/* | |

* INET An implementation of the TCP/IP protocol suite for the LINUX | |

* operating system. INET is implemented using the BSD Socket | |

* interface as the means of communication with the user level. | |

* | |

* IP/TCP/UDP checksumming routines | |

* | |

* Authors: Jorge Cwik, <jorge@laser.satlink.net> | |

* Arnt Gulbrandsen, <agulbra@nvg.unit.no> | |

* Tom May, <ftom@netcom.com> | |

* Andreas Schwab, <schwab@issan.informatik.uni-dortmund.de> | |

* Lots of code moved from tcp.c and ip.c; see those files | |

* for more names. | |

* | |

* 03/02/96 Jes Sorensen, Andreas Schwab, Roman Hodek: | |

* Fixed some nasty bugs, causing some horrible crashes. | |

* A: At some points, the sum (%0) was used as | |

* length-counter instead of the length counter | |

* (%1). Thanks to Roman Hodek for pointing this out. | |

* B: GCC seems to mess up if one uses too many | |

* data-registers to hold input values and one tries to | |

* specify d0 and d1 as scratch registers. Letting gcc choose these | |

* registers itself solves the problem. | |

* | |

* This program is free software; you can redistribute it and/or | |

* modify it under the terms of the GNU General Public License | |

* as published by the Free Software Foundation; either version | |

* 2 of the License, or (at your option) any later version. | |

*/ | |

/* Revised by Kenneth Albanowski for m68knommu. Basic problem: unaligned access kills, so most | |

of the assembly has to go. */ | |

#include <net/checksum.h> | |

#include <linux/module.h> | |

static inline unsigned short from32to16(unsigned long x) | |

{ | |

/* add up 16-bit and 16-bit for 16+c bit */ | |

x = (x & 0xffff) + (x >> 16); | |

/* add up carry.. */ | |

x = (x & 0xffff) + (x >> 16); | |

return x; | |

} | |

static unsigned long do_csum(const unsigned char * buff, int len) | |

{ | |

int odd, count; | |

unsigned long result = 0; | |

if (len <= 0) | |

goto out; | |

odd = 1 & (unsigned long) buff; | |

if (odd) { | |

result = *buff; | |

len--; | |

buff++; | |

} | |

count = len >> 1; /* nr of 16-bit words.. */ | |

if (count) { | |

if (2 & (unsigned long) buff) { | |

result += *(unsigned short *) buff; | |

count--; | |

len -= 2; | |

buff += 2; | |

} | |

count >>= 1; /* nr of 32-bit words.. */ | |

if (count) { | |

unsigned long carry = 0; | |

do { | |

unsigned long w = *(unsigned long *) buff; | |

count--; | |

buff += 4; | |

result += carry; | |

result += w; | |

carry = (w > result); | |

} while (count); | |

result += carry; | |

result = (result & 0xffff) + (result >> 16); | |

} | |

if (len & 2) { | |

result += *(unsigned short *) buff; | |

buff += 2; | |

} | |

} | |

if (len & 1) | |

result += (*buff << 8); | |

result = from32to16(result); | |

if (odd) | |

result = ((result >> 8) & 0xff) | ((result & 0xff) << 8); | |

out: | |

return result; | |

} | |

/* | |

* This is a version of ip_compute_csum() optimized for IP headers, | |

* which always checksum on 4 octet boundaries. | |

*/ | |

__sum16 ip_fast_csum(const void *iph, unsigned int ihl) | |

{ | |

return (__force __sum16)~do_csum(iph,ihl*4); | |

} | |

/* | |

* computes the checksum of a memory block at buff, length len, | |

* and adds in "sum" (32-bit) | |

* | |

* returns a 32-bit number suitable for feeding into itself | |

* or csum_tcpudp_magic | |

* | |

* this function must be called with even lengths, except | |

* for the last fragment, which may be odd | |

* | |

* it's best to have buff aligned on a 32-bit boundary | |

*/ | |

/* | |

* Egads... That thing apparently assumes that *all* checksums it ever sees will | |

* be folded. Very likely a bug. | |

*/ | |

__wsum csum_partial(const void *buff, int len, __wsum sum) | |

{ | |

unsigned int result = do_csum(buff, len); | |

/* add in old sum, and carry.. */ | |

result += (__force u32)sum; | |

/* 16+c bits -> 16 bits */ | |

result = (result & 0xffff) + (result >> 16); | |

return (__force __wsum)result; | |

} | |

EXPORT_SYMBOL(csum_partial); | |

/* | |

* this routine is used for miscellaneous IP-like checksums, mainly | |

* in icmp.c | |

*/ | |

__sum16 ip_compute_csum(const void *buff, int len) | |

{ | |

return (__force __sum16)~do_csum(buff,len); | |

} | |

/* | |

* copy from fs while checksumming, otherwise like csum_partial | |

*/ | |

__wsum | |

csum_partial_copy_from_user(const void __user *src, void *dst, int len, | |

__wsum sum, int *csum_err) | |

{ | |

if (csum_err) *csum_err = 0; | |

memcpy(dst, (__force const void *)src, len); | |

return csum_partial(dst, len, sum); | |

} | |

/* | |

* copy from ds while checksumming, otherwise like csum_partial | |

*/ | |

__wsum | |

csum_partial_copy_nocheck(const void *src, void *dst, int len, __wsum sum) | |

{ | |

memcpy(dst, src, len); | |

return csum_partial(dst, len, sum); | |

} |