linux / linux / kernel / git / gregkh / char-misc / refs/tags/v2.6.13-rc1 / . / arch / alpha / lib / checksum.c

/* | |

* arch/alpha/lib/checksum.c | |

* | |

* This file contains network checksum routines that are better done | |

* in an architecture-specific manner due to speed.. | |

* Comments in other versions indicate that the algorithms are from RFC1071 | |

* | |

* accellerated versions (and 21264 assembly versions ) contributed by | |

* Rick Gorton <rick.gorton@alpha-processor.com> | |

*/ | |

#include <linux/module.h> | |

#include <linux/string.h> | |

#include <asm/byteorder.h> | |

static inline unsigned short from64to16(unsigned long x) | |

{ | |

/* Using extract instructions is a bit more efficient | |

than the original shift/bitmask version. */ | |

union { | |

unsigned long ul; | |

unsigned int ui[2]; | |

unsigned short us[4]; | |

} in_v, tmp_v, out_v; | |

in_v.ul = x; | |

tmp_v.ul = (unsigned long) in_v.ui[0] + (unsigned long) in_v.ui[1]; | |

/* Since the bits of tmp_v.sh[3] are going to always be zero, | |

we don't have to bother to add that in. */ | |

out_v.ul = (unsigned long) tmp_v.us[0] + (unsigned long) tmp_v.us[1] | |

+ (unsigned long) tmp_v.us[2]; | |

/* Similarly, out_v.us[2] is always zero for the final add. */ | |

return out_v.us[0] + out_v.us[1]; | |

} | |

/* | |

* computes the checksum of the TCP/UDP pseudo-header | |

* returns a 16-bit checksum, already complemented. | |

*/ | |

unsigned short int csum_tcpudp_magic(unsigned long saddr, | |

unsigned long daddr, | |

unsigned short len, | |

unsigned short proto, | |

unsigned int sum) | |

{ | |

return ~from64to16(saddr + daddr + sum + | |

((unsigned long) ntohs(len) << 16) + | |

((unsigned long) proto << 8)); | |

} | |

unsigned int csum_tcpudp_nofold(unsigned long saddr, | |

unsigned long daddr, | |

unsigned short len, | |

unsigned short proto, | |

unsigned int sum) | |

{ | |

unsigned long result; | |

result = (saddr + daddr + sum + | |

((unsigned long) ntohs(len) << 16) + | |

((unsigned long) proto << 8)); | |

/* Fold down to 32-bits so we don't lose in the typedef-less | |

network stack. */ | |

/* 64 to 33 */ | |

result = (result & 0xffffffff) + (result >> 32); | |

/* 33 to 32 */ | |

result = (result & 0xffffffff) + (result >> 32); | |

return result; | |

} | |

/* | |

* Do a 64-bit checksum on an arbitrary memory area.. | |

* | |

* This isn't a great routine, but it's not _horrible_ either. The | |

* inner loop could be unrolled a bit further, and there are better | |

* ways to do the carry, but this is reasonable. | |

*/ | |

static inline 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 << 8; | |

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) { | |

if (4 & (unsigned long) buff) { | |

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

count--; | |

len -= 4; | |

buff += 4; | |

} | |

count >>= 1; /* nr of 64-bit words.. */ | |

if (count) { | |

unsigned long carry = 0; | |

do { | |

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

count--; | |

buff += 8; | |

result += carry; | |

result += w; | |

carry = (w > result); | |

} while (count); | |

result += carry; | |

result = (result & 0xffffffff) + (result >> 32); | |

} | |

if (len & 4) { | |

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

buff += 4; | |

} | |

} | |

if (len & 2) { | |

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

buff += 2; | |

} | |

} | |

if (len & 1) | |

result += *buff; | |

result = from64to16(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. | |

*/ | |

unsigned short ip_fast_csum(unsigned char * iph, unsigned int ihl) | |

{ | |

return ~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 | |

*/ | |

unsigned int csum_partial(const unsigned char * buff, int len, unsigned int sum) | |

{ | |

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

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

result += sum; | |

/* 32+c bits -> 32 bits */ | |

result = (result & 0xffffffff) + (result >> 32); | |

return result; | |

} | |

EXPORT_SYMBOL(csum_partial); | |

/* | |

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

* in icmp.c | |

*/ | |

unsigned short ip_compute_csum(unsigned char * buff, int len) | |

{ | |

return ~from64to16(do_csum(buff,len)); | |

} |