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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 |
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; |
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); |
100 | out: |
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 | } |
114 | EXPORT_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 | } |
140 | EXPORT_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 | } |
150 | EXPORT_SYMBOL(ip_compute_csum); |
151 | |
152 | /* |
153 | * copy from fs while checksumming, otherwise like csum_partial |
154 | */ |
155 | __wsum |
156 | csum_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 | } |
170 | EXPORT_SYMBOL(csum_partial_copy_from_user); |
171 | |
172 | /* |
173 | * copy from ds while checksumming, otherwise like csum_partial |
174 | */ |
175 | __wsum |
176 | csum_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 | } |
181 | EXPORT_SYMBOL(csum_partial_copy); |
182 | |
183 | #ifndef csum_tcpudp_nofold |
184 | __wsum csum_tcpudp_nofold(__be32 saddr, __be32 daddr, |
185 | unsigned short len, |
186 | unsigned short proto, |
187 | __wsum sum) |
188 | { |
189 | unsigned long long s = (__force u32)sum; |
190 | |
191 | s += (__force u32)saddr; |
192 | s += (__force u32)daddr; |
193 | #ifdef __BIG_ENDIAN |
194 | s += proto + len; |
195 | #else |
196 | s += (proto + len) << 8; |
197 | #endif |
198 | s += (s >> 32); |
199 | return (__force __wsum)s; |
200 | } |
201 | EXPORT_SYMBOL(csum_tcpudp_nofold); |
202 | #endif |
203 |
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