Subject: [PATCH bpf 2/2] bpf/selftests: Add check for updating XDP bpf_link with wrong program type

From: Toke Høiland-Jørgensen <[email-masked]>
Date: Fri, 7 Jan 2022 19:30:49 +0100

Add a check to the xdp_link selftest that the kernel rejects replacing an
XDP program with a different program type on link update. Convert the
selftest to use the preferred ASSERT_* macros while we're at it.

Signed-off-by: Toke Høiland-Jørgensen <[email-masked]>
---
 .../selftests/bpf/prog_tests/xdp_link.c       | 62 +++++++++----------
 .../selftests/bpf/progs/test_xdp_link.c       |  6 ++
 2 files changed, 37 insertions(+), 31 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_link.c b/tools/testing/selftests/bpf/prog_tests/xdp_link.c
index 983ab0b47d30..8660e68383ea 100644
--- a/tools/testing/selftests/bpf/prog_tests/xdp_link.c
+++ b/tools/testing/selftests/bpf/prog_tests/xdp_link.c
@@ -8,46 +8,47 @@
 
 void serial_test_xdp_link(void)
 {
-	__u32 duration = 0, id1, id2, id0 = 0, prog_fd1, prog_fd2, err;
 	DECLARE_LIBBPF_OPTS(bpf_xdp_set_link_opts, opts, .old_fd = -1);
 	struct test_xdp_link *skel1 = NULL, *skel2 = NULL;
+	__u32 id1, id2, id0 = 0, prog_fd1, prog_fd2;
 	struct bpf_link_info link_info;
 	struct bpf_prog_info prog_info;
 	struct bpf_link *link;
+	int err;
 	__u32 link_info_len = sizeof(link_info);
 	__u32 prog_info_len = sizeof(prog_info);
 
 	skel1 = test_xdp_link__open_and_load();
-	if (CHECK(!skel1, "skel_load", "skeleton open and load failed\n"))
+	if (!ASSERT_OK_PTR(skel1, "skel_load"))
 		goto cleanup;
 	prog_fd1 = bpf_program__fd(skel1->progs.xdp_handler);
 
 	skel2 = test_xdp_link__open_and_load();
-	if (CHECK(!skel2, "skel_load", "skeleton open and load failed\n"))
+	if (!ASSERT_OK_PTR(skel2, "skel_load"))
 		goto cleanup;
 	prog_fd2 = bpf_program__fd(skel2->progs.xdp_handler);
 
 	memset(&prog_info, 0, sizeof(prog_info));
 	err = bpf_obj_get_info_by_fd(prog_fd1, &prog_info, &prog_info_len);
-	if (CHECK(err, "fd_info1", "failed %d\n", -errno))
+	if (!ASSERT_OK(err, "fd_info1"))
 		goto cleanup;
 	id1 = prog_info.id;
 
 	memset(&prog_info, 0, sizeof(prog_info));
 	err = bpf_obj_get_info_by_fd(prog_fd2, &prog_info, &prog_info_len);
-	if (CHECK(err, "fd_info2", "failed %d\n", -errno))
+	if (!ASSERT_OK(err, "fd_info2"))
 		goto cleanup;
 	id2 = prog_info.id;
 
 	/* set initial prog attachment */
 	err = bpf_set_link_xdp_fd_opts(IFINDEX_LO, prog_fd1, XDP_FLAGS_REPLACE, &opts);
-	if (CHECK(err, "fd_attach", "initial prog attach failed: %d\n", err))
+	if (!ASSERT_OK(err, "fd_attach"))
 		goto cleanup;
 
 	/* validate prog ID */
 	err = bpf_get_link_xdp_id(IFINDEX_LO, &id0, 0);
-	CHECK(err || id0 != id1, "id1_check",
-	      "loaded prog id %u != id1 %u, err %d", id0, id1, err);
+	if (!ASSERT_OK(err, "id1_check_err") || !ASSERT_EQ(id0, id1, "id1_check_val"))
+		goto cleanup;
 
 	/* BPF link is not allowed to replace prog attachment */
 	link = bpf_program__attach_xdp(skel1->progs.xdp_handler, IFINDEX_LO);
@@ -62,7 +63,7 @@ void serial_test_xdp_link(void)
 	/* detach BPF program */
 	opts.old_fd = prog_fd1;
 	err = bpf_set_link_xdp_fd_opts(IFINDEX_LO, -1, XDP_FLAGS_REPLACE, &opts);
-	if (CHECK(err, "prog_detach", "failed %d\n", err))
+	if (!ASSERT_OK(err, "prog_detach"))
 		goto cleanup;
 
 	/* now BPF link should attach successfully */
@@ -73,24 +74,23 @@ void serial_test_xdp_link(void)
 
 	/* validate prog ID */
 	err = bpf_get_link_xdp_id(IFINDEX_LO, &id0, 0);
-	if (CHECK(err || id0 != id1, "id1_check",
-		  "loaded prog id %u != id1 %u, err %d", id0, id1, err))
+	if (!ASSERT_OK(err, "id1_check_err") || !ASSERT_EQ(id0, id1, "id1_check_val"))
 		goto cleanup;
 
