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