checksum.c

  1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * arch/alpha/lib/checksum.c
  4 *
  5 * This file contains network checksum routines that are better done
  6 * in an architecture-specific manner due to speed..
  7 * Comments in other versions indicate that the algorithms are from RFC1071
  8 *
  9 * accelerated versions (and 21264 assembly versions ) contributed by
 10 *	Rick Gorton	<rick.gorton@alpha-processor.com>
 11 */
 12 
 13#include <linux/module.h>
 14#include <linux/string.h>
 15#include <net/checksum.h>
 16
 17#include <asm/byteorder.h>
 18#include <asm/checksum.h>
 19
 20static inline unsigned short from64to16(unsigned long x)
 21{
 22	/* Using extract instructions is a bit more efficient
 23	   than the original shift/bitmask version.  */
 24
 25	union {
 26		unsigned long	ul;
 27		unsigned int	ui[2];
 28		unsigned short	us[4];
 29	} in_v, tmp_v, out_v;
 30
 31	in_v.ul = x;
 32	tmp_v.ul = (unsigned long) in_v.ui[0] + (unsigned long) in_v.ui[1];
 33
 34	/* Since the bits of tmp_v.sh[3] are going to always be zero,
 35	   we don't have to bother to add that in.  */
 36	out_v.ul = (unsigned long) tmp_v.us[0] + (unsigned long) tmp_v.us[1]
 37			+ (unsigned long) tmp_v.us[2];
 38
 39	/* Similarly, out_v.us[2] is always zero for the final add.  */
 40	return out_v.us[0] + out_v.us[1];
 41}
 42
 43/*
 44 * computes the checksum of the TCP/UDP pseudo-header
 45 * returns a 16-bit checksum, already complemented.
 46 */
 47__sum16 csum_tcpudp_magic(__be32 saddr, __be32 daddr,
 48			  __u32 len, __u8 proto, __wsum sum)
 49{
 50	return (__force __sum16)~from64to16(
 51		(__force u64)saddr + (__force u64)daddr +
 52		(__force u64)sum + ((len + proto) << 8));
 53}
 54EXPORT_SYMBOL(csum_tcpudp_magic);
 55
 56__wsum csum_tcpudp_nofold(__be32 saddr, __be32 daddr,
 57			  __u32 len, __u8 proto, __wsum sum)
 58{
 59	unsigned long result;
 60
 61	result = (__force u64)saddr + (__force u64)daddr +
 62		 (__force u64)sum + ((len + proto) << 8);
 63
 64	/* Fold down to 32-bits so we don't lose in the typedef-less 
 65	   network stack.  */
 66	/* 64 to 33 */
 67	result = (result & 0xffffffff) + (result >> 32);
 68	/* 33 to 32 */
 69	result = (result & 0xffffffff) + (result >> 32);
 70	return (__force __wsum)result;
 71}
 72EXPORT_SYMBOL(csum_tcpudp_nofold);
 73
 74/*
 75 * Do a 64-bit checksum on an arbitrary memory area..
 76 *
 77 * This isn't a great routine, but it's not _horrible_ either. The
 78 * inner loop could be unrolled a bit further, and there are better
 79 * ways to do the carry, but this is reasonable.
 80 */
 81static inline unsigned long do_csum(const unsigned char * buff, int len)
 82{
 83	int odd, count;
 84	unsigned long result = 0;
 85
 86	if (len <= 0)
 87		goto out;
 88	odd = 1 & (unsigned long) buff;
 89	if (odd) {
 90		result = *buff << 8;
 91		len--;
 92		buff++;
 93	}
 94	count = len >> 1;		/* nr of 16-bit words.. */
 95	if (count) {
 96		if (2 & (unsigned long) buff) {
 97			result += *(unsigned short *) buff;
 98			count--;
 99			len -= 2;
100			buff += 2;
101		}
102		count >>= 1;		/* nr of 32-bit words.. */
103		if (count) {
104			if (4 & (unsigned long) buff) {
105				result += *(unsigned int *) buff;
106				count--;
107				len -= 4;
108				buff += 4;
109			}
110			count >>= 1;	/* nr of 64-bit words.. */
111			if (count) {
112				unsigned long carry = 0;
113				do {
114					unsigned long w = *(unsigned long *) buff;
115					count--;
116					buff += 8;
117					result += carry;
118					result += w;
119					carry = (w > result);
120				} while (count);
121				result += carry;
122				result = (result & 0xffffffff) + (result >> 32);
123			}
124			if (len & 4) {
125				result += *(unsigned int *) buff;
126				buff += 4;
127			}
128		}
129		if (len & 2) {
130			result += *(unsigned short *) buff;
131			buff += 2;
132		}
133	}
134	if (len & 1)
135		result += *buff;
136	result = from64to16(result);
137	if (odd)
138		result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
139out:
140	return result;
141}
142
143/*
144 *	This is a version of ip_compute_csum() optimized for IP headers,
145 *	which always checksum on 4 octet boundaries.
146 */
147__sum16 ip_fast_csum(const void *iph, unsigned int ihl)
148{
149	return (__force __sum16)~do_csum(iph,ihl*4);
150}
151EXPORT_SYMBOL(ip_fast_csum);
152
153/*
154 * computes the checksum of a memory block at buff, length len,
155 * and adds in "sum" (32-bit)
156 *
157 * returns a 32-bit number suitable for feeding into itself
158 * or csum_tcpudp_magic
159 *
160 * this function must be called with even lengths, except
161 * for the last fragment, which may be odd
162 *
163 * it's best to have buff aligned on a 32-bit boundary
164 */
165__wsum csum_partial(const void *buff, int len, __wsum sum)
166{
167	unsigned long result = do_csum(buff, len);
168
169	/* add in old sum, and carry.. */
170	result += (__force u32)sum;
171	/* 32+c bits -> 32 bits */
172	result = (result & 0xffffffff) + (result >> 32);
173	return (__force __wsum)result;
174}
175
176EXPORT_SYMBOL(csum_partial);
177
178/*
179 * this routine is used for miscellaneous IP-like checksums, mainly
180 * in icmp.c
181 */
182__sum16 ip_compute_csum(const void *buff, int len)
183{
184	return (__force __sum16)~from64to16(do_csum(buff,len));
185}
186EXPORT_SYMBOL(ip_compute_csum);