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Fixed lwip_standard_chksum() for unaligned memory access. Verified to work on c16x and BSD on P4.

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This commit is contained in:
christiaans 2005-12-09 08:59:08 +00:00
parent 33fbb06604
commit 43d448e73f
1 changed files with 36 additions and 23 deletions
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59
src/core/inet.c
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@ -60,37 +60,50 @@
*/
#ifndef LWIP_CHKSUM
#define LWIP_CHKSUM lwip_standard_chksum
/**
* lwip checksum
*
* @param dataptr points to start of data to be summed at any boundary
* @param len length of data to be summed
* @return network order (!) lwip checksum (non-inverted Internet sum)
*
* @note accumulator size limits summable lenght to 64k
* @note host endianess is irrelevant (p3 RFC1071)
*/
static u16_t
lwip_standard_chksum(void *dataptr, int len)
lwip_standard_chksum(void *dataptr, u16_t len)
{
u32_t acc;
LWIP_DEBUGF(INET_DEBUG, ("lwip_chksum(%p, %"S16_F")\n", (void *)dataptr, len));
u16_t src;
u8_t *octetptr;
/* iterate by two bytes at once */
for(acc = 0; len > 1; len -= 2) {
/* WAS: acc = acc + *((u16_t *)dataptr)++; BUT THIS IS BROKEN FOR
* ARCHITECTURES WHICH DO NOT ALLOW UNALIGNED 16-BIT ACCESSES */
#if MEM_ALIGNMENT >= 2
acc += htons( ((u16_t)(((u8_t *)dataptr)[0])<<8) | ((u8_t *)dataptr)[1] );
(void *)((u16_t *)dataptr + 1);
#else
acc += *(u16_t *)dataptr;
dataptr = (void *)((u16_t *)dataptr + 1);
#endif
acc = 0;
/* dataptr may be at odd or even addresses */
octetptr = (u8_t*)dataptr;
while (len > 1)
{
/* first octet is most significant */
src = (*octetptr) << 8;
octetptr++;
/* second octet is least significant */
src |= (*octetptr);
octetptr++;
acc += src;
len -= 2;
}
/* add up any last odd byte */
if (len == 1) {
acc += htons((u16_t)((*(u8_t *)dataptr) & 0xff) << 8);
LWIP_DEBUGF(INET_DEBUG, ("inet: chksum: odd byte %"U16_F"\n", (u16_t)(*(u8_t *)dataptr)));
} else {
LWIP_DEBUGF(INET_DEBUG, ("inet: chksum: no odd byte\n"));
if (len > 0)
{
/* accumulate remaining octet */
acc += (*octetptr);
}
acc = (acc >> 16) + (acc & 0xffffUL);
/* add deferred carry bits */
acc = (acc >> 16) + (acc & 0x0000ffffUL);
if ((acc & 0xffff0000) != 0) {
acc = (acc >> 16) + (acc & 0xffffUL);
acc = (acc >> 16) + (acc & 0x0000ffffUL);
}
return (u16_t)acc;
/* caller must invert bits for Internet sum ! */
return htons((u16_t)acc);
}
#endif