Date:	Mon, 9 May 2016 14:35:52 -0700
From:	Alexander Duyck <alexander.duyck@...il.com>
To:	Tom Herbert <tom@...bertland.com>
Cc:	David Miller <davem@...emloft.net>,
	Netdev <netdev@...r.kernel.org>, Kernel Team <kernel-team@...com>
Subject: Re: [PATCH v3 net-next 00/11] ipv6: Enable GUEoIPv6 and more fixes
 for v6 tunneling

On Mon, May 9, 2016 at 10:32 AM, Alexander Duyck
<alexander.duyck@...il.com> wrote:
> On Mon, May 9, 2016 at 9:56 AM, Tom Herbert <tom@...bertland.com> wrote:
>> On Fri, May 6, 2016 at 8:03 PM, Alexander Duyck
>> <alexander.duyck@...il.com> wrote:
>>> On Fri, May 6, 2016 at 7:11 PM, Tom Herbert <tom@...bertland.com> wrote:
>>>> On Fri, May 6, 2016 at 7:03 PM, Alexander Duyck
>>>> <alexander.duyck@...il.com> wrote:
>>>>> On Fri, May 6, 2016 at 6:57 PM, Tom Herbert <tom@...bertland.com> wrote:
>>>>>> On Fri, May 6, 2016 at 6:09 PM, Alexander Duyck
>>>>>> <alexander.duyck@...il.com> wrote:
>>>>>>> On Fri, May 6, 2016 at 3:11 PM, Tom Herbert <tom@...bertland.com> wrote:
>>>>>>>> This patch set:
>>>>>>>>   - Fixes GRE6 to process translate flags correctly from configuration
>>>>>>>>   - Adds support for GSO and GRO for ip6ip6 and ip4ip6
>>>>>>>>   - Add support for FOU and GUE in IPv6
>>>>>>>>   - Support GRE, ip6ip6 and ip4ip6 over FOU/GUE
>>>>>>>>   - Fixes ip6_input to deal with UDP encapsulations
>>>>>>>>   - Some other minor fixes
>>>>>>>>
>>>>>>>> v2:
>>>>>>>>   - Removed a check of GSO types in MPLS
>>>>>>>>   - Define GSO type SKB_GSO_IPXIP6 and SKB_GSO_IPXIP4 (based on input
>>>>>>>>     from Alexander)
>>>>>>>>   - Don't define GSO types specifally for IP6IP6 and IP4IP6, above
>>>>>>>>     fix makes that uncessary
>>>>>>>>   - Don't bother clearing encapsulation flag in UDP tunnel segment
>>>>>>>>     (another item suggested by Alexander).
>>>>>>>>
>>>>>>>> v3:
>>>>>>>>   - Address some minor comments from Alexander
>>>>>>>>
>>>>>>>> Tested:
>>>>>>>>    Tested a variety of case, but not the full matrix (which is quite
>>>>>>>>    large now). Most of the obivous cases (e.g. GRE) work fine. Still
>>>>>>>>    some issues probably with GSO/GRO being effective in all cases.
>>>>>>>>
>>>>>>>>     - IPv4/GRE/GUE/IPv6 with RCO
>>>>>>>>       1 TCP_STREAM
>>>>>>>>         6616 Mbps
>>>>>>>>       200 TCP_RR
>>>>>>>>         1244043 tps
>>>>>>>>         141/243/446 90/95/99% latencies
>>>>>>>>         86.61% CPU utilization
>>>>>>>>     - IPv6/GRE/GUE/IPv6 with RCO
>>>>>>>>       1 TCP_STREAM
>>>>>>>>         6940 Mbps
>>>>>>>>       200 TCP_RR
>>>>>>>>         1270903 tps
>>>>>>>>         138/236/440 90/95/99% latencies
>>>>>>>>         87.51% CPU utilization
>>>>>>>>
>>>>>>>>      - IP6IP6
>>>>>>>>       1 TCP_STREAM
>>>>>>>>         2576 Mbps
>>>>>>>>       200 TCP_RR
>>>>>>>>         498981 tps
>>>>>>>>         388/498/631 90/95/99% latencies
>>>>>>>>         19.75% CPU utilization (1 CPU saturated)
>>>>>>>>
>>>>>>>>      - IP6IP6/GUE/IPv6 with RCO
>>>>>>>>       1 TCP_STREAM
>>>>>>>>         1854 Mbps
>>>>>>>>       200 TCP_RR
>>>>>>>>         1233818 tps
>>>>>>>>         143/244/451 90/95/99% latencies
>>>>>>>>         87.57 CPU utilization
>>>>>>>>
>>>>>>>>      - IP4IP6
>>>>>>>>       1 TCP_STREAM
>>>>>>>>       200 TCP_RR
>>>>>>>>         763774 tps
>>>>>>>>         250/318/466 90/95/99% latencies
>>>>>>>>         35.25% CPU utilization (1 CPU saturated)
>>>>>>>>
>>>>>>>>      - GRE with keyid
>>>>>>>>       200 TCP_RR
>>>>>>>>         744173 tps
>>>>>>>>         258/332/461 90/95/99% latencies
>>>>>>>>         34.59% CPU utilization (1 CPU saturated)
>>>>>>>
>>>>>>> So I tried testing your patch set and it looks like I cannot get GRE
>>>>>>> working for any netperf test.  If I pop the patches off it is even
>>>>>>> worse since it looks like patch 3 fixes some tunnel flags issues, but
>>>>>>> still doesn't resolve all the issues introduced with b05229f44228
>>>>>>> ("gre6: Cleanup GREv6 transmit path, call common GRE functions").
>>>>>>> Reverting the entire patch seems to resolve the issues, but I will try
>>>>>>> to pick it apart tonight to see if I can find the other issues that
>>>>>>> weren't addressed in this patch series.
>>>>>>>
>>>>>>
>>>>>> Can you give details about configuration, test you're running, and HW?
>>>>>
>>>>> The issue looks like it may be specific to ip6gretap.  I'm running the
>>>>> test over an i40e adapter, but it shouldn't make much difference.  I'm
>>>>> thinking it may have something to do with the MTU configuration as
>>>>> that is one of the things I am noticing has changed between the
>>>>> working and the broken version of the code.
>>>>>
>>>> I'm not seeing any issue with configuring:
>>>>
>>>> ip link add name tun8 type ip6gretap remote
>>>> 2401:db00:20:911a:face:0:27:0 local 2401:db00:20:911a:face:0:25:0 ttl
>>>> 225
>>>>
>>>> MTU issues would not surprise me with IPv6 though. This is part of the
>>>> area of code that seems drastically different than what IPv4 is doing.
>>>
>>> I am also using a key.
>>>
>>>         ip link add $name type ip6gretap key $net \
>>>                 local fec0::1 remote $addr6 ttl 225 dev $PF0
>>>
>> I don't see any issue with key enabled.
>>
>>> Does the device you are using support any kind of checksum offload for
>>> inner headers on GRE tunnels?  It looks like if I turn off checksums
>>
>> I don't believe so.
>>
>>> and correct the MTU I can then send traffic without issues.  I'd say
>>> that the Tx cleanup probably introduced 3 regressions.  The first one
>>> you addressed in patch 3 which fixes the flags.  The second being the
>>> fact that the MTU is wrong, and the third being something that
>>> apparently broke checksum and maybe segmentation offload for
>>> ip6gretap.
>>>
>> The MTU can be set in place in IPv6 code that doesn't exist in Ipv4. I
>> am especially wondering about the "if (p->flags & IP6_TNL_F_CAP_XMIT)"
>> block.

