87 lines
2.1 KiB
C
87 lines
2.1 KiB
C
/*
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* INET An implementation of the TCP/IP protocol suite for the LINUX
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* operating system. INET is implemented using the BSD Socket
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* interface as the means of communication with the user level.
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*
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* IP/TCP/UDP checksumming routines
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*
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* Authors: Jorge Cwik, <jorge@laser.satlink.net>
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* Arnt Gulbrandsen, <agulbra@nvg.unit.no>
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* Tom May, <ftom@netcom.com>
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* Lots of code moved from tcp.c and ip.c; see those files
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* for more names.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <net/checksum.h>
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#include <net/module.h>
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#undef PROFILE_CHECKSUM
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#ifdef PROFILE_CHECKSUM
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/* these are just for profiling the checksum code with an oscillioscope.. uh */
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#if 0
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#define BITOFF *((unsigned char *)0xb0000030) = 0xff
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#define BITON *((unsigned char *)0xb0000030) = 0x0
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#endif
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#include <asm/io.h>
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#define CBITON LED_ACTIVE_SET(1)
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#define CBITOFF LED_ACTIVE_SET(0)
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#define BITOFF
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#define BITON
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#else
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#define BITOFF
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#define BITON
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#define CBITOFF
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#define CBITON
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#endif
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/*
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* computes a partial checksum, e.g. for TCP/UDP fragments
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*/
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#include <asm/delay.h>
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__wsum csum_partial(const void *p, int len, __wsum __sum)
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{
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u32 sum = (__force u32)__sum;
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const u16 *buff = p;
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/*
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* Experiments with ethernet and slip connections show that buff
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* is aligned on either a 2-byte or 4-byte boundary.
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*/
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const void *endMarker = p + len;
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const void *marker = endMarker - (len % 16);
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#if 0
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if((int)buff & 0x3)
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printk("unaligned buff %p\n", buff);
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__delay(900); /* extra delay of 90 us to test performance hit */
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#endif
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BITON;
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while (buff < marker) {
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sum += *buff++;
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sum += *buff++;
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sum += *buff++;
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sum += *buff++;
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sum += *buff++;
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sum += *buff++;
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sum += *buff++;
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sum += *buff++;
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}
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marker = endMarker - (len % 2);
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while (buff < marker)
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sum += *buff++;
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if (endMarker > buff)
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sum += *(const u8 *)buff; /* add extra byte separately */
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BITOFF;
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return (__force __wsum)sum;
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}
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EXPORT_SYMBOL(csum_partial);
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