tcp udp数据报定义结构体

文章链接：https://codemouse.online/archives/2020-06-30-21-08-22

tcp udp数据报定义结构体

由于结构体写在结构体里面容易出现结构体内存对齐问题，需要将对齐值改为1，防止出错。

#pragma pack（1） //设置对齐数

udp报文头定义：

struct udphdr { unsigned short sport; unsigned short dport; unsigned short length; unsigned short check; };

tcp报文头定义：

struct tcphdr { unsigned short sport; unsigned short dport; unsigned int seq; unsigned int ack; unsigned char hdrlen:4 resc:4; unsigned char cwr:1, ece:1, urg:1, ack:1, psh:1, rst:1, syn:1, fin:1; unsigned short wsize; unsigned short check; unsigned short upoint; unsigned char options[0]; };

#define ETH_LENGTH 6 struct ethhdr { unsigned char dest[ETH_LENGTH]; unsigned char src[ETH_LENGTH]; unsigned short proto; };

以太网帧格式与ip头格式的定义：

struct iphdr { unsigned char version:4, hdrlen:4; unsigned char tos; // unsigned short tot_len; unsigned short id; unsigned short flag:3, offset:13; unsigned char ttl; unsigned char proto; unsigned short check; unsigned int sip; unsigned int dip; };

udp数据报定义：

struct udppkt { struct ethhdr eh; struct iphdr ip; struct udphdr udp; unsigned char body[0]; };

tcp数据报定义：

struct tcppkt { struct ethhdr eh; struct iphdr ip; struct tcphdr tcp; unsigned char body[0]; };