selftests/bpf: Test case for BPF_SOCK_OPS_TCP_LISTEN_CB

Cover new TCP-BPF callback in test_tcpbpf: when listen() is called on
socket, set BPF_SOCK_OPS_STATE_CB_FLAG so that BPF_SOCK_OPS_STATE_CB
callback can be called on future state transition, and when such a
transition happens (TCP_LISTEN -> TCP_CLOSE), track it in the map and
verify it in user space later.
Signed-off-by: Andrey Ignatov <rdna@fb.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

tools/testing/selftests/bpf/test_tcpbpf.h

@@ -12,5 +12,6 @@ struct tcpbpf_globals {
 	__u32 good_cb_test_rv;
 	__u64 bytes_received;
 	__u64 bytes_acked;
+	__u32 num_listen;
 };
 #endif

tools/testing/selftests/bpf/test_tcpbpf_kern.c

@@ -96,15 +96,22 @@ int bpf_testcb(struct bpf_sock_ops *skops)
 			if (!gp)
 				break;
 			g = *gp;
+			if (skops->args[0] == BPF_TCP_LISTEN) {
+				g.num_listen++;
+			} else {
 				g.total_retrans = skops->total_retrans;
 				g.data_segs_in = skops->data_segs_in;
 				g.data_segs_out = skops->data_segs_out;
 				g.bytes_received = skops->bytes_received;
 				g.bytes_acked = skops->bytes_acked;
+			}
 			bpf_map_update_elem(&global_map, &key, &g,
 					    BPF_ANY);
 		}
 		break;
+	case BPF_SOCK_OPS_TCP_LISTEN_CB:
+		bpf_sock_ops_cb_flags_set(skops, BPF_SOCK_OPS_STATE_CB_FLAG);
+		break;
 	default:
 		rv = -1;
 	}

tools/testing/selftests/bpf/test_tcpbpf_user.c

@@ -37,7 +37,8 @@ int verify_result(const struct tcpbpf_globals *result)
 			   (1 << BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB) |
 			   (1 << BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB) |
 			   (1 << BPF_SOCK_OPS_NEEDS_ECN) |
-			   (1 << BPF_SOCK_OPS_STATE_CB));
+			   (1 << BPF_SOCK_OPS_STATE_CB) |
+			   (1 << BPF_SOCK_OPS_TCP_LISTEN_CB));
 
 	EXPECT_EQ(expected_events, result->event_map, "#" PRIx32);
 	EXPECT_EQ(501ULL, result->bytes_received, "llu");
@@ -46,6 +47,7 @@ int verify_result(const struct tcpbpf_globals *result)
 	EXPECT_EQ(1, result->data_segs_out, PRIu32);
 	EXPECT_EQ(0x80, result->bad_cb_test_rv, PRIu32);
 	EXPECT_EQ(0, result->good_cb_test_rv, PRIu32);
+	EXPECT_EQ(1, result->num_listen, PRIu32);
 
 	return 0;
 err: