net: introduce net_crc32_le() function

This provides a standard ethernet CRC32 little-endian implementation.
Signed-off-by: NMark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reviewed-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NPhilippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: NJason Wang <jasowang@redhat.com>

include/net/net.h

@@ -228,7 +228,9 @@ NetClientState *net_hub_port_find(int hub_id);
 void qdev_set_nic_properties(DeviceState *dev, NICInfo *nd);
 
 #define POLYNOMIAL_BE 0x04c11db6
+#define POLYNOMIAL_LE 0xedb88320
 uint32_t net_crc32(const uint8_t *p, int len);
+uint32_t net_crc32_le(const uint8_t *p, int len);
 unsigned compute_mcast_idx(const uint8_t *ep);
 
 #define vmstate_offset_macaddr(_state, _field)                       \

net/net.c

@@ -1603,6 +1603,28 @@ uint32_t net_crc32(const uint8_t *p, int len)
     return crc;
 }
 
+uint32_t net_crc32_le(const uint8_t *p, int len)
+{
+    uint32_t crc;
+    int carry, i, j;
+    uint8_t b;
+
+    crc = 0xffffffff;
+    for (i = 0; i < len; i++) {
+        b = *p++;
+        for (j = 0; j < 8; j++) {
+            carry = (crc & 0x1) ^ (b & 0x01);
+            crc >>= 1;
+            b >>= 1;
+            if (carry) {
+                crc ^= POLYNOMIAL_LE;
+            }
+        }
+    }
+
+    return crc;
+}
+
 unsigned compute_mcast_idx(const uint8_t *ep)
 {
     return net_crc32(ep, ETH_ALEN) >> 26;