linux/include/asm-generic/checksum.h
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   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#ifndef csum_partial_copy_nocheck
  37#define csum_partial_copy_nocheck(src, dst, len, sum)   \
  38        csum_partial_copy((src), (dst), (len), (sum))
  39#endif
  40
  41/*
  42 * This is a version of ip_compute_csum() optimized for IP headers,
  43 * which always checksum on 4 octet boundaries.
  44 */
  45extern __sum16 ip_fast_csum(const void *iph, unsigned int ihl);
  46
  47/*
  48 * Fold a partial checksum
  49 */
  50static inline __sum16 csum_fold(__wsum csum)
  51{
  52        u32 sum = (__force u32)csum;
  53        sum = (sum & 0xffff) + (sum >> 16);
  54        sum = (sum & 0xffff) + (sum >> 16);
  55        return (__force __sum16)~sum;
  56}
  57
  58#ifndef csum_tcpudp_nofold
  59/*
  60 * computes the checksum of the TCP/UDP pseudo-header
  61 * returns a 16-bit checksum, already complemented
  62 */
  63extern __wsum
  64csum_tcpudp_nofold(__be32 saddr, __be32 daddr, unsigned short len,
  65                unsigned short proto, __wsum sum);
  66#endif
  67
  68#ifndef csum_tcpudp_magic
  69static inline __sum16
  70csum_tcpudp_magic(__be32 saddr, __be32 daddr, unsigned short len,
  71                  unsigned short proto, __wsum sum)
  72{
  73        return csum_fold(csum_tcpudp_nofold(saddr, daddr, len, proto, sum));
  74}
  75#endif
  76
  77/*
  78 * this routine is used for miscellaneous IP-like checksums, mainly
  79 * in icmp.c
  80 */
  81extern __sum16 ip_compute_csum(const void *buff, int len);
  82
  83#endif /* __ASM_GENERIC_CHECKSUM_H */
  84
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