bpf: Add tests for bpf_sk_storage to bpf_tcp_ca

This patch adds test to exercise the bpf_sk_storage_get()
and bpf_sk_storage_delete() helper from the bpf_dctcp.c.

The setup and check on the sk_storage is done immediately
before and after the connect().

This patch also takes this chance to move the pthread_create()
after the connect() has been done.  That will remove the need of
the "wait_thread" label.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20200320152107.2169904-1-kafai@fb.com

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

@@ -11,6 +11,7 @@
 static const unsigned int total_bytes = 10 * 1024 * 1024;
 static const struct timeval timeo_sec = { .tv_sec = 10 };
 static const size_t timeo_optlen = sizeof(timeo_sec);
+static int expected_stg = 0xeB9F;
 static int stop, duration;
 
 static int settimeo(int fd)
@@ -88,7 +89,7 @@ static void *server(void *arg)
 	return NULL;
 }
 
-static void do_test(const char *tcp_ca)
+static void do_test(const char *tcp_ca, const struct bpf_map *sk_stg_map)
 {
 	struct sockaddr_in6 sa6 = {};
 	ssize_t nr_recv = 0, bytes = 0;
@@ -126,14 +127,34 @@ static void do_test(const char *tcp_ca)
 	err = listen(lfd, 1);
 	if (CHECK(err == -1, "listen", "errno:%d\n", errno))
 		goto done;
-	err = pthread_create(&srv_thread, NULL, server, (void *)(long)lfd);
-	if (CHECK(err != 0, "pthread_create", "err:%d\n", err))
+
+	if (sk_stg_map) {
+		err = bpf_map_update_elem(bpf_map__fd(sk_stg_map), &fd,
+					  &expected_stg, BPF_NOEXIST);
+		if (CHECK(err, "bpf_map_update_elem(sk_stg_map)",
+			  "err:%d errno:%d\n", err, errno))
 			goto done;
+	}
 
 	/* connect to server */
 	err = connect(fd, (struct sockaddr *)&sa6, addrlen);
 	if (CHECK(err == -1, "connect", "errno:%d\n", errno))
-		goto wait_thread;
+		goto done;
+
+	if (sk_stg_map) {
+		int tmp_stg;
+
+		err = bpf_map_lookup_elem(bpf_map__fd(sk_stg_map), &fd,
+					  &tmp_stg);
+		if (CHECK(!err || errno != ENOENT,
+			  "bpf_map_lookup_elem(sk_stg_map)",
+			  "err:%d errno:%d\n", err, errno))
+			goto done;
+	}
+
+	err = pthread_create(&srv_thread, NULL, server, (void *)(long)lfd);
+	if (CHECK(err != 0, "pthread_create", "err:%d errno:%d\n", err, errno))
+		goto done;
 
 	/* recv total_bytes */
 	while (bytes < total_bytes && !READ_ONCE(stop)) {
@@ -149,7 +170,6 @@ static void do_test(const char *tcp_ca)
 	CHECK(bytes != total_bytes, "recv", "%zd != %u nr_recv:%zd errno:%d\n",
 	      bytes, total_bytes, nr_recv, errno);
 
-wait_thread:
 	WRITE_ONCