netdev - Re: [PATCH v2 bpf-next 3/3] veth: allow jumbo frames in xdp mode

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Date:   Tue, 22 Feb 2022 19:03:26 +0100
From:   Lorenzo Bianconi <lorenzo.bianconi@...hat.com>
To:     Paolo Abeni <pabeni@...hat.com>
Cc:     Lorenzo Bianconi <lorenzo@...nel.org>, bpf@...r.kernel.org,
        netdev@...r.kernel.org, davem@...emloft.net, kuba@...nel.org,
        ast@...nel.org, daniel@...earbox.net, brouer@...hat.com,
        toke@...hat.com, echaudro@...hat.com, toshiaki.makita1@...il.com,
        andrii@...nel.org
Subject: Re: [PATCH v2 bpf-next 3/3] veth: allow jumbo frames in xdp mode

> On Tue, 2022-02-15 at 14:08 +0100, Lorenzo Bianconi wrote:
> > Allow increasing the MTU over page boundaries on veth devices
> > if the attached xdp program declares to support xdp fragments.
> > Enable NETIF_F_ALL_TSO when the device is running in xdp mode.
> > 
> > Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
> > ---
> >  drivers/net/veth.c | 26 +++++++++++---------------
> >  1 file changed, 11 insertions(+), 15 deletions(-)
> > 
> > diff --git a/drivers/net/veth.c b/drivers/net/veth.c
> > index a45aaaecc21f..2e048f957bc6 100644
> > --- a/drivers/net/veth.c
> > +++ b/drivers/net/veth.c
> > @@ -292,8 +292,6 @@ static int veth_forward_skb(struct net_device *dev, struct sk_buff *skb,
> >  /* return true if the specified skb has chances of GRO aggregation
> >   * Don't strive for accuracy, but try to avoid GRO overhead in the most
> >   * common scenarios.
> > - * When XDP is enabled, all traffic is considered eligible, as the xmit
> > - * device has TSO off.
> >   * When TSO is enabled on the xmit device, we are likely interested only
> >   * in UDP aggregation, explicitly check for that if the skb is suspected
> >   * - the sock_wfree destructor is used by UDP, ICMP and XDP sockets -
> > @@ -334,7 +332,8 @@ static netdev_tx_t veth_xmit(struct sk_buff *skb, struct net_device *dev)
> >  		 * Don't bother with napi/GRO if the skb can't be aggregated
> >  		 */
> >  		use_napi = rcu_access_pointer(rq->napi) &&
> > -			   veth_skb_is_eligible_for_gro(dev, rcv, skb);
> > +			   (rcu_access_pointer(rq->xdp_prog) ||
> > +			    veth_skb_is_eligible_for_gro(dev, rcv, skb));
> 
> Sorry for the late feedback. I think the code would be more readable if
> you move the additional check inside 'veth_skb_is_eligible_for_gro' and
> adjust veth_skb_is_eligible_for_gro() comment accordingly.

Hi Paolo,

sure, will do in v3.

Regards,
Lorenzo

> 
> Thanks!
> 
> Paolo
> 

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