some method for calc crc for enthernet fcs.

fcs.c

#include <stdint.h>
#include <stdio.h>
#include <zlib.h>
// gcc fcs.c -lz
#define CRC_POLY UINT32_C(0xEDB88320)

uint32_t crc_ether(const uint8_t *data, size_t len) {
    uint32_t accum = ~UINT32_C(0);
    for (size_t n = 0; n < len; ++n) {
        accum ^= data[n];
        for (int b = 0; b < 8; ++b) {
            if (accum & 1) {
                accum = (accum >> 1) ^ CRC_POLY;
            } else {
                accum >>= 1;
            }
        }
    }
    return ~accum;
}

 uint32_t ethCalcCrc_bit(const void *data, size_t length)
 {

 //Bit by bit CRC calculation
    unsigned int i;
    unsigned int j;

    //Point to the data over which to calculate the CRC
    const uint8_t *p = (uint8_t *) data;
    //CRC preset value
    uint32_t crc = 0xFFFFFFFF;

    //Loop through data
    for(i = 0; i < length; i++)
    {
       //Update CRC value
       crc ^= p[i];

       //The message is processed bit by bit
       for(j = 0; j < 8; j++)
       {
          if(crc & 0x00000001)
          {
             crc = (crc >> 1) ^ 0xEDB88320;
          }
          else
          {
             crc = crc >> 1;
          }
       }
    }

    //Return 1's complement value
    return ~crc;
 }

// https://www.oryx-embedded.com/doc/ethernet__misc_8c_source.html
 static const uint32_t crc32Table[256] =
 {
    0x00000000, 0x77073096, 0xEE0E612C, 0x990951BA,
    0x076DC419, 0x706AF48F, 0xE963A535, 0x9E6495A3,
    0x0EDB8832, 0x79DCB8A4, 0xE0D5E91E, 0x97D2D988,
    0x09B64C2B, 0x7EB17CBD, 0xE7B82D07, 0x90BF1D91,
    0x1DB71064, 0x6AB020F2, 0xF3B97148, 0x84BE41DE,
    0x1ADAD47D, 0x6DDDE4EB, 0xF4D4B551, 0x83D385C7,
    0x136C9856, 0x646BA8C0, 0xFD62F97A, 0x8A65C9EC,
    0x14015C4F, 0x63066CD9, 0xFA0F3D63, 0x8D080DF5,
    0x3B6E20C8, 0x4C69105E, 0xD56041E4, 0xA2677172,
    0x3C03E4D1, 0x4B04D447, 0xD20D85FD, 0xA50AB56B,
    0x35B5A8FA, 0x42B2986C, 0xDBBBC9D6, 0xACBCF940,
    0x32D86CE3, 0x45DF5C75, 0xDCD60DCF, 0xABD13D59,
    0x26D930AC, 0x51DE003A, 0xC8D75180, 0xBFD06116,
    0x21B4F4B5, 0x56B3C423, 0xCFBA9599, 0xB8BDA50F,
    0x2802B89E, 0x5F058808, 0xC60CD9B2, 0xB10BE924,
    0x2F6F7C87, 0x58684C11, 0xC1611DAB, 0xB6662D3D,
    0x76DC4190, 0x01DB7106, 0x98D220BC, 0xEFD5102A,
    0x71B18589, 0x06B6B51F, 0x9FBFE4A5, 0xE8B8D433,
    0x7807C9A2, 0x0F00F934, 0x9609A88E, 0xE10E9818,
    0x7F6A0DBB, 0x086D3D2D, 0x91646C97, 0xE6635C01,
    0x6B6B51F4, 0x1C6C6162, 0x856530D8, 0xF262004E,
    0x6C0695ED, 0x1B01A57B, 0x8208F4C1, 0xF50FC457,
    0x65B0D9C6, 0x12B7E950, 0x8BBEB8EA, 0xFCB9887C,
    0x62DD1DDF, 0x15DA2D49, 0x8CD37CF3, 0xFBD44C65,
    0x4DB26158, 0x3AB551CE, 0xA3BC0074, 0xD4BB30E2,
    0x4ADFA541, 0x3DD895D7, 0xA4D1C46D, 0xD3D6F4FB,
    0x4369E96A, 0x346ED9FC, 0xAD678846, 0xDA60B8D0,
    0x44042D73, 0x33031DE5, 0xAA0A4C5F, 0xDD0D7CC9,
    0x5005713C, 0x270241AA, 0xBE0B1010, 0xC90C2086,
    0x5768B525, 0x206F85B3, 0xB966D409, 0xCE61E49F,
    0x5EDEF90E, 0x29D9C998, 0xB0D09822, 0xC7D7A8B4,
    0x59B33D17, 0x2EB40D81, 0xB7BD5C3B, 0xC0BA6CAD,
    0xEDB88320, 0x9ABFB3B6, 0x03B6E20C, 0x74B1D29A,
    0xEAD54739, 0x9DD277AF, 0x04DB2615, 0x73DC1683,
    0xE3630B12, 0x94643B84, 0x0D6D6A3E, 0x7A6A5AA8,
    0xE40ECF0B, 0x9309FF9D, 0x0A00AE27, 0x7D079EB1,
    0xF00F9344, 0x8708A3D2, 0x1E01F268, 0x6906C2FE,
    0xF762575D, 0x806567CB, 0x196C3671, 0x6E6B06E7,
    0xFED41B76, 0x89D32BE0, 0x10DA7A5A, 0x67DD4ACC,
    0xF9B9DF6F, 0x8EBEEFF9, 0x17B7BE43, 0x60B08ED5,
    0xD6D6A3E8, 0xA1D1937E, 0x38D8C2C4, 0x4FDFF252,
    0xD1BB67F1, 0xA6BC5767, 0x3FB506DD, 0x48B2364B,
    0xD80D2BDA, 0xAF0A1B4C, 0x36034AF6, 0x41047A60,
    0xDF60EFC3, 0xA867DF55, 0x316E8EEF, 0x4669BE79,
    0xCB61B38C, 0xBC66831A, 0x256FD2A0, 0x5268E236,
    0xCC0C7795, 0xBB0B4703, 0x220216B9, 0x5505262F,
    0xC5BA3BBE, 0xB2BD0B28, 0x2BB45A92, 0x5CB36A04,
    0xC2D7FFA7, 0xB5D0CF31, 0x2CD99E8B, 0x5BDEAE1D,
    0x9B64C2B0, 0xEC63F226, 0x756AA39C, 0x026D930A,
    0x9C0906A9, 0xEB0E363F, 0x72076785, 0x05005713,
    0x95BF4A82, 0xE2B87A14, 0x7BB12BAE, 0x0CB61B38,
    0x92D28E9B, 0xE5D5BE0D, 0x7CDCEFB7, 0x0BDBDF21,
    0x86D3D2D4, 0xF1D4E242, 0x68DDB3F8, 0x1FDA836E,
    0x81BE16CD, 0xF6B9265B, 0x6FB077E1, 0x18B74777,
    0x88085AE6, 0xFF0F6A70, 0x66063BCA, 0x11010B5C,
    0x8F659EFF, 0xF862AE69, 0x616BFFD3, 0x166CCF45,
    0xA00AE278, 0xD70DD2EE, 0x4E048354, 0x3903B3C2,
    0xA7672661, 0xD06016F7, 0x4969474D, 0x3E6E77DB,
    0xAED16A4A, 0xD9D65ADC, 0x40DF0B66, 0x37D83BF0,
    0xA9BCAE53, 0xDEBB9EC5, 0x47B2CF7F, 0x30B5FFE9,
    0xBDBDF21C, 0xCABAC28A, 0x53B39330, 0x24B4A3A6,
    0xBAD03605, 0xCDD70693, 0x54DE5729, 0x23D967BF,
    0xB3667A2E, 0xC4614AB8, 0x5D681B02, 0x2A6F2B94,
    0xB40BBE37, 0xC30C8EA1, 0x5A05DF1B, 0x2D02EF8D
 };


