blob: 44e16d59bc1085c2306519809826772bf8bafcc4 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * INET An implementation of the TCP/IP protocol suite for the LINUX
3 * operating system. INET is implemented using the BSD Socket
4 * interface as the means of communication with the user level.
5 *
6 * IP/TCP/UDP checksumming routines
7 *
8 * Authors: Jorge Cwik, <jorge@laser.satlink.net>
9 * Arnt Gulbrandsen, <agulbra@nvg.unit.no>
10 * Tom May, <ftom@netcom.com>
11 * Andreas Schwab, <schwab@issan.informatik.uni-dortmund.de>
12 * Lots of code moved from tcp.c and ip.c; see those files
13 * for more names.
14 *
15 * 03/02/96 Jes Sorensen, Andreas Schwab, Roman Hodek:
16 * Fixed some nasty bugs, causing some horrible crashes.
17 * A: At some points, the sum (%0) was used as
18 * length-counter instead of the length counter
19 * (%1). Thanks to Roman Hodek for pointing this out.
20 * B: GCC seems to mess up if one uses too many
21 * data-registers to hold input values and one tries to
22 * specify d0 and d1 as scratch registers. Letting gcc choose these
23 * registers itself solves the problem.
24 *
25 * This program is free software; you can redistribute it and/or
26 * modify it under the terms of the GNU General Public License
27 * as published by the Free Software Foundation; either version
28 * 2 of the License, or (at your option) any later version.
29 */
30
31/* Revised by Kenneth Albanowski for m68knommu. Basic problem: unaligned access kills, so most
32 of the assembly has to go. */
33
34#include <net/checksum.h>
David Howells40234402006-01-08 01:01:19 -080035#include <linux/module.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070036
37static inline unsigned short from32to16(unsigned long x)
38{
39 /* add up 16-bit and 16-bit for 16+c bit */
40 x = (x & 0xffff) + (x >> 16);
41 /* add up carry.. */
42 x = (x & 0xffff) + (x >> 16);
43 return x;
44}
45
46static unsigned long do_csum(const unsigned char * buff, int len)
47{
48 int odd, count;
49 unsigned long result = 0;
50
51 if (len <= 0)
52 goto out;
53 odd = 1 & (unsigned long) buff;
54 if (odd) {
55 result = *buff;
56 len--;
57 buff++;
58 }
59 count = len >> 1; /* nr of 16-bit words.. */
60 if (count) {
61 if (2 & (unsigned long) buff) {
62 result += *(unsigned short *) buff;
63 count--;
64 len -= 2;
65 buff += 2;
66 }
67 count >>= 1; /* nr of 32-bit words.. */
68 if (count) {
69 unsigned long carry = 0;
70 do {
71 unsigned long w = *(unsigned long *) buff;
72 count--;
73 buff += 4;
74 result += carry;
75 result += w;
76 carry = (w > result);
77 } while (count);
78 result += carry;
79 result = (result & 0xffff) + (result >> 16);
80 }
81 if (len & 2) {
82 result += *(unsigned short *) buff;
83 buff += 2;
84 }
85 }
86 if (len & 1)
87 result += (*buff << 8);
88 result = from32to16(result);
89 if (odd)
90 result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
91out:
92 return result;
93}
94
95/*
96 * computes the checksum of a memory block at buff, length len,
97 * and adds in "sum" (32-bit)
98 *
99 * returns a 32-bit number suitable for feeding into itself
100 * or csum_tcpudp_magic
101 *
102 * this function must be called with even lengths, except
103 * for the last fragment, which may be odd
104 *
105 * it's best to have buff aligned on a 32-bit boundary
106 */
Al Viro8042c442006-11-14 21:15:40 -0800107__wsum csum_partial(const void *buff, int len, __wsum sum)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700108{
109 unsigned int result = do_csum(buff, len);
110
111 /* add in old sum, and carry.. */
Al Viro8042c442006-11-14 21:15:40 -0800112 result += (__force u32)sum;
113 if ((__force u32)sum > result)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700114 result += 1;
Al Viro8042c442006-11-14 21:15:40 -0800115 return (__force __wsum)result;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700116}
117
David Howells40234402006-01-08 01:01:19 -0800118EXPORT_SYMBOL(csum_partial);
119
Linus Torvalds1da177e2005-04-16 15:20:36 -0700120/*
121 * this routine is used for miscellaneous IP-like checksums, mainly
122 * in icmp.c
123 */
Al Viro8042c442006-11-14 21:15:40 -0800124__sum16 ip_compute_csum(const void *buff, int len)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700125{
Al Viro8042c442006-11-14 21:15:40 -0800126 return (__force __sum16)~do_csum(buff, len);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700127}
128
David Howells40234402006-01-08 01:01:19 -0800129EXPORT_SYMBOL(ip_compute_csum);
130
Linus Torvalds1da177e2005-04-16 15:20:36 -0700131/*
132 * copy from fs while checksumming, otherwise like csum_partial
133 */
Al Viro8042c442006-11-14 21:15:40 -0800134__wsum
135csum_partial_copy_from_user(const void __user *src, void *dst,
136 int len, __wsum sum, int *csum_err)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700137{
David Howells40234402006-01-08 01:01:19 -0800138 int rem;
139
140 if (csum_err)
141 *csum_err = 0;
142
143 rem = copy_from_user(dst, src, len);
144 if (rem != 0) {
145 if (csum_err)
146 *csum_err = -EFAULT;
147 memset(dst + len - rem, 0, rem);
148 len = rem;
149 }
150
Linus Torvalds1da177e2005-04-16 15:20:36 -0700151 return csum_partial(dst, len, sum);
152}
153
David Howells40234402006-01-08 01:01:19 -0800154EXPORT_SYMBOL(csum_partial_copy_from_user);
155
Linus Torvalds1da177e2005-04-16 15:20:36 -0700156/*
157 * copy from ds while checksumming, otherwise like csum_partial
158 */
Al Viro8042c442006-11-14 21:15:40 -0800159__wsum
160csum_partial_copy_nocheck(const void *src, void *dst, int len, __wsum sum)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700161{
162 memcpy(dst, src, len);
163 return csum_partial(dst, len, sum);
164}
David Howells40234402006-01-08 01:01:19 -0800165
Al Viro8042c442006-11-14 21:15:40 -0800166EXPORT_SYMBOL(csum_partial_copy_nocheck);