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4906e26 @omegamoon Initial commit; Original 'BQ Edison' code
authored
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
41 static 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
50 static 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);
103 out:
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 }
116 EXPORT_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 }
141 EXPORT_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 }
151 EXPORT_SYMBOL(ip_compute_csum);
152
153 /*
154 * copy from fs while checksumming, otherwise like csum_partial
155 */
156 __wsum
157 csum_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 }
171 EXPORT_SYMBOL(csum_partial_copy_from_user);
172
173 /*
174 * copy from ds while checksumming, otherwise like csum_partial
175 */
176 __wsum
177 csum_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 }
182 EXPORT_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 }
202 EXPORT_SYMBOL(csum_tcpudp_nofold);
203 #endif
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