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本文摘自 linux kernel ip.h,感谢开源的GNU
struct ip
{
#if __BYTE_ORDER == __LITTLE_ENDIAN
unsigned int ip_hl:4; /* header length */
unsigned int ip_v:4; /* version */
#endif
#if __BYTE_ORDER == __BIG_ENDIAN
unsigned int ip_v:4; /* version */
unsigned int ip_hl:4; /* header length */
#endif
u_int8_t 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 /* dont fragment flag */
#define IP_MF 0x2000 /* more fragments flag */
#define IP_OFFMASK 0x1fff /* mask for fragmenting bits */
u_int8_t ip_ttl; /* time to live */
u_int8_t ip_p; /* protocol */
u_short ip_sum; /* checksum */
struct in_addr ip_src, ip_dst; /* source and dest address */
};
struct timestamp
{
u_int8_t len;
u_int8_t ptr;
#if __BYTE_ORDER == __LITTLE_ENDIAN
unsigned int flags:4;
unsigned int overflow:4;
#elif __BYTE_ORDER == __BIG_ENDIAN
unsigned int overflow:4;
unsigned int flags:4;
#else
# error "Please fix <bits/endian.h>"
#endif
u_int32_t data[9];
};
struct iphdr
{
#if __BYTE_ORDER == __LITTLE_ENDIAN
unsigned int ihl:4;
unsigned int version:4;
#elif __BYTE_ORDER == __BIG_ENDIAN
unsigned int version:4;
unsigned int ihl:4;
#else
# error "Please fix <bits/endian.h>"
#endif
u_int8_t tos;
u_int16_t tot_len;
u_int16_t id;
u_int16_t frag_off;
u_int8_t ttl;
u_int8_t protocol;
u_int16_t check;
u_int32_t saddr;
u_int32_t daddr;
/*The options start here. */
};
/*
* Time stamp option structure.
*/
struct ip_timestamp
{
u_int8_t ipt_code; /* IPOPT_TS */
u_int8_t ipt_len; /* size of structure (variable) */
u_int8_t ipt_ptr; /* index of current entry */
#if __BYTE_ORDER == __LITTLE_ENDIAN
unsigned int ipt_flg:4; /* flags, see below */
unsigned int ipt_oflw:4; /* overflow counter */
#endif
#if __BYTE_ORDER == __BIG_ENDIAN
unsigned int ipt_oflw:4; /* overflow counter */
unsigned int ipt_flg:4; /* flags, see below */
#endif
u_int32_t data[9];
};
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原文地址：http://www.cnblogs.com/guxuanqing/p/4812105.html
