It appears that TCP checksum offloading has been broken for
Q-in-Q vlans. The behavior was execerbated by the
series that that enabled accleleration features on stacked
vlans (commit afb0bc972b526 "Merge branch 'stacked_vlan_tso'")
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 actualy 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.toshi...@lab.ntt.co.jp>
CC: Michal Kubecek <mkube...@suse.cz>
Signed-off-by: Vladislav Yasevich <vyase...@redhat.com>
---
include/linux/if_vlan.h | 18 ++++++++++--------
1 file changed, 10 insertions(+), 8 deletions(-)
diff --git a/include/linux/if_vlan.h b/include/linux/if_vlan.h
index 8d5fcd6..6686d0f 100644
--- a/include/linux/if_vlan.h
+++ b/include/linux/if_vlan.h
@@ -614,14 +614,16 @@ static inline bool skb_vlan_tagged_multi(const struct
sk_buff *skb)
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;
}
--
2.7.4
