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 extern __wsum csum_partial_copy(const void *src, void *dst, int len, __wsum sum);
  27
  28 #ifndef csum_partial_copy_nocheck
  29 #define csum_partial_copy_nocheck(src, dst, len, sum)   \
  30         csum_partial_copy((src), (dst), (len), (sum))
  31 #endif
  32
  33 #ifndef ip_fast_csum
  34 /*
  35  * This is a version of ip_compute_csum() optimized for IP headers,
  36  * which always checksum on 4 octet boundaries.
  37  */
  38 extern __sum16 ip_fast_csum(const void *iph, unsigned int ihl);
  39 #endif
  40
  41 #ifndef csum_fold
  42 /*
  43  * Fold a partial checksum
  44  */
  45 static inline __sum16 csum_fold(__wsum csum)
  46 {
  47         u32 sum = (__force u32)csum;
  48         sum = (sum & 0xffff) + (sum >> 16);
  49         sum = (sum & 0xffff) + (sum >> 16);
  50         return (__force __sum16)~sum;
  51 }
  52 #endif
  53
  54 #ifndef csum_tcpudp_nofold
  55 /*
  56  * computes the checksum of the TCP/UDP pseudo-header
  57  * returns a 16-bit checksum, already complemented
  58  */
  59 extern __wsum
  60 csum_tcpudp_nofold(__be32 saddr, __be32 daddr, __u32 len,
  61                    __u8 proto, __wsum sum);
  62 #endif
  63
  64 #ifndef csum_tcpudp_magic
  65 static inline __sum16
  66 csum_tcpudp_magic(__be32 saddr, __be32 daddr, __u32 len,
  67                   __u8 proto, __wsum sum)
  68 {
  69         return csum_fold(csum_tcpudp_nofold(saddr, daddr, len, proto, sum));
  70 }
  71 #endif
  72
  73 /*
  74  * this routine is used for miscellaneous IP-like checksums, mainly
  75  * in icmp.c
  76  */
  77 extern __sum16 ip_compute_csum(const void *buff, int len);
  78
  79 #endif /* __ASM_GENERIC_CHECKSUM_H */