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Add helper functions to calculate the standard ethernet CRC in

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little/big endian fashion, so that network drivers can just reference
the standard implementation and don't have to bring their own.

As discussed on arch@.

Obtained from:	NetBSD
This commit is contained in:
Christian Weisgerber 2004-06-02 21:34:14 +00:00
parent 59ee11bbbe
commit 16b4a34316
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=130015
2 changed files with 75 additions and 0 deletions
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2
sys/net/ethernet.h
View File

@ -350,6 +350,8 @@ struct mbuf;
struct rtentry;
struct sockaddr;
extern uint32_t ether_crc32_le(const uint8_t *, size_t);
extern uint32_t ether_crc32_be(const uint8_t *, size_t);
extern void ether_demux(struct ifnet *, struct mbuf *);
extern void ether_ifattach(struct ifnet *, const u_int8_t *);
extern void ether_ifdetach(struct ifnet *);

73
sys/net/if_ethersubr.c
View File

@ -879,6 +879,79 @@ SYSCTL_NODE(_net_link, IFT_ETHER, ether, CTLFLAG_RW, 0, "Ethernet");
SYSCTL_INT(_net_link_ether, OID_AUTO, ipfw, CTLFLAG_RW,
&ether_ipfw,0,"Pass ether pkts through firewall");
#if 0
/*
* This is for reference. We have a table-driven version
* of the little-endian crc32 generator, which is faster
* than the double-loop.
*/
uint32_t
ether_crc32_le(const uint8_t *buf, size_t len)
{
size_t i;
uint32_t crc;
int bit;
uint8_t data;
crc = 0xffffffff; /* initial value */
for (i = 0; i < len; i++) {
for (data = *buf++, bit = 0; bit < 8; bit++, data >>= 1)
carry = (crc ^ data) & 1;
crc >>= 1;
if (carry)
crc = (crc ^ ETHER_CRC_POLY_LE);
}
return (crc);
}
#else
uint32_t
ether_crc32_le(const uint8_t *buf, size_t len)
{
static const uint32_t crctab[] = {
0x00000000, 0x1db71064, 0x3b6e20c8, 0x26d930ac,
0x76dc4190, 0x6b6b51f4, 0x4db26158, 0x5005713c,
0xedb88320, 0xf00f9344, 0xd6d6a3e8, 0xcb61b38c,
0x9b64c2b0, 0x86d3d2d4, 0xa00ae278, 0xbdbdf21c
};
size_t i;
uint32_t crc;
crc = 0xffffffff; /* initial value */
for (i = 0; i < len; i++) {
crc ^= buf[i];
crc = (crc >> 4) ^ crctab[crc & 0xf];
crc = (crc >> 4) ^ crctab[crc & 0xf];
}
return (crc);
}
#endif
uint32_t
ether_crc32_be(const uint8_t *buf, size_t len)
{
size_t i;
uint32_t crc, carry;
int bit;
uint8_t data;
crc = 0xffffffff; /* initial value */
for (i = 0; i < len; i++) {
for (data = *buf++, bit = 0; bit < 8; bit++, data >>= 1) {
carry = ((crc & 0x80000000) ? 1 : 0) ^ (data & 0x01);
crc <<= 1;
if (carry)
crc = (crc ^ ETHER_CRC_POLY_BE) | carry;
}
}
return (crc);
}
int
ether_ioctl(struct ifnet *ifp, int command, caddr_t data)
{