數據包報頭

//以太網報頭14字節

typedef struct ethdr

{unsigned char destination_mac[6]; //目的MAC 6字節

unsigned char source_mac[6]; //源MAC 6字節

unsigned short type; //後面的協議類型2字節ARP-0806;IP-0800}ET_HEADER,*PETHDR;

//地址解析協議(Address Resolution Protocol)

//arp報頭28字節

typedef struct arphdr

{unsigned short hard_tpye; //硬件類型2字節通常為0x0001(以太網)

unsigned short protocol; //協議類型2字節通常為0x0800 (IP)

unsigned char hard_length; //硬件地址長度1字節通常為6

unsigned char protocol_length; //協議地址長度1字節通常為4 (IP協議)

unsigned short operation_type; //操作類型1為ARP請求，2為ARP應答，3為RARP請求，4為RARP應答

unsigned char source_mac[6]; //源MAC

unsigned char source_ip[4]; //源IP地址

unsigned char destination_mac[6]; //目的MAC

unsigned char destination_ip[4]; //目的IP地址}ARP_HEADER,*PARPHDR;

//互聯網協議(Internet Protocol)

//IP數據報頭

typedef struct iphdr

{unsigned char VIHL; // Version and IHL 版本4bit = 4 和首部長度4bit = 5

unsigned char TOS; // Type Of Service 服務類型1字節

unsigned short TotLen; // Total Length 總長度2字節，包括數據和報頭

unsigned short ID; // Identification 標識符2字節

unsigned short FlagOff; // Flags and Fragment Offset 標誌3bit 和分段偏移量13bit

unsigned char TTL; // Time To Live 生存期1字節，為經過路由器的總次數

unsigned char Protocol; // Protocol 協議類型1字節 ICMP-1,TCP-6,UDP-17

unsigned short Checksum; // Checksum 首部(只是IP首部。!)校驗和2字節

unsigned char source_ip[4]; // Source IP 源IP地址

unsigned char destination_ip[4]; // Destination IP 目的IP地址}IP_HEADER, *PIP_HEADER;

//傳輸控制協議(Transmission Control Protocol)

//TCP數據報頭

typedef struct tcphdr

{unsigned short source_port; //源端口

unsigned short destination_port; //目的端口

unsigned long sequence; //32位序號

unsigned long ack_sequence; //32位確認序號

unsigned char header_length; //首部長度,只用高4位通常為5

unsigned char flags; //標誌位 X | X | URG | ACK | PSH | RST | SYN | FIN

unsigned short window_size; //窗口大小

unsigned short checksum; //校驗和

unsigned short exigency_pointer; //緊急指針

}TCP_HEADER;

//用户數據報協議(User Datagram Protocol)

//UDP數據報頭

typedef struct udphdr

{unsigned short source_port; //源端口

unsigned short destination_port; //目的端口

unsigned short length; //數據長度

unsigned short checksum; //校驗和包括數據!} UDP_HEADER;

//以太網消息控制協議(Internet Control Messages Protocol)

//ICMP數據報頭

typedef struct icmphdr

{u_char Type; // 類型 0-請求,8-應答,11-超時

u_char Code; // 代碼0

u_short Checksum; // 校驗和

u_short ID; // 標識符

u_short Seq; // 序列號}ICMP_HEADER, *PICMP_HEADER;

//域名服務器(Domain Name Server)

//DNS數據報

typedef struct dns

{unsigned short id; //標識，通過它客户端可以將DNS的請求與應答相匹配；

unsigned short flags; //標誌：[QR | opcode | AA| TC| RD| RA | zero | rcode ]

unsigned short quests; //問題數目；

unsigned short answers; //資源記錄數目；

unsigned short author; //授權資源記錄數目；

unsigned short addition; //額外資源記錄數目；}DNS,*PDNS;

//在16位的標誌中：QR位判斷是查詢/響應報文，opcode區別查詢類型，AA判斷是否為授權回答，TC判斷

//是否可截斷，RD判斷是否期望遞歸查詢，RA判斷是否為可用遞歸，zero必須為0，rcode為返回碼字段。

typedef struct psd //偽報頭，用於計算UDP校驗和

{unsigned int source_ip; //源IP

unsigned int destination_ip; //目的IP

char mbz; // 0

char protocol; //協議UDP = 17

unsigned short udp_length; //UDP 長度

}PSD,*PPSD;

//DNS查詢數據報：

typedef struct query

{unsigned short type; //查詢類型，大約有20個不同的類型

unsigned short classes; //查詢類,通常是A類既查詢IP地址。}QUERY,*PQUERY;

//DNS響應數據報：

typedef struct response

{unsigned short name; //查詢的域名

unsigned short type; //查詢類型

unsigned short classes; //類型碼

unsigned int ttl; //生存時間

unsigned short length; //資源數據長度

unsigned int addr; //資源數據}RESPONSE,*PRESPONSE;