1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Network checksum routines
  4 *
  5 * Copyright (C) 1999, 2003 Hewlett-Packard Co
  6 *	Stephane Eranian <eranian@hpl.hp.com>
  7 *
  8 * Most of the code coming from arch/alpha/lib/checksum.c
  9 *
 10 * This file contains network checksum routines that are better done
 11 * in an architecture-specific manner due to speed..
 12 */
 13
 14#include <linux/module.h>
 15#include <linux/string.h>
 16
 17#include <asm/byteorder.h>
 18
 19static inline unsigned short
 20from64to16 (unsigned long x)
 21{
 22	/* add up 32-bit words for 33 bits */
 23	x = (x & 0xffffffff) + (x >> 32);
 24	/* add up 16-bit and 17-bit words for 17+c bits */
 25	x = (x & 0xffff) + (x >> 16);
 26	/* add up 16-bit and 2-bit for 16+c bit */
 27	x = (x & 0xffff) + (x >> 16);
 28	/* add up carry.. */
 29	x = (x & 0xffff) + (x >> 16);
 30	return x;
 31}
 32
 33/*
 34 * computes the checksum of the TCP/UDP pseudo-header
 35 * returns a 16-bit checksum, already complemented.
 36 */
 37__sum16
 38csum_tcpudp_magic(__be32 saddr, __be32 daddr, __u32 len,
 39		  __u8 proto, __wsum sum)
 40{
 41	return (__force __sum16)~from64to16(
 42		(__force u64)saddr + (__force u64)daddr +
 43		(__force u64)sum + ((len + proto) << 8));
 44}
 45
 46EXPORT_SYMBOL(csum_tcpudp_magic);
 47
 48__wsum
 49csum_tcpudp_nofold(__be32 saddr, __be32 daddr, __u32 len,
 50		   __u8 proto, __wsum sum)
 51{
 52	unsigned long result;
 53
 54	result = (__force u64)saddr + (__force u64)daddr +
 55		 (__force u64)sum + ((len + proto) << 8);
 56
 57	/* Fold down to 32-bits so we don't lose in the typedef-less network stack.  */
 58	/* 64 to 33 */
 59	result = (result & 0xffffffff) + (result >> 32);
 60	/* 33 to 32 */
 61	result = (result & 0xffffffff) + (result >> 32);
 62	return (__force __wsum)result;
 63}
 64EXPORT_SYMBOL(csum_tcpudp_nofold);
 65
 66extern unsigned long do_csum (const unsigned char *, long);
 67
 68/*
 69 * computes the checksum of a memory block at buff, length len,
 70 * and adds in "sum" (32-bit)
 71 *
 72 * returns a 32-bit number suitable for feeding into itself
 73 * or csum_tcpudp_magic
 74 *
 75 * this function must be called with even lengths, except
 76 * for the last fragment, which may be odd
 77 *
 78 * it's best to have buff aligned on a 32-bit boundary
 79 */
 80__wsum csum_partial(const void *buff, int len, __wsum sum)
 81{
 82	u64 result = do_csum(buff, len);
 83
 84	/* add in old sum, and carry.. */
 85	result += (__force u32)sum;
 86	/* 32+c bits -> 32 bits */
 87	result = (result & 0xffffffff) + (result >> 32);
 88	return (__force __wsum)result;
 89}
 90
 91EXPORT_SYMBOL(csum_partial);
 92
 93/*
 94 * this routine is used for miscellaneous IP-like checksums, mainly
 95 * in icmp.c
 96 */
 97__sum16 ip_compute_csum (const void *buff, int len)
 98{
 99	return (__force __sum16)~do_csum(buff,len);
100}
101
102EXPORT_SYMBOL(ip_compute_csum);