netdev - Re: [PATCH v2 net-next 3/5] l2tp: remove l2specific_len dependency in l2tp

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Date:   Mon, 15 Jan 2018 22:11:04 +0100
From:   Lorenzo Bianconi <lorenzo.bianconi@...hat.com>
To:     Guillaume Nault <g.nault@...halink.fr>
Cc:     "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        James Chapman <jchapman@...alix.com>
Subject: Re: [PATCH v2 net-next 3/5] l2tp: remove l2specific_len dependency in l2tp_core

> On Mon, Jan 15, 2018 at 07:43:18PM +0100, Lorenzo Bianconi wrote:
>> > On Sun, Jan 14, 2018 at 03:50:56PM +0100, Lorenzo Bianconi wrote:
>> >> --- a/net/l2tp/l2tp_core.h
>> >> +++ b/net/l2tp/l2tp_core.h
>> >> @@ -302,6 +302,17 @@ static inline void l2tp_session_dec_refcount(struct l2tp_session *session)
>> >>               l2tp_session_free(session);
>> >>  }
>> >>
>> >> +static inline int l2tp_get_l2specific_len(struct l2tp_session *session)
>> >> +{
>> >> +     switch (session->l2specific_type) {
>> >> +     case L2TP_L2SPECTYPE_NONE:
>> >> +             return 0;
>> >> +     case L2TP_L2SPECTYPE_DEFAULT:
>> >> +     default:
>> >> +             return 4;
>> >> +     }
>> >> +}
>> >>
>> > The data path only compares ->l2specific_type to L2SPECTYPE_DEFAULT and
>> > treats any other value as L2SPECTYPE_NONE. Therefore, we should keep
>> > this logic here and return 0 for unknown types.
>>
>> The data path only compares l2specific_type to L2SPECTYPE_DEFAULT
>> since in the other supported case (L2SPECTYPE_NONE) there is no action
>> required. Moreover L2SPECTYPE_DEFAULT is default configured value if
>> the user does not provide any value for l2specific_type so there are
>> no 'unknown' types and I thought L2TP_L2SPECTYPE_DEFAULT was a better
>> choice for default value
>>
> Yes, but what I meant is that the data patch treats unknow values as
> L2SPECTYPE_NONE, while l2tp_get_l2specific_len() now treats them as
> L2TP_L2SPECTYPE_DEFAULT. I'd just prefer to avoid that inconsistency;
> it makes it easier to reason about the code.
>
> But if you really prefer L2SPECTYPE_DEFAULT, then fine. Unless someone
> messes with new l2spec types, we should never reach this case.

Yes, there are now way to hit just default case so there are no
difference to use L2SPECTYPE_DEFAULT or L2SPECTYPE_NONE as default
actually.
Moreover from now on there are no 'unknow' values for l2specific_type.
Anyway if you think that change is important I can respin a v3, no
issue from my side.

Regards,
Lorenzo