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checksum.h
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1 #ifndef __ASM_GENERIC_CHECKSUM_H
2 #define __ASM_GENERIC_CHECKSUM_H
3 
4 /*
5  * computes the checksum of a memory block at buff, length len,
6  * and adds in "sum" (32-bit)
7  *
8  * returns a 32-bit number suitable for feeding into itself
9  * or csum_tcpudp_magic
10  *
11  * this function must be called with even lengths, except
12  * for the last fragment, which may be odd
13  *
14  * it's best to have buff aligned on a 32-bit boundary
15  */
16 extern __wsum csum_partial(const void *buff, int len, __wsum sum);
17 
18 /*
19  * the same as csum_partial, but copies from src while it
20  * checksums
21  *
22  * here even more important to align src and dst on a 32-bit (or even
23  * better 64-bit) boundary
24  */
25 extern __wsum csum_partial_copy(const void *src, void *dst, int len, __wsum sum);
26 
27 /*
28  * the same as csum_partial_copy, but copies from user space.
29  *
30  * here even more important to align src and dst on a 32-bit (or even
31  * better 64-bit) boundary
32  */
33 extern __wsum csum_partial_copy_from_user(const void __user *src, void *dst,
34  int len, __wsum sum, int *csum_err);
35 
36 #ifndef csum_partial_copy_nocheck
37 #define csum_partial_copy_nocheck(src, dst, len, sum) \
38  csum_partial_copy((src), (dst), (len), (sum))
39 #endif
40 
41 /*
42  * This is a version of ip_compute_csum() optimized for IP headers,
43  * which always checksum on 4 octet boundaries.
44  */
45 extern __sum16 ip_fast_csum(const void *iph, unsigned int ihl);
46 
47 /*
48  * Fold a partial checksum
49  */
50 static inline __sum16 csum_fold(__wsum csum)
51 {
52  u32 sum = (__force u32)csum;
53  sum = (sum & 0xffff) + (sum >> 16);
54  sum = (sum & 0xffff) + (sum >> 16);
55  return (__force __sum16)~sum;
56 }
57 
58 #ifndef csum_tcpudp_nofold
59 /*
60  * computes the checksum of the TCP/UDP pseudo-header
61  * returns a 16-bit checksum, already complemented
62  */
63 extern __wsum
64 csum_tcpudp_nofold(__be32 saddr, __be32 daddr, unsigned short len,
65  unsigned short proto, __wsum sum);
66 #endif
67 
68 #ifndef csum_tcpudp_magic
69 static inline __sum16
70 csum_tcpudp_magic(__be32 saddr, __be32 daddr, unsigned short len,
71  unsigned short proto, __wsum sum)
72 {
73  return csum_fold(csum_tcpudp_nofold(saddr, daddr, len, proto, sum));
74 }
75 #endif
76 
77 /*
78  * this routine is used for miscellaneous IP-like checksums, mainly
79  * in icmp.c
80  */
81 extern __sum16 ip_compute_csum(const void *buff, int len);
82 
83 #endif /* __ASM_GENERIC_CHECKSUM_H */