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106 lines
2.2 KiB
C
106 lines
2.2 KiB
C
/*
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* COPYRIGHT: See COPYING in the top level directory
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* PROJECT: ReactOS TCP/IP protocol driver
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* FILE: tcpip/checksum.c
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* PURPOSE: Checksum routines
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* NOTES: The checksum routine is from RFC 1071
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* PROGRAMMERS: Casper S. Hornstrup (chorns@users.sourceforge.net)
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* REVISIONS:
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* CSH 01/08-2000 Created
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*/
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#include "precomp.h"
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ULONG ChecksumFold(
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ULONG Sum)
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{
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/* Fold 32-bit sum to 16 bits */
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while (Sum >> 16)
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{
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Sum = (Sum & 0xFFFF) + (Sum >> 16);
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}
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return Sum;
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}
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ULONG ChecksumCompute(
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PVOID Data,
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UINT Count,
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ULONG Seed)
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/*
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* FUNCTION: Calculate checksum of a buffer
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* ARGUMENTS:
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* Data = Pointer to buffer with data
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* Count = Number of bytes in buffer
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* Seed = Previously calculated checksum (if any)
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* RETURNS:
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* Checksum of buffer
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*/
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{
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register ULONG Sum = Seed;
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while (Count > 1)
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{
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Sum += *(PUSHORT)Data;
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Count -= 2;
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Data = (PVOID)((ULONG_PTR) Data + 2);
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}
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/* Add left-over byte, if any */
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if (Count > 0)
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{
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Sum += *(PUCHAR)Data;
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}
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return Sum;
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}
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ULONG
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UDPv4ChecksumCalculate(
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PIPv4_HEADER IPHeader,
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PUCHAR PacketBuffer,
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ULONG DataLength)
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{
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ULONG Sum = 0;
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USHORT TmpSum;
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ULONG i;
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BOOLEAN Pad;
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/* Pad the data if needed */
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Pad = (DataLength & 1);
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if (Pad)
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DataLength++;
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/* Add from the UDP header and data */
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for (i = 0; i < DataLength; i += 2)
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{
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TmpSum = ((PacketBuffer[i] << 8) & 0xFF00) +
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((Pad && i == DataLength - 2) ? 0 : (PacketBuffer[i+1] & 0x00FF));
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Sum += TmpSum;
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}
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/* Add the source address */
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for (i = 0; i < sizeof(IPv4_RAW_ADDRESS); i += 2)
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{
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TmpSum = ((((PUCHAR)&IPHeader->SrcAddr)[i] << 8) & 0xFF00) +
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(((PUCHAR)&IPHeader->SrcAddr)[i+1] & 0x00FF);
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Sum += TmpSum;
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}
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/* Add the destination address */
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for (i = 0; i < sizeof(IPv4_RAW_ADDRESS); i += 2)
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{
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TmpSum = ((((PUCHAR)&IPHeader->DstAddr)[i] << 8) & 0xFF00) +
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(((PUCHAR)&IPHeader->DstAddr)[i+1] & 0x00FF);
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Sum += TmpSum;
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}
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/* Add the proto number and length */
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Sum += IPPROTO_UDP + (DataLength - (Pad ? 1 : 0));
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/* Fold the checksum and return the one's complement */
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return ~ChecksumFold(Sum);
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}
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