virtio-net: don't update mac_table in error state

mac_table was always cleaned up first in handling
VIRTIO_NET_CTRL_MAC_TABLE_SET command, and we din't recover
mac_table content in error state, it's not correct.

This patch makes all the changes in temporal variables,
only update the real mac_table if everything is ok.
We won't change mac_table in error state, so rxfilter
notification isn't needed.

This patch also fixed same problame in
 http://lists.nongnu.org/archive/html/qemu-devel/2013-11/msg01188.html
 (not merge)

I will send patch for virtio spec to clarifying this change.

Signed-off-by: Amos Kong <akong@redhat.com>
Reviewed-by: Vlad Yasevich <vyasevic@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

hw/net/virtio-net.c

@@ -610,11 +610,11 @@ static int virtio_net_handle_mac(VirtIONet *n, uint8_t cmd,
         return VIRTIO_NET_ERR;
     }
 
-    n->mac_table.in_use = 0;
-    n->mac_table.first_multi = 0;
-    n->mac_table.uni_overflow = 0;
-    n->mac_table.multi_overflow = 0;
-    memset(n->mac_table.macs, 0, MAC_TABLE_ENTRIES * ETH_ALEN);
+    int in_use = 0;
+    int first_multi = 0;
+    uint8_t uni_overflow = 0;
+    uint8_t multi_overflow = 0;
+    uint8_t *macs = g_malloc0(MAC_TABLE_ENTRIES * ETH_ALEN);
 
     s = iov_to_buf(iov, iov_cnt, 0, &mac_data.entries,
                    sizeof(mac_data.entries));
@@ -629,19 +629,19 @@ static int virtio_net_handle_mac(VirtIONet *n, uint8_t cmd,
     }
 
     if (mac_data.entries <= MAC_TABLE_ENTRIES) {
-        s = iov_to_buf(iov, iov_cnt, 0, n->mac_table.macs,
+        s = iov_to_buf(iov, iov_cnt, 0, macs,
                        mac_data.entries * ETH_ALEN);
         if (s != mac_data.entries * ETH_ALEN) {
             goto error;
         }
-        n->mac_table.in_use += mac_data.entries;
+        in_use += mac_data.entries;
     } else {
-        n->mac_table.uni_overflow = 1;
+        uni_overflow = 1;
     }
 
     iov_discard_front(&iov, &iov_cnt, mac_data.entries * ETH_ALEN);
 
-    n->mac_table.first_multi = n->mac_table.in_use;
+    first_multi = in_use;
 
     s = iov_to_buf(iov, iov_cnt, 0, &mac_data.entries,
                    sizeof(mac_data.entries));
@@ -656,24 +656,29 @@ static int virtio_net_handle_mac(VirtIONet *n, uint8_t cmd,
         goto error;
     }
 
-    if (n->mac_table.in_use + mac_data.entries <= MAC_TABLE_ENTRIES) {
-        s = iov_to_buf(iov, iov_cnt, 0,
-                       &n->mac_table.macs[n->mac_table.in_use * ETH_ALEN],
+    if (in_use + mac_data.entries <= MAC_TABLE_ENTRIES) {
+        s = iov_to_buf(iov, iov_cnt, 0, &macs[in_use * ETH_ALEN],
                        mac_data.entries * ETH_ALEN);
         if (s != mac_data.entries * ETH_ALEN) {
             goto error;
         }
-        n->mac_table.in_use += mac_data.entries;
+        in_use += mac_data.entries;
     } else {
-        n->mac_table.multi_overflow = 1;
+        multi_overflow = 1;
     }
 
+    n->mac_table.in_use = in_use;
+    n->mac_table.first_multi = first_multi;
+    n->mac_table.uni_overflow = uni_overflow;
+    n->mac_table.multi_overflow = multi_overflow;
+    memcpy(n->mac_table.macs, macs, MAC_TABLE_ENTRIES * ETH_ALEN);
+    g_free(macs);
     rxfilter_notify(nc);
 
     return VIRTIO_NET_OK;
 
 error:
-    rxfilter_notify(nc);
+    g_free(macs);
     return VIRTIO_NET_ERR;
 }