Re: [dpdk-dev] [PATCH] kni: implement header_ops parse method

[Ferruh Yigit <ferruh.yigit@intel.com>]

On 1/24/2019 4:35 PM, Igor Ryzhov wrote:
> Hi Ferruh,
> 
> I already answered your question in my previous email, header_ops.parse method
> is used by packet(7) interface for packet parsing and filling sockaddr_ll structure.
> Here is the link on the usage –
> https://elixir.bootlin.com/linux/latest/source/net/packet/af_packet.c#L2100

I saw your previous reply. That is why changed the question slightly, from 'what
it does' to 'what is the use case'.
Trying to understand do we need it, please help me understand.

> 
> Regarding the question about eth_header_ops usage:
> Right now both already existing functions, kni_net_header and
> kni_net_rebuild_header, are implemented as copies, not using eth_header_ops
> functions.

OK, I see your reasoning, but if there is an already Linux API that does what we
want, I suggest calling it instead of re-implementing it, unless there is a good
reason to not do so.

> That's why I think my patch should be accepted as is, and the problem of
> eth_header_ops usage should be investigated separately, and possibly resolved by
> a separate patch.

Agreed, eth_header_ops usage should be investigated separately.

> 
> Best regards,
> Igor
> 
> On Thu, Jan 24, 2019 at 5:10 PM Ferruh Yigit <ferruh.yigit@intel.com
> <mailto:ferruh.yigit@intel.com>> wrote:
> 
>     On 1/24/2019 9:18 AM, Igor Ryzhov wrote:
>     > Hi Ferruh,
>     >
>     > What about this patch?
>     > Can you merge it as-is, or should I change it to use relevant eth_header_ops
>     > functions? Or maybe completely use eth_header_ops?
> 
>     Hi Igor,
> 
>     I am not clear about motivation of the patch, what use case enabled by this
>     patch? What is not working with current code?
>     I am for rejecting the patch without need justified.
> 
>     And if the need is justified, still there is a question that why not use
>     'eth_header_parse()' directly but implement our copy?
> 
> 
>     And an extended question/investigation about why not use 'eth_header_ops', which
>     seems done intentionally but I am missing the reasoning.
> 
>     >
>     > Best regards,
>     > Igor
>     >
>     > On Fri, Nov 30, 2018 at 10:07 PM Igor Ryzhov <iryzhov@nfware.com
>     <mailto:iryzhov@nfware.com>
>     > <mailto:iryzhov@nfware.com <mailto:iryzhov@nfware.com>>> wrote:
>     >
>     >     Hi Ferruh,
>     >
>     >     header_ops.parse method is used by raw-sockets to fill sockaddr_ll
>     structure.
>     >     It is used, for example, in isisd for frrouting.
>     >
>     >     Regarding your question about eth_header_ops – I, unfortunately, don't
>     know
>     >     why .cache and .cache_update are disabled for KNI.
>     >     I also think that it will be better to use default eth_header_ops.
>     >
>     >     Best regards,
>     >     Igor
>     >
>     >     On Tue, Oct 2, 2018 at 7:58 PM Ferruh Yigit <ferruh.yigit@intel.com
>     <mailto:ferruh.yigit@intel.com>
>     >     <mailto:ferruh.yigit@intel.com <mailto:ferruh.yigit@intel.com>>> wrote:
>     >
>     >         On 9/27/2018 1:02 AM, Igor Ryzhov wrote:
>     >         > Signed-off-by: Igor Ryzhov <iryzhov@nfware.com
>     <mailto:iryzhov@nfware.com>
>     >         <mailto:iryzhov@nfware.com <mailto:iryzhov@nfware.com>>>
>     >
>     >         Hi Igor,
>     >
>     >         What is the motivation to add this support? What is enabled by this?
>     >
>     >
>     >         Meanwhile, why we are not using eth_header_ops, which is already
>     set by
>     >         ether_setup().
>     >         To disable .cache & .cache_update?
>     >
>     >         If so why not using relevant eth_header_ops (eth_header,
>     >         eth_header_parse ..)
>     >         instead of implementing ours?
>     >
>     >         > ---
>     >         >  kernel/linux/kni/kni_net.c | 14 ++++++++++++++
>     >         >  1 file changed, 14 insertions(+)
>     >         >
>     >         > diff --git a/kernel/linux/kni/kni_net.c b/kernel/linux/kni/kni_net.c
>     >         > index 7fcfa106c..128a5477c 100644
>     >         > --- a/kernel/linux/kni/kni_net.c
>     >         > +++ b/kernel/linux/kni/kni_net.c
>     >         > @@ -678,6 +678,19 @@ kni_net_header(struct sk_buff *skb, struct
>     >         net_device *dev,
>     >         >       return dev->hard_header_len;
>     >         >  }
>     >         > 
>     >         > +/*
>     >         > + *  Extract hardware address from packet
>     >         > + */
>     >         > +static int
>     >         > +kni_net_header_parse(const struct sk_buff *skb, unsigned char
>     *haddr)
>     >         > +{
>     >         > +     const struct ethhdr *eth = eth_hdr(skb);
>     >         > +
>     >         > +     memcpy(haddr, eth->h_source, ETH_ALEN);
>     >         > +
>     >         > +     return ETH_ALEN;
>     >         > +}
>     >         > +
>     >         >  /*
>     >         >   * Re-fill the eth header
>     >         >   */
>     >         > @@ -739,6 +752,7 @@ kni_net_change_carrier(struct net_device *dev,
>     >         bool new_carrier)
>     >         > 
>     >         >  static const struct header_ops kni_net_header_ops = {
>     >         >       .create  = kni_net_header,
>     >         > +     .parse   = kni_net_header_parse,
>     >         >  #ifdef HAVE_REBUILD_HEADER
>     >         >       .rebuild = kni_net_rebuild_header,
>     >         >  #endif /* < 4.1.0  */
>     >         >
>     >
>