netdev - Re: [PATCH net-next 2/7] nfp: compile flower vxlan tunnel metadata match fields

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Date:   Tue, 26 Sep 2017 16:11:02 +0100
From:   John Hurley <john.hurley@...ronome.com>
To:     Or Gerlitz <gerlitz.or@...il.com>
Cc:     Simon Horman <simon.horman@...ronome.com>,
        David Miller <davem@...emloft.net>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Linux Netdev List <netdev@...r.kernel.org>,
        oss-drivers@...ronome.com
Subject: Re: [PATCH net-next 2/7] nfp: compile flower vxlan tunnel metadata
 match fields

On Tue, Sep 26, 2017 at 3:12 PM, Or Gerlitz <gerlitz.or@...il.com> wrote:
> On Tue, Sep 26, 2017 at 4:58 PM, John Hurley <john.hurley@...ronome.com> wrote:
>> On Mon, Sep 25, 2017 at 7:35 PM, Or Gerlitz <gerlitz.or@...il.com> wrote:
>>> On Mon, Sep 25, 2017 at 1:23 PM, Simon Horman
>>> <simon.horman@...ronome.com> wrote:
>>>> From: John Hurley <john.hurley@...ronome.com>
>>>>
>>>> Compile ovs-tc flower vxlan metadata match fields for offloading. Only
>>>
>>> anything in the npf kernel bits has direct relation to ovs? what?
>>>
>>
>> Sorry, this is a typo  and should refer to TC.
>>
>>>> +++ b/drivers/net/ethernet/netronome/nfp/flower/offload.c
>>>> @@ -52,8 +52,25 @@
>>>>          BIT(FLOW_DISSECTOR_KEY_PORTS) | \
>>>>          BIT(FLOW_DISSECTOR_KEY_ETH_ADDRS) | \
>>>>          BIT(FLOW_DISSECTOR_KEY_VLAN) | \
>>>> +        BIT(FLOW_DISSECTOR_KEY_ENC_KEYID) | \
>>>> +        BIT(FLOW_DISSECTOR_KEY_ENC_IPV4_ADDRS) | \
>>>> +        BIT(FLOW_DISSECTOR_KEY_ENC_IPV6_ADDRS) | \
>>>
>>> this series takes care of IPv6 tunnels too?
>>
>> IPv6 is not included in this set.
>> The reason the IPv6 bit is included here is to account for behavior we
>> have noticed in TC flower.
>> If, for example, I add a filter with the following match fields:
>> 'protocol ip flower enc_src_ip 10.0.0.1 enc_dst_ip 10.0.0.2
>> enc_dst_port 4789 enc_key_id 123'
>> The 'used_keys' value in the dissector marks both IPv4 and IPv6 encap
>> addresses as 'used'.
>> I am not sure if this is a bug in TC or that we are expected to check
>> the enc_control fields to determine if IPv4 or v6 addresses are used.
>
> you should have your code to check enc_control->addr_type to be
> FLOW_DISSECTOR_KEY_IPV4_ADDRS or IPV6_ADDRS
>
>
>> Including the IPv6 used_keys bit in our whitelist approach allows us
>> to accept legitimate IPv4 tunnel rules in these situations.
>
> mmm can please take a look on fl_init_dissector() and tell me if you
> see why FLOW_DISSECTOR_KEY_IPV6_ADDRS is set for ipv4 tunnels,
> I am not sure.


The fl_init_dissector uses the FL_KEY_SET_IF_MASKED macro to set an
array of keys which are then translated to the used_keys values.
The FL_KEY_SET_IF_MASKED takes a 'struct fl_flow_key' as input and
checks if any mask bits are set in a particular field - if so it
eventually marks it as used.
In struct fl_flow_key, the encap ipv4 and ipv6 addresses are
represented as a union of the 2.
Therefore, if we have masked bits set for IPv4, they are also being
set for the IPv6 field.


>
>> If it is found to be IPv6 when the rule is parsed, it will be rejected here.