skcsum.c

该软件根据网络数据生成NetFlow记录。NetFlow可用于网络规划、负载均衡、安全监控等

		SKCS_IDX(pIpHeader, SKCS_OFS_IP_HEADER_VERSION_AND_LENGTH);

	/* Get the Internet Header Version (IHV). */
	/* Note: The IHV is stored in the upper four bits. */

	InternetHeaderVersion = Tmp >> 4;

	/* Check the Internet Header Version. */
	/* Note: We currently only support IP version 4. */

	if (InternetHeaderVersion != 4) {	/* IPv4? */
		SK_DBG_MSG(pAc, SK_DBGMOD_CSUM, SK_DBGCAT_ERR | SK_DBGCAT_TX,
			("Tx: Unknown Internet Header Version %u.\n",
			InternetHeaderVersion));
		pPacketInfo->ProtocolFlags = 0;
		pAc->Csum.ProtoStats[NetNumber][SKCS_PROTO_STATS_IP].TxUnableCts++;
		return;
	}

	/* Get the IP header length (IHL). */
	/*
	 * Note: The IHL is stored in the lower four bits as the number of
	 * 4-byte words.
	 */

	IpHeaderLength = (Tmp & 0xf) * 4;
	pPacketInfo->IpHeaderLength = IpHeaderLength;

	/* Check the IP header length. */

	/* 04-Aug-1998 sw - Really check the IHL? Necessary? */

	if (IpHeaderLength < 5*4) {
		SK_DBG_MSG(pAc, SK_DBGMOD_CSUM, SK_DBGCAT_ERR | SK_DBGCAT_TX,
			("Tx: Invalid IP Header Length %u.\n", IpHeaderLength));
		pPacketInfo->ProtocolFlags = 0;
		pAc->Csum.ProtoStats[NetNumber][SKCS_PROTO_STATS_IP].TxUnableCts++;
		return;
	}

	/* This is an IPv4 frame with a header of valid length. */

	pAc->Csum.ProtoStats[NetNumber][SKCS_PROTO_STATS_IP].TxOkCts++;

	/* Check if we should calculate the IP header checksum. */

	ProtocolFlags = pPacketInfo->ProtocolFlags;

	if (ProtocolFlags & SKCS_PROTO_IP) {
		pPacketInfo->IpHeaderChecksum =
			SkCsCalculateChecksum(pIpHeader, IpHeaderLength);
	}

	/* Get the next level protocol identifier. */

	NextLevelProtocol =
		*(SK_U8 *) SKCS_IDX(pIpHeader, SKCS_OFS_IP_NEXT_LEVEL_PROTOCOL);

	/*
	 * Check if this is a TCP or UDP frame and if we should calculate the
	 * TCP/UDP pseudo header checksum.
	 *
	 * Also clear all protocol bit flags of protocols not present in the
	 * frame.
	 */

	if ((ProtocolFlags & SKCS_PROTO_TCP) != 0 &&
		NextLevelProtocol == SKCS_PROTO_ID_TCP) {
		/* TCP/IP frame. */
		ProtocolFlags &= SKCS_PROTO_TCP | SKCS_PROTO_IP;
		NextLevelProtoStats =
			&pAc->Csum.ProtoStats[NetNumber][SKCS_PROTO_STATS_TCP];
	}
	else if ((ProtocolFlags & SKCS_PROTO_UDP) != 0 &&
		NextLevelProtocol == SKCS_PROTO_ID_UDP) {
		/* UDP/IP frame. */
		ProtocolFlags &= SKCS_PROTO_UDP | SKCS_PROTO_IP;
		NextLevelProtoStats =
			&pAc->Csum.ProtoStats[NetNumber][SKCS_PROTO_STATS_UDP];
	}
	else {
		/*
		 * Either not a TCP or UDP frame and/or TCP/UDP processing not
		 * specified.
		 */
		pPacketInfo->ProtocolFlags = ProtocolFlags & SKCS_PROTO_IP;
		return;
	}

	/* Check if this is an IP fragment. */

	/*
	 * Note: An IP fragment has a non-zero "Fragment Offset" field and/or
	 * the "More Fragments" bit set. Thus, if both the "Fragment Offset"
	 * and the "More Fragments" are zero, it is *not* a fragment. We can
	 * easily check both at the same time since they are in the same 16-bit
	 * word.
	 */

	if ((*(SK_U16 *)
		SKCS_IDX(pIpHeader, SKCS_OFS_IP_FLAGS_AND_FRAGMENT_OFFSET) &
		~SKCS_IP_DONT_FRAGMENT) != 0) {
		/* IP fragment; ignore all other protocols. */
		pPacketInfo->ProtocolFlags = ProtocolFlags & SKCS_PROTO_IP;
		NextLevelProtoStats->TxUnableCts++;
		return;
	}

