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
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>
35 #include <asm/checksum.h>
36 #include <linux/module.h>
38 static inline unsigned short from32to16(unsigned long x
)
40 /* add up 16-bit and 16-bit for 16+c bit */
41 x
= (x
& 0xffff) + (x
>> 16);
43 x
= (x
& 0xffff) + (x
>> 16);
47 static unsigned long do_csum(const unsigned char * buff
, int len
)
50 unsigned long result
= 0;
54 odd
= 1 & (unsigned long) buff
;
60 count
= len
>> 1; /* nr of 16-bit words.. */
62 if (2 & (unsigned long) buff
) {
63 result
+= *(unsigned short *) buff
;
68 count
>>= 1; /* nr of 32-bit words.. */
70 unsigned long carry
= 0;
72 unsigned long w
= *(unsigned long *) buff
;
80 result
= (result
& 0xffff) + (result
>> 16);
83 result
+= *(unsigned short *) buff
;
88 result
+= (*buff
<< 8);
89 result
= from32to16(result
);
91 result
= ((result
>> 8) & 0xff) | ((result
& 0xff) << 8);
97 * computes the checksum of a memory block at buff, length len,
98 * and adds in "sum" (32-bit)
100 * returns a 32-bit number suitable for feeding into itself
101 * or csum_tcpudp_magic
103 * this function must be called with even lengths, except
104 * for the last fragment, which may be odd
106 * it's best to have buff aligned on a 32-bit boundary
108 unsigned int csum_partial(const unsigned char * buff
, int len
, unsigned int sum
)
110 unsigned int result
= do_csum(buff
, len
);
112 /* add in old sum, and carry.. */
119 EXPORT_SYMBOL(csum_partial
);
122 * this routine is used for miscellaneous IP-like checksums, mainly
125 unsigned short ip_compute_csum(const unsigned char * buff
, int len
)
127 return ~do_csum(buff
, len
);
130 EXPORT_SYMBOL(ip_compute_csum
);
133 * copy from fs while checksumming, otherwise like csum_partial
136 csum_partial_copy_from_user(const char __user
*src
, char *dst
,
137 int len
, int sum
, int *csum_err
)
144 rem
= copy_from_user(dst
, src
, len
);
148 memset(dst
+ len
- rem
, 0, rem
);
152 return csum_partial(dst
, len
, sum
);
155 EXPORT_SYMBOL(csum_partial_copy_from_user
);
158 * copy from ds while checksumming, otherwise like csum_partial
161 csum_partial_copy(const char *src
, char *dst
, int len
, int sum
)
163 memcpy(dst
, src
, len
);
164 return csum_partial(dst
, len
, sum
);
167 EXPORT_SYMBOL(csum_partial_copy
);