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* [PATCH bpf-next] xdp: introduce convert_to_xdp_buff utility routine
@ 2020-05-26 13:48 Lorenzo Bianconi
  2020-05-26 14:20 ` Jesper Dangaard Brouer
  0 siblings, 1 reply; 3+ messages in thread
From: Lorenzo Bianconi @ 2020-05-26 13:48 UTC (permalink / raw)
  To: bpf, netdev
  Cc: ast, davem, brouer, daniel, lorenzo.bianconi, dsahern, toshiaki.makita1

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@redhat.com>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
---
 drivers/net/veth.c | 12 ++----------
 include/net/xdp.h  | 10 ++++++++++
 2 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/drivers/net/veth.c b/drivers/net/veth.c
index b586d2fa5551..dfbe553f967e 100644
--- a/drivers/net/veth.c
+++ b/drivers/net/veth.c
@@ -559,27 +559,19 @@ static struct sk_buff *veth_xdp_rcv_one(struct veth_rq *rq,
 					struct veth_xdp_tx_bq *bq,
 					struct veth_stats *stats)
 {
-	void *hard_start = frame->data - frame->headroom;
 	int len = frame->len, delta = 0;
 	struct xdp_frame orig_frame;
 	struct bpf_prog *xdp_prog;
 	unsigned int headroom;
 	struct sk_buff *skb;
 
-	/* bpf_xdp_adjust_head() assures BPF cannot access xdp_frame area */
-	hard_start -= sizeof(struct xdp_frame);
-
 	rcu_read_lock();
 	xdp_prog = rcu_dereference(rq->xdp_prog);
 	if (likely(xdp_prog)) {
 		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);
@@ -626,7 +618,7 @@ static struct sk_buff *veth_xdp_rcv_one(struct veth_rq *rq,
 	rcu_read_unlock();
 
 	headroom = sizeof(struct xdp_frame) + frame->headroom - delta;
-	skb = veth_build_skb(hard_start, headroom, len, frame->frame_sz);
+	skb = veth_build_skb(frame, headroom, len, frame->frame_sz);
 	if (!skb) {
 		xdp_return_frame(frame);
 		stats->rx_drops++;
diff --git a/include/net/xdp.h b/include/net/xdp.h
index 90f11760bd12..5dbdd65866a9 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 = (void *)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;
+}
+
 /* Convert xdp_buff to xdp_frame */
 static inline
 struct xdp_frame *convert_to_xdp_frame(struct xdp_buff *xdp)
-- 
2.26.2


^ permalink raw reply related	[flat|nested] 3+ messages in thread
* Re: [PATCH bpf-next] xdp: introduce convert_to_xdp_buff utility routine
  2020-05-26 13:48 [PATCH bpf-next] xdp: introduce convert_to_xdp_buff utility routine Lorenzo Bianconi
@ 2020-05-26 14:20 ` Jesper Dangaard Brouer
  2020-05-26 14:33   ` Lorenzo Bianconi
  0 siblings, 1 reply; 3+ messages in thread
From: Jesper Dangaard Brouer @ 2020-05-26 14:20 UTC (permalink / raw)
  To: Lorenzo Bianconi
  Cc: bpf, netdev, ast, davem, daniel, lorenzo.bianconi, dsahern,
	toshiaki.makita1, brouer

