netdev - Re: [net PATCH] gro: Allow tunnel stacking in the case of FOU/GUE

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Date:	Tue, 29 Mar 2016 14:26:46 -0700
From:	Alexander Duyck <alexander.duyck@...il.com>
To:	Tom Herbert <tom@...bertland.com>
Cc:	Alexander Duyck <aduyck@...antis.com>,
	Jesse Gross <jesse@...nel.org>,
	Linux Kernel Network Developers <netdev@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [net PATCH] gro: Allow tunnel stacking in the case of FOU/GUE

On Tue, Mar 29, 2016 at 2:13 PM, Tom Herbert <tom@...bertland.com> wrote:
> On Mon, Mar 28, 2016 at 4:58 PM, Alexander Duyck <aduyck@...antis.com> wrote:
>> This patch should fix the issues seen with a recent fix to prevent
>> tunnel-in-tunnel frames from being generated with GRO.  The fix itself is
>> correct for now as long as we do not add any devices that support
>> NETIF_F_GSO_GRE_CSUM.  When such a device is added it could have the
>> potential to mess things up due to the fact that the outer transport header
>> points to the outer UDP header and not the GRE header as would be expected.
>>
>> Fixes: fac8e0f579695 ("tunnels: Don't apply GRO to multiple layers of encapsulation.")
>> Signed-off-by: Alexander Duyck <aduyck@...antis.com>
>> ---
>>
>> This should allow us to keep the fix that Jesse added without breaking the
>> 3 cases that Tom called out in terms of FOU/GUE.
>>
>> Additional work will be needed in net-next as we probably need to make it
>> so that offloads work correctly when we get around to supporting
>> NETIF_F_GSO_GRE_CSUM.
>>
>>  net/ipv4/fou.c |   32 ++++++++++++++++++++++++++++++++
>>  1 file changed, 32 insertions(+)
>>
>> diff --git a/net/ipv4/fou.c b/net/ipv4/fou.c
>> index 4136da9275b2..2c30256ee959 100644
>> --- a/net/ipv4/fou.c
>> +++ b/net/ipv4/fou.c
>> @@ -195,6 +195,22 @@ static struct sk_buff **fou_gro_receive(struct sk_buff **head,
>>         u8 proto = NAPI_GRO_CB(skb)->proto;
>>         const struct net_offload **offloads;
>>
>> +       switch (proto) {
>> +       case IPPROTO_IPIP:
>> +       case IPPROTO_IPV6:
>> +       case IPPROTO_GRE:
>> +               /* We can clear the encap_mark for these 3 protocols as
>> +                * we are either adding an L4 tunnel header to the outer
>> +                * L3 tunnel header, or we are are simply treating the
>> +                * GRE tunnel header as though it is a UDP protocol
>> +                * specific header such as VXLAN or GENEVE.
>> +                */
>> +               NAPI_GRO_CB(skb)->encap_mark = 0;
>> +               /* fall-through */
>> +       default:
>> +               break;
>> +       }
>
> Switch statement is not needed, just do NAPI_GRO_CB(skb)->encap_mark = 0;
>
>> +
>>         rcu_read_lock();
>>         offloads = NAPI_GRO_CB(skb)->is_ipv6 ? inet6_offloads : inet_offloads;
>>         ops = rcu_dereference(offloads[proto]);
>> @@ -359,6 +375,22 @@ static struct sk_buff **gue_gro_receive(struct sk_buff **head,
>>                 NAPI_GRO_CB(p)->flush |= NAPI_GRO_CB(p)->flush_id;
>>         }
>>
>> +       switch (guehdr->proto_ctype) {
>> +       case IPPROTO_IPIP:
>> +       case IPPROTO_IPV6:
>> +       case IPPROTO_GRE:
>> +               /* We can clear the encap_mark for these 3 protocols as
>> +                * we are either adding an L4 tunnel header to the outer
>> +                * L3 tunnel header, or we are are simply treating the
>> +                * GRE tunnel header as though it is a UDP protocol
>> +                * specific header such as VXLAN or GENEVE.
>> +                */
>> +               NAPI_GRO_CB(skb)->encap_mark = 0;
>> +               /* fall-through */
>> +       default:
>> +               break;
>> +       }
>> +
> Here also.
>
>>         rcu_read_lock();
>>         offloads = NAPI_GRO_CB(skb)->is_ipv6 ? inet6_offloads : inet_offloads;
>>         ops = rcu_dereference(offloads[guehdr->proto_ctype]);
>>

Okay, I can update that and submit a v2.  The only real reason why I
had the switch statements was out of an abundance of caution since
those were the only 3 cases where I knew we would run into issues.

- Alex