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.
5 *
6 *		Checksumming functions for IP, TCP, UDP and so on
7 *
8 * Authors:	Jorge Cwik, <jorge@laser.satlink.net>
9 *		Arnt Gulbrandsen, <agulbra@nvg.unit.no>
10 *		Borrows very liberally from tcp.c and ip.c, see those
11 *		files for more names.
12 *
13 *		This program is free software; you can redistribute it and/or
14 *		modify it under the terms of the GNU General Public License
15 *		as published by the Free Software Foundation; either version
16 *		2 of the License, or (at your option) any later version.
17 */
18
19#ifndef _CHECKSUM_H
20#define _CHECKSUM_H
21
22#include <linux/errno.h>
23#include <asm/types.h>
24#include <asm/byteorder.h>
25#include <asm/uaccess.h>
26#include <asm/checksum.h>
27
28#ifndef _HAVE_ARCH_COPY_AND_CSUM_FROM_USER
29static inline
30__wsum csum_and_copy_from_user (const void __user *src, void *dst,
31				      int len, __wsum sum, int *err_ptr)
32{
33	if (access_ok(VERIFY_READ, src, len))
34		return csum_partial_copy_from_user(src, dst, len, sum, err_ptr);
35
36	if (len)
37		*err_ptr = -EFAULT;
38
39	return sum;
40}
41#endif
42
43#ifndef HAVE_CSUM_COPY_USER
44static __inline__ __wsum csum_and_copy_to_user
45(const void *src, void __user *dst, int len, __wsum sum, int *err_ptr)
46{
47	sum = csum_partial(src, len, sum);
48
49	if (access_ok(VERIFY_WRITE, dst, len)) {
50		if (copy_to_user(dst, src, len) == 0)
51			return sum;
52	}
53	if (len)
54		*err_ptr = -EFAULT;
55
56	return (__force __wsum)-1; /* invalid checksum */
57}
58#endif
59
60#ifndef HAVE_ARCH_CSUM_ADD
61static inline __wsum csum_add(__wsum csum, __wsum addend)
62{
63	u32 res = (__force u32)csum;
64	res += (__force u32)addend;
65	return (__force __wsum)(res + (res < (__force u32)addend));
66}
67#endif
68
69static inline __wsum csum_sub(__wsum csum, __wsum addend)
70{
71	return csum_add(csum, ~addend);
72}
73
74static inline __sum16 csum16_add(__sum16 csum, __be16 addend)
75{
76	u16 res = (__force u16)csum;
77
78	res += (__force u16)addend;
79	return (__force __sum16)(res + (res < (__force u16)addend));
80}
81
82static inline __sum16 csum16_sub(__sum16 csum, __be16 addend)
83{
84	return csum16_add(csum, ~addend);
85}
86
87static inline __wsum
88csum_block_add(__wsum csum, __wsum csum2, int offset)
89{
90	u32 sum = (__force u32)csum2;
91	if (offset&1)
92		sum = ((sum&0xFF00FF)<<8)+((sum>>8)&0xFF00FF);
93	return csum_add(csum, (__force __wsum)sum);
94}
95
96static inline __wsum
97csum_block_add_ext(__wsum csum, __wsum csum2, int offset, int len)
98{
99	return csum_block_add(csum, csum2, offset);
100}
101
102static inline __wsum
103csum_block_sub(__wsum csum, __wsum csum2, int offset)
104{
105	u32 sum = (__force u32)csum2;
106	if (offset&1)
107		sum = ((sum&0xFF00FF)<<8)+((sum>>8)&0xFF00FF);
108	return csum_sub(csum, (__force __wsum)sum);
109}
110
111static inline __wsum csum_unfold(__sum16 n)
112{
113	return (__force __wsum)n;
114}
115
116static inline __wsum csum_partial_ext(const void *buff, int len, __wsum sum)
117{
118	return csum_partial(buff, len, sum);
119}
120
121#define CSUM_MANGLED_0 ((__force __sum16)0xffff)
122
123static inline void csum_replace4(__sum16 *sum, __be32 from, __be32 to)
124{
125	*sum = csum_fold(csum_add(csum_sub(~csum_unfold(*sum), from), to));
126}
127
128/* Implements RFC 1624 (Incremental Internet Checksum)
129 * 3. Discussion states :
130 *     HC' = ~(~HC + ~m + m')
131 *  m : old value of a 16bit field
132 *  m' : new value of a 16bit field
133 */
134static inline void csum_replace2(__sum16 *sum, __be16 old, __be16 new)
135{
136	*sum = ~csum16_add(csum16_sub(~(*sum), old), new);
137}
138
139struct sk_buff;
140void inet_proto_csum_replace4(__sum16 *sum, struct sk_buff *skb,
141			      __be32 from, __be32 to, int pseudohdr);
142void inet_proto_csum_replace16(__sum16 *sum, struct sk_buff *skb,
143			       const __be32 *from, const __be32 *to,
144			       int pseudohdr);
145
146static inline void inet_proto_csum_replace2(__sum16 *sum, struct sk_buff *skb,
147					    __be16 from, __be16 to,
148					    int pseudohdr)
149{
150	inet_proto_csum_replace4(sum, skb, (__force __be32)from,
151				 (__force __be32)to, pseudohdr);
152}
153
154static inline __wsum remcsum_adjust(void *ptr, __wsum csum,
155				    int start, int offset)
156{
157	__sum16 *psum = (__sum16 *)(ptr + offset);
158	__wsum delta;
159
160	/* Subtract out checksum up to start */
161	csum = csum_sub(csum, csum_partial(ptr, start, 0));
162
163	/* Set derived checksum in packet */
164	delta = csum_sub(csum_fold(csum), *psum);
165	*psum = csum_fold(csum);
166
167	return delta;
168}
169
170static inline void remcsum_unadjust(__sum16 *psum, __wsum delta)
171{
172	*psum = csum_fold(csum_sub(delta, *psum));
173}
174
175#endif
176