LXR linux/include/asm-generic/checksum.h

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