IP Data Structures

This digest is from Linux kernel ip.h, thanks to the open source 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 */

#defineIP_RF 0x8000/* Reserved Fragment flag * *

#defineIP_DF 0x4000/* dont fragment flag * *

#defineIP_MF 0x2000/* MORE Fragments flag * *

#defineIP_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];

  };

IP Data Structures