 	/* BPF prog attach is not allowed to replace BPF link */
 	opts.old_fd = prog_fd1;
 	err = bpf_set_link_xdp_fd_opts(IFINDEX_LO, prog_fd2, XDP_FLAGS_REPLACE, &opts);
-	if (CHECK(!err, "prog_attach_fail", "unexpected success\n"))
+	if (!ASSERT_ERR(err, "prog_attach_fail"))
 		goto cleanup;
 
 	/* Can't force-update when BPF link is active */
 	err = bpf_set_link_xdp_fd(IFINDEX_LO, prog_fd2, 0);
-	if (CHECK(!err, "prog_update_fail", "unexpected success\n"))
+	if (!ASSERT_ERR(err, "prog_update_fail"))
 		goto cleanup;
 
 	/* Can't force-detach when BPF link is active */
 	err = bpf_set_link_xdp_fd(IFINDEX_LO, -1, 0);
-	if (CHECK(!err, "prog_detach_fail", "unexpected success\n"))
+	if (!ASSERT_ERR(err, "prog_detach_fail"))
 		goto cleanup;
 
 	/* BPF link is not allowed to replace another BPF link */
@@ -110,40 +110,40 @@ void serial_test_xdp_link(void)
 	skel2->links.xdp_handler = link;
 
 	err = bpf_get_link_xdp_id(IFINDEX_LO, &id0, 0);
-	if (CHECK(err || id0 != id2, "id2_check",
-		  "loaded prog id %u != id2 %u, err %d", id0, id1, err))
+	if (!ASSERT_OK(err, "id2_check_err") || !ASSERT_EQ(id0, id2, "id2_check_val"))
 		goto cleanup;
 
 	/* updating program under active BPF link works as expected */
 	err = bpf_link__update_program(link, skel1->progs.xdp_handler);
-	if (CHECK(err, "link_upd", "failed: %d\n", err))
+	if (!ASSERT_OK(err, "link_upd"))
 		goto cleanup;
 
 	memset(&link_info, 0, sizeof(link_info));
 	err = bpf_obj_get_info_by_fd(bpf_link__fd(link), &link_info, &link_info_len);
-	if (CHECK(err, "link_info", "failed: %d\n", err))
+	if (!ASSERT_OK(err, "link_info"))
+		goto cleanup;
+
+	if (!ASSERT_EQ(link_info.type, BPF_LINK_TYPE_XDP, "link_type") ||
+	    !ASSERT_EQ(link_info.prog_id, id1, "link_prog_id") ||
+	    !ASSERT_EQ(link_info.xdp.ifindex, IFINDEX_LO, "link_ifindex"))
 		goto cleanup;
 
-	CHECK(link_info.type != BPF_LINK_TYPE_XDP, "link_type",
-	      "got %u != exp %u\n", link_info.type, BPF_LINK_TYPE_XDP);
-	CHECK(link_info.prog_id != id1, "link_prog_id",
-	      "got %u != exp %u\n", link_info.prog_id, id1);
-	CHECK(link_info.xdp.ifindex != IFINDEX_LO, "link_ifindex",
-	      "got %u != exp %u\n", link_info.xdp.ifindex, IFINDEX_LO);
+	/* updating program under active BPF link with different type fails */
+	err = bpf_link__update_program(link, skel1->progs.tc_handler);
+	if (!ASSERT_ERR(err, "link_upd_invalid"))
+		goto cleanup;
 
 	err = bpf_link__detach(link);
-	if (CHECK(err, "link_detach", "failed %d\n", err))
+	if (!ASSERT_OK(err, "link_detach"))
 		goto cleanup;
 
 	memset(&link_info, 0, sizeof(link_info));
 	err = bpf_obj_get_info_by_fd(bpf_link__fd(link), &link_info, &link_info_len);
-	if (CHECK(err, "link_info", "failed: %d\n", err))
+	if (!ASSERT_OK(err, "link_info") ||
+	    !ASSERT_EQ(link_info.prog_id, id1, "link_prog_id") ||
+	    /* ifindex should be zeroed out */
+	    !ASSERT_EQ(link_info.xdp.ifindex, 0, "link_ifindex"))
 		goto cleanup;
-	CHECK(link_info.prog_id != id1, "link_prog_id",
-	      "got %u != exp %u\n", link_info.prog_id, id1);
-	/* ifindex should be zeroed out */
-	CHECK(link_info.xdp.ifindex != 0, "link_ifindex",
-	      "got %u != exp %u\n", link_info.xdp.ifindex, 0);
 
 cleanup:
 	test_xdp_link__destroy(skel1);
diff --git a/tools/testing/selftests/bpf/progs/test_xdp_link.c b/tools/testing/selftests/bpf/progs/test_xdp_link.c
index ee7d6ac0f615..64ff32eaae92 100644
--- a/tools/testing/selftests/bpf/progs/test_xdp_link.c
+++ b/tools/testing/selftests/bpf/progs/test_xdp_link.c
@@ -10,3 +10,9 @@ int xdp_handler(struct xdp_md *xdp)
 {
 	return 0;
 }
+
+SEC("tc")
+int tc_handler(struct __sk_buff *skb)
+{
+	return 0;
+}
-- 
2.34.1