 /**
  * @brief Ethernet CRC calculation
  * @param[in] data Pointer to the data over which to calculate the CRC
  * @param[in] length Number of bytes to process
  * @return Resulting CRC value
  **/

 uint32_t ethCalcCrc(const void *data, size_t length)
 {
 //A lookup table can be used to speed up CRC calculation
    unsigned int i;

    //Point to the data over which to calculate the CRC
    const uint8_t *p = (uint8_t *) data;
    //CRC preset value
    uint32_t crc = 0xFFFFFFFF;

    //Loop through data
    for(i = 0; i < length; i++)
    {
       //The message is processed byte by byte
       crc = (crc >> 8) ^ crc32Table[(crc & 0xFF) ^ p[i]];
    }

    //Return 1's complement value
    return ~crc;
 }

int main(){
        // ethernet data
        uint8_t a[] = {
                0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0xD5, // preamble + SFD
                0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // dest mac
                0xF8, 0xB7, 0xE2, 0x04, 0x0C, 0x19, // src mac
                0x08, 0x06, // lengthe / type
                0x00, 0x01, 0x08, 0x00, 0x06, 0x04, 0x00, 0x01, 0xF8, 0xB7, 0xE2, 0x04, 0x0C, 0x19, 0x44, 0x0F, 0x43, 0xF1, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x44, 0x0F, 0x43, 0xFE, // data
                0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // data padding to 64bit
                0x69, 0x70, 0x39, 0xBB, // FCS
        };
        printf("data size is %ld\n\r", sizeof(a)/sizeof(uint8_t));
        uint32_t crc = crc32(0, Z_NULL, 0);
        crc = crc32(crc, &a[8], sizeof(a)/sizeof(uint8_t)-8-4);
        printf("crc32: \t\t 0x%08x\n", crc);
         crc = crc32(0, Z_NULL, 0);
        crc = crc32(crc, &a[8], sizeof(a)/sizeof(uint8_t)-8);
        printf("crc32: \t\t 0x%08x\n", crc);
        uint32_t r = crc_ether(&a[8], sizeof(a)/sizeof(uint8_t)-8);
        printf("crc bit by bit: \t 0x%08x\n", crc);
        crc =  ethCalcCrc(&a[8], sizeof(a)/sizeof(uint8_t)-8);
        printf("crc lookup table: \t 0x%08x\n", crc);
        crc =  ethCalcCrc_bit(&a[8], sizeof(a)/sizeof(uint8_t)-8);
        printf("crc bit by bit: \t 0x%08x\n", crc);

}