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

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Message-ID: <87zg1rjzx2.fsf@toke.dk>
Date: Tue, 12 Sep 2023 15:15:21 +0200
From: Toke Høiland-Jørgensen <toke@...hat.com>
To: Paolo Abeni <pabeni@...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

Paolo Abeni <pabeni@...hat.com> writes:

> 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.

ACK, SGTM!

-Toke