9b0e35cb48
Move the checksum code out into its own file so it can be used elsewhere. Also use a new version which supports a length which is not a multiple of 2 and add a new function to add two checksums. Signed-off-by: Simon Glass <sjg@chromium.org>
61 lines
1.2 KiB
C
61 lines
1.2 KiB
C
/*
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* This file was originally taken from the FreeBSD project.
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*
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* Copyright (c) 2001 Charles Mott <cm@linktel.net>
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* Copyright (c) 2008 coresystems GmbH
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* All rights reserved.
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <common.h>
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#include <net.h>
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unsigned compute_ip_checksum(const void *vptr, unsigned nbytes)
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{
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int sum, oddbyte;
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const unsigned short *ptr = vptr;
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sum = 0;
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while (nbytes > 1) {
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sum += *ptr++;
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nbytes -= 2;
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}
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if (nbytes == 1) {
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oddbyte = 0;
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((u8 *)&oddbyte)[0] = *(u8 *)ptr;
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((u8 *)&oddbyte)[1] = 0;
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sum += oddbyte;
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}
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sum = (sum >> 16) + (sum & 0xffff);
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sum += (sum >> 16);
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sum = ~sum & 0xffff;
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return sum;
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}
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unsigned add_ip_checksums(unsigned offset, unsigned sum, unsigned new)
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{
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unsigned long checksum;
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sum = ~sum & 0xffff;
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new = ~new & 0xffff;
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if (offset & 1) {
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/*
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* byte-swap the sum if it came from an odd offset; since the
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* computation is endian independant this works.
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*/
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new = ((new >> 8) & 0xff) | ((new << 8) & 0xff00);
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}
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checksum = sum + new;
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if (checksum > 0xffff)
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checksum -= 0xffff;
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return (~checksum) & 0xffff;
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}
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int ip_checksum_ok(const void *addr, unsigned nbytes)
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{
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return !(compute_ip_checksum(addr, nbytes) & 0xfffe);
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}
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