  
{  
    int skfd;  
    struct rtentry rt;  
  
    struct sockaddr_in dst;  
    //struct sockaddr_in gw;  
    struct sockaddr_in genmask;  
  
    memset(&rt, 0, sizeof(rt));  
  
    genmask.sin_addr.s_addr = inet_addr("255.255.255.255");  
  
    bzero(&dst,sizeof(struct sockaddr_in));  
    dst.sin_family = PF_INET;  
    dst.sin_addr.s_addr = inet_addr("10.0.0.1");  
  
    rt.rt_metric = 0;  
    rt.rt_dst = *(struct sockaddr*) &dst;  
    rt.rt_genmask = *(struct sockaddr*) &genmask;  
  
    rt.rt_dev = interface_name;  
    rt.rt_flags = RTF_UP | RTF_HOST ;  
  
    skfd = socket(AF_INET, SOCK_DGRAM, 0);  
    if(ioctl(skfd, SIOCADDRT, &rt) < 0)   
    {  
        printf("Error route add :%d\n", errno);  
        return -1;  
    }
    return 0;
}  
int main(int argc, char *argv[])  
{  
    int tun, ret;  
    char tun_name[IFNAMSIZ];  
    unsigned char buf[4096];  
    unsigned char ip[4];  
  
    tun_name[0] = '\0';  
    tun = tun_create(tun_name, IFF_TUN | IFF_NO_PI);  
    if (tun < 0)   
    {  
        return 1;  
    }  
    printf("TUN name is %s\n", tun_name);  
  
    //激活虚拟网卡增加到虚拟网卡的路由  
    interface_up(tun_name);  
    route_add(tun_name);  
  
    while (1) {  
  
        ret = read(tun, buf, sizeof(buf));  
        printf("read %d bytes\n", ret);  
        int i;  
        for(i=0;i

main中while循环代码简答地处理了ICMP的ECHO包，并回应以ECHO REPLY。

测试方法：

1 先编译运行此程序，监听数据的读写。

2 开启另外一个终端，执行ping命令,就是本地发一个测试包到10.0.0.1

即可看到收到和接收的数据包IP包了。

http://blog.csdn.net/xuxinyl/article/details/6454536