Root/include/asm-generic/checksum.h

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 */
16extern __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 */
25extern __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 */
33extern __wsum csum_partial_copy_from_user(const void __user *src, void *dst,
34                    int len, __wsum sum, int *csum_err);
35
36#define csum_partial_copy_nocheck(src, dst, len, sum) \
37    csum_partial_copy((src), (dst), (len), (sum))
38
39/*
40 * This is a version of ip_compute_csum() optimized for IP headers,
41 * which always checksum on 4 octet boundaries.
42 */
43extern __sum16 ip_fast_csum(const void *iph, unsigned int ihl);
44
45/*
46 * Fold a partial checksum
47 */
48static inline __sum16 csum_fold(__wsum csum)
49{
50    u32 sum = (__force u32)csum;
51    sum = (sum & 0xffff) + (sum >> 16);
52    sum = (sum & 0xffff) + (sum >> 16);
53    return (__force __sum16)~sum;
54}
55
56#ifndef csum_tcpudp_nofold
57/*
58 * computes the checksum of the TCP/UDP pseudo-header
59 * returns a 16-bit checksum, already complemented
60 */
61extern __wsum
62csum_tcpudp_nofold(__be32 saddr, __be32 daddr, unsigned short len,
63        unsigned short proto, __wsum sum);
64#endif
65
66static inline __sum16
67csum_tcpudp_magic(__be32 saddr, __be32 daddr, unsigned short len,
68          unsigned short proto, __wsum sum)
69{
70    return csum_fold(csum_tcpudp_nofold(saddr, daddr, len, proto, sum));
71}
72
73/*
74 * this routine is used for miscellaneous IP-like checksums, mainly
75 * in icmp.c
76 */
77extern __sum16 ip_compute_csum(const void *buff, int len);
78
79#endif /* __ASM_GENERIC_CHECKSUM_H */
80

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