blob: 886b48db4f28861cbaf65065d641b00fbb2ee99a [file] [log] [blame]
Arnd Bergmann26a28fa2009-05-13 22:56:38 +00001/*
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
Arnd Bergmannc44ba9f2009-06-23 21:22:58 +020040static inline unsigned short from32to16(unsigned int x)
Arnd Bergmann26a28fa2009-05-13 22:56:38 +000041{
42 /* add up 16-bit and 16-bit for 16+c bit */
43 x = (x & 0xffff) + (x >> 16);
44 /* add up carry.. */
45 x = (x & 0xffff) + (x >> 16);
46 return x;
47}
48
49static unsigned int do_csum(const unsigned char *buff, int len)
50{
51 int odd, count;
Arnd Bergmannc44ba9f2009-06-23 21:22:58 +020052 unsigned int result = 0;
Arnd Bergmann26a28fa2009-05-13 22:56:38 +000053
54 if (len <= 0)
55 goto out;
56 odd = 1 & (unsigned long) buff;
57 if (odd) {
Arnd Bergmann32a9ff92009-06-19 10:41:19 +020058#ifdef __LITTLE_ENDIAN
Arnd Bergmann26a28fa2009-05-13 22:56:38 +000059 result = *buff;
Arnd Bergmann32a9ff92009-06-19 10:41:19 +020060#else
61 result += (*buff << 8);
62#endif
Arnd Bergmann26a28fa2009-05-13 22:56:38 +000063 len--;
64 buff++;
65 }
66 count = len >> 1; /* nr of 16-bit words.. */
67 if (count) {
68 if (2 & (unsigned long) buff) {
69 result += *(unsigned short *) buff;
70 count--;
71 len -= 2;
72 buff += 2;
73 }
74 count >>= 1; /* nr of 32-bit words.. */
75 if (count) {
Arnd Bergmannc44ba9f2009-06-23 21:22:58 +020076 unsigned int carry = 0;
Arnd Bergmann26a28fa2009-05-13 22:56:38 +000077 do {
Arnd Bergmannc44ba9f2009-06-23 21:22:58 +020078 unsigned int w = *(unsigned int *) buff;
Arnd Bergmann26a28fa2009-05-13 22:56:38 +000079 count--;
80 buff += 4;
81 result += carry;
82 result += w;
83 carry = (w > result);
84 } while (count);
85 result += carry;
86 result = (result & 0xffff) + (result >> 16);
87 }
88 if (len & 2) {
89 result += *(unsigned short *) buff;
90 buff += 2;
91 }
92 }
93 if (len & 1)
Arnd Bergmann32a9ff92009-06-19 10:41:19 +020094#ifdef __LITTLE_ENDIAN
95 result += *buff;
96#else
Arnd Bergmann26a28fa2009-05-13 22:56:38 +000097 result += (*buff << 8);
Arnd Bergmann32a9ff92009-06-19 10:41:19 +020098#endif
Arnd Bergmann26a28fa2009-05-13 22:56:38 +000099 result = from32to16(result);
100 if (odd)
101 result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
102out:
103 return result;
104}
105
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
116/*
117 * computes the checksum of a memory block at buff, length len,
118 * and adds in "sum" (32-bit)
119 *
120 * returns a 32-bit number suitable for feeding into itself
121 * or csum_tcpudp_magic
122 *
123 * this function must be called with even lengths, except
124 * for the last fragment, which may be odd
125 *
126 * it's best to have buff aligned on a 32-bit boundary
127 */
128__wsum csum_partial(const void *buff, int len, __wsum wsum)
129{
130 unsigned int sum = (__force unsigned int)wsum;
131 unsigned int result = do_csum(buff, len);
132
133 /* add in old sum, and carry.. */
134 result += sum;
135 if (sum > result)
136 result += 1;
137 return (__force __wsum)result;
138}
139EXPORT_SYMBOL(csum_partial);
140
141/*
142 * this routine is used for miscellaneous IP-like checksums, mainly
143 * in icmp.c
144 */
145__sum16 ip_compute_csum(const void *buff, int len)
146{
147 return (__force __sum16)~do_csum(buff, len);
148}
149EXPORT_SYMBOL(ip_compute_csum);
150
151/*
152 * copy from fs while checksumming, otherwise like csum_partial
153 */
154__wsum
155csum_partial_copy_from_user(const void __user *src, void *dst, int len,
156 __wsum sum, int *csum_err)
157{
158 int missing;
159
160 missing = __copy_from_user(dst, src, len);
161 if (missing) {
162 memset(dst + len - missing, 0, missing);
163 *csum_err = -EFAULT;
164 } else
165 *csum_err = 0;
166
167 return csum_partial(dst, len, sum);
168}
169EXPORT_SYMBOL(csum_partial_copy_from_user);
170
171/*
172 * copy from ds while checksumming, otherwise like csum_partial
173 */
174__wsum
175csum_partial_copy(const void *src, void *dst, int len, __wsum sum)
176{
177 memcpy(dst, src, len);
178 return csum_partial(dst, len, sum);
179}
180EXPORT_SYMBOL(csum_partial_copy);
181
182#ifndef csum_tcpudp_nofold
183__wsum csum_tcpudp_nofold(__be32 saddr, __be32 daddr,
184 unsigned short len,
185 unsigned short proto,
186 __wsum sum)
187{
188 unsigned long long s = (__force u32)sum;
189
190 s += (__force u32)saddr;
191 s += (__force u32)daddr;
192#ifdef __BIG_ENDIAN
193 s += proto + len;
194#else
195 s += (proto + len) << 8;
196#endif
197 s += (s >> 32);
198 return (__force __wsum)s;
199}
200EXPORT_SYMBOL(csum_tcpudp_nofold);
201#endif