netdev - Re: [PATCH net] veth: Update XDP feature set when bringing up device

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Date: Tue, 12 Sep 2023 15:10:03 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: Toke Høiland-Jørgensen <toke@...hat.com>, "David S.
 Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub
 Kicinski <kuba@...nel.org>,  Alexei Starovoitov <ast@...nel.org>, Daniel
 Borkmann <daniel@...earbox.net>, Jesper Dangaard Brouer <hawk@...nel.org>,
 John Fastabend <john.fastabend@...il.com>, Lorenzo Bianconi
 <lorenzo@...nel.org>, Kumar Kartikeya Dwivedi <memxor@...il.com>, Stanislav
 Fomichev <sdf@...gle.com>, Gerhard Engleder
 <gerhard@...leder-embedded.com>, Simon Horman <horms@...nel.org>
Cc: Marek Majtyka <alardam@...il.com>, netdev@...r.kernel.org, 
	bpf@...r.kernel.org
Subject: Re: [PATCH net] veth: Update XDP feature set when bringing up device

On Tue, 2023-09-12 at 14:54 +0200, Toke Høiland-Jørgensen wrote:
> Paolo Abeni <pabeni@...hat.com> writes:
> 
> > Hi,
> > 
> > On Mon, 2023-09-11 at 15:58 +0200, Toke Høiland-Jørgensen wrote:
> > > There's an early return in veth_set_features() if the device is in a down
> > > state, which leads to the XDP feature flags not being updated when enabling
> > > GRO while the device is down. Which in turn leads to XDP_REDIRECT not
> > > working, because the redirect code now checks the flags.
> > > 
> > > Fix this by updating the feature flags after bringing the device up.
> > > 
> > > Before this patch:
> > > 
> > > NETDEV_XDP_ACT_BASIC:		yes
> > > NETDEV_XDP_ACT_REDIRECT:	yes
> > > NETDEV_XDP_ACT_NDO_XMIT:	no
> > > NETDEV_XDP_ACT_XSK_ZEROCOPY:	no
> > > NETDEV_XDP_ACT_HW_OFFLOAD:	no
> > > NETDEV_XDP_ACT_RX_SG:		yes
> > > NETDEV_XDP_ACT_NDO_XMIT_SG:	no
> > > 
> > > After this patch:
> > > 
> > > NETDEV_XDP_ACT_BASIC:		yes
> > > NETDEV_XDP_ACT_REDIRECT:	yes
> > > NETDEV_XDP_ACT_NDO_XMIT:	yes
> > > NETDEV_XDP_ACT_XSK_ZEROCOPY:	no
> > > NETDEV_XDP_ACT_HW_OFFLOAD:	no
> > > NETDEV_XDP_ACT_RX_SG:		yes
> > > NETDEV_XDP_ACT_NDO_XMIT_SG:	yes
> > > 
> > > Fixes: fccca038f300 ("veth: take into account device reconfiguration for xdp_features flag")
> > > Fixes: 66c0e13ad236 ("drivers: net: turn on XDP features")
> > > Signed-off-by: Toke Høiland-Jørgensen <toke@...hat.com>
> > > ---
> > >  drivers/net/veth.c | 2 ++
> > >  1 file changed, 2 insertions(+)
> > > 
> > > diff --git a/drivers/net/veth.c b/drivers/net/veth.c
> > > index 9c6f4f83f22b..0deefd1573cf 100644
> > > --- a/drivers/net/veth.c
> > > +++ b/drivers/net/veth.c
> > > @@ -1446,6 +1446,8 @@ static int veth_open(struct net_device *dev)
> > >  		netif_carrier_on(peer);
> > >  	}
> > >  
> > > +	veth_set_xdp_features(dev);
> > > +
> > >  	return 0;
> > >  }
> > 
> > The patch LGTM, thanks!
> > 
> > I think it would be nice to add some specific self-tests here. Could
> > you please consider following-up with them?
> 
> Sure! Do you want me to resubmit this as well, or are you just going to
> apply it as-is and do the selftest as a follow-up?

I think the latter is simpler and works for me. The self-test could
target net-next, the fix is going to land there shortly after -net.

Thanks!

Paolo