Replace the lame big endian crc with wpaul's standard big endian crc

algorithm, supplied by wpaul himself.  The lame one has an origin
that's been called into question, so rather than argue about that (one
could make an excellent fair use argument), replace it with better
code since that's what FreeBSD is about.

Submitted by: wpaul[1], Klaus Klein

[1] Bill called this a silly bikeshed.  Maybe his is not incorrect.

1 files changed, 9 insertions, 23 deletions

diff --git a/sys/dev/sk/if_sk.c b/sys/dev/sk/if_sk.c
index 272bdc5..14ff623 100644
--- a/sys/dev/sk/if_sk.c
+++ b/sys/dev/sk/if_sk.c
@@ -745,38 +745,24 @@ sk_xmchash(addr)
 	return (~crc & ((1 << HASH_BITS) - 1));
 }
 
+/* gmchash is just a big endian crc */
 static u_int32_t
 sk_gmchash(addr)
 	const uint8_t *addr;
 {
-	u_int32_t crc;
-	u_int idx, bit;
-	uint8_t tmpData, data;
+	uint32_t crc, carry;
+	int idx, bit;
+	uint8_t data;
 
 	/* Compute CRC for the address value. */
 	crc = 0xFFFFFFFF; /* initial value */
 
 	for (idx = 0; idx < 6; idx++) {
-		data = *addr++;
-
-		/* Change bit order in byte. */
-		tmpData = data;
-		for (bit = 0; bit < 8; bit++) {
-			if (tmpData & 1) {
-				data |=  1 << (7 - bit);
-			} else {
-				data &= ~(1 << (7 - bit));
-			}
-			tmpData >>= 1;
-		}
-
-		crc ^= (data << 24);
-		for (bit = 0; bit < 8; bit++) {
-			if (crc & 0x80000000) {
-				crc = (crc << 1) ^ GMAC_POLY;
-			} else {
-				crc <<= 1;
-			}
+		for (data = *addr++, bit = 0; bit < 8; bit++, data >>= 1) {
+			carry = ((crc & 0x80000000) ? 1 : 0) ^ (data & 0x01);
+			crc <<= 1;
+			if (carry)
+				crc = (crc ^ GMAC_POLY) | carry;
 		}
 	}