几个常用且重要的网络数据结构

来源：互联网发布：磁性自瞄源码原理编辑：程序博客网时间：2024/04/29 22:38

当接收到原始数据包后，为了不用指针定位所需要的字段，LINUX其实定义好了几个常用的结构。暂时先记录下来。

1，IP数据包的分析： #include <netinet/ip.h>

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 */
  };

2，ICMP 数据包的分析：#include <netinet/ip_icmp.h>

struct icmp
{
char icmp_type;
char icmp_code;
unsigned short icmp_cksum;
unsigned short icmp_id;
unsigned short icmp_seq;
char icmp_data[20];
};

TCP数据包分析： #include <netinet/tcp.h>

struct tcphdr
{
u_int16_t source;
u_int16_t dest;
u_int32_t seq;
u_int32_t ack_seq;
# if __BYTE_ORDER == __LITTLE_ENDIAN
u_int16_t res1:4;
u_int16_t doff:4;
u_int16_t fin:1;
u_int16_t syn:1;
u_int16_t rst:1;
u_int16_t psh:1;
u_int16_t ack:1;
u_int16_t urg:1;
u_int16_t res2:2;
# elif __BYTE_ORDER == __BIG_ENDIAN
u_int16_t doff:4;
u_int16_t res1:4;
u_int16_t res2:2;
u_int16_t urg:1;
u_int16_t ack:1;
u_int16_t psh:1;
u_int16_t rst:1;
u_int16_t syn:1;
u_int16_t fin:1;
# else
# error "Adjust your <bits/endian.h> defines"
# endif
u_int16_t window;
u_int16_t check;
u_int16_t urg_ptr;
};

UDP数据包分析： #include<netinet/udp.h>

struct udphdr
{
u_int16_t source;
u_int16_t dest;
u_int16_t len;
u_int16_t check;
};

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