下文摘自：红黑联盟
TCP/IP协议头部结构体简析
// i386 is little_endian. #ifndef LITTLE_ENDIAN #define LITTLE_ENDIAN (1) //BYTE ORDER #else #error Redefine LITTLE_ORDER #endif //Mac头部，总长度14字节 typedef struct _eth_hdr { unsigned char dstmac[6]; //目标mac地址 unsigned char srcmac[6]; //源mac地址 unsigned short eth_type; //以太网类型 }eth_hdr; //IP头部，总长度20字节 typedef struct _ip_hdr { #if LITTLE_ENDIAN unsigned char ihl:4; //首部长度 unsigned char version:4, //版本 #else www.2cto.com unsigned char version:4, //版本 unsigned char ihl:4; //首部长度 #endif unsigned char tos; //服务类型 unsigned short tot_len; //总长度 unsigned short id; //标志 unsigned short frag_off; //分片偏移 unsigned char ttl; //生存时间 unsigned char protocol; //协议 unsigned short chk_sum; //检验和 struct in_addr srcaddr; //源IP地址 struct in_addr dstaddr; //目的IP地址 }ip_hdr; //TCP头部，总长度20字节 typedef struct _tcp_hdr { unsigned short src_port; //源端口号 unsigned short dst_port; //目的端口号 unsigned int seq_no; //序列号 unsigned int ack_no; //确认号 #if LITTLE_ENDIAN unsigned char reserved_1:4; //保留6位中的4位首部长度 unsigned char thl:4; //tcp头部长度 unsigned char flag:6; //6位标志 unsigned char reseverd_2:2; //保留6位中的2位 #else unsigned char thl:4; //tcp头部长度 unsigned char reserved_1:4; //保留6位中的4位首部长度 unsigned char reseverd_2:2; //保留6位中的2位 unsigned char flag:6; //6位标志 #endif unsigned short wnd_size; //16位窗口大小 unsigned short chk_sum; //16位TCP检验和 unsigned short urgt_p; //16为紧急指针 }tcp_hdr; www.2cto.com //UDP头部，总长度8字节 typedef struct _udp_hdr { unsigned short src_port; //远端口号 unsigned short dst_port; //目的端口号 unsigned short uhl; //udp头部长度 unsigned short chk_sum; //16位udp检验和 }udp_hdr; //ICMP头部，总长度4字节 typedef struct _icmp_hdr { unsigned char icmp_type; //类型 unsigned char code; //代码 unsigned short chk_sum; //16位检验和 }icmp_hdr;
作者 辛勤耕耘