So I think I have figured out the MTU problem.  You need to go through
and audit the spots where you are using GRE_ flags instead of TUNNEL_
flags.  Specifically in ip6gre_tnl_link_config you are using GRE_
flags to test o_flags which is configured to use the TUNNEL_ prefixed
flags.  When I changed those out then the MTU started coming out
correct again.  There were a couple other places you were using
GRE_SEQ where you should have been using TUNNEL_SEQ as well so you
could probably clean those up and add them to patch 3 of your set that
was fixing the flags so that they should be TUNNEL_ prefixed.

>>> Really I think the transmit path cleanup should have probably been
>>> broken down into a set of patches rather than slamming it in all in
>>> one block.  I can spend some time next week trying to sort it out if
>>> you don't have any hardware that supports GRE segmentation or checksum
>>> offload.  If worse comes to worse I will just try breaking the revert
>>> down into a set of smaller patches so I can figure out exactly which
>>> change broke things.
>>>
>> I am still trying to reproduce.
>
> What NICs are you testing with?  Depending on the NIC I might be able
> to point you in the direction of something that can reproduce the
> issue.
>
> At this point I am thinking it is an issue with a header offset since
> I believe GSO resets all that and probably corrects the issue.

I'm still doing some digging on my end.  I'm hoping to have this
figured out by the end of today.

- Alex

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