1/*
2 *
3 * INET		An implementation of the TCP/IP protocol suite for the LINUX
4 *		operating system.  INET is implemented using the  BSD Socket
5 *		interface as the means of communication with the user level.
6 *
7 *		IP/TCP/UDP checksumming routines
8 *
9 * Authors:	Jorge Cwik, <jorge@laser.satlink.net>
10 *		Arnt Gulbrandsen, <agulbra@nvg.unit.no>
11 *		Tom May, <ftom@netcom.com>
12 *		Andreas Schwab, <schwab@issan.informatik.uni-dortmund.de>
13 *		Lots of code moved from tcp.c and ip.c; see those files
14 *		for more names.
15 *
16 * 03/02/96	Jes Sorensen, Andreas Schwab, Roman Hodek:
17 *		Fixed some nasty bugs, causing some horrible crashes.
18 *		A: At some points, the sum (%0) was used as
19 *		length-counter instead of the length counter
20 *		(%1). Thanks to Roman Hodek for pointing this out.
21 *		B: GCC seems to mess up if one uses too many
22 *		data-registers to hold input values and one tries to
23 *		specify d0 and d1 as scratch registers. Letting gcc
24 *		choose these registers itself solves the problem.
25 *
26 *		This program is free software; you can redistribute it and/or
27 *		modify it under the terms of the GNU General Public License
28 *		as published by the Free Software Foundation; either version
29 *		2 of the License, or (at your option) any later version.
30 */
31
32/* Revised by Kenneth Albanowski for m68knommu. Basic problem: unaligned access
33 kills, so most of the assembly has to go. */
34
35#include <linux/export.h>
36#include <net/checksum.h>
37
38#include <asm/byteorder.h>
39
40#ifndef do_csum
41static inline unsigned short from32to16(unsigned int x)
42{
43	/* add up 16-bit and 16-bit for 16+c bit */
44	x = (x & 0xffff) + (x >> 16);
45	/* add up carry.. */
46	x = (x & 0xffff) + (x >> 16);
47	return x;
48}
49
50static unsigned int do_csum(const unsigned char *buff, int len)
51{
52	int odd;
53	unsigned int result = 0;
54
55	if (len <= 0)
56		goto out;
57	odd = 1 & (unsigned long) buff;
58	if (odd) {
59#ifdef __LITTLE_ENDIAN
60		result += (*buff << 8);
61#else
62		result = *buff;
63#endif
64		len--;
65		buff++;
66	}
67	if (len >= 2) {
68		if (2 & (unsigned long) buff) {
69			result += *(unsigned short *) buff;
70			len -= 2;
71			buff += 2;
72		}
73		if (len >= 4) {
74			const unsigned char *end = buff + ((unsigned)len & ~3);
75			unsigned int carry = 0;
76			do {
77				unsigned int w = *(unsigned int *) buff;
78				buff += 4;
79				result += carry;
80				result += w;
81				carry = (w > result);
82			} while (buff < end);
83			result += carry;
84			result = (result & 0xffff) + (result >> 16);
85		}
86		if (len & 2) {
87			result += *(unsigned short *) buff;
88			buff += 2;
89		}
90	}
91	if (len & 1)
92#ifdef __LITTLE_ENDIAN
93		result += *buff;
94#else
95		result += (*buff << 8);
96#endif
97	result = from32to16(result);
98	if (odd)
99		result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
100out:
101	return result;
102}
103#endif
104
105#ifndef ip_fast_csum
106/*
107 *	This is a version of ip_compute_csum() optimized for IP headers,
108 *	which always checksum on 4 octet boundaries.
109 */
110__sum16 ip_fast_csum(const void *iph, unsigned int ihl)
111{
112	return (__force __sum16)~do_csum(iph, ihl*4);
113}
114EXPORT_SYMBOL(ip_fast_csum);
115#endif
116
117/*
118 * computes the checksum of a memory block at buff, length len,
119 * and adds in "sum" (32-bit)
120 *
121 * returns a 32-bit number suitable for feeding into itself
122 * or csum_tcpudp_magic
123 *
124 * this function must be called with even lengths, except
125 * for the last fragment, which may be odd
126 *
127 * it's best to have buff aligned on a 32-bit boundary
128 */
129__wsum csum_partial(const void *buff, int len, __wsum wsum)
130{
131	unsigned int sum = (__force unsigned int)wsum;
132	unsigned int result = do_csum(buff, len);
133
134	/* add in old sum, and carry.. */
135	result += sum;
136	if (sum > result)
137		result += 1;
138	return (__force __wsum)result;
139}
140EXPORT_SYMBOL(csum_partial);
141
142/*
143 * this routine is used for miscellaneous IP-like checksums, mainly
144 * in icmp.c
145 */
146__sum16 ip_compute_csum(const void *buff, int len)
147{
148	return (__force __sum16)~do_csum(buff, len);
149}
150EXPORT_SYMBOL(ip_compute_csum);
151
152/*
153 * copy from fs while checksumming, otherwise like csum_partial
154 */
155__wsum
156csum_partial_copy_from_user(const void __user *src, void *dst, int len,
157						__wsum sum, int *csum_err)
158{
159	int missing;
160
161	missing = __copy_from_user(dst, src, len);
162	if (missing) {
163		memset(dst + len - missing, 0, missing);
164		*csum_err = -EFAULT;
165	} else
166		*csum_err = 0;
167
168	return csum_partial(dst, len, sum);
169}
170EXPORT_SYMBOL(csum_partial_copy_from_user);
171
172/*
173 * copy from ds while checksumming, otherwise like csum_partial
174 */
175__wsum
176csum_partial_copy(const void *src, void *dst, int len, __wsum sum)
177{
178	memcpy(dst, src, len);
179	return csum_partial(dst, len, sum);
180}
181EXPORT_SYMBOL(csum_partial_copy);
182
183#ifndef csum_tcpudp_nofold
184static inline u32 from64to32(u64 x)
185{
186	/* add up 32-bit and 32-bit for 32+c bit */
187	x = (x & 0xffffffff) + (x >> 32);
188	/* add up carry.. */
189	x = (x & 0xffffffff) + (x >> 32);
190	return (u32)x;
191}
192
193__wsum csum_tcpudp_nofold(__be32 saddr, __be32 daddr,
194			unsigned short len,
195			unsigned short proto,
196			__wsum sum)
197{
198	unsigned long long s = (__force u32)sum;
199
200	s += (__force u32)saddr;
201	s += (__force u32)daddr;
202#ifdef __BIG_ENDIAN
203	s += proto + len;
204#else
205	s += (proto + len) << 8;
206#endif
207	return (__force __wsum)from64to32(s);
208}
209EXPORT_SYMBOL(csum_tcpudp_nofold);
210#endif
211