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1/* SPDX-License-Identifier: GPL-2.0-or-later */
2/*
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.
6 *
7 * Checksumming functions for IP, TCP, UDP and so on
8 *
9 * Authors: Jorge Cwik, <jorge@laser.satlink.net>
10 * Arnt Gulbrandsen, <agulbra@nvg.unit.no>
11 * Borrows very liberally from tcp.c and ip.c, see those
12 * files for more names.
13 */
14
15#ifndef _CHECKSUM_H
16#define _CHECKSUM_H
17
18#include <linux/errno.h>
19#include <asm/types.h>
20#include <asm/byteorder.h>
21#include <asm/checksum.h>
22#if !defined(_HAVE_ARCH_COPY_AND_CSUM_FROM_USER) || !defined(HAVE_CSUM_COPY_USER)
23#include <linux/uaccess.h>
24#endif
25
26#ifndef _HAVE_ARCH_COPY_AND_CSUM_FROM_USER
27static __always_inline
28__wsum csum_and_copy_from_user (const void __user *src, void *dst,
29 int len)
30{
31 if (copy_from_user(to: dst, from: src, n: len))
32 return 0;
33 return csum_partial(buff: dst, len, sum: ~0U);
34}
35#endif
36
37#ifndef HAVE_CSUM_COPY_USER
38static __always_inline __wsum csum_and_copy_to_user
39(const void *src, void __user *dst, int len)
40{
41 __wsum sum = csum_partial(buff: src, len, sum: ~0U);
42
43 if (copy_to_user(to: dst, from: src, n: len) == 0)
44 return sum;
45 return 0;
46}
47#endif
48
49#ifndef _HAVE_ARCH_CSUM_AND_COPY
50static __always_inline __wsum
51csum_partial_copy_nocheck(const void *src, void *dst, int len)
52{
53 memcpy(dst, src, len);
54 return csum_partial(buff: dst, len, sum: 0);
55}
56#endif
57
58#ifndef HAVE_ARCH_CSUM_ADD
59static __always_inline __wsum csum_add(__wsum csum, __wsum addend)
60{
61 u32 res = (__force u32)csum;
62 res += (__force u32)addend;
63 return (__force __wsum)(res + (res < (__force u32)addend));
64}
65#endif
66
67static __always_inline __wsum csum_sub(__wsum csum, __wsum addend)
68{
69 return csum_add(csum, addend: ~addend);
70}
71
72static __always_inline __sum16 csum16_add(__sum16 csum, __be16 addend)
73{
74 u16 res = (__force u16)csum;
75
76 res += (__force u16)addend;
77 return (__force __sum16)(res + (res < (__force u16)addend));
78}
79
80static __always_inline __sum16 csum16_sub(__sum16 csum, __be16 addend)
81{
82 return csum16_add(csum, addend: ~addend);
83}
84
85#ifndef HAVE_ARCH_CSUM_SHIFT
86static __always_inline __wsum csum_shift(__wsum sum, int offset)
87{
88 /* rotate sum to align it with a 16b boundary */
89 if (offset & 1)
90 return (__force __wsum)ror32(word: (__force u32)sum, shift: 8);
91 return sum;
92}
93#endif
94
95static __always_inline __wsum
96csum_block_add(__wsum csum, __wsum csum2, int offset)
97{
98 return csum_add(csum, addend: csum_shift(sum: csum2, offset));
99}
100
101static __always_inline __wsum
102csum_block_sub(__wsum csum, __wsum csum2, int offset)
103{
104 return csum_block_add(csum, csum2: ~csum2, offset);
105}
106
107static __always_inline __wsum csum_unfold(__sum16 n)
108{
109 return (__force __wsum)n;
110}
111
112#define CSUM_MANGLED_0 ((__force __sum16)0xffff)
113
114static __always_inline void csum_replace_by_diff(__sum16 *sum, __wsum diff)
115{
116 *sum = csum_fold(csum: csum_add(csum: diff, addend: ~csum_unfold(n: *sum)));
117}
118
119static __always_inline void csum_replace4(__sum16 *sum, __be32 from, __be32 to)
120{
121 __wsum tmp = csum_sub(csum: ~csum_unfold(n: *sum), addend: (__force __wsum)from);
122
123 *sum = csum_fold(csum: csum_add(csum: tmp, addend: (__force __wsum)to));
124}
125
126/* Implements RFC 1624 (Incremental Internet Checksum)
127 * 3. Discussion states :
128 * HC' = ~(~HC + ~m + m')
129 * m : old value of a 16bit field
130 * m' : new value of a 16bit field
131 */
132static __always_inline void csum_replace2(__sum16 *sum, __be16 old, __be16 new)
133{
134 *sum = ~csum16_add(csum: csum16_sub(csum: ~(*sum), addend: old), addend: new);
135}
136
137static inline void csum_replace(__wsum *csum, __wsum old, __wsum new)
138{
139 *csum = csum_add(csum: csum_sub(csum: *csum, addend: old), addend: new);
140}
141
142static inline unsigned short csum_from32to16(unsigned int sum)
143{
144 sum += (sum >> 16) | (sum << 16);
145 return (unsigned short)(sum >> 16);
146}
147
148struct sk_buff;
149void inet_proto_csum_replace4(__sum16 *sum, struct sk_buff *skb,
150 __be32 from, __be32 to, bool pseudohdr);
151void inet_proto_csum_replace16(__sum16 *sum, struct sk_buff *skb,
152 const __be32 *from, const __be32 *to,
153 bool pseudohdr);
154void inet_proto_csum_replace_by_diff(__sum16 *sum, struct sk_buff *skb,
155 __wsum diff, bool pseudohdr, bool ipv6);
156
157static __always_inline
158void inet_proto_csum_replace2(__sum16 *sum, struct sk_buff *skb,
159 __be16 from, __be16 to, bool pseudohdr)
160{
161 inet_proto_csum_replace4(sum, skb, from: (__force __be32)from,
162 to: (__force __be32)to, pseudohdr);
163}
164
165static __always_inline __wsum remcsum_adjust(void *ptr, __wsum csum,
166 int start, int offset)
167{
168 __sum16 *psum = (__sum16 *)(ptr + offset);
169 __wsum delta;
170
171 /* Subtract out checksum up to start */
172 csum = csum_sub(csum, addend: csum_partial(buff: ptr, len: start, sum: 0));
173
174 /* Set derived checksum in packet */
175 delta = csum_sub(csum: (__force __wsum)csum_fold(csum),
176 addend: (__force __wsum)*psum);
177 *psum = csum_fold(csum);
178
179 return delta;
180}
181
182static __always_inline void remcsum_unadjust(__sum16 *psum, __wsum delta)
183{
184 *psum = csum_fold(csum: csum_sub(csum: delta, addend: (__force __wsum)*psum));
185}
186
187static __always_inline __wsum wsum_negate(__wsum val)
188{
189 return (__force __wsum)-((__force u32)val);
190}
191#endif
192

source code of linux/include/net/checksum.h