	/*
	 * Calculate the TCP/UDP pseudo header checksum.
	 */

	/* Get total length of IP header and data. */

	IpDataLength =
		*(SK_U16 *) SKCS_IDX(pIpHeader, SKCS_OFS_IP_TOTAL_LENGTH);

	/* Get length of IP data portion. */

	IpDataLength = SKCS_NTOH16(IpDataLength) - IpHeaderLength;

	/* Calculate the sum of all pseudo header fields (16-bit). */

	PseudoHeaderChecksum =
		(unsigned long) *(SK_U16 *) SKCS_IDX(pIpHeader,
			SKCS_OFS_IP_SOURCE_ADDRESS + 0) +
		(unsigned long) *(SK_U16 *) SKCS_IDX(pIpHeader,
			SKCS_OFS_IP_SOURCE_ADDRESS + 2) +
		(unsigned long) *(SK_U16 *) SKCS_IDX(pIpHeader,
			SKCS_OFS_IP_DESTINATION_ADDRESS + 0) +
		(unsigned long) *(SK_U16 *) SKCS_IDX(pIpHeader,
			SKCS_OFS_IP_DESTINATION_ADDRESS + 2) +
		(unsigned long) SKCS_HTON16(NextLevelProtocol) +
		(unsigned long) SKCS_HTON16(IpDataLength);
	
	/* Add-in any carries. */

	SKCS_OC_ADD(PseudoHeaderChecksum, PseudoHeaderChecksum, 0);

	/* Add-in any new carry. */

	SKCS_OC_ADD(pPacketInfo->PseudoHeaderChecksum, PseudoHeaderChecksum, 0);

	pPacketInfo->ProtocolFlags = ProtocolFlags;
	NextLevelProtoStats->TxOkCts++;	/* Success. */
}	/* SkCsGetSendInfo */


/******************************************************************************
 *
 *	SkCsGetReceiveInfo - verify checksum information for a received packet
 *
 * Description:
 *	Verify a received frame's checksum. The function returns a status code
 *	reflecting the result of the verification.
 *
 * Note:
 *	Before calling this function you have to verify that the frame is
 *	not padded and Checksum1 and Checksum2 are bigger than 1.
 *
 * Arguments:
 *	pAc - Pointer to adapter context struct.
 *
 *	pIpHeader - Pointer to IP header. Must be at least the length in bytes
 *	of the received IP header including any option fields. For UDP packets,
 *	8 additional bytes are needed to access the UDP checksum.
 *
 *	Note: The actual length of the IP header is stored in the lower four
 *	bits of the first octet of the IP header as the number of 4-byte words,
 *	so it must be multiplied by four to get the length in bytes. Thus, the
 *	maximum IP header length is 15 * 4 = 60 bytes.
 *
 *	Checksum1 - The first 16-bit Internet Checksum calculated by the
 *	hardware starting at the offset returned by SkCsSetReceiveFlags().
 *
 *	Checksum2 - The second 16-bit Internet Checksum calculated by the
 *	hardware starting at the offset returned by SkCsSetReceiveFlags().
 *
 * Returns:
 *	SKCS_STATUS_UNKNOWN_IP_VERSION - Not an IP v4 frame.
 *	SKCS_STATUS_IP_CSUM_ERROR - IP checksum error.
 *	SKCS_STATUS_IP_CSUM_ERROR_TCP - IP checksum error in TCP frame.
 *	SKCS_STATUS_IP_CSUM_ERROR_UDP - IP checksum error in UDP frame
 *	SKCS_STATUS_IP_FRAGMENT - IP fragment (IP checksum ok).
 *	SKCS_STATUS_IP_CSUM_OK - IP checksum ok (not a TCP or UDP frame).
 *	SKCS_STATUS_TCP_CSUM_ERROR - TCP checksum error (IP checksum ok).
 *	SKCS_STATUS_UDP_CSUM_ERROR - UDP checksum error (IP checksum ok).
 *	SKCS_STATUS_TCP_CSUM_OK - IP and TCP checksum ok.
 *	SKCS_STATUS_UDP_CSUM_OK - IP and UDP checksum ok.
 *	SKCS_STATUS_IP_CSUM_OK_NO_UDP - IP checksum OK and no UDP checksum.
 *
 *	Note: If SKCS_OVERWRITE_STATUS is defined, the SKCS_STATUS_XXX values
 *	returned here can be defined in some header file by the module using CSUM.
 *	In this way, the calling module can assign return values for its own needs,
 *	e.g. by assigning bit flags to the individual protocols.
 */
SKCS_STATUS SkCsGetReceiveInfo(
SK_AC		*pAc,		/* Adapter context struct. */
void		*pIpHeader,	/* IP header. */
unsigned	Checksum1,	/* Hardware checksum 1. */
unsigned	Checksum2,	/* Hardware checksum 2. */
int			NetNumber)	/* Net number */
{
	/* Internet Header Version found in IP header. */
	unsigned InternetHeaderVersion;

