Changes in uspace/lib/net/generic/net_checksum.c [ccca251:00d7e1b] in mainline

File:

• uspace/lib/net/generic/net_checksum.c (modified) (3 diffs)

uspace/lib/net/generic/net_checksum.c

@@ -40 +40 @@
 
 /** Big-endian encoding CRC divider. */
-#define CRC_DIVIDER_BE  0x04c11db7
+#define CRC_DIVIDER_BE  0x04c11db7
 
 /** Little-endian encoding CRC divider. */
-#define CRC_DIVIDER_LE  0xedb88320
+#define CRC_DIVIDER_LE  0xedb88320
+
+/** Polynomial used in multicast address hashing */
+#define CRC_MCAST_POLYNOMIAL  0x04c11db6
 
 /** Compacts the computed checksum to the 16 bit number adding the carries.
@@ -203 +206 @@
 }
 
-/** Computes the ip header checksum.
+/** Compute the IP header checksum.
  *
  * To compute the checksum of a new packet, the checksum header field must be
@@ -221 +224 @@
 }
 
+/** Compute the standard hash from MAC
+ *
+ * Hashing MAC into 64 possible values and using the value as index to
+ * 64bit number.
+ *
+ * The code is copied from qemu-0.13's implementation of ne2000 and rt8139
+ * drivers, but according to documentation there it originates in FreeBSD.
+ *
+ * @param[in] addr The 6-byte MAC address to be hashed
+ *
+ * @return 64-bit number with only single bit set to 1
+ *
+ */
+uint64_t multicast_hash(const uint8_t addr[6])
+{
+        uint32_t crc;
+    int carry, i, j;
+    uint8_t b;
+
+    crc = 0xffffffff;
+    for (i = 0; i < 6; i++) {
+        b = addr[i];
+        for (j = 0; j < 8; j++) {
+            carry = ((crc & 0x80000000L) ? 1 : 0) ^ (b & 0x01);
+            crc <<= 1;
+            b >>= 1;
+            if (carry)
+                crc = ((crc ^ CRC_MCAST_POLYNOMIAL) | carry);
+        }
+    }
+        
+    uint64_t one64 = 1;
+    return one64 << (crc >> 26);
+}
+
 /** @}
  */