add support of IFF_XMIT_DST_RELEASE bit in vlan

Some time ago Eric Dumazet suggested a "hack the IFF_XMIT_DST_RELEASE
flag on the vlan netdev". But the last comment was "does not support
properly bonding/team.(If the real_dev->privflags IFF_XMIT_DST_RELEASE
bit changes, we want to update all the vlans at the same time )"

I've extended that patch to support changes of IFF_XMIT_DST_RELEASE in
bonding/team.
Both bonding and team call netdev_change_features() after recalculation
of features including priv_flags IFF_XMIT_DST_RELEASE bit. So the only
thing needed to support is to recheck this bit in
vlan_transfer_features().
Suggested-by: NEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: NVadim Fedorenko <vfedorenko@yandex-team.ru>
Reviewed-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/8021q/vlan.c

@@ -328,6 +328,9 @@ static void vlan_transfer_features(struct net_device *dev,
 	vlandev->fcoe_ddp_xid = dev->fcoe_ddp_xid;
 #endif
 
+	vlandev->priv_flags &= ~IFF_XMIT_DST_RELEASE;
+	vlandev->priv_flags |= (vlan->real_dev->priv_flags & IFF_XMIT_DST_RELEASE);
+
 	netdev_update_features(vlandev);
 }
 

net/8021q/vlan_netlink.c

@@ -143,6 +143,7 @@ static int vlan_newlink(struct net *src_net, struct net_device *dev,
 	vlan->vlan_proto = proto;
 	vlan->vlan_id	 = nla_get_u16(data[IFLA_VLAN_ID]);
 	vlan->real_dev	 = real_dev;
+	dev->priv_flags |= (real_dev->priv_flags & IFF_XMIT_DST_RELEASE);
 	vlan->flags	 = VLAN_FLAG_REORDER_HDR;
 
 	err = vlan_check_real_dev(real_dev, vlan->vlan_proto, vlan->vlan_id);