	/* Length of the IP header as found in IP header. */
	unsigned IpHeaderLength;

	/* Length of IP data portion. */
	unsigned IpDataLength;

	/* IP header checksum. */
	unsigned IpHeaderChecksum;

	/* IP header options checksum, if any. */
	unsigned IpOptionsChecksum;

	/* IP data checksum, i.e. TCP/UDP checksum. */
	unsigned IpDataChecksum;

	/* Next level protocol identifier found in IP header. */
	unsigned NextLevelProtocol;

	/* The checksum of the "next level protocol", i.e. TCP or UDP. */
	unsigned long NextLevelProtocolChecksum;

	/* Pointer to next level protocol statistics structure. */
	SKCS_PROTO_STATS *NextLevelProtoStats;

	/* Temporary variable. */
	unsigned Tmp;

	Tmp = *(SK_U8 *)
		SKCS_IDX(pIpHeader, SKCS_OFS_IP_HEADER_VERSION_AND_LENGTH);

	/* Get the Internet Header Version (IHV). */
	/* Note: The IHV is stored in the upper four bits. */

	InternetHeaderVersion = Tmp >> 4;

	/* Check the Internet Header Version. */
	/* Note: We currently only support IP version 4. */

	if (InternetHeaderVersion != 4) {	/* IPv4? */
		SK_DBG_MSG(pAc, SK_DBGMOD_CSUM, SK_DBGCAT_ERR | SK_DBGCAT_RX,
			("Rx: Unknown Internet Header Version %u.\n",
			InternetHeaderVersion));
		pAc->Csum.ProtoStats[NetNumber][SKCS_PROTO_STATS_IP].RxUnableCts++;
		return (SKCS_STATUS_UNKNOWN_IP_VERSION);
	}

	/* Get the IP header length (IHL). */
	/*
	 * Note: The IHL is stored in the lower four bits as the number of
	 * 4-byte words.
	 */

	IpHeaderLength = (Tmp & 0xf) * 4;

	/* Check the IP header length. */

	/* 04-Aug-1998 sw - Really check the IHL? Necessary? */

	if (IpHeaderLength < 5*4) {
		SK_DBG_MSG(pAc, SK_DBGMOD_CSUM, SK_DBGCAT_ERR | SK_DBGCAT_RX,
			("Rx: Invalid IP Header Length %u.\n", IpHeaderLength));
		pAc->Csum.ProtoStats[NetNumber][SKCS_PROTO_STATS_IP].RxErrCts++;
		return (SKCS_STATUS_IP_CSUM_ERROR);
	}

	/* This is an IPv4 frame with a header of valid length. */

	/* Get the IP header and data checksum. */

	IpDataChecksum = Checksum2;

	/*
	 * The IP header checksum is calculated as follows:
	 *
	 *	IpHeaderChecksum = Checksum1 - Checksum2
	 */

	SKCS_OC_SUB(IpHeaderChecksum, Checksum1, Checksum2);

	/* Check if any IP header options. */

	if (IpHeaderLength > SKCS_IP_HEADER_SIZE) {

		/* Get the IP options checksum. */

		IpOptionsChecksum = SkCsCalculateChecksum(
			SKCS_IDX(pIpHeader, SKCS_IP_HEADER_SIZE),
			IpHeaderLength - SKCS_IP_HEADER_SIZE);

		/* Adjust the IP header and IP data checksums. */

		SKCS_OC_ADD(IpHeaderChecksum, IpHeaderChecksum, IpOptionsChecksum);

		SKCS_OC_SUB(IpDataChecksum, IpDataChecksum, IpOptionsChecksum);
	}

	/*
	 * Check if the IP header checksum is ok.
	 *
	 * NOTE: We must check the IP header checksum even if the caller just wants
	 * us to check upper-layer checksums, because we cannot do any further
	 * processing of the packet without a valid IP checksum.
	 */
	
	/* Get the next level protocol identifier. */
	
	NextLevelProtocol = *(SK_U8 *)
		SKCS_IDX(pIpHeader, SKCS_OFS_IP_NEXT_LEVEL_PROTOCOL);

	if (IpHeaderChecksum != 0xffff) {