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/*
* 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/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 loose 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;
}
/*
* 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));
}
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