tether.c

VIA VT6656 USB linux source code.

/*
 * Copyright (c) 2003 VIA Networking, Inc. All rights reserved.
 *
 * This software is copyrighted by and is the sole property of
 * VIA Networking, Inc. This software may only be used in accordance
 * with the corresponding license agreement. Any unauthorized use,
 * duplication, transmission, distribution, or disclosure of this
 * software is expressly forbidden.
 *
 * This software is provided by VIA Networking, Inc. "as is" and any
 * express or implied warranties, including, but not limited to, the
 * implied warranties of merchantability and fitness for a particular
 * purpose are disclaimed. In no event shall VIA Networking, Inc. be
 * liable for any direct, indirect, incidental, special, exemplary, or
 * consequential damages.
 *
 *
 * File: tether.c
 *
 * Purpose:
 *
 * Author: Tevin Chen
 *
 * Date: May 21, 1996
 *
 * Functions: 
 *      ETHbyGetHashIndexByCrc32 - Caculate multicast hash value by CRC32
 *      ETHbIsBufferCrc32Ok - Check CRC value of the buffer if Ok or not
 *
 * Revision History:
 *
 */

#if !defined(__DEVICE_H__)
#include "device.h"
#endif
#if !defined(__TMACRO_H__)
#include "tmacro.h"
#endif
#if !defined(__TBIT_H__)
#include "tbit.h"
#endif
#if !defined(__TCRC_H__)
#include "tcrc.h"
#endif
#if !defined(__TETHER_H__)
#include "tether.h"
#endif




/*---------------------  Static Definitions -------------------------*/

/*---------------------  Static Classes  ----------------------------*/

/*---------------------  Static Variables  --------------------------*/

/*---------------------  Static Functions  --------------------------*/

/*---------------------  Export Variables  --------------------------*/



/* 
 * Description: Caculate multicast hash value by CRC32
 *
 * Parameters:
 *  In:
 *		pbyMultiAddr    - Multicast Address
 *  Out:
 *      none
 *
 * Return Value: Hash value
 *
 */
BYTE ETHbyGetHashIndexByCrc32 (PBYTE pbyMultiAddr)
{
    int     ii;
    BYTE    byTmpHash;
    BYTE    byHash = 0;

    // get the least 6-bits from CRC generator
    byTmpHash = (BYTE)(CRCdwCrc32(pbyMultiAddr, U_ETHER_ADDR_LEN, 
            0xFFFFFFFFL) & 0x3F);
    // reverse most bit to least bit
    for (ii = 0; ii < (sizeof(byTmpHash) * 8); ii++) {
        byHash <<= 1;
        if (BITbIsBitOn(byTmpHash, 0x01)) 
            byHash |= 1;
        byTmpHash >>= 1;
    }

    // adjust 6-bits to the right most
    return (byHash >> 2);
}


/* 
 * Description: Check CRC value of the buffer if Ok or not
 *
 * Parameters:
 *  In:
 *		pbyBuffer	    - pointer of buffer (normally is rx buffer)
 *		cbFrameLength	- length of buffer, including CRC portion
 *  Out:
 *      none
 *
 * Return Value: TRUE if ok; FALSE if error.
 *
 */
BOOL ETHbIsBufferCrc32Ok (PBYTE pbyBuffer, UINT cbFrameLength)
{
    DWORD dwCRC;

    dwCRC = CRCdwGetCrc32(pbyBuffer, cbFrameLength - 4);
    if (cpu_to_le32(*((PDWORD)(pbyBuffer + cbFrameLength - 4))) != dwCRC) {
        return FALSE;
    }
    return TRUE;
}