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Linux/include/net/checksum.h

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  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
 29 static 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
 44 static __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
 61 static 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 
 69 static inline __wsum csum_sub(__wsum csum, __wsum addend)
 70 {
 71         return csum_add(csum, ~addend);
 72 }
 73 
 74 static 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 
 82 static inline __sum16 csum16_sub(__sum16 csum, __be16 addend)
 83 {
 84         return csum16_add(csum, ~addend);
 85 }
 86 
 87 static inline __wsum
 88 csum_block_add(__wsum csum, __wsum csum2, int offset)
 89 {
 90         u32 sum = (__force u32)csum2;
 91 
 92         /* rotate sum to align it with a 16b boundary */
 93         if (offset & 1)
 94                 sum = ror32(sum, 8);
 95 
 96         return csum_add(csum, (__force __wsum)sum);
 97 }
 98 
 99 static inline __wsum
100 csum_block_add_ext(__wsum csum, __wsum csum2, int offset, int len)
101 {
102         return csum_block_add(csum, csum2, offset);
103 }
104 
105 static inline __wsum
106 csum_block_sub(__wsum csum, __wsum csum2, int offset)
107 {
108         return csum_block_add(csum, ~csum2, offset);
109 }
110 
111 static inline __wsum csum_unfold(__sum16 n)
112 {
113         return (__force __wsum)n;
114 }
115 
116 static 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 
123 static inline void csum_replace_by_diff(__sum16 *sum, __wsum diff)
124 {
125         *sum = csum_fold(csum_add(diff, ~csum_unfold(*sum)));
126 }
127 
128 static inline void csum_replace4(__sum16 *sum, __be32 from, __be32 to)
129 {
130         __wsum tmp = csum_sub(~csum_unfold(*sum), (__force __wsum)from);
131 
132         *sum = csum_fold(csum_add(tmp, (__force __wsum)to));
133 }
134 
135 /* Implements RFC 1624 (Incremental Internet Checksum)
136  * 3. Discussion states :
137  *     HC' = ~(~HC + ~m + m')
138  *  m : old value of a 16bit field
139  *  m' : new value of a 16bit field
140  */
141 static inline void csum_replace2(__sum16 *sum, __be16 old, __be16 new)
142 {
143         *sum = ~csum16_add(csum16_sub(~(*sum), old), new);
144 }
145 
146 struct sk_buff;
147 void inet_proto_csum_replace4(__sum16 *sum, struct sk_buff *skb,
148                               __be32 from, __be32 to, bool pseudohdr);
149 void inet_proto_csum_replace16(__sum16 *sum, struct sk_buff *skb,
150                                const __be32 *from, const __be32 *to,
151                                bool pseudohdr);
152 void inet_proto_csum_replace_by_diff(__sum16 *sum, struct sk_buff *skb,
153                                      __wsum diff, bool pseudohdr);
154 
155 static inline void inet_proto_csum_replace2(__sum16 *sum, struct sk_buff *skb,
156                                             __be16 from, __be16 to,
157                                             bool pseudohdr)
158 {
159         inet_proto_csum_replace4(sum, skb, (__force __be32)from,
160                                  (__force __be32)to, pseudohdr);
161 }
162 
163 static inline __wsum remcsum_adjust(void *ptr, __wsum csum,
164                                     int start, int offset)
165 {
166         __sum16 *psum = (__sum16 *)(ptr + offset);
167         __wsum delta;
168 
169         /* Subtract out checksum up to start */
170         csum = csum_sub(csum, csum_partial(ptr, start, 0));
171 
172         /* Set derived checksum in packet */
173         delta = csum_sub((__force __wsum)csum_fold(csum),
174                          (__force __wsum)*psum);
175         *psum = csum_fold(csum);
176 
177         return delta;
178 }
179 
180 static inline void remcsum_unadjust(__sum16 *psum, __wsum delta)
181 {
182         *psum = csum_fold(csum_sub(delta, *psum));
183 }
184 
185 #endif
186 

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