网络编程:数据包的封装----libnet库

使用libnet库封装数据包
安装库sudo apt-get install libnet-dev
1、数据包内存初始化
libnet_t *libnet_init(int injection_type, char *device, char *err_buf)
2、构造数据包，由应用层UDP/TCP到MAC层的顺序构造
封装udp数据包的函数

libnet_ptag_t libnet_build_udp(u_int16_t sp, u_int16_t dp,u_int16_t len, u_int16_t sum,u_int8_t *payload, u_int32_t payload_s,libnet_t *l, libnet_ptag_t ptag)

封装IP数据报的函数

libnet_ptag_t libnet_build_ipv4(u_int16_t ip_len, u_int8_t tos,u_int16_t id, u_int16_t frag,u_int8_t ttl, u_int8_t prot,u_int16 sum, u_int32_t src,u_int32_t dst, u_int8_t *payload,u_int32_t payload_s,libnet_t *l, libnet_ptag_t ptag)

封装mac数据包的函数

libnet_ptag_t libnet_build_ethernet(u_int8_t *dst,u_int8_t *src,u_int16_t type,u_int8_t *payload,u_int32_t payload_s,libnet_t *l,libnet_ptag_t ptag)

3、发送数据

int libnet_write(libnet_t * l)

4、释放资源

void libnet_destroy(libnet_t *l);

代码示例:

#include <libnet.h>
#include <stdio.h>
#include <string.h>int main(int argc, char const *argv[])
{//1. 初始化libnet操作空间libnet_t *net = libnet_init(LIBNET_LINK_ADV, "ens33", NULL);if(net != NULL){printf("libnet init ok\n");// udp报文中的数据unsigned char data[] = "hello, window for libnet!";int datalen = strlen(data) % 2 == 0?strlen(data): strlen(data)+1;//2.构造各层的数据报(从应用层)//2.1 构造udpif(libnet_build_udp(9000, 8000, 8+datalen, 0, data, datalen, net, 0) == -1){printf("build udp fail!\n");goto freenet;}// 2.2 构造IP报文if(libnet_build_ipv4(20+8+datalen, 0, 0, 0, 32, 17, 0,inet_addr("10.35.184.140"),inet_addr("10.35.184.221"), NULL, 0, net, 0) == -1){printf("build ip fail!\n");goto freenet;}//2.3 构造mac报文if(libnet_build_ethernet("4c:e1:73:47:16:3a", "00:0c:29:b0:8f:42", 0x0800, NULL, 0, net, 0) == -1){printf("build ip fail!\n");goto freenet;}// 3 发送数据if(libnet_write(net) != -1){printf("send ok\n");}freenet:// 释放libnet空间libnet_destroy(net);}return 0;
}