netdev - Re: [PATCH bpf] selftests/bpf: fix xdp_redirect xdp-features for xdp

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Date:   Sat, 15 Apr 2023 00:10:37 +0200
From:   Lorenzo Bianconi <lorenzo@...nel.org>
To:     Daniel Borkmann <daniel@...earbox.net>
Cc:     bpf@...r.kernel.org, netdev@...r.kernel.org,
        lorenzo.bianconi@...hat.com, ast@...nel.org, andrii@...nel.org,
        martin.lau@...ux.dev, joamaki@...il.com
Subject: Re: [PATCH bpf] selftests/bpf: fix xdp_redirect xdp-features for
 xdp_bonding selftest

> On 4/14/23 11:21 PM, Lorenzo Bianconi wrote:
> > NETDEV_XDP_ACT_NDO_XMIT is not enabled by default for veth driver but it
> > depends on the device configuration. Fix XDP_REDIRECT xdp-features in
> > xdp_bonding selftest loading a dummy XDP program on veth2_2 device.
> > 
> > Fixes: fccca038f300 ("veth: take into account device reconfiguration for xdp_features flag")
> 
> Hm, does that mean we're changing^breaking existing user behavior iff after
> fccca038f300 you can only make it work by loading dummy prog?

nope, even before in order to enable ndo_xdp_xmit for veth you should load a dummy
program on the device peer or enable gro on the device peer:

https://github.com/torvalds/linux/blob/master/drivers/net/veth.c#L477

we are just reflecting this behaviour in the xdp_features flag.

Regards,
Lorenzo

> 
> > Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
> > ---
> >   tools/testing/selftests/bpf/prog_tests/xdp_bonding.c | 11 +++++++++++
> >   1 file changed, 11 insertions(+)
> > 
> > diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_bonding.c b/tools/testing/selftests/bpf/prog_tests/xdp_bonding.c
> > index 5e3a26b15ec6..dcbe30c81291 100644
> > --- a/tools/testing/selftests/bpf/prog_tests/xdp_bonding.c
> > +++ b/tools/testing/selftests/bpf/prog_tests/xdp_bonding.c
> > @@ -168,6 +168,17 @@ static int bonding_setup(struct skeletons *skeletons, int mode, int xmit_policy,
> >   		if (xdp_attach(skeletons, skeletons->xdp_dummy->progs.xdp_dummy_prog, "veth1_2"))
> >   			return -1;
> > +
> > +		if (!ASSERT_OK(setns_by_name("ns_dst"), "set netns to ns_dst"))
> > +			return -1;
> > +
> > +		/* Load a dummy XDP program on veth2_2 in order to enable
> > +		 * NETDEV_XDP_ACT_NDO_XMIT feature
> > +		 */
> > +		if (xdp_attach(skeletons, skeletons->xdp_dummy->progs.xdp_dummy_prog, "veth2_2"))
> > +			return -1;
> > +
> > +		restore_root_netns();
> >   	}
> >   	SYS("ip -netns ns_dst link set veth2_1 master bond2");
> > 
> 

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