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Calculates now the correct checksum.

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FossilOrigin-Name: 1f8472323fb0cca4727a06718fcd2f8df9b75a504c6fd6fb1db0c9126225ca57
This commit is contained in:
7u83@mail.ru 2015-01-04 09:01:04 +00:00
parent 6466a2ba24
commit 825d2954af
1 changed files with 14 additions and 39 deletions
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53
src/capwap/lw_checksum.c
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@ -20,49 +20,24 @@
/** /**
* Calculate the 16-bit checksum for LWAPP image data message * Calculate the 16-bit checksum for LWAPP image data message
* elements with opcode 3 - used by Cisco also in CAPWAP * elements with opcode 3 - also used by Cisco in CAPWAP
* (But it's not always correct, the real algo might be another)
*/ */
uint16_t lw1_checksum(uint8_t * d, int len)
{
int i;
// uint32_t cs = 0xffff;
if (len == 0)
return 0xffff;
uint32_t cs = 0;
for (i = 0; i < len; i += 2) {
uint16_t w = d[i] << 8;
if (i + 1 < len)
w |= d[i + 1];
cs += w ^= 0xffff;
cs += cs >> 16;
cs &= 0xffff;
}
return (uint16_t) cs & 0xffff;
}
uint16_t lw_checksum(uint8_t * d, int len) uint16_t lw_checksum(uint8_t * d, int len)
{ {
int i; int32_t sum = 0;
// uint32_t cs = 0xffff; uint16_t *w = (uint16_t *) d;
if (len == 0)
return 0xffff;
uint32_t cs = 0x0; while (len > 1) {
for (i = 0; i < len; i += 2) { sum += ntohs(*w++);
cs += (cs >> 16); len -= 2;
cs &= 0xffff;
uint16_t w = d[i] << 8;
if (i + 1 < len)
w |= d[i + 1];
cs += w ^= 0xffff;
} }
cs += (cs >> 16);
return (uint16_t) cs & 0xffff; if (len == 1)
sum += (*(uint8_t *) w) << 8;
sum = (sum >> 16) + (sum & 0xffff);
sum += (sum >> 16);
return (~sum) & 0xffff;
} }