[PATCH net-next] veth: check for NAPI instead of xdp_prog before xmit of XDP frame

[PATCH net-next] veth: check for NAPI instead of xdp_prog before xmit of XDP frame

[Toke Høiland-Jørgensen]

The recent patch that tied enabling of veth NAPI to the GRO flag also has
the nice side effect that a veth device can be the target of an
XDP_REDIRECT without an XDP program needing to be loaded on the peer
device. However, the patch adding this extra NAPI mode didn't actually
change the check in veth_xdp_xmit() to also look at the new NAPI pointer,
so let's fix that.

Fixes: 6788fa154546 ("veth: allow enabling NAPI even without XDP")
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
---
 drivers/net/veth.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/net/veth.c b/drivers/net/veth.c
index 15b2e3923c47..bdb7ce3cb054 100644
--- a/drivers/net/veth.c
+++ b/drivers/net/veth.c
@@ -486,11 +486,10 @@ static int veth_xdp_xmit(struct net_device *dev, int n,
 
 	rcv_priv = netdev_priv(rcv);
 	rq = &rcv_priv->rq[veth_select_rxq(rcv)];
-	/* Non-NULL xdp_prog ensures that xdp_ring is initialized on receive
-	 * side. This means an XDP program is loaded on the peer and the peer
-	 * device is up.
+	/* The napi pointer is set if NAPI is enabled, which ensures that
+	 * xdp_ring is initialized on receive side and the peer device is up.
 	 */
-	if (!rcu_access_pointer(rq->xdp_prog))
+	if (!rcu_access_pointer(rq->napi))
 		goto out;
 
 	max_len = rcv->mtu + rcv->hard_header_len + VLAN_HLEN;
-- 
2.31.1

Re: [PATCH net-next] veth: check for NAPI instead of xdp_prog before xmit of XDP frame

[Jesper Dangaard Brouer]

On Fri, 16 Apr 2021 17:47:45 +0200
Toke Høiland-Jørgensen <toke@redhat.com> wrote:

> The recent patch that tied enabling of veth NAPI to the GRO flag also has
> the nice side effect that a veth device can be the target of an
> XDP_REDIRECT without an XDP program needing to be loaded on the peer
> device. However, the patch adding this extra NAPI mode didn't actually
> change the check in veth_xdp_xmit() to also look at the new NAPI pointer,
> so let's fix that.
> 
> Fixes: 6788fa154546 ("veth: allow enabling NAPI even without XDP")
> Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
> ---
>  drivers/net/veth.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)

Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>

Very happy to see this strange requirement of loading an xdp_prog on
the veth peer (inside the netns) being lifted.  Multiple people/users
have hit this issue and complained.  Thanks for the followup to fix
this! :-)

> diff --git a/drivers/net/veth.c b/drivers/net/veth.c
> index 15b2e3923c47..bdb7ce3cb054 100644
> --- a/drivers/net/veth.c
> +++ b/drivers/net/veth.c
> @@ -486,11 +486,10 @@ static int veth_xdp_xmit(struct net_device *dev, int n,
>  
>  	rcv_priv = netdev_priv(rcv);
>  	rq = &rcv_priv->rq[veth_select_rxq(rcv)];
> -	/* Non-NULL xdp_prog ensures that xdp_ring is initialized on receive
> -	 * side. This means an XDP program is loaded on the peer and the peer
> -	 * device is up.
> +	/* The napi pointer is set if NAPI is enabled, which ensures that
> +	 * xdp_ring is initialized on receive side and the peer device is up.
>  	 */
> -	if (!rcu_access_pointer(rq->xdp_prog))
> +	if (!rcu_access_pointer(rq->napi))
>  		goto out;
>  
>  	max_len = rcv->mtu + rcv->hard_header_len + VLAN_HLEN;



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

Re: [PATCH net-next] veth: check for NAPI instead of xdp_prog before xmit of XDP frame

[Paolo Abeni]

On Fri, 2021-04-16 at 17:47 +0200, Toke Høiland-Jørgensen wrote:
> The recent patch that tied enabling of veth NAPI to the GRO flag also has
> the nice side effect that a veth device can be the target of an
> XDP_REDIRECT without an XDP program needing to be loaded on the peer
> device. However, the patch adding this extra NAPI mode didn't actually
> change the check in veth_xdp_xmit() to also look at the new NAPI pointer,
> so let's fix that.
> 
> Fixes: 6788fa154546 ("veth: allow enabling NAPI even without XDP")
> Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
> ---
>  drivers/net/veth.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/veth.c b/drivers/net/veth.c
> index 15b2e3923c47..bdb7ce3cb054 100644
> --- a/drivers/net/veth.c
> +++ b/drivers/net/veth.c
> @@ -486,11 +486,10 @@ static int veth_xdp_xmit(struct net_device *dev, int n,
>  
>  	rcv_priv = netdev_priv(rcv);
>  	rq = &rcv_priv->rq[veth_select_rxq(rcv)];
> -	/* Non-NULL xdp_prog ensures that xdp_ring is initialized on receive
> -	 * side. This means an XDP program is loaded on the peer and the peer
> -	 * device is up.
> +	/* The napi pointer is set if NAPI is enabled, which ensures that
> +	 * xdp_ring is initialized on receive side and the peer device is up.
>  	 */
> -	if (!rcu_access_pointer(rq->xdp_prog))
> +	if (!rcu_access_pointer(rq->napi))
>  		goto out;
>  
>  	max_len = rcv->mtu + rcv->hard_header_len + VLAN_HLEN;

Acked-by: Paolo Abeni <pabeni@redhat.com>

Thanks for the quick turn-around!

Re: [PATCH net-next] veth: check for NAPI instead of xdp_prog before xmit of XDP frame

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (refs/heads/master):

On Fri, 16 Apr 2021 17:47:45 +0200 you wrote:
> The recent patch that tied enabling of veth NAPI to the GRO flag also has
> the nice side effect that a veth device can be the target of an
> XDP_REDIRECT without an XDP program needing to be loaded on the peer
> device. However, the patch adding this extra NAPI mode didn't actually
> change the check in veth_xdp_xmit() to also look at the new NAPI pointer,
> so let's fix that.
> 
> [...]

Here is the summary with links:
  - [net-next] veth: check for NAPI instead of xdp_prog before xmit of XDP frame
    https://git.kernel.org/netdev/net-next/c/0e672f306a28

You are awesome, thank you!
--
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html