From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vladislav Yasevich Subject: [PATCH V2 net 1/3] vlan: Fix tcp checksum offloads in Q-in-Q vlans Date: Tue, 23 May 2017 12:53:10 -0400 Message-ID: <1495558392-1238-2-git-send-email-vyasevic@redhat.com> References: <1495558392-1238-1-git-send-email-vyasevic@redhat.com> Cc: alexander.duyck@gmail.com, makita.toshiaki@lab.ntt.co.jp, Vladislav Yasevich , Michal Kubecek To: netdev@vger.kernel.org Return-path: Received: from mail-qt0-f195.google.com ([209.85.216.195]:36178 "EHLO mail-qt0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750987AbdEWQxW (ORCPT ); Tue, 23 May 2017 12:53:22 -0400 Received: by mail-qt0-f195.google.com with SMTP id j13so22965298qta.3 for ; Tue, 23 May 2017 09:53:21 -0700 (PDT) In-Reply-To: <1495558392-1238-1-git-send-email-vyasevic@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: 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 CC: Michal Kubecek Signed-off-by: Vladislav Yasevich --- 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