release/src-rt-6.x.4708/linux/linux-2.6.36/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  */
  16 extern __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  */
  25 extern __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  */
  33 extern __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  */
  43 extern __sum16 ip_fast_csum(const void *iph, unsigned int ihl);
  44
  45 /*
  46  * Fold a partial checksum
  47  */
  48 static 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  */
  61 extern __wsum
  62 csum_tcpudp_nofold(__be32 saddr, __be32 daddr, unsigned short len,
  63                 unsigned short proto, __wsum sum);
  64 #endif
  65
  66 static inline __sum16
  67 csum_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  */
  77 extern __sum16 ip_compute_csum(const void *buff, int len);
  78
  79 #endif /* __ASM_GENERIC_CHECKSUM_H */