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net: move CRC32 calculation from compute_mcast_idx() into its own net_crc32() function

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Separate out the standard ethernet CRC32 calculation into a new net_crc32()
function, renaming the constant POLYNOMIAL to POLYNOMIAL_BE to make it clear
that this is a big-endian CRC32 calculation.

As part of the constant rename, remove the duplicate definition of POLYNOMIAL
from eepro100.c and use the new POLYNOMIAL_BE constant instead.

Once this is complete remove the existing CRC32 implementation from
compute_mcast_idx() and call the new net_crc32() function in its place.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Jason Wang <jasowang@redhat.com>
This commit is contained in:
Mark Cave-Ayland 2017-12-15 18:41:43 +00:00 • committed by Jason Wang
parent d62644b46a
commit eaba8f34f0
3 changed files with 14 additions and 9 deletions
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16
net/net.c
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@ -1581,25 +1581,31 @@ int net_client_parse(QemuOptsList *opts_list, const char *optarg)
/* From FreeBSD */
/* XXX: optimize */
unsigned compute_mcast_idx(const uint8_t *ep)
uint32_t net_crc32(const uint8_t *p, int len)
{
uint32_t crc;
int carry, i, j;
uint8_t b;
crc = 0xffffffff;
for (i = 0; i < 6; i++) {
b = *ep++;
for (i = 0; i < len; i++) {
b = *p++;
for (j = 0; j < 8; j++) {
carry = ((crc & 0x80000000L) ? 1 : 0) ^ (b & 0x01);
crc <<= 1;
b >>= 1;
if (carry) {
crc = ((crc ^ POLYNOMIAL) | carry);
crc = ((crc ^ POLYNOMIAL_BE) | carry);
}
}
}
return crc >> 26;
return crc;
}
unsigned compute_mcast_idx(const uint8_t *ep)
{
return net_crc32(ep, ETH_ALEN) >> 26;
}
QemuOptsList qemu_netdev_opts = {