bpf: add selftest for bpf's (set|get)_sockopt for SAVE_SYN

adding selftest for feature, introduced in commit 9452048c79404 ("bpf:
add TCP_SAVE_SYN/TCP_SAVED_SYN options for bpf_(set|get)sockopt").

Signed-off-by: Nikita V. Shirokov <tehnerd@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

tools/testing/selftests/bpf/test_tcpbpf_kern.c

@@ -5,6 +5,7 @@
 #include <linux/if_ether.h>
 #include <linux/if_packet.h>
 #include <linux/ip.h>
+#include <linux/ipv6.h>
 #include <linux/types.h>
 #include <linux/socket.h>
 #include <linux/tcp.h>
@@ -17,6 +18,13 @@ struct bpf_map_def SEC("maps") global_map = {
 	.type = BPF_MAP_TYPE_ARRAY,
 	.key_size = sizeof(__u32),
 	.value_size = sizeof(struct tcpbpf_globals),
+	.max_entries = 4,
+};
+
+struct bpf_map_def SEC("maps") sockopt_results = {
+	.type = BPF_MAP_TYPE_ARRAY,
+	.key_size = sizeof(__u32),
+	.value_size = sizeof(int),
 	.max_entries = 2,
 };
 
@@ -45,11 +53,14 @@ int _version SEC("version") = 1;
 SEC("sockops")
 int bpf_testcb(struct bpf_sock_ops *skops)
 {
-	int rv = -1;
-	int bad_call_rv = 0;
+	char header[sizeof(struct ipv6hdr) + sizeof(struct tcphdr)];
+	struct tcphdr *thdr;
 	int good_call_rv = 0;
-	int op;
+	int bad_call_rv = 0;
+	int save_syn = 1;
+	int rv = -1;
 	int v = 0;
+	int op;
 
 	op = (int) skops->op;
 
@@ -82,6 +93,21 @@ int bpf_testcb(struct bpf_sock_ops *skops)
 		v = 0xff;
 		rv = bpf_setsockopt(skops, SOL_IPV6, IPV6_TCLASS, &v,
 				    sizeof(v));
+		if (skops->family == AF_INET6) {
+			v = bpf_getsockopt(skops, IPPROTO_TCP, TCP_SAVED_SYN,
+					   header, (sizeof(struct ipv6hdr) +
+						    sizeof(struct tcphdr)));
+			if (!v) {
+				int offset = sizeof(struct ipv6hdr);
+
+				thdr = (struct tcphdr *)(header + offset);
+				v = thdr->syn;
+				__u32 key = 1;
+
+				bpf_map_update_elem(&sockopt_results, &key, &v,
+						    BPF_ANY);
+			}
+		}
 		break;
 	case BPF_SOCK_OPS_RTO_CB:
 		break;
@@ -111,6 +137,12 @@ int bpf_testcb(struct bpf_sock_ops *skops)
 		break;
 	case BPF_SOCK_OPS_TCP_LISTEN_CB:
 		bpf_sock_ops_cb_flags_set(skops, BPF_SOCK_OPS_STATE_CB_FLAG);
+		v = bpf_setsockopt(skops, IPPROTO_TCP, TCP_SAVE_SYN,
+				   &save_syn, sizeof(save_syn));
+		/* Update global map w/ result of setsock opt */
+		__u32 key = 0;
+
+		bpf_map_update_elem(&sockopt_results, &key, &v, BPF_ANY);
 		break;
 	default:
 		rv = -1;

tools/testing/selftests/bpf/test_tcpbpf_user.c

@@ -54,6 +54,26 @@ int verify_result(const struct tcpbpf_globals *result)
 	return -1;
 }
 
+int verify_sockopt_result(int sock_map_fd)
+{
+	__u32 key = 0;
+	int res;
+	int rv;
+
+	/* check setsockopt for SAVE_SYN */
+	rv = bpf_map_lookup_elem(sock_map_fd, &key, &res);
+	EXPECT_EQ(0, rv, "d");
+	EXPECT_EQ(0, res, "d");
+	key = 1;
+	/* check getsockopt for SAVED_SYN */
+	rv = bpf_map_lookup_elem(sock_map_fd, &key, &res);
+	EXPECT_EQ(0, rv, "d");
+	EXPECT_EQ(1, res, "d");
+	return 0;
+err:
+	return -1;
+}
+
 static int bpf_find_map(const char *test, struct bpf_object *obj,
 			const char *name)
 {
@@ -70,11 +90,11 @@ static int bpf_find_map(const char *test, struct bpf_object *obj,
 int main(int argc, char **argv)
 {
 	const char *file = "test_tcpbpf_kern.o";
+	int prog_fd, map_fd, sock_map_fd;
 	struct tcpbpf_globals g = {0};
 	const char *cg_path = "/foo";
 	int error = EXIT_FAILURE;
 	struct bpf_object *obj;
-	int prog_fd, map_fd;
 	int cg_fd = -1;
 	__u32 key = 0;
 	int rv;
@@ -110,6 +130,10 @@ int main(int argc, char **argv)
 	if (map_fd < 0)
 		goto err;
 
+	sock_map_fd = bpf_find_map(__func__, obj, "sockopt_results");
+	if (sock_map_fd < 0)
+		goto err;
+
 	rv = bpf_map_lookup_elem(map_fd, &key, &g);
 	if (rv != 0) {
 		printf("FAILED: bpf_map_lookup_elem returns %d\n", rv);
@@ -121,6 +145,11 @@ int main(int argc, char **argv)
 		goto err;
 	}
 
+	if (verify_sockopt_result(sock_map_fd)) {
+		printf("FAILED: Wrong sockopt stats\n");
+		goto err;
+	}
+
 	printf("PASSED!\n");
 	error = 0;
 err: