initial commit with v2.6.9
[linux-2.6.9-moxart.git] / arch / m68knommu / lib / checksum.c
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1 /*
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.
6 * IP/TCP/UDP checksumming routines
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.
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.
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.
31 /* Revised by Kenneth Albanowski for m68knommu. Basic problem: unaligned access kills, so most
32 of the assembly has to go. */
34 #include <net/checksum.h>
36 static inline unsigned short from32to16(unsigned long x)
38 /* add up 16-bit and 16-bit for 16+c bit */
39 x = (x & 0xffff) + (x >> 16);
40 /* add up carry.. */
41 x = (x & 0xffff) + (x >> 16);
42 return x;
45 static unsigned long do_csum(const unsigned char * buff, int len)
47 int odd, count;
48 unsigned long result = 0;
50 if (len <= 0)
51 goto out;
52 odd = 1 & (unsigned long) buff;
53 if (odd) {
54 result = *buff;
55 len--;
56 buff++;
58 count = len >> 1; /* nr of 16-bit words.. */
59 if (count) {
60 if (2 & (unsigned long) buff) {
61 result += *(unsigned short *) buff;
62 count--;
63 len -= 2;
64 buff += 2;
66 count >>= 1; /* nr of 32-bit words.. */
67 if (count) {
68 unsigned long carry = 0;
69 do {
70 unsigned long w = *(unsigned long *) buff;
71 count--;
72 buff += 4;
73 result += carry;
74 result += w;
75 carry = (w > result);
76 } while (count);
77 result += carry;
78 result = (result & 0xffff) + (result >> 16);
80 if (len & 2) {
81 result += *(unsigned short *) buff;
82 buff += 2;
85 if (len & 1)
86 result += (*buff << 8);
87 result = from32to16(result);
88 if (odd)
89 result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
90 out:
91 return result;
95 * This is a version of ip_compute_csum() optimized for IP headers,
96 * which always checksum on 4 octet boundaries.
98 unsigned short ip_fast_csum(unsigned char * iph, unsigned int ihl)
100 return ~do_csum(iph,ihl*4);
104 * computes the checksum of a memory block at buff, length len,
105 * and adds in "sum" (32-bit)
107 * returns a 32-bit number suitable for feeding into itself
108 * or csum_tcpudp_magic
110 * this function must be called with even lengths, except
111 * for the last fragment, which may be odd
113 * it's best to have buff aligned on a 32-bit boundary
115 unsigned int csum_partial(const unsigned char * buff, int len, unsigned int sum)
117 unsigned int result = do_csum(buff, len);
119 /* add in old sum, and carry.. */
120 result += sum;
121 if (sum > result)
122 result += 1;
123 return result;
126 EXPORT_SYMBOL(csum_partial);
129 * this routine is used for miscellaneous IP-like checksums, mainly
130 * in icmp.c
132 unsigned short ip_compute_csum(const unsigned char * buff, int len)
134 return ~do_csum(buff,len);
138 * copy from fs while checksumming, otherwise like csum_partial
141 unsigned int
142 csum_partial_copy_from_user(const char *src, char *dst, int len, int sum, int *csum_err)
144 if (csum_err) *csum_err = 0;
145 memcpy(dst, src, len);
146 return csum_partial(dst, len, sum);
150 * copy from ds while checksumming, otherwise like csum_partial
153 unsigned int
154 csum_partial_copy(const char *src, char *dst, int len, int sum)
156 memcpy(dst, src, len);
157 return csum_partial(dst, len, sum);