1/*
2 * File:         arch/blackfin/lib/checksum.c
3 * Based on:     none - original work
4 * Author:
5 *
6 * Created:
7 * Description:  An implementation of the TCP/IP protocol suite for the LINUX
8 *               operating system.  INET is implemented using the  BSD Socket
9 *               interface as the means of communication with the user level.
10 *
11 * Modified:
12 *               Copyright 2004-2006 Analog Devices Inc.
13 *
14 * Bugs:         Enter bugs at http://blackfin.uclinux.org/
15 *
16 * This program is free software; you can redistribute it and/or modify
17 * it under the terms of the GNU General Public License as published by
18 * the Free Software Foundation; either version 2 of the License, or
19 * (at your option) any later version.
20 *
21 * This program is distributed in the hope that it will be useful,
22 * but WITHOUT ANY WARRANTY; without even the implied warranty of
23 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
24 * GNU General Public License for more details.
25 *
26 * You should have received a copy of the GNU General Public License
27 * along with this program; if not, see the file COPYING, or write
28 * to the Free Software Foundation, Inc.,
29 * 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
30 */
31
32#include <net/checksum.h>
33#include <asm/checksum.h>
34
35#ifdef CONFIG_IP_CHECKSUM_L1
36static unsigned short do_csum(const unsigned char *buff, int len)__attribute__((l1_text));
37#endif
38
39static unsigned short do_csum(const unsigned char *buff, int len)
40{
41	register unsigned long sum = 0;
42	int swappem = 0;
43
44	if (1 & (unsigned long)buff) {
45		sum = *buff << 8;
46		buff++;
47		len--;
48		++swappem;
49	}
50
51	while (len > 1) {
52		sum += *(unsigned short *)buff;
53		buff += 2;
54		len -= 2;
55	}
56
57	if (len > 0)
58		sum += *buff;
59
60	/*  Fold 32-bit sum to 16 bits */
61	while (sum >> 16)
62		sum = (sum & 0xffff) + (sum >> 16);
63
64	if (swappem)
65		sum = ((sum & 0xff00) >> 8) + ((sum & 0x00ff) << 8);
66
67	return sum;
68
69}
70
71/*
72 *	This is a version of ip_compute_csum() optimized for IP headers,
73 *	which always checksum on 4 octet boundaries.
74 */
75unsigned short ip_fast_csum(unsigned char *iph, unsigned int ihl)
76{
77	return ~do_csum(iph, ihl * 4);
78}
79
80/*
81 * computes the checksum of a memory block at buff, length len,
82 * and adds in "sum" (32-bit)
83 *
84 * returns a 32-bit number suitable for feeding into itself
85 * or csum_tcpudp_magic
86 *
87 * this function must be called with even lengths, except
88 * for the last fragment, which may be odd
89 *
90 * it's best to have buff aligned on a 32-bit boundary
91 */
92unsigned int csum_partial(const unsigned char *buff, int len, unsigned int sum)
93{
94	/*
95	 * Just in case we get nasty checksum data...
96	 * Like 0xffff6ec3 in the case of our IPv6 multicast header.
97	 * We fold to begin with, as well as at the end.
98	 */
99	sum = (sum & 0xffff) + (sum >> 16);
100
101	sum += do_csum(buff, len);
102
103	sum = (sum & 0xffff) + (sum >> 16);
104
105	return sum;
106}
107
108/*
109 * this routine is used for miscellaneous IP-like checksums, mainly
110 * in icmp.c
111 */
112unsigned short ip_compute_csum(const unsigned char *buff, int len)
113{
114	return ~do_csum(buff, len);
115}
116
117/*
118 * copy from fs while checksumming, otherwise like csum_partial
119 */
120
121unsigned int
122csum_partial_copy_from_user(const unsigned char *src, unsigned char *dst,
123			    int len, int sum, int *csum_err)
124{
125	if (csum_err)
126		*csum_err = 0;
127	memcpy(dst, src, len);
128	return csum_partial(dst, len, sum);
129}
130
131/*
132 * copy from ds while checksumming, otherwise like csum_partial
133 */
134
135unsigned int csum_partial_copy(const unsigned char *src, unsigned char *dst,
136			       int len, int sum)
137{
138	memcpy(dst, src, len);
139	return csum_partial(dst, len, sum);
140}
141