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100 lines
2.5 KiB
100 lines
2.5 KiB
/*
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* Network checksum routines
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*
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* Copyright (C) 1999, 2003 Hewlett-Packard Co
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* Stephane Eranian <eranian@hpl.hp.com>
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*
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* Most of the code coming from arch/alpha/lib/checksum.c
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*
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* This file contains network checksum routines that are better done
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* in an architecture-specific manner due to speed..
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*/
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#include <linux/module.h>
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#include <linux/string.h>
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#include <asm/byteorder.h>
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static inline unsigned short
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from64to16 (unsigned long x)
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{
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/* add up 32-bit words for 33 bits */
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x = (x & 0xffffffff) + (x >> 32);
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/* add up 16-bit and 17-bit words for 17+c bits */
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x = (x & 0xffff) + (x >> 16);
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/* add up 16-bit and 2-bit for 16+c bit */
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x = (x & 0xffff) + (x >> 16);
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/* add up carry.. */
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x = (x & 0xffff) + (x >> 16);
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return x;
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}
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/*
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* computes the checksum of the TCP/UDP pseudo-header
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* returns a 16-bit checksum, already complemented.
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*/
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__sum16
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csum_tcpudp_magic (__be32 saddr, __be32 daddr, unsigned short len,
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unsigned short proto, __wsum sum)
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{
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return (__force __sum16)~from64to16(
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(__force u64)saddr + (__force u64)daddr +
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(__force u64)sum + ((len + proto) << 8));
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}
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EXPORT_SYMBOL(csum_tcpudp_magic);
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__wsum
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csum_tcpudp_nofold (__be32 saddr, __be32 daddr, unsigned short len,
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unsigned short proto, __wsum sum)
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{
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unsigned long result;
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result = (__force u64)saddr + (__force u64)daddr +
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(__force u64)sum + ((len + proto) << 8);
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/* Fold down to 32-bits so we don't lose in the typedef-less network stack. */
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/* 64 to 33 */
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result = (result & 0xffffffff) + (result >> 32);
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/* 33 to 32 */
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result = (result & 0xffffffff) + (result >> 32);
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return (__force __wsum)result;
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}
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extern unsigned long do_csum (const unsigned char *, long);
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/*
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* computes the checksum of a memory block at buff, length len,
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* and adds in "sum" (32-bit)
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*
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* returns a 32-bit number suitable for feeding into itself
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* or csum_tcpudp_magic
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*
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* this function must be called with even lengths, except
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* for the last fragment, which may be odd
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*
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* it's best to have buff aligned on a 32-bit boundary
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*/
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__wsum csum_partial(const void *buff, int len, __wsum sum)
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{
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u64 result = do_csum(buff, len);
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/* add in old sum, and carry.. */
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result += (__force u32)sum;
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/* 32+c bits -> 32 bits */
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result = (result & 0xffffffff) + (result >> 32);
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return (__force __wsum)result;
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}
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EXPORT_SYMBOL(csum_partial);
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/*
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* this routine is used for miscellaneous IP-like checksums, mainly
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* in icmp.c
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*/
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__sum16 ip_compute_csum (const void *buff, int len)
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{
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return (__force __sum16)~do_csum(buff,len);
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}
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EXPORT_SYMBOL(ip_compute_csum);
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