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/module.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, count;
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	count = len >> 1;		/* nr of 16-bit words.. */
68	if (count) {
69		if (2 & (unsigned long) buff) {
70			result += *(unsigned short *) buff;
71			count--;
72			len -= 2;
73			buff += 2;
74		}
75		count >>= 1;		/* nr of 32-bit words.. */
76		if (count) {
77			unsigned int carry = 0;
78			do {
79				unsigned int w = *(unsigned int *) buff;
80				count--;
81				buff += 4;
82				result += carry;
83				result += w;
84				carry = (w > result);
85			} while (count);
86			result += carry;
87			result = (result & 0xffff) + (result >> 16);
88		}
89		if (len & 2) {
90			result += *(unsigned short *) buff;
91			buff += 2;
92		}
93	}
94	if (len & 1)
95#ifdef __LITTLE_ENDIAN
96		result += *buff;
97#else
98		result += (*buff << 8);
99#endif
100	result = from32to16(result);
101	if (odd)
102		result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
103out:
104	return result;
105}
106#endif
107
108/*
109 *	This is a version of ip_compute_csum() optimized for IP headers,
110 *	which always checksum on 4 octet boundaries.
111 */
112__sum16 ip_fast_csum(const void *iph, unsigned int ihl)
113{
114	return (__force __sum16)~do_csum(iph, ihl*4);
115}
116EXPORT_SYMBOL(ip_fast_csum);
117
118/*
119 * computes the checksum of a memory block at buff, length len,
120 * and adds in "sum" (32-bit)
121 *
122 * returns a 32-bit number suitable for feeding into itself
123 * or csum_tcpudp_magic
124 *
125 * this function must be called with even lengths, except
126 * for the last fragment, which may be odd
127 *
128 * it's best to have buff aligned on a 32-bit boundary
129 */
130__wsum csum_partial(const void *buff, int len, __wsum wsum)
131{
132	unsigned int sum = (__force unsigned int)wsum;
133	unsigned int result = do_csum(buff, len);
134
135	/* add in old sum, and carry.. */
136	result += sum;
137	if (sum > result)
138		result += 1;
139	return (__force __wsum)result;
140}
141EXPORT_SYMBOL(csum_partial);
142
143/*
144 * this routine is used for miscellaneous IP-like checksums, mainly
145 * in icmp.c
146 */
147__sum16 ip_compute_csum(const void *buff, int len)
148{
149	return (__force __sum16)~do_csum(buff, len);
150}
151EXPORT_SYMBOL(ip_compute_csum);
152
153/*
154 * copy from fs while checksumming, otherwise like csum_partial
155 */
156__wsum
157csum_partial_copy_from_user(const void __user *src, void *dst, int len,
158						__wsum sum, int *csum_err)
159{
160	int missing;
161
162	missing = __copy_from_user(dst, src, len);
163	if (missing) {
164		memset(dst + len - missing, 0, missing);
165		*csum_err = -EFAULT;
166	} else
167		*csum_err = 0;
168
169	return csum_partial(dst, len, sum);
170}
171EXPORT_SYMBOL(csum_partial_copy_from_user);
172
173/*
174 * copy from ds while checksumming, otherwise like csum_partial
175 */
176__wsum
177csum_partial_copy(const void *src, void *dst, int len, __wsum sum)
178{
179	memcpy(dst, src, len);
180	return csum_partial(dst, len, sum);
181}
182EXPORT_SYMBOL(csum_partial_copy);
183
184#ifndef csum_tcpudp_nofold
185__wsum csum_tcpudp_nofold(__be32 saddr, __be32 daddr,
186			unsigned short len,
187			unsigned short proto,
188			__wsum sum)
189{
190	unsigned long long s = (__force u32)sum;
191
192	s += (__force u32)saddr;
193	s += (__force u32)daddr;
194#ifdef __BIG_ENDIAN
195	s += proto + len;
196#else
197	s += (proto + len) << 8;
198#endif
199	s += (s >> 32);
200	return (__force __wsum)s;
201}
202EXPORT_SYMBOL(csum_tcpudp_nofold);
203#endif
204