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.
7 * IP/TCP/UDP checksumming routines
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
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.
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.
32 /* Revised by Kenneth Albanowski for m68knommu. Basic problem: unaligned access
33 kills, so most of the assembly has to go. */
35 #include <linux/module.h>
36 #include <net/checksum.h>
38 #include <asm/byteorder.h>
41 static inline unsigned short from32to16(unsigned int x)
43 /* add up 16-bit and 16-bit for 16+c bit */
44 x = (x & 0xffff) + (x >> 16);
46 x = (x & 0xffff) + (x >> 16);
50 static unsigned int do_csum(const unsigned char *buff, int len)
53 unsigned int result = 0;
57 odd = 1 & (unsigned long) buff;
59 #ifdef __LITTLE_ENDIAN
60 result += (*buff << 8);
67 count = len >> 1; /* nr of 16-bit words.. */
69 if (2 & (unsigned long) buff) {
70 result += *(unsigned short *) buff;
75 count >>= 1; /* nr of 32-bit words.. */
77 unsigned int carry = 0;
79 unsigned int w = *(unsigned int *) buff;
87 result = (result & 0xffff) + (result >> 16);
90 result += *(unsigned short *) buff;
95 #ifdef __LITTLE_ENDIAN
98 result += (*buff << 8);
100 result = from32to16(result);
102 result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
109 * This is a version of ip_compute_csum() optimized for IP headers,
110 * which always checksum on 4 octet boundaries.
112 __sum16 ip_fast_csum(const void *iph, unsigned int ihl)
114 return (__force __sum16)~do_csum(iph, ihl*4);
116 EXPORT_SYMBOL(ip_fast_csum);
119 * computes the checksum of a memory block at buff, length len,
120 * and adds in "sum" (32-bit)
122 * returns a 32-bit number suitable for feeding into itself
123 * or csum_tcpudp_magic
125 * this function must be called with even lengths, except
126 * for the last fragment, which may be odd
128 * it's best to have buff aligned on a 32-bit boundary
130 __wsum csum_partial(const void *buff, int len, __wsum wsum)
132 unsigned int sum = (__force unsigned int)wsum;
133 unsigned int result = do_csum(buff, len);
135 /* add in old sum, and carry.. */
139 return (__force __wsum)result;
141 EXPORT_SYMBOL(csum_partial);
144 * this routine is used for miscellaneous IP-like checksums, mainly
147 __sum16 ip_compute_csum(const void *buff, int len)
149 return (__force __sum16)~do_csum(buff, len);
151 EXPORT_SYMBOL(ip_compute_csum);
154 * copy from fs while checksumming, otherwise like csum_partial
157 csum_partial_copy_from_user(const void __user *src, void *dst, int len,
158 __wsum sum, int *csum_err)
162 missing = __copy_from_user(dst, src, len);
164 memset(dst + len - missing, 0, missing);
169 return csum_partial(dst, len, sum);
171 EXPORT_SYMBOL(csum_partial_copy_from_user);
174 * copy from ds while checksumming, otherwise like csum_partial
177 csum_partial_copy(const void *src, void *dst, int len, __wsum sum)
179 memcpy(dst, src, len);
180 return csum_partial(dst, len, sum);
182 EXPORT_SYMBOL(csum_partial_copy);
184 #ifndef csum_tcpudp_nofold
185 __wsum csum_tcpudp_nofold(__be32 saddr, __be32 daddr,
187 unsigned short proto,
190 unsigned long long s = (__force u32)sum;
192 s += (__force u32)saddr;
193 s += (__force u32)daddr;
197 s += (proto + len) << 8;
200 return (__force __wsum)s;
202 EXPORT_SYMBOL(csum_tcpudp_nofold);