include/asm-generic/checksum.h

   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  */
  19 extern __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  */
  26 extern __sum16 ip_fast_csum(const void *iph, unsigned int ihl);
  27 #endif
  28
  29 #ifndef csum_fold
  30 /*
  31  * Fold a partial checksum
  32  */
  33 static inline __sum16 csum_fold(__wsum csum)
  34 {
  35         u32 sum = (__force u32)csum;
  36         return (__force __sum16)((~sum - ror32(sum, 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  */
  45 extern __wsum
  46 csum_tcpudp_nofold(__be32 saddr, __be32 daddr, __u32 len,
  47                    __u8 proto, __wsum sum);
  48 #endif
  49
  50 #ifndef csum_tcpudp_magic
  51 static inline __sum16
  52 csum_tcpudp_magic(__be32 saddr, __be32 daddr, __u32 len,
  53                   __u8 proto, __wsum sum)
  54 {
  55         return csum_fold(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  */
  63 extern __sum16 ip_compute_csum(const void *buff, int len);
  64
  65 #endif /* __ASM_GENERIC_CHECKSUM_H */