packetHeader.h

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#ifndef PACKET_HDR_H
#define PACKET_HDR_H

// standard C headers
#include <string.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>

// protocol headers
#include <linux/if_ether.h>
#include <net/if_arp.h>
#include <netinet/ip.h>
#include <netinet/ip_icmp.h>
#include <netinet/tcp.h>
#include <netinet/udp.h>
#include <netinet/udp.h>

#include <string.h> // for memset, memcpy

#define RST_ETH_HDR_LEN 14
#define RST_ARP_HDR_LEN 28
#define RST_IP_HDR_LEN 20       // without options
#define RST_TCP_HDR_LEN 20      // without options
#define RST_UDP_HDR_LEN 8
#define RST_ICMP_HDR_LEN 8

struct rst_arphdr {
        // fixed portion
        unsigned short int format2;     // layer 2 address format
        unsigned short int format3;     // layer 3 address format
        unsigned char length2;          // layer 2 address length
        unsigned char length3;          // layer3 address length
        unsigned short int opCode;      // ARP opcode

        // variable portion, specialized here for Ethernet/IP
        unsigned char senderMAC[6]; // sender hardware address
        unsigned char senderIP[4];  // sender IP address
        unsigned char targetMAC[6]; // target hardware address
        unsigned char targetIP[4];  // target IP address
};

// ***** header initialization

void rst_initEth(struct ethhdr*,unsigned char*,unsigned char*,unsigned short);

void rst_initARPrequest(struct rst_arphdr*,
 unsigned char*,unsigned int,unsigned int);

void rst_initARPreply(struct rst_arphdr*,
 unsigned char*,unsigned int,unsigned char*,unsigned int);

void rst_initIP(struct iphdr*,
 unsigned short,unsigned char,unsigned int,unsigned int);

void rst_initICMP(struct icmphdr *,unsigned char);

void rst_initTCP(struct tcphdr*,unsigned short,unsigned short);

void rst_initUDP(struct udphdr *,unsigned short,unsigned short,unsigned short);

// ***** htonp and ntohp: byte swap and checksum calculations

#define RST_ETH_HDR     0x01
#define RST_ARP_HDR     0x02
#define RST_IP_HDR      0x04
#define RST_ICMP_HDR    0x20
#define RST_TCP_HDR     0x08
#define RST_UDP_HDR     0x10

struct rst_buf {
        unsigned char* buf;
        int bufLen;

        struct ethhdr* ethhdr;
        struct rst_arphdr* arphdr;
        struct iphdr* iphdr;
        struct icmphdr* icmphdr;
        struct tcphdr* tcphdr;
        struct udphdr* udphdr;
};

void rst_initRbuf(struct rst_buf*,unsigned char*,int,unsigned int);

int rst_verifyRbuf(struct rst_buf*);

void rst_htonp(struct rst_buf*);

void rst_ntohp(struct rst_buf*);

unsigned char* rst_ethData(struct rst_buf*);

unsigned char* rst_ipData(struct rst_buf*);

unsigned char* rst_icmpData(struct rst_buf*);

unsigned char* rst_tcpData(struct rst_buf*);

unsigned char* rst_udpData(struct rst_buf*);

// ***** checksum calculation

unsigned short rst_getIPchecksum(struct iphdr*);

unsigned short rst_getICMPchecksum(struct icmphdr*,unsigned short);

unsigned short rst_getTCPchecksum(struct iphdr*,struct tcphdr*,unsigned short);

unsigned short rst_getUDPchecksum(struct iphdr*,struct udphdr*,unsigned short);

#endif

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