net: move compute_mcast_idx() to net.h

Reduce duplicated codes.

Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 23 insertions, 0 deletions

diff --git a/net.c b/net.c
index c34474fe5f..1922d8abd1 100644
--- a/net.c
+++ b/net.c
@@ -1475,3 +1475,26 @@ int net_client_parse(QemuOptsList *opts_list, const char *optarg)
     default_net = 0;
     return 0;
 }
+
+/* From FreeBSD */
+/* XXX: optimize */
+unsigned compute_mcast_idx(const uint8_t *ep)
+{
+    uint32_t crc;
+    int carry, i, j;
+    uint8_t b;
+
+    crc = 0xffffffff;
+    for (i = 0; i < 6; i++) {
+        b = *ep++;
+        for (j = 0; j < 8; j++) {
+            carry = ((crc & 0x80000000L) ? 1 : 0) ^ (b & 0x01);
+            crc <<= 1;
+            b >>= 1;
+            if (carry) {
+                crc = ((crc ^ POLYNOMIAL) | carry);
+            }
+        }
+    }
+    return crc >> 26;
+}