1da177e4c3
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
103 lines
2.5 KiB
C
103 lines
2.5 KiB
C
/*
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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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unsigned short int
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csum_tcpudp_magic (unsigned long saddr, unsigned long daddr, unsigned short len,
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unsigned short proto, unsigned int sum)
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{
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return ~from64to16(saddr + daddr + sum + ((unsigned long) ntohs(len) << 16) +
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((unsigned long) proto << 8));
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}
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EXPORT_SYMBOL(csum_tcpudp_magic);
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unsigned int
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csum_tcpudp_nofold (unsigned long saddr, unsigned long daddr, unsigned short len,
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unsigned short proto, unsigned int sum)
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{
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unsigned long result;
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result = (saddr + daddr + sum +
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((unsigned long) ntohs(len) << 16) +
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((unsigned long) 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 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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unsigned int
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csum_partial (const unsigned char * buff, int len, unsigned int sum)
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{
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unsigned long result = do_csum(buff, len);
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/* add in old sum, and carry.. */
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result += sum;
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/* 32+c bits -> 32 bits */
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result = (result & 0xffffffff) + (result >> 32);
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return 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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unsigned short
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ip_compute_csum (unsigned char * buff, int len)
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{
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return ~do_csum(buff,len);
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}
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EXPORT_SYMBOL(ip_compute_csum);
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