4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Vlad Yasevich <vyasevich@xxxxxxxxx> [ Upstream commit 35d2f80b07bbe03fb358afb0bdeff7437a7d67ff ] It appears that TCP checksum offloading has been broken for Q-in-Q vlans. The behavior was execerbated by the series commit afb0bc972b52 ("Merge branch 'stacked_vlan_tso'") that that enabled accleleration features on stacked vlans. However, event without that series, it is possible to trigger this issue. It just requires a lot more specialized configuration. The root cause is the interaction between how netdev_intersect_features() works, the features actually set on the vlan devices and HW having the ability to run checksum with longer headers. The issue starts when netdev_interesect_features() replaces NETIF_F_HW_CSUM with a combination of NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM, if the HW advertises IP|IPV6 specific checksums. This happens for tagged and multi-tagged packets. However, HW that enables IP|IPV6 checksum offloading doesn't gurantee that packets with arbitrarily long headers can be checksummed. This patch disables IP|IPV6 checksums on the packet for multi-tagged packets. CC: Toshiaki Makita <makita.toshiaki@xxxxxxxxxxxxx> CC: Michal Kubecek <mkubecek@xxxxxxx> Signed-off-by: Vladislav Yasevich <vyasevic@xxxxxxxxxx> Acked-by: Toshiaki Makita <makita.toshiaki@xxxxxxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- include/linux/if_vlan.h | 18 ++++++++++-------- 1 file changed, 10 insertions(+), 8 deletions(-) --- a/include/linux/if_vlan.h +++ b/include/linux/if_vlan.h @@ -630,14 +630,16 @@ static inline bool skb_vlan_tagged_multi static inline netdev_features_t vlan_features_check(const struct sk_buff *skb, netdev_features_t features) { - if (skb_vlan_tagged_multi(skb)) - features = netdev_intersect_features(features, - NETIF_F_SG | - NETIF_F_HIGHDMA | - NETIF_F_FRAGLIST | - NETIF_F_HW_CSUM | - NETIF_F_HW_VLAN_CTAG_TX | - NETIF_F_HW_VLAN_STAG_TX); + if (skb_vlan_tagged_multi(skb)) { + /* In the case of multi-tagged packets, use a direct mask + * instead of using netdev_interesect_features(), to make + * sure that only devices supporting NETIF_F_HW_CSUM will + * have checksum offloading support. + */ + features &= NETIF_F_SG | NETIF_F_HIGHDMA | NETIF_F_HW_CSUM | + NETIF_F_FRAGLIST | NETIF_F_HW_VLAN_CTAG_TX | + NETIF_F_HW_VLAN_STAG_TX; + } return features; }