bpf: selftest: Ensure the child sk inherited all bpf_sock_ops_cb_flags

This patch adds a test to ensure the child sk inherited everything
from the bpf_sock_ops_cb_flags of the listen sk:
1. Sets one more cb_flags (BPF_SOCK_OPS_STATE_CB_FLAG) to the listen sk
in test_tcp_hdr_options.c
2. Saves the skops->bpf_sock_ops_cb_flags when handling the newly
established passive connection
3. CHECK() it is the same as the listen sk

This also covers the fastopen case as the existing test_tcp_hdr_options.c
does.

Signed-off-by: Martin KaFai Lau <[e-mail]>
Signed-off-by: Alexei Starovoitov <[e-mail]>
Link: https://lore.kernel.org/bpf/[e-mail]

tools/testing/selftests/bpf/prog_tests/tcp_hdr_options.c

···
 
 static void check_hdr_and_close_fds(struct sk_fds *sk_fds)
 {
+	const __u32 expected_inherit_cb_flags =
+		BPF_SOCK_OPS_PARSE_UNKNOWN_HDR_OPT_CB_FLAG |
+		BPF_SOCK_OPS_WRITE_HDR_OPT_CB_FLAG |
+		BPF_SOCK_OPS_STATE_CB_FLAG;
+
 	if (sk_fds_shutdown(sk_fds))
+		goto check_linum;
+
+	if (CHECK(expected_inherit_cb_flags != skel->bss->inherit_cb_flags,
+		  "Unexpected inherit_cb_flags", "0x%x != 0x%x\n",
+		  skel->bss->inherit_cb_flags, expected_inherit_cb_flags))
 		goto check_linum;
 
 	if (check_hdr_stg(&exp_passive_hdr_stg, sk_fds->passive_fd,
···
 
 	memset(&skel->bss->active_estab_in, 0, optsize);
 	memset(&skel->bss->active_fin_in, 0, optsize);
+
+	skel->bss->inherit_cb_flags = 0;
 
 	skel->data->test_kind = TCPOPT_EXP;
 	skel->data->test_magic = 0xeB9F;

tools/testing/selftests/bpf/progs/test_misc_tcp_hdr_options.c

···
 		passive_lport_n = __bpf_htons(passive_lport_h);
 		bpf_setsockopt(skops, SOL_TCP, TCP_SAVE_SYN,
 			       &true_val, sizeof(true_val));
-		set_hdr_cb_flags(skops);
+		set_hdr_cb_flags(skops, 0);
 		break;
 	case BPF_SOCK_OPS_TCP_CONNECT_CB:
-		set_hdr_cb_flags(skops);
+		set_hdr_cb_flags(skops, 0);
 		break;
 	case BPF_SOCK_OPS_PARSE_HDR_OPT_CB:
 		return handle_parse_hdr(skops);

tools/testing/selftests/bpf/progs/test_tcp_hdr_options.c

···
 
 __u8 test_kind = TCPOPT_EXP;
 __u16 test_magic = 0xeB9F;
+__u32 inherit_cb_flags = 0;
 
 struct bpf_test_option passive_synack_out = {};
 struct bpf_test_option passive_fin_out	= {};
···
 	struct tcphdr *th;
 	int err;
 
+	inherit_cb_flags = skops->bpf_sock_ops_cb_flags;
+
 	err = load_option(skops, &passive_estab_in, true);
 	if (err == -ENOENT) {
 		/* saved_syn is not found. It was in syncookie mode.
···
 	case BPF_SOCK_OPS_TCP_LISTEN_CB:
 		bpf_setsockopt(skops, SOL_TCP, TCP_SAVE_SYN,
 			       &true_val, sizeof(true_val));
-		set_hdr_cb_flags(skops);
+		set_hdr_cb_flags(skops, BPF_SOCK_OPS_STATE_CB_FLAG);
 		break;
 	case BPF_SOCK_OPS_TCP_CONNECT_CB:
-		set_hdr_cb_flags(skops);
+		set_hdr_cb_flags(skops, 0);
 		break;
 	case BPF_SOCK_OPS_PARSE_HDR_OPT_CB:
 		return handle_parse_hdr(skops);

tools/testing/selftests/bpf/test_tcp_hdr_options.h

···
 				    BPF_SOCK_OPS_WRITE_HDR_OPT_CB_FLAG));
 }
 
-static inline void set_hdr_cb_flags(struct bpf_sock_ops *skops)
+static inline void set_hdr_cb_flags(struct bpf_sock_ops *skops, __u32 extra)
 {
 	bpf_sock_ops_cb_flags_set(skops,
 				  skops->bpf_sock_ops_cb_flags |
 				  BPF_SOCK_OPS_PARSE_UNKNOWN_HDR_OPT_CB_FLAG |
-				  BPF_SOCK_OPS_WRITE_HDR_OPT_CB_FLAG);
+				  BPF_SOCK_OPS_WRITE_HDR_OPT_CB_FLAG |
+				  extra);
 }
 static inline void
 clear_parse_all_hdr_cb_flags(struct bpf_sock_ops *skops)