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
from32to16(unsigned int x)40 static inline unsigned short from32to16(unsigned int x)
41 {
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
do_csum(const unsigned char * buff,int len)49 static unsigned int do_csum(const unsigned char *buff, int len)
50 {
51 int odd;
52 unsigned int result = 0;
53
54 if (len <= 0)
55 goto out;
56 odd = 1 & (unsigned long) buff;
57 if (odd) {
58 #ifdef __LITTLE_ENDIAN
59 result += (*buff << 8);
60 #else
61 result = *buff;
62 #endif
63 len--;
64 buff++;
65 }
66 if (len >= 2) {
67 if (2 & (unsigned long) buff) {
68 result += *(unsigned short *) buff;
69 len -= 2;
70 buff += 2;
71 }
72 if (len >= 4) {
73 const unsigned char *end = buff + ((unsigned)len & ~3);
74 unsigned int carry = 0;
75 do {
76 unsigned int w = *(unsigned int *) buff;
77 buff += 4;
78 result += carry;
79 result += w;
80 carry = (w > result);
81 } while (buff < end);
82 result += carry;
83 result = (result & 0xffff) + (result >> 16);
84 }
85 if (len & 2) {
86 result += *(unsigned short *) buff;
87 buff += 2;
88 }
89 }
90 if (len & 1)
91 #ifdef __LITTLE_ENDIAN
92 result += *buff;
93 #else
94 result += (*buff << 8);
95 #endif
96 result = from32to16(result);
97 if (odd)
98 result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
99 out:
100 return result;
101 }
102 EXPORT_SYMBOL(ip_fast_csum);
103
104 /*
105 * computes the checksum of a memory block at buff, length len,
106 * and adds in "sum" (32-bit)
107 *
108 * returns a 32-bit number suitable for feeding into itself
109 * or csum_tcpudp_magic
110 *
111 * this function must be called with even lengths, except
112 * for the last fragment, which may be odd
113 *
114 * it's best to have buff aligned on a 32-bit boundary
115 */
csum_partial(const void * buff,int len,__wsum wsum)116 __wsum csum_partial(const void *buff, int len, __wsum wsum)
117 {
118 unsigned int sum = (__force unsigned int)wsum;
119 unsigned int result = do_csum(buff, len);
120
121 /* add in old sum, and carry.. */
122 result += sum;
123 if (sum > result)
124 result += 1;
125 return (__force __wsum)result;
126 }
127
128 /*
129 * this routine is used for miscellaneous IP-like checksums, mainly
130 * in icmp.c
131 */
ip_compute_csum(const void * buff,int len)132 __sum16 ip_compute_csum(const void *buff, int len)
133 {
134 return (__force __sum16)~do_csum(buff, len);
135 }
136 EXPORT_SYMBOL(ip_compute_csum);
137
138 /*
139 * copy from fs while checksumming, otherwise like csum_partial
140 */
141 __wsum
csum_partial_copy_from_user(const void __user * src,void * dst,int len,__wsum sum,int * csum_err)142 csum_partial_copy_from_user(const void __user *src, void *dst, int len,
143 __wsum sum, int *csum_err)
144 {
145 int missing;
146
147 missing = __copy_from_user(dst, src, len);
148 if (missing) {
149 memset(dst + len - missing, 0, missing);
150 *csum_err = -EFAULT;
151 } else
152 *csum_err = 0;
153
154 return csum_partial(dst, len, sum);
155 }
156 EXPORT_SYMBOL(csum_partial_copy_from_user);
157
158 /*
159 * copy from ds while checksumming, otherwise like csum_partial
160 */
161 __wsum
csum_partial_copy(const void * src,void * dst,int len,__wsum sum)162 csum_partial_copy(const void *src, void *dst, int len, __wsum sum)
163 {
164 memcpy(dst, src, len);
165 return csum_partial(dst, len, sum);
166 }
167 EXPORT_SYMBOL(csum_partial_copy);
168