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 /*
   6  * computes the checksum of a memory block at buff, length len,
   7  * and adds in "sum" (32-bit)
   8  *
   9  * returns a 32-bit number suitable for feeding into itself
  10  * or csum_tcpudp_magic
  11  *
  12  * this function must be called with even lengths, except
  13  * for the last fragment, which may be odd
  14  *
  15  * it's best to have buff aligned on a 32-bit boundary
  16  */
  17 extern __wsum csum_partial(const void *buff, int len, __wsum sum);
  18
  19 /*
  20  * the same as csum_partial, but copies from src while it
  21  * checksums
  22  *
  23  * here even more important to align src and dst on a 32-bit (or even
  24  * better 64-bit) boundary
  25  */
  26 #ifndef csum_partial_copy_nocheck
  27 __wsum csum_partial_copy_nocheck(const void *src, void *dst, int len,
  28                 __wsum sum);
  29 #endif
  30
  31 #ifndef ip_fast_csum
  32 /*
  33  * This is a version of ip_compute_csum() optimized for IP headers,
  34  * which always checksum on 4 octet boundaries.
  35  */
  36 extern __sum16 ip_fast_csum(const void *iph, unsigned int ihl);
  37 #endif
  38
  39 #ifndef csum_fold
  40 /*
  41  * Fold a partial checksum
  42  */
  43 static inline __sum16 csum_fold(__wsum csum)
  44 {
  45         u32 sum = (__force u32)csum;
  46         sum = (sum & 0xffff) + (sum >> 16);
  47         sum = (sum & 0xffff) + (sum >> 16);
  48         return (__force __sum16)~sum;
  49 }
  50 #endif
  51
  52 #ifndef csum_tcpudp_nofold
  53 /*
  54  * computes the checksum of the TCP/UDP pseudo-header
  55  * returns a 16-bit checksum, already complemented
  56  */
  57 extern __wsum
  58 csum_tcpudp_nofold(__be32 saddr, __be32 daddr, __u32 len,
  59                    __u8 proto, __wsum sum);
  60 #endif
  61
  62 #ifndef csum_tcpudp_magic
  63 static inline __sum16
  64 csum_tcpudp_magic(__be32 saddr, __be32 daddr, __u32 len,
  65                   __u8 proto, __wsum sum)
  66 {
  67         return csum_fold(csum_tcpudp_nofold(saddr, daddr, len, proto, sum));
  68 }
  69 #endif
  70
  71 /*
  72  * this routine is used for miscellaneous IP-like checksums, mainly
  73  * in icmp.c
  74  */
  75 extern __sum16 ip_compute_csum(const void *buff, int len);
  76
  77 #endif /* __ASM_GENERIC_CHECKSUM_H */