1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef __ASM_GENERIC_CHECKSUM_H
3#define __ASM_GENERIC_CHECKSUM_H
4
5#include <linux/bitops.h>
6
7/*
8 * computes the checksum of a memory block at buff, length len,
9 * and adds in "sum" (32-bit)
10 *
11 * returns a 32-bit number suitable for feeding into itself
12 * or csum_tcpudp_magic
13 *
14 * this function must be called with even lengths, except
15 * for the last fragment, which may be odd
16 *
17 * it's best to have buff aligned on a 32-bit boundary
18 */
19extern __wsum csum_partial(const void *buff, int len, __wsum sum);
20
21#ifndef ip_fast_csum
22/*
23 * This is a version of ip_compute_csum() optimized for IP headers,
24 * which always checksum on 4 octet boundaries.
25 */
26extern __sum16 ip_fast_csum(const void *iph, unsigned int ihl);
27#endif
28
29#ifndef csum_fold
30/*
31 * Fold a partial checksum
32 */
33static inline __sum16 csum_fold(__wsum csum)
34{
35 u32 sum = (__force u32)csum;
36 return (__force __sum16)((~sum - ror32(word: sum, shift: 16)) >> 16);
37}
38#endif
39
40#ifndef csum_tcpudp_nofold
41/*
42 * computes the checksum of the TCP/UDP pseudo-header
43 * returns a 16-bit checksum, already complemented
44 */
45extern __wsum
46csum_tcpudp_nofold(__be32 saddr, __be32 daddr, __u32 len,
47 __u8 proto, __wsum sum);
48#endif
49
50#ifndef csum_tcpudp_magic
51static inline __sum16
52csum_tcpudp_magic(__be32 saddr, __be32 daddr, __u32 len,
53 __u8 proto, __wsum sum)
54{
55 return csum_fold(csum: csum_tcpudp_nofold(saddr, daddr, len, proto, sum));
56}
57#endif
58
59/*
60 * this routine is used for miscellaneous IP-like checksums, mainly
61 * in icmp.c
62 */
63extern __sum16 ip_compute_csum(const void *buff, int len);
64
65#endif /* __ASM_GENERIC_CHECKSUM_H */
66

source code of linux/include/asm-generic/checksum.h