typedef struct _iphdr //定义IP首部
{
unsigned char h_lenver; //4位首部长度+4位IP版本号
unsigned char tos; //8位服务类型TOS
unsigned short total_len; //16位总长度（字节）
unsigned short ident; //16位标识
unsigned short frag_and_flags; //3位标志位
unsigned char ttl; //8位生存时间 TTL
unsigned char proto; //8位协议 (TCP, UDP 或其他)
unsigned short checksum; //16位IP首部校验和
unsigned int sourceIP; //32位源IP地址
unsigned int destIP; //32位目的IP地址
}IP_HEADER;
/*
* Structure of an internet header, naked of options.
*/
struct ip {
#ifdef _IP_VHL
u_char ip_vhl; /* version << 4 | header length >> 2 */
#else
#ifdef __REACTOS__
#if BYTE_ORDER == LITTLE_ENDIAN
u_char ip_hl : 4, /* header length */
ip_v : 4; /* version */
#endif
#if BYTE_ORDER == BIG_ENDIAN
u_char ip_v : 4, /* version */
ip_hl : 4; /* header length */
#endif
#else
#if BYTE_ORDER == LITTLE_ENDIAN
u_int ip_hl:4, /* header length */
ip_v:4; /* version */
#endif
#if BYTE_ORDER == BIG_ENDIAN
u_int ip_v:4, /* version */
ip_hl:4; /* header length */
#endif
#endif /* __REACTOS__ */
#endif /* not _IP_VHL */
u_char ip_tos; /* type of service */
u_short ip_len; /* total length */
u_short ip_id; /* identification */
u_short ip_off; /* fragment offset field */
#define IP_RF 0x8000 /* reserved fragment flag */
#define IP_DF 0x4000 /* don't fragment flag */
#define IP_MF 0x2000 /* more fragments flag */
#define IP_OFFMASK 0x1fff /* mask for fragmenting bits */
u_char ip_ttl; /* time to live */
u_char ip_p; /* protocol */
u_short ip_sum; /* checksum */
struct in_addr ip_src,ip_dst; /* source and dest address */
};
