1/*
  2 * Network checksum routines
  3 *
  4 * Copyright (C) 1999, 2003 Hewlett-Packard Co
  5 *	Stephane Eranian <eranian@hpl.hp.com>
  6 *
  7 * Most of the code coming from arch/alpha/lib/checksum.c
  8 *
  9 * This file contains network checksum routines that are better done
 10 * in an architecture-specific manner due to speed..
 11 */
 12
 13#include <linux/module.h>
 14#include <linux/string.h>
 15
 16#include <asm/byteorder.h>
 17
 18static inline unsigned short
 19from64to16 (unsigned long x)
 20{
 21	/* add up 32-bit words for 33 bits */
 22	x = (x & 0xffffffff) + (x >> 32);
 23	/* add up 16-bit and 17-bit words for 17+c bits */
 24	x = (x & 0xffff) + (x >> 16);
 25	/* add up 16-bit and 2-bit for 16+c bit */
 26	x = (x & 0xffff) + (x >> 16);
 27	/* add up carry.. */
 28	x = (x & 0xffff) + (x >> 16);
 29	return x;
 30}
 31
 32/*
 33 * computes the checksum of the TCP/UDP pseudo-header
 34 * returns a 16-bit checksum, already complemented.
 35 */
 36__sum16
 37csum_tcpudp_magic (__be32 saddr, __be32 daddr, unsigned short len,
 38		   unsigned short proto, __wsum sum)
 39{
 40	return (__force __sum16)~from64to16(
 41		(__force u64)saddr + (__force u64)daddr +
 42		(__force u64)sum + ((len + proto) << 8));
 43}
 44
 45EXPORT_SYMBOL(csum_tcpudp_magic);
 46
 47__wsum
 48csum_tcpudp_nofold (__be32 saddr, __be32 daddr, unsigned short len,
 49		    unsigned short proto, __wsum sum)
 50{
 51	unsigned long result;
 52
 53	result = (__force u64)saddr + (__force u64)daddr +
 54		 (__force u64)sum + ((len + proto) << 8);
 55
 56	/* Fold down to 32-bits so we don't lose in the typedef-less network stack.  */
 57	/* 64 to 33 */
 58	result = (result & 0xffffffff) + (result >> 32);
 59	/* 33 to 32 */
 60	result = (result & 0xffffffff) + (result >> 32);
 61	return (__force __wsum)result;
 62}
 63EXPORT_SYMBOL(csum_tcpudp_nofold);
 64
 65extern unsigned long do_csum (const unsigned char *, long);
 66
 67/*
 68 * computes the checksum of a memory block at buff, length len,
 69 * and adds in "sum" (32-bit)
 70 *
 71 * returns a 32-bit number suitable for feeding into itself
 72 * or csum_tcpudp_magic
 73 *
 74 * this function must be called with even lengths, except
 75 * for the last fragment, which may be odd
 76 *
 77 * it's best to have buff aligned on a 32-bit boundary
 78 */
 79__wsum csum_partial(const void *buff, int len, __wsum sum)
 80{
 81	u64 result = do_csum(buff, len);
 82
 83	/* add in old sum, and carry.. */
 84	result += (__force u32)sum;
 85	/* 32+c bits -> 32 bits */
 86	result = (result & 0xffffffff) + (result >> 32);
 87	return (__force __wsum)result;
 88}
 89
 90EXPORT_SYMBOL(csum_partial);
 91
 92/*
 93 * this routine is used for miscellaneous IP-like checksums, mainly
 94 * in icmp.c
 95 */
 96__sum16 ip_compute_csum (const void *buff, int len)
 97{
 98	return (__force __sum16)~do_csum(buff,len);
 99}
100
101EXPORT_SYMBOL(ip_compute_csum);