linux-kernel - Re: [PATCH bpf-next v4 12/14] selftests/bpf: test_xdp_veth: Add XDP broadcast redirection tests

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Message-ID: <1b2965bc-87d6-4b44-bf7d-e491a08d89cd@bootlin.com>
Date: Mon, 3 Feb 2025 13:59:08 +0100
From: Bastien Curutchet <bastien.curutchet@...tlin.com>
To: Martin KaFai Lau <martin.lau@...ux.dev>
Cc: Alexei Starovoitov <ast@...nel.org>,
 Daniel Borkmann <daniel@...earbox.net>, "David S. Miller"
 <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
 Jesper Dangaard Brouer <hawk@...nel.org>,
 John Fastabend <john.fastabend@...il.com>,
 Andrii Nakryiko <andrii@...nel.org>, Eduard Zingerman <eddyz87@...il.com>,
 Song Liu <song@...nel.org>, Yonghong Song <yonghong.song@...ux.dev>,
 KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...ichev.me>,
 Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
 Mykola Lysenko <mykolal@...com>, Shuah Khan <shuah@...nel.org>,
 Alexis Lothore <alexis.lothore@...tlin.com>,
 Thomas Petazzoni <thomas.petazzoni@...tlin.com>, netdev@...r.kernel.org,
 bpf@...r.kernel.org, linux-kselftest@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH bpf-next v4 12/14] selftests/bpf: test_xdp_veth: Add XDP
 broadcast redirection tests

Hi Martin,

On 2/1/25 2:33 AM, Martin KaFai Lau wrote:
> On 1/30/25 11:21 PM, Bastien Curutchet (eBPF Foundation) wrote:
>> +#define BROADCAST_REDIRECT_SKEL_NB    2
>> +static void xdp_veth_broadcast_redirect(u32 attach_flags, u64

[...]

>> +
>> +    group_map = bpf_map__fd(xdp_redirect_multi_kern->maps.map_all);
>> +    if (!ASSERT_OK_FD(group_map, "open map_all"))
>> +        goto destroy_xdp_redirect_map;
>> +
>> +    flags_map = bpf_map__fd(xdp_redirect_multi_kern- 
>> >maps.redirect_flags);
>> +    if (!ASSERT_OK_FD(group_map, "open map_all"))
>> +        goto destroy_xdp_redirect_map;
>> +
>> +    err = bpf_map_update_elem(flags_map, &protocol, &redirect_flags, 
>> BPF_NOEXIST);
>> +    if (!ASSERT_OK(err, "init IP count"))
>> +        goto destroy_xdp_redirect_map;
>> +
>> +    cnt_map = bpf_map__fd(xdp_redirect_map->maps.rxcnt);
>> +    if (!ASSERT_OK_FD(cnt_map, "open rxcnt map"))
>> +        goto destroy_xdp_redirect_map;
>> +
>> +    bpf_objs[0] = xdp_redirect_multi_kern->obj;
>> +    bpf_objs[1] = xdp_redirect_map->obj;
>> +    for (i = 0; i < VETH_PAIRS_COUNT; i++) {
>> +        int ifindex = if_nametoindex(net_config[i].local_veth);
>> +
>> +        if (attach_programs_to_veth_pair(bpf_objs, 
>> BROADCAST_REDIRECT_SKEL_NB,
>> +                         net_config, prog_cfg, i))
>> +            goto destroy_xdp_redirect_map;
>> +
>> +        SYS(destroy_xdp_redirect_map,
>> +            "ip -n %s neigh add %s lladdr 00:00:00:00:00:01 dev %s",
>> +            net_config[i].namespace, IP_NEIGH, 
>> net_config[i].remote_veth);
>> +
>> +        devmap_val.ifindex = ifindex;
>> +        err = bpf_map_update_elem(group_map, &ifindex, &devmap_val, 0);
> 
> I ran this test in a loop and failed at this line permanently (errno 
> E2BIG -7) after enough iterations. I believe the problem is the 
> group_map (aka "map_all" in the BPF program) has a max_entries 1024 and 
> ifindex can go beyond 1024 after some "./test_progs" iterations. 
> Understood that it is likely an existing assumption in the "map_all" 
> definition but it needs to be addressed first before moving to test_progs.
> 
>> +        if (!ASSERT_OK(err, "bpf_map_update_elem"))
>> +            goto destroy_xdp_redirect_map;
>> +
>> +    }
>> +

[...]

>> diff --git a/tools/testing/selftests/bpf/progs/xdp_redirect_map.c b/ 
>> tools/testing/selftests/bpf/progs/xdp_redirect_map.c
>> index 
>> 682dda8dabbc9abbb5d1b0b22dd5f81124142e79..14385df71d7fc40c3b0ee5c6ea0760d0e7336d71 100644
>> --- a/tools/testing/selftests/bpf/progs/xdp_redirect_map.c
>> +++ b/tools/testing/selftests/bpf/progs/xdp_redirect_map.c
>> @@ -1,7 +1,11 @@
>>   // SPDX-License-Identifier: GPL-2.0
>> +#include <linux/if_ether.h>
>> +#include <linux/ip.h>
> 
> I have compiler error complaining about __always_inline not defined. 
> Likely ordering issue and environment specific. Regardless, I believe 
> the ip.h is unnecessary, so better clean it up.
> 
> I am going to land the patch 1-10 and change the cover letter a little 
> to reflect the fact that patch 11-14 will be a followup. Please post the 
> remaining patches after fixing the bpf_map_update_elem issue. Thanks.
> 

Ok thank you, I plan to solve this issue by using a dedicated namespace 
instead of the root namespace so the index won't be incremented every 
time `test_progs` is launched.
I'll send the new iteration once tested on my side.

Best regards,
Bastien