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 <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20201002013454.2542367-1-kafai@fb.com

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

@@ -264,9 +264,19 @@ static int check_error_linum(const struct sk_fds *sk_fds)
 
 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,
 			  "passive_hdr_stg"))
 		goto check_linum;
@@ -321,6 +331,8 @@ static void reset_test(void)
 	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

@@ -304,10 +304,10 @@ int misc_estab(struct bpf_sock_ops *skops)
 		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

@@ -21,6 +21,7 @@
 
 __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	= {};
@@ -467,6 +468,8 @@ static int handle_passive_estab(struct bpf_sock_ops *skops)
 	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.
@@ -600,10 +603,10 @@ int estab(struct bpf_sock_ops *skops)
 	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

@@ -110,12 +110,13 @@ static inline void clear_hdr_cb_flags(struct bpf_sock_ops *skops)
 				    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)