[PATCH net-next 5/5] selftests/bpf: check replacing and detaching XDP on a bond through a link

[Jakub Kicinski <kuba@kernel.org>]

The bond tests attach and destroy links, but never replace the program
behind one, or detach it without closing the link. Both only ever
operate on the device the link was created on, and rely on the bond to
pass the change down to its slaves.

Check that the slave follows the replacement and the detach, and that
the program which got replaced is released - the bond used to leak it.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
 .../selftests/bpf/prog_tests/xdp_bonding.c    | 96 +++++++++++++++++++
 1 file changed, 96 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_bonding.c b/tools/testing/selftests/bpf/prog_tests/xdp_bonding.c
index ab0f01be4131..05f2e8079858 100644
--- a/tools/testing/selftests/bpf/prog_tests/xdp_bonding.c
+++ b/tools/testing/selftests/bpf/prog_tests/xdp_bonding.c
@@ -516,6 +516,99 @@ static void test_xdp_bonding_nested(struct skeletons *skeletons)
 	system("ip link del bond_nest2");
 }
 
+/*
+ * Replace, then detach the program on a bond through its link. The link only
+ * knows about the bond, the slave has to follow it, and the replaced program
+ * has to be released.
+ */
+static void test_xdp_bonding_link_update(struct skeletons *skeletons)
+{
+	LIBBPF_OPTS(bpf_prog_load_opts, opts, .expected_attach_type = BPF_XDP);
+	struct bpf_program *new_prog = skeletons->xdp_dummy->progs.xdp_dummy_prog;
+	struct bpf_insn insns[] = {
+		BPF_MOV64_IMM(BPF_REG_0, XDP_PASS),
+		BPF_EXIT_INSN(),
+	};
+	int veth, bond, err, fd, old_fd = -1, link_fd = -1;
+	struct bpf_prog_info info = {};
+	__u32 old_id, new_id, id, len;
+
+	if (!ASSERT_OK(system("ip link add veth type veth"), "add veth"))
+		goto out;
+	if (!ASSERT_OK(system("ip link add bond type bond"), "add bond"))
+		goto out;
+
+	veth = if_nametoindex("veth");
+	if (!ASSERT_GT(veth, 0, "if_nametoindex veth"))
+		goto out;
+	bond = if_nametoindex("bond");
+	if (!ASSERT_GT(bond, 0, "if_nametoindex bond"))
+		goto out;
+
+	err = system("ip link set veth master bond");
+	if (!ASSERT_OK(err, "set veth master"))
+		goto out;
+
+	/* same attach type as the skeleton's, or the link won't take it */
+	old_fd = bpf_prog_load(BPF_PROG_TYPE_XDP, "xdp_old", "GPL", insns,
+			       ARRAY_SIZE(insns), &opts);
+	if (!ASSERT_GE(old_fd, 0, "load old program"))
+		goto out;
+	len = sizeof(info);
+	if (!ASSERT_OK(bpf_prog_get_info_by_fd(old_fd, &info, &len), "old program info"))
+		goto out;
+	old_id = info.id;
+
+	memset(&info, 0, sizeof(info));
+	len = sizeof(info);
+	err = bpf_prog_get_info_by_fd(bpf_program__fd(new_prog), &info, &len);
+	if (!ASSERT_OK(err, "new program info"))
+		goto out;
+	new_id = info.id;
+
+	link_fd = bpf_link_create(old_fd, bond, BPF_XDP, NULL);
+	if (!ASSERT_GE(link_fd, 0, "attach old program to bond"))
+		goto out;
+
+	err = bpf_xdp_query_id(veth, XDP_FLAGS_DRV_MODE, &id);
+	if (!ASSERT_OK(err, "query veth") ||
+	    !ASSERT_EQ(id, old_id, "veth runs the old program"))
+		goto out;
+
+	err = bpf_link_update(link_fd, bpf_program__fd(new_prog), NULL);
+	if (!ASSERT_OK(err, "replace the program through the link"))
+		goto out;
+
+	err = bpf_xdp_query_id(veth, XDP_FLAGS_DRV_MODE, &id);
+	if (!ASSERT_OK(err, "query veth") ||
+	    !ASSERT_EQ(id, new_id, "veth follows to the new program"))
+		goto out;
+
+	/* nothing but our fd should be holding on to the old program now */
+	close(old_fd);
+	old_fd = -1;
+	fd = bpf_prog_get_fd_by_id(old_id);
+	if (!ASSERT_EQ(fd, -ENOENT, "old program released") && fd >= 0)
+		close(fd);
+
+	err = bpf_link_detach(link_fd);
+	if (!ASSERT_OK(err, "detach the link"))
+		goto out;
+
+	err = bpf_xdp_query_id(veth, XDP_FLAGS_DRV_MODE, &id);
+	if (!ASSERT_OK(err, "query veth"))
+		goto out;
+	ASSERT_EQ(id, 0, "veth has no program left");
+
+out:
+	if (link_fd >= 0)
+		close(link_fd);
+	if (old_fd >= 0)
+		close(old_fd);
+	system("ip link del veth");
+	system("ip link del bond");
+}
+
 /*
  * Test that XDP redirect via xdp_master_redirect() does not crash when
  * the bond master device is not up. When bond is in round-robin mode but
@@ -826,6 +919,9 @@ void serial_test_xdp_bonding(void)
 	if (test__start_subtest("xdp_bonding_nested"))
 		test_xdp_bonding_nested(&skeletons);
 
+	if (test__start_subtest("xdp_bonding_link_update"))
+		test_xdp_bonding_link_update(&skeletons);
+
 	if (test__start_subtest("xdp_bonding_features"))
 		test_xdp_bonding_features(&skeletons);
 
-- 
2.56.0