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

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Message-ID: <dc040740-6823-c524-2580-e9604e04dcb0@iogearbox.net>
Date:   Sat, 15 Apr 2023 00:15:28 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Lorenzo Bianconi <lorenzo@...nel.org>
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 4/15/23 12:10 AM, Lorenzo Bianconi wrote:
>> 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.

Ok, I'm confused then why it passed before?

>>> 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");