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

[Igor Ryzhov]

Hi Ferruh,

Ok, no problem. Generally, it is needed for all applications using
packet(7) interface, running over KNI interfaces.
More specifically, one example of such application is FRRouting, I suppose
you are familiar with it.
FRR's ISIS daemon is using AF_PACKET sockets and checking received
sockaddr_ll.
Here is the link on one of the usages –
https://github.com/FRRouting/frr/blob/master/isisd/isis_pfpacket.c#L294

When we are good with motivation, I'll send v2 using eth_header_parse.

Best regards,
Igor

On Thu, Jan 24, 2019 at 8:15 PM Ferruh Yigit <ferruh.yigit at intel.com> wrote:

> 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 at intel.com
> > <mailto:ferruh.yigit at 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 at nfware.com
> >     <mailto:iryzhov at nfware.com>
> >     > <mailto:iryzhov at nfware.com <mailto:iryzhov at 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 at intel.com
> >     <mailto:ferruh.yigit at intel.com>
> >     >     <mailto:ferruh.yigit at intel.com <mailto:ferruh.yigit at intel.com>>>
> wrote:
> >     >
> >     >         On 9/27/2018 1:02 AM, Igor Ryzhov wrote:
> >     >         > Signed-off-by: Igor Ryzhov <iryzhov at nfware.com
> >     <mailto:iryzhov at nfware.com>
> >     >         <mailto:iryzhov at nfware.com <mailto:iryzhov at 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  */
> >     >         >
> >     >
> >
>
>