Re: [PATCH bpf-next v2 2/2] selftests/bpf: test that dst is cleared on same-protocol encap
From: Daniel Borkmann <daniel@iogearbox.net>
Date: 2026-03-30 08:03:51
Also in:
bpf, linux-kselftest
Subsystem:
bpf [general] (safe dynamic programs and tools), bpf [selftests] (test runners & infrastructure), kernel selftest framework, the rest · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Shuah Khan, Linus Torvalds
On 3/29/26 8:04 PM, Jakub Kicinski wrote:
Verify that bpf_skb_adjust_room() clears the routing dst even when the encap L3 protocol matches the original packet (e.g. IPIP). The dst selected for the inner packet is not valid for the encapsulated result; a stale dst could lead to misrouting. Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net> For new tests we should ideally only be using tcx links and not the old qdisc approach unless there is specifc reason to. Any objections if I fold this in while applying? .../selftests/bpf/prog_tests/test_dst_clear.c | 23 ++++++------------- .../selftests/bpf/progs/test_dst_clear.c | 2 +- 2 files changed, 8 insertions(+), 17 deletions(-)
diff --git a/tools/testing/selftests/bpf/prog_tests/test_dst_clear.c b/tools/testing/selftests/bpf/prog_tests/test_dst_clear.c
index 8190c56556fb..c8e9c6947a2c 100644
--- a/tools/testing/selftests/bpf/prog_tests/test_dst_clear.c
+++ b/tools/testing/selftests/bpf/prog_tests/test_dst_clear.c@@ -15,11 +15,11 @@ void test_dst_clear(void) { - LIBBPF_OPTS(bpf_tc_hook, qdisc_hook, .attach_point = BPF_TC_EGRESS); - LIBBPF_OPTS(bpf_tc_opts, tc_attach); + LIBBPF_OPTS(bpf_tcx_opts, tcx_opts); struct nstoken *nstoken = NULL; struct test_dst_clear *skel; struct sockaddr_in addr; + struct bpf_link *link; socklen_t addrlen; char buf[128] = {}; int sockfd, err;
@@ -36,18 +36,11 @@ void test_dst_clear(void) if (!ASSERT_OK_PTR(nstoken, "open_netns")) goto fail; - qdisc_hook.ifindex = if_nametoindex("lo"); - if (!ASSERT_GT(qdisc_hook.ifindex, 0, "if_nametoindex lo")) - goto fail; - - err = bpf_tc_hook_create(&qdisc_hook); - if (!ASSERT_OK(err, "create qdisc hook")) - goto fail; - - tc_attach.prog_fd = bpf_program__fd(skel->progs.dst_clear); - err = bpf_tc_attach(&qdisc_hook, &tc_attach); - if (!ASSERT_OK(err, "attach filter")) + link = bpf_program__attach_tcx(skel->progs.dst_clear, + if_nametoindex("lo"), &tcx_opts); + if (!ASSERT_OK_PTR(link, "attach_tcx")) goto fail; + skel->links.dst_clear = link; addrlen = sizeof(addr); err = make_sockaddr(AF_INET, IPV4_IFACE_ADDR, UDP_TEST_PORT,
@@ -66,10 +59,8 @@ void test_dst_clear(void) ASSERT_TRUE(skel->bss->dst_cleared, "dst_cleared"); fail: - if (nstoken) { - bpf_tc_hook_destroy(&qdisc_hook); + if (nstoken) close_netns(nstoken); - } SYS_NOFAIL("ip netns del " NS_TEST); test_dst_clear__destroy(skel); }
diff --git a/tools/testing/selftests/bpf/progs/test_dst_clear.c b/tools/testing/selftests/bpf/progs/test_dst_clear.c
index 7ac9604fd99c..c22a6eeb4798 100644
--- a/tools/testing/selftests/bpf/progs/test_dst_clear.c
+++ b/tools/testing/selftests/bpf/progs/test_dst_clear.c@@ -13,7 +13,7 @@ void *bpf_cast_to_kern_ctx(void *) __ksym; bool had_dst = false; bool dst_cleared = false; -SEC("tc") +SEC("tc/egress") int dst_clear(struct __sk_buff *skb) { struct sk_buff *kskb;
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2.43.0