常用tcp/ip协议头介绍

嘿嘿，原帖在这里 http://www.cnblogs.com/dubingsky/archive/2010/01/21/1653650.html

我这里自己参考修改了下↖(^ω^)↗

//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
struct ip_hdr{
#if BYTE_ORDER == LITTLE_ENDIAN
    unsigned char    ip_hl:4,    /*header length*/
                    ip_v:4;        /*version */
#endif
#if BYTE_ORDER == BIG_ENDIAN
    unsigned char    ip_v:4,        /*version */
                    ip_hl:4;    /*header length*/
#endif
    unsigned char    ip_tos;        /*type of service */
    short    ip_len;        /*total length */
    unsigned short    ip_id;        /*identification */
    short    ip_off;        /*fragment offset field */
#define    IP_DF    0x4000    /*dont fragment flag */
#define    IP_MF    0x2000    /*more fragments flag*/
#define IP_OFFMASK 0x1fff    /*mask for fragment bits*/
    unsigned char    ip_ttl;        /*time to live*/
    unsigned char    ip_p;        /*protocol */
    unsigned short    ip_sum;        /*checksum*/
    struct in_addr ip_src,ip_dst;    /*source and dest address */
};

//TCP头部，总长度20字节
struct tcp_hdr{
    unsigned short th_sport;    /*source port*/
    unsigned short th_dport;    /*destination port*/
    unsigned int th_seq;        /*sequence number*/
    unsigned int th_ack;        /*acknowledgement number*/
#if BYTE_ORDER == LITTLE_ENDIAN
    unsigned char     th_x2:4,    /*(unused)*/
                    th_off:4;    /*data offset*/
#endif
#if BYTE_ORDER == BIG_ENDIAN
    unsigned char     th_off:4,    /*data offset */
                    th_x2:4;    /*(unused)*/
#endif
    unsigned char    th_flags;    /*ACK,FIN,PUSH,RST,SYN,URG*/
    unsigned short    th_win;        /*advertised window */
    unsigned short     th_sum;        /*checksum*/
    unsigned short     th_urp;        /*urgent offset*/
};

//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;