Re: [PATCH net-next 06/15] selftests/bpf: Test passing metadata across veth and GRE

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] bpf: test flakiness due to hardcoded netns/device name collision
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commit 4f7f4b87639860030b5545295e6b1cde37989dbf
Author: Jakub Sitnicki <jakub@cloudflare.com>

selftests/bpf: Test passing metadata across veth and GRE

This commit adds tests to stash metadata at TC egress and read it back at
TC ingress after the packet crosses veth and GRE device boundaries.

> diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_context_test_run.c b/tools/testing/selftests/bpf/prog_tests/xdp_context_test_run.c
> --- a/tools/testing/selftests/bpf/prog_tests/xdp_context_test_run.c
> +++ b/tools/testing/selftests/bpf/prog_tests/xdp_context_test_run.c

[ ... ]

> +/* Test if skb_ext survives veth cross-netns forward */
> +static void test_skb_trace__veth(struct test_xdp_meta *skel)
> +{
> +	LIBBPF_OPTS(bpf_tc_hook, tx_hook, .attach_point = BPF_TC_EGRESS);
> +	LIBBPF_OPTS(bpf_tc_opts, tx_opts, .handle = 1, .priority = 1);
> +	LIBBPF_OPTS(bpf_tc_hook, rx_hook, .attach_point = BPF_TC_INGRESS);
> +	LIBBPF_OPTS(bpf_tc_opts, rx_opts, .handle = 1, .priority = 1);
> +	struct netns_obj *rx_ns = NULL, *tx_ns = NULL;
> +	struct bpf_link *put_link = NULL;
> +	struct nstoken *nstoken = NULL;
> +	int rx_ifindex, tx_ifindex;
> +	int ret;
> +	int i;
> +
> +	put_link = bpf_program__attach(skel->progs.skb_free);
> +	if (!ASSERT_OK_PTR(put_link, "put_attach"))
> +		return;
> +
> +	tx_ns = netns_new(TX_NETNS, false);
> +	if (!ASSERT_OK_PTR(tx_ns, "create tx_ns"))
> +		goto close;
> +
> +	rx_ns = netns_new(RX_NETNS, false);
> +	if (!ASSERT_OK_PTR(rx_ns, "create rx_ns"))
> +		goto close;
> +
> +	SYS(close, "ip link add " RX_NAME " netns " RX_NETNS
> +	    " type veth peer name " TX_NAME " netns " TX_NETNS);

[Severity: Medium]
Does this cause test flakiness due to hardcoded netns/device name collisions?

When test_progs executes independent top-level tests in parallel using
multiple workers (-j), tests using identical globally-visible network
namespaces and device names can concurrently attempt to create the same
resources. This results in an "already exists" failure for the slower test.

Since TX_NETNS, RX_NETNS, TX_NAME, and RX_NAME are identical to those used
by test_xdp_context_veth in the same file, would it be better to use
dynamically generated or test-specific names here to avoid collisions when
these tests run concurrently?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260928-bpf-meta-gated-tracepoints-v1-0-844dbf3e1edf@cloudflare.com?part=6