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 <fcntl.h>#include <stdio.h>#include <string.h>#include <sys/socket.h>#include <sys/ioctl.h>#include <linux/if.h>#include <linux/if_tun.h>#include <sys/types.h>#include <errno.h>#include <net/route.h>/** * 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 :%m/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 :%m/n",interface_name, errno); return -1; } ifr.ifr_ifru.ifru_flags |= flag; if(ioctl(s, SIOCSIFFLAGS, &ifr) < 0) { printf("Error up %s :%m/n",interface_name, errno); return -1; } return 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 :%m/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 :%m/n",interface_name, errno); return -1; } return 0;}/** * 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 :%m/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 :%m/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 :%m/n", errno); return -1; }}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<ret;i++) { printf("%02x ",buf[i]); } printf("/n"); if (ret < 0) break; memcpy(ip, &buf[12], 4); memcpy(&buf[12], &buf[16], 4); memcpy(&buf[16], ip, 4); buf[20] = 0; *((unsigned short*)&buf[22]) += 8; ret = write(tun, buf, ret); printf("write %d bytes/n", ret); } return 0;}

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。