Subject: Re: [PATCH v3 net-next 06/12] bpf: helpers: add multibuffer support

From: Jesper Dangaard Brouer <[email-masked]>
Date: Thu, 1 Oct 2020 11:47:00 +0200

On Wed, 30 Sep 2020 12:11:21 -0700
Alexei Starovoitov <[email-masked]> wrote:

> On Wed, Sep 30, 2020 at 05:41:57PM +0200, Lorenzo Bianconi wrote:
> > From: Sameeh Jubran <[email-masked]>
> > 
> > The implementation is based on this [0] draft by Jesper D. Brouer.

First of all I think you are giving me too much credit, and this is
both not really relevant and also not specific enough.  The link[0]
contains several proposals (actually from different people) and it is
not clear which of these proposal you reference.

I think this patch need to explain and argue why these BPF-helpers
makes sense... this will become BPF UAPI.

> > Provided two new helpers:
> > 
> > * bpf_xdp_get_frag_count()
> > * bpf_xdp_get_frags_total_size()

Why was the "frag" and "frags" name chosen?

> > [0] xdp mb design - https://github.com/xdp-project/xdp-project/blob/master/areas/core/xdp-multi-buffer01-design.org
> > Signed-off-by: Sameeh Jubran <[email-masked]>
> > Co-developed-by: Lorenzo Bianconi <[email-masked]>
> > Signed-off-by: Lorenzo Bianconi <[email-masked]>
> > ---
> >  include/uapi/linux/bpf.h       | 14 ++++++++++++
> >  net/core/filter.c              | 42 ++++++++++++++++++++++++++++++++++
> >  tools/include/uapi/linux/bpf.h | 14 ++++++++++++
> >  3 files changed, 70 insertions(+)
> > 
> > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> > index a22812561064..6f97dce8cccf 100644
> > --- a/include/uapi/linux/bpf.h
> > +++ b/include/uapi/linux/bpf.h
> > @@ -3586,6 +3586,18 @@ union bpf_attr {
> >   * 		the data in *dst*. This is a wrapper of **copy_from_user**\ ().
> >   * 	Return
> >   * 		0 on success, or a negative error in case of failure.
> > + *
> > + * int bpf_xdp_get_frag_count(struct xdp_buff *xdp_md)
> > + *	Description
> > + *		Get the number of fragments for a given xdp multi-buffer.
> > + *	Return
> > + *		The number of fragments
> > + *
> > + * int bpf_xdp_get_frags_total_size(struct xdp_buff *xdp_md)
> > + *	Description
> > + *		Get the total size of fragments for a given xdp multi-buffer.
> > + *	Return
> > + *		The total size of fragments for a given xdp multi-buffer.
> >   */
> >  #define __BPF_FUNC_MAPPER(FN)		\
> >  	FN(unspec),			\
> > @@ -3737,6 +3749,8 @@ union bpf_attr {
> >  	FN(inode_storage_delete),	\
> >  	FN(d_path),			\
> >  	FN(copy_from_user),		\
> > +	FN(xdp_get_frag_count),		\
> > +	FN(xdp_get_frags_total_size),	\
> >  	/* */  
> 
> Please route the set via bpf-next otherwise merge conflicts will be severe.
> 

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer