tun: remove bogus hardware vlan acceleration flags from vlan_features

Even though only the outer vlan tag can be HW accelerated in the transmission
path, in the TUN/TAP driver vlan_features mirrors hw_features, which happens
to have the NETIF_F_HW_VLAN_?TAG_TX flags set. Because of this, during packet
tranmisssion through a stacked vlan device dev_hard_start_xmit, (incorrectly)
assuming that the vlan device supports hardware vlan acceleration, does not
add the vlan header to the skb payload and the inner vlan tags are lost
(vlan_tci contains the outer vlan tag when userspace reads the packet from
the tap device).

Signed-off-by: Fernando Luis Vazquez Cao <fernando@oss.ntt.co.jp>
Signed-off-by: Toshiaki Makita <makita.toshiaki@lab.ntt.co.jp>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 1 deletions

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 8fe9cb7d0f72..26f8635b027d 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1686,7 +1686,9 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
                                    TUN_USER_FEATURES | NETIF_F_HW_VLAN_CTAG_TX |
                                    NETIF_F_HW_VLAN_STAG_TX;
                 dev->features = dev->hw_features;
-                dev->vlan_features = dev->features;
+                dev->vlan_features = dev->features &
+                                     ~(NETIF_F_HW_VLAN_CTAG_TX |
+                                       NETIF_F_HW_VLAN_STAG_TX);
 
                 INIT_LIST_HEAD(&tun->disabled);
                 err = tun_attach(tun, file, false);