[PATCH v2] bonding: Add vlan tx offload to hw_enc_features

[YueHaibing]

As commit 30d8177e8ac7 ("bonding: Always enable vlan tx offload")
said, we should always enable bonding's vlan tx offload, pass the
vlan packets to the slave devices with vlan tci, let them to handle
vlan implementation.

Now if encapsulation protocols like VXLAN is used, skb->encapsulation
may be set, then the packet is passed to vlan device which based on
bonding device. However in netif_skb_features(), the check of
hw_enc_features:

	 if (skb->encapsulation)
                 features &= dev->hw_enc_features;

clears NETIF_F_HW_VLAN_CTAG_TX/NETIF_F_HW_VLAN_STAG_TX. This results
in same issue in commit 30d8177e8ac7 like this:

vlan_dev_hard_start_xmit
  -->dev_queue_xmit
    -->validate_xmit_skb
      -->netif_skb_features //NETIF_F_HW_VLAN_CTAG_TX is cleared
      -->validate_xmit_vlan
        -->__vlan_hwaccel_push_inside //skb->tci is cleared
...
 --> bond_start_xmit
   --> bond_xmit_hash //BOND_XMIT_POLICY_ENCAP34
     --> __skb_flow_dissect // nhoff point to IP header
        -->  case htons(ETH_P_8021Q)
             // skb_vlan_tag_present is false, so
             vlan = __skb_header_pointer(skb, nhoff, sizeof(_vlan),
             //vlan point to ip header wrongly

Fixes: b2a103e6d0af ("bonding: convert to ndo_fix_features")
Signed-off-by: YueHaibing <yuehaibing@xxxxxxxxxx>
Acked-by: Jay Vosburgh <jay.vosburgh@xxxxxxxxxxxxx>
---
v2: fix a log typo, add Fixes tag
---
 drivers/net/bonding/bond_main.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 02fd782..931d9d9 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -1126,6 +1126,8 @@ static void bond_compute_features(struct bonding *bond)
 done:
 	bond_dev->vlan_features = vlan_features;
 	bond_dev->hw_enc_features = enc_features | NETIF_F_GSO_ENCAP_ALL |
+				    NETIF_F_HW_VLAN_CTAG_TX |
+				    NETIF_F_HW_VLAN_STAG_TX |
 				    NETIF_F_GSO_UDP_L4;
 	bond_dev->mpls_features = mpls_features;
 	bond_dev->gso_max_segs = gso_max_segs;
-- 
2.7.4