From mboxrd@z Thu Jan  1 00:00:00 1970
From: Sean Harte <seanbh@gmail.com>
Subject: Re: [PATCH v6 4/8] ethdev: add GTP items to support flow
	API
Date: Tue, 3 Oct 2017 09:56:58 +0100
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Cc: "Xing, Beilei" <beilei.xing@intel.com>, "Wu,
 Jingjing" <jingjing.wu@intel.com>,
 "Chilikin, Andrey" <andrey.chilikin@intel.com>, "dev@dpdk.org" <dev@dpdk.org>
To: Adrien Mazarguil <adrien.mazarguil@6wind.com>
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On 2 October 2017 at 13:27, Adrien Mazarguil <adrien.mazarguil@6wind.com> wrote:
> On Fri, Sep 29, 2017 at 10:29:55AM +0100, Sean Harte wrote:
>> On 29 September 2017 at 09:54, Xing, Beilei <beilei.xing@intel.com> wrote:
> <snip>
>> >> >  /**
>> >> > + * RTE_FLOW_ITEM_TYPE_GTP.
>> >> > + *
>> >> > + * Matches a GTPv1 header.
>> >> > + */
>> >> > +struct rte_flow_item_gtp {
>> >> > +       /**
>> >> > +        * Version (3b), protocol type (1b), reserved (1b),
>> >> > +        * Extension header flag (1b),
>> >> > +        * Sequence number flag (1b),
>> >> > +        * N-PDU number flag (1b).
>> >> > +        */
>> >> > +       uint8_t v_pt_rsv_flags;
>> >> > +       uint8_t msg_type; /**< Message type. */
>> >> > +       rte_be16_t msg_len; /**< Message length. */
>> >> > +       rte_be32_t teid; /**< Tunnel endpoint identifier. */ };
>> >>
>> >> In future, you might add support for GTPv2 (which is used since LTE).
>> >> Maybe this structure should have v1 in its name to avoid confusion?
>> >
>> > I considered it before. But I think we can modify it when we support GTPv2 in future, and keep concise 'GTP' currently:)  since I have described it matches v1 header.
>> >
>>
>> You could rename v_pt_rsv_flags to version_flags to avoid some future
>> code changes to support GTPv2. There's still the issue that not all
>> GTPv2 messages have a TEID though.
>
> Although they have the same size, the header of these two protocols
> obviously differs. My suggestion would be to go with a separate GTPv2
> pattern item using its own dedicated structure instead.
>
> --
> Adrien Mazarguil
> 6WIND

The 1st four bytes are the same (flags in first byte have different
meanings, but the bits indicating the version are in the same
location). After that, different fields in each version are optional,
and the headers have variable size. A single structure could be used
if the first field is renamed to something like "version_flags", and
then check that the teid field in item->mask is not set if
((version_flags >> 5 == 2) && ((version_flags >> 4) & 1) == 1). If
there's going to be two structures, it would be good to put v1 and v2
in the names, in my opinion.