On Tue, 26 May 2020 15:48:13 +0200
Lorenzo Bianconi <lorenzo@kernel.org> 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@redhat.com>
> Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
> ---
>  drivers/net/veth.c | 12 ++----------
>  include/net/xdp.h  | 10 ++++++++++
>  2 files changed, 12 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/net/veth.c b/drivers/net/veth.c
> index b586d2fa5551..dfbe553f967e 100644
> --- a/drivers/net/veth.c
> +++ b/drivers/net/veth.c
> @@ -559,27 +559,19 @@ static struct sk_buff *veth_xdp_rcv_one(struct veth_rq *rq,
>  					struct veth_xdp_tx_bq *bq,
>  					struct veth_stats *stats)
>  {
> -	void *hard_start = frame->data - frame->headroom;
>  	int len = frame->len, delta = 0;
>  	struct xdp_frame orig_frame;
>  	struct bpf_prog *xdp_prog;
>  	unsigned int headroom;
>  	struct sk_buff *skb;
>  
> -	/* bpf_xdp_adjust_head() assures BPF cannot access xdp_frame area */
> -	hard_start -= sizeof(struct xdp_frame);
> -
>  	rcu_read_lock();
>  	xdp_prog = rcu_dereference(rq->xdp_prog);
>  	if (likely(xdp_prog)) {
>  		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);
> @@ -626,7 +618,7 @@ static struct sk_buff *veth_xdp_rcv_one(struct veth_rq *rq,
>  	rcu_read_unlock();
>  
>  	headroom = sizeof(struct xdp_frame) + frame->headroom - delta;
> -	skb = veth_build_skb(hard_start, headroom, len, frame->frame_sz);
> +	skb = veth_build_skb(frame, headroom, len, frame->frame_sz);
>  	if (!skb) {
>  		xdp_return_frame(frame);
>  		stats->rx_drops++;
> diff --git a/include/net/xdp.h b/include/net/xdp.h
> index 90f11760bd12..5dbdd65866a9 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 = (void *)frame;

This assumption is problematic.  You are suppose to deduct this from
frame->data pointer.

Currently the xdp_frame is designed and access such that is is possible
to use another memory area for xdp_frame.  That would break after this
change.

This should instead be:

 xdp->data_hard_start = frame->data - (frame->headroom + sizeof(struct xdp_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;
> +}
> +

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


^ permalink raw reply	[flat|nested] 3+ messages in thread
* Re: [PATCH bpf-next] xdp: introduce convert_to_xdp_buff utility routine
  2020-05-26 14:20 ` Jesper Dangaard Brouer
@ 2020-05-26 14:33   ` Lorenzo Bianconi
  0 siblings, 0 replies; 3+ messages in thread
From: Lorenzo Bianconi @ 2020-05-26 14:33 UTC (permalink / raw)
  To: Jesper Dangaard Brouer
  Cc: bpf, netdev, ast, davem, daniel, lorenzo.bianconi, dsahern,
	toshiaki.makita1

[-- Attachment #1: Type: text/plain, Size: 1387 bytes --]

> On Tue, 26 May 2020 15:48:13 +0200
> Lorenzo Bianconi <lorenzo@kernel.org> wrote:
> 

[...]

> > diff --git a/include/net/xdp.h b/include/net/xdp.h
> > index 90f11760bd12..5dbdd65866a9 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 = (void *)frame;
> 
> This assumption is problematic.  You are suppose to deduct this from
> frame->data pointer.
> 
> Currently the xdp_frame is designed and access such that is is possible
> to use another memory area for xdp_frame.  That would break after this
> change.
> 
> This should instead be:
> 
>  xdp->data_hard_start = frame->data - (frame->headroom + sizeof(struct xdp_frame));

ack, fine. I will fix it v2.

Regards,
Lorenzo

> 
> > +	xdp->data = frame->data;
> > +	xdp->data_end = frame->data + frame->len;
> > +	xdp->data_meta = frame->data - frame->metasize;
> > +	xdp->frame_sz = frame->frame_sz;
> > +}
> > +
> 
> -- 
> Best regards,
>   Jesper Dangaard Brouer
>   MSc.CS, Principal Kernel Engineer at Red Hat
>   LinkedIn: http://www.linkedin.com/in/brouer
> 

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^ permalink raw reply	[flat|nested] 3+ messages in thread
end of thread, other threads:[~2020-05-26 14:33 UTC | newest]

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2020-05-26 13:48 [PATCH bpf-next] xdp: introduce convert_to_xdp_buff utility routine Lorenzo Bianconi
2020-05-26 14:20 ` Jesper Dangaard Brouer
2020-05-26 14:33   ` Lorenzo Bianconi

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