netdev - Re: [PATCH v2 bpf-next] xdp: introduce convert_to_xdp

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Date:   Thu, 28 May 2020 16:24:00 +0200
From:   Lorenzo Bianconi <lorenzo.bianconi@...hat.com>
To:     Daniel Borkmann <daniel@...earbox.net>
Cc:     Lorenzo Bianconi <lorenzo@...nel.org>, bpf@...r.kernel.org,
        netdev@...r.kernel.org, ast@...nel.org, davem@...emloft.net,
        brouer@...hat.com, dsahern@...nel.org, toshiaki.makita1@...il.com
Subject: Re: [PATCH v2 bpf-next] xdp: introduce convert_to_xdp_buff utility
 routine

> On Wed, May 27, 2020 at 11:28:03AM +0200, Lorenzo Bianconi wrote:
> > Introduce convert_to_xdp_buff utility routine to initialize xdp_buff
> > fields from xdp_frames ones. Rely on convert_to_xdp_buff in veth xdp
> > code
> > 
> > Suggested-by: Jesper Dangaard Brouer <brouer@...hat.com>
> > Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
> > ---
> > Changes since v1:
> > - rely on frame->data pointer to compute xdp->data_hard_start one
> > ---
> >  drivers/net/veth.c |  6 +-----
> >  include/net/xdp.h  | 10 ++++++++++
> >  2 files changed, 11 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/net/veth.c b/drivers/net/veth.c
> > index b586d2fa5551..9f91e79b7823 100644
> > --- a/drivers/net/veth.c
> > +++ b/drivers/net/veth.c
> > @@ -575,11 +575,7 @@ static struct sk_buff *veth_xdp_rcv_one(struct veth_rq *rq,
> >  		struct xdp_buff xdp;
> >  		u32 act;
> >  
> > -		xdp.data_hard_start = hard_start;
> > -		xdp.data = frame->data;
> > -		xdp.data_end = frame->data + frame->len;
> > -		xdp.data_meta = frame->data - frame->metasize;
> > -		xdp.frame_sz = frame->frame_sz;
> > +		convert_to_xdp_buff(frame, &xdp);
> >  		xdp.rxq = &rq->xdp_rxq;
> >  
> >  		act = bpf_prog_run_xdp(xdp_prog, &xdp);
> > diff --git a/include/net/xdp.h b/include/net/xdp.h
> > index 90f11760bd12..df99d5d267b2 100644
> > --- a/include/net/xdp.h
> > +++ b/include/net/xdp.h
> > @@ -106,6 +106,16 @@ void xdp_warn(const char *msg, const char *func, const int line);
> >  
> >  struct xdp_frame *xdp_convert_zc_to_xdp_frame(struct xdp_buff *xdp);
> >  
> > +static inline
> > +void convert_to_xdp_buff(struct xdp_frame *frame, struct xdp_buff *xdp)
> > +{
> > +	xdp->data_hard_start = frame->data - frame->headroom - sizeof(*frame);
> > +	xdp->data = frame->data;
> > +	xdp->data_end = frame->data + frame->len;
> > +	xdp->data_meta = frame->data - frame->metasize;
> > +	xdp->frame_sz = frame->frame_sz;
> > +}
> 
> From an API PoV, could we please prefix these with xdp_*(). Looks like there
> is also convert_to_xdp_frame() as an outlier in there, but lets clean these
> up once in the tree to avoid getting this more messy and harder to fix later
> on. How about:
> 
>   - xdp_convert_frame_to_buff()
>   - xdp_convert_buff_to_frame()
> 
> This will have both more self-documented and makes it obvious from where to
> where we convert something.

ack fine to me, I will fix it in v3.

Regards,
Lorenzo

> 
> Thanks,
> Daniel
> 

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