netdev - Re: [PATCH net] sit: Set skb->protocol properly in ipip6_tunnel

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Date:   Mon, 28 Nov 2016 09:45:35 -0800
From:   Alexander Duyck <alexander.duyck@...il.com>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     David Miller <davem@...emloft.net>, sfr@...b.auug.org.au,
        elicooper@....com, Netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net] sit: Set skb->protocol properly in ipip6_tunnel_xmit()

On Mon, Nov 28, 2016 at 8:53 AM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> On Mon, 2016-11-28 at 11:47 -0500, David Miller wrote:
>> From: Stephen Rothwell <sfr@...b.auug.org.au>
>> Date: Sun, 27 Nov 2016 13:04:00 +1100
>>
>> > [Just for Dave's information]
>> >
>> > On Fri, 25 Nov 2016 13:50:17 +0800 Eli Cooper <elicooper@....com> wrote:
>> >>
>> >> Similar to commit ae148b085876
>> >> ("ip6_tunnel: Update skb->protocol to ETH_P_IPV6 in ip6_tnl_xmit()"),
>> >> sit tunnels also need to update skb->protocol; otherwise, TSO/GSO packets
>> >> might not be properly segmented, which causes the packets being dropped.
>> >>
>> >> Reported-by: Stephen Rothwell <sfr@...b.auug.org.au>
>> >> Tested-by: Eli Cooper <elicooper@....com>
>> >> Cc: stable@...r.kernel.org
>> >> Signed-off-by: Eli Cooper <elicooper@....com>
>> >
>> > I tested this patch and it does *not* solve my problem.
>>
>> I'm torn on this patch, because it looked exactly like it would solve the
>> kind of problem Stephen is running into.
>>
>> Even though it doesn't fix his case, it seems correct to me.
>>
>> I was wondering if it was also important to set the skb->protocol
>> before the call to ip_tunnel_encap() but I couldn't find a dependency.
>>
>> In any event I'd like to see some other people review this change
>> before I apply it.
>>
>> My only other guess for Stephen's problem is somehow the SKB headers
>> aren't set up properly for what the GSO engine expects.
>
> Well, mlx4 just works, and uses GSO engine just fine.
>
> So my guess is this is a bug in Intel IGB driver.
>
>
> Alexander, can you take a look ?
>
> Features for eth0:
> rx-checksumming: on
> tx-checksumming: on
>         tx-checksum-ipv4: off [fixed]
>         tx-checksum-ip-generic: on
>         tx-checksum-ipv6: off [fixed]
>         tx-checksum-fcoe-crc: off [fixed]
>         tx-checksum-sctp: on
> scatter-gather: on
>         tx-scatter-gather: on
>         tx-scatter-gather-fraglist: off [fixed]
> tcp-segmentation-offload: on
>         tx-tcp-segmentation: on
>         tx-tcp-ecn-segmentation: off [fixed]
>         tx-tcp-mangleid-segmentation: off
>         tx-tcp6-segmentation: on
> udp-fragmentation-offload: off [fixed]
> generic-segmentation-offload: on
> generic-receive-offload: on
> large-receive-offload: off [fixed]
> rx-vlan-offload: on
> tx-vlan-offload: on
> ntuple-filters: off
> receive-hashing: on
> highdma: on [fixed]
> rx-vlan-filter: on [fixed]
> vlan-challenged: off [fixed]
> tx-lockless: off [fixed]
> netns-local: off [fixed]
> tx-gso-robust: off [fixed]
> tx-fcoe-segmentation: off [fixed]
> tx-gre-segmentation: on
> tx-gre-csum-segmentation: on
> tx-ipxip4-segmentation: on
> tx-ipxip6-segmentation: on
> tx-udp_tnl-segmentation: on
> tx-udp_tnl-csum-segmentation: on
> tx-gso-partial: on
> fcoe-mtu: off [fixed]
> tx-nocache-copy: off
> loopback: off [fixed]
> rx-fcs: off [fixed]
> rx-all: off
> tx-vlan-stag-hw-insert: off [fixed]
> rx-vlan-stag-hw-parse: off [fixed]
> rx-vlan-stag-filter: off [fixed]
> l2-fwd-offload: off [fixed]
> busy-poll: off [fixed]
> hw-tc-offload: off [fixed]

I agree.  This sounds like a bug with the GSO partial on igb.

I'll try setting up a SIT tunnel on my systems here and see if I can
reproduce the issue.

- Alex