bridge: Don't include NDA_VLAN for FDB entries with vid 0

An FDB entry with vlan_id 0 doesn't mean it is used in vlan 0, but used when
vlan_filtering is disabled.

There is inconsistency around NDA_VLAN whose payload is 0 - even if we add
an entry by RTM_NEWNEIGH without any NDA_VLAN, and even though adding an
entry with NDA_VLAN 0 is prohibited, we get an entry with NDA_VLAN 0 by
RTM_GETNEIGH.

Dumping an FDB entry with vlan_id 0 shouldn't include NDA_VLAN.

Signed-off-by: Toshiaki Makita <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/bridge/br_fdb.c

···
 	if (nla_put(skb, NDA_CACHEINFO, sizeof(ci), &ci))
 		goto nla_put_failure;
 
-	if (nla_put(skb, NDA_VLAN, sizeof(u16), &fdb->vlan_id))
+	if (fdb->vlan_id && nla_put(skb, NDA_VLAN, sizeof(u16), &fdb->vlan_id))
 		goto nla_put_failure;
 
 	return nlmsg_end(skb, nlh);