libbpf: Always specify expected_attach_type on program load if supported

For some types of BPF programs that utilize expected_attach_type, libbpf won't
set load_attr.expected_attach_type, even if expected_attach_type is known from
section definition. This was done to preserve backwards compatibility with old
kernels that didn't recognize expected_attach_type attribute yet (which was
added in 5e43f899b03a ("bpf: Check attach type at prog load time"). But this
is problematic for some BPF programs that utilize newer features that require
kernel to know specific expected_attach_type (e.g., extended set of return
codes for cgroup_skb/egress programs).

This patch makes libbpf specify expected_attach_type by default, but also
detect support for this field in kernel and not set it during program load.
This allows to have a good metadata for bpf_program
(e.g., bpf_program__get_extected_attach_type()), but still work with old
kernels (for cases where it can work at all).

Additionally, due to expected_attach_type being always set for recognized
program types, bpf_program__attach_cgroup doesn't have to do extra checks to
determine correct attach type, so remove that additional logic.

Also adjust section_names selftest to account for this change.

More detailed discussion can be found in [0].

  [0] https://lore.kernel.org/bpf/20200412003604.GA15986@rdna-mbp.dhcp.thefacebook.com/

Fixes: 5cf1e9145630 ("bpf: cgroup inet skb programs can return 0 to 3")
Fixes: 5e43f899b03a ("bpf: Check attach type at prog load time")
Reported-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Song Liu <songliubraving@fb.com>
Acked-by: Andrey Ignatov <rdna@fb.com>
Link: https://lore.kernel.org/bpf/20200414182645.1368174-1-andriin@fb.com

1 files changed, 27 insertions, 15 deletions

diff --git a/tools/testing/selftests/bpf/prog_tests/section_names.c b/tools/testing/selftests/bpf/prog_tests/section_names.c
index 9d9351dc2ded..713167449c98 100644
--- a/tools/testing/selftests/bpf/prog_tests/section_names.c
+++ b/tools/testing/selftests/bpf/prog_tests/section_names.c
@@ -43,18 +43,18 @@ static struct sec_name_test tests[] = {
 	{"lwt_seg6local", {0, BPF_PROG_TYPE_LWT_SEG6LOCAL, 0}, {-EINVAL, 0} },
 	{
 		"cgroup_skb/ingress",
-		{0, BPF_PROG_TYPE_CGROUP_SKB, 0},
+		{0, BPF_PROG_TYPE_CGROUP_SKB, BPF_CGROUP_INET_INGRESS},
 		{0, BPF_CGROUP_INET_INGRESS},
 	},
 	{
 		"cgroup_skb/egress",
-		{0, BPF_PROG_TYPE_CGROUP_SKB, 0},
+		{0, BPF_PROG_TYPE_CGROUP_SKB, BPF_CGROUP_INET_EGRESS},
 		{0, BPF_CGROUP_INET_EGRESS},
 	},
 	{"cgroup/skb", {0, BPF_PROG_TYPE_CGROUP_SKB, 0}, {-EINVAL, 0} },
 	{
 		"cgroup/sock",
-		{0, BPF_PROG_TYPE_CGROUP_SOCK, 0},
+		{0, BPF_PROG_TYPE_CGROUP_SOCK, BPF_CGROUP_INET_SOCK_CREATE},
 		{0, BPF_CGROUP_INET_SOCK_CREATE},
 	},
 	{
@@ -69,26 +69,38 @@ static struct sec_name_test tests[] = {
 	},
 	{
 		"cgroup/dev",
-		{0, BPF_PROG_TYPE_CGROUP_DEVICE, 0},
+		{0, BPF_PROG_TYPE_CGROUP_DEVICE, BPF_CGROUP_DEVICE},
 		{0, BPF_CGROUP_DEVICE},
 	},
-	{"sockops", {0, BPF_PROG_TYPE_SOCK_OPS, 0}, {0, BPF_CGROUP_SOCK_OPS} },
+	{
+		"sockops",
+		{0, BPF_PROG_TYPE_SOCK_OPS, BPF_CGROUP_SOCK_OPS},
+		{0, BPF_CGROUP_SOCK_OPS},
+	},
 	{
 		"sk_skb/stream_parser",
-		{0, BPF_PROG_TYPE_SK_SKB, 0},
+		{0, BPF_PROG_TYPE_SK_SKB, BPF_SK_SKB_STREAM_PARSER},
 		{0, BPF_SK_SKB_STREAM_PARSER},
 	},
 	{
 		"sk_skb/stream_verdict",
-		{0, BPF_PROG_TYPE_SK_SKB, 0},
+		{0, BPF_PROG_TYPE_SK_SKB, BPF_SK_SKB_STREAM_VERDICT},
 		{0, BPF_SK_SKB_STREAM_VERDICT},
 	},
 	{"sk_skb", {0, BPF_PROG_TYPE_SK_SKB, 0}, {-EINVAL, 0} },
-	{"sk_msg", {0, BPF_PROG_TYPE_SK_MSG, 0}, {0, BPF_SK_MSG_VERDICT} },
-	{"lirc_mode2", {0, BPF_PROG_TYPE_LIRC_MODE2, 0}, {0, BPF_LIRC_MODE2} },
+	{
+		"sk_msg",
+		{0, BPF_PROG_TYPE_SK_MSG, BPF_SK_MSG_VERDICT},
+		{0, BPF_SK_MSG_VERDICT},
+	},
+	{
+		"lirc_mode2",
+		{0, BPF_PROG_TYPE_LIRC_MODE2, BPF_LIRC_MODE2},
+		{0, BPF_LIRC_MODE2},
+	},
 	{
 		"flow_dissector",
-		{0, BPF_PROG_TYPE_FLOW_DISSECTOR, 0},
+		{0, BPF_PROG_TYPE_FLOW_DISSECTOR, BPF_FLOW_DISSECTOR},
 		{0, BPF_FLOW_DISSECTOR},
 	},
 	{
@@ -158,17 +170,17 @@ static void test_prog_type_by_name(const struct sec_name_test *test)
 				      &expected_attach_type);
 
 	CHECK(rc != test->expected_load.rc, "check_code",
-	      "prog: unexpected rc=%d for %s", rc, test->sec_name);
+	      "prog: unexpected rc=%d for %s\n", rc, test->sec_name);
 
 	if (rc)
 		return;
 
 	CHECK(prog_type != test->expected_load.prog_type, "check_prog_type",
-	      "prog: unexpected prog_type=%d for %s",
+	      "prog: unexpected prog_type=%d for %s\n",
 	      prog_type, test->sec_name);
 
 	CHECK(expected_attach_type != test->expected_load.expected_attach_type,
-	      "check_attach_type", "prog: unexpected expected_attach_type=%d for %s",
+	      "check_attach_type", "prog: unexpected expected_attach_type=%d for %s\n",
 	      expected_attach_type, test->sec_name);
 }
 
@@ -180,13 +192,13 @@ static void test_attach_type_by_name(const struct sec_name_test *test)
 	rc = libbpf_attach_type_by_name(test->sec_name, &attach_type);
 
 	CHECK(rc != test->expected_attach.rc, "check_ret",
-	      "attach: unexpected rc=%d for %s", rc, test->sec_name);
+	      "attach: unexpected rc=%d for %s\n", rc, test->sec_name);
 
 	if (rc)
 		return;
 
 	CHECK(attach_type != test->expected_attach.attach_type,
-	      "check_attach_type", "attach: unexpected attach_type=%d for %s",
+	      "check_attach_type", "attach: unexpected attach_type=%d for %s\n",
 	      attach_type, test->sec_name);
 }