#include <stdio.h>
#include <stdlib.h>

struct ArpPacket
{
    unsigned char hType[2];
    unsigned char pType[2];
    unsigned char hLen;
    unsigned char pLen;
    unsigned char op[2];
    unsigned char* senderAddr;
    unsigned char* srcPAddr;
    unsigned char* targetAddr;
    unsigned char* pAddr;
};

struct EthPacket
{
    unsigned char destMacAddr[6];
    unsigned char srcMacAddr[6];
    unsigned char ethType[2];
    struct ArpPacket arpPkt;
};

/* Grabs an arbitrary number of bytes (specified by the length
 * parameter) and stuffs them in the pointer we pass.
 */
int getData(int length, unsigned char* dataPtr, FILE* filePtr);
void printData(struct EthPacket ethPkt, struct ArpPacket arpPkt);

int main(int argc, char* argv[])
{
    int fileFlag = 1;
    struct EthPacket ethPkt;
    struct ArpPacket arpPkt;
    FILE* file;

    file = fopen&#40;"packet.bin", "r"&#41;;

    fileFlag = getData(6, ethPkt.destMacAddr, file);
    fileFlag = getData(6, ethPkt.srcMacAddr, file);
    fileFlag = getData(2, ethPkt.ethType, file);
    fileFlag = getData(2, arpPkt.hType, file);
    fileFlag = getData(2, arpPkt.pType, file);
    fileFlag = getData(1, &arpPkt;.hLen, file);
    fileFlag = getData(1, &arpPkt;.pLen, file);
    fileFlag = getData(2, arpPkt.op, file);

    arpPkt.senderAddr = malloc(arpPkt.hLen);
    arpPkt.srcPAddr = malloc(arpPkt.pLen);
    arpPkt.targetAddr = malloc(arpPkt.hLen);
    arpPkt.pAddr = malloc(arpPkt.pLen);

    fileFlag = getData(arpPkt.hLen, arpPkt.senderAddr, file);
    fileFlag = getData(arpPkt.pLen, arpPkt.srcPAddr, file);
    fileFlag = getData(arpPkt.hLen, arpPkt.targetAddr, file);
    fileFlag = getData(arpPkt.pLen, arpPkt.pAddr, file);

    if (fileFlag)
    {
 printData(ethPkt, arpPkt);
    }
    else
    {
 printf("Oops, there was a problem parsing the packet. :(\n");
    }

    free(arpPkt.senderAddr);
    free(arpPkt.targetAddr);
    free(arpPkt.pAddr);
    fclose(file);
    return 0;
}

int getData(int length, unsigned char* dataPtr, FILE* filePtr)
{
    int counter;

    if (length == 1)
    {
 if ((*dataPtr = fgetc(filePtr)) == EOF)
 {
     return 0;
 }

 return 1;
    }

    for (counter = 0; counter < length; counter++)
    {
 if ((dataPtr[counter] = fgetc(filePtr)) == EOF)
 {
     return 0;
 }
    }

    return 1;
}

void printData(struct EthPacket ethPkt, struct ArpPacket arpPkt)
{
    int counter;
    printf("ETHERNET HEADER\n--------------------\n");
    printf("Destination MAC Address: ");
    
    for (counter = 0; counter < 6; counter++)
    {
 printf("%.2x", ethPkt.destMacAddr[counter]);

 if (counter != 5)
 {
     printf(":");
 }
 else
 {
     printf("\n");
 }
    }

    printf("Source MAC Address: ");
    for (counter = 0; counter < 6; counter++)
    {
 printf("%.2x", ethPkt.srcMacAddr[counter]);

 if (counter != 5)
 {
     printf(":");
 }
 else
 {
     printf("\n");
 }
    }

    printf("Ethertype: 0x%.4x\n\n", (ethPkt.ethType[0] * 256) + ethPkt.ethType[1]);

    printf("ARP PACKET\n------------------\n");
    printf("Hardware Type: %d\n", (arpPkt.hType[0] * 256) + arpPkt.hType[1]);
    printf("Protocol Type: 0x%.4x\n", (arpPkt.pType[0] * 256) + arpPkt.pType[1]);
    printf("Packet Type: ");

    switch (arpPkt.op[1])
    {
 case 1:
 {
     printf("REQUEST\n");
     break;
 }
 case 2:
 {
     printf("REPLY\n");
     break;
 }
    }

    printf("Sender MAC Address: ");
    for (counter = 0; counter < arpPkt.hLen; counter++)
    {
 printf("%.2x", arpPkt.senderAddr[counter]);

 if (counter != arpPkt.hLen - 1)
 {
     printf(":");
 }
 else
 {
     printf("\n");
 }
    }

    printf("Sender Protocol Address: ");
    for (counter = 0; counter < arpPkt.pLen; counter++)
    {
 printf("%d", arpPkt.srcPAddr[counter]);

 if (counter != arpPkt.pLen - 1)
 {
     printf(".");
 }
 else
 {
     printf("\n");
 }
    }

    printf("Target MAC Address: ");
    for (counter = 0; counter < arpPkt.hLen; counter++)
    {
 printf("%.2x", arpPkt.targetAddr[counter]);

 if (counter != arpPkt.hLen - 1)
 {
     printf(":");
 }
 else
 {
     printf("\n");
 }
    }

    printf("Target Protocol Address: ");
    for (counter = 0; counter < arpPkt.pLen; counter++)
    {
 printf("%d", arpPkt.pAddr[counter]);

 if (counter != arpPkt.pLen - 1)
 {
     printf(".");
 }
 else
 {
     printf("\n");
 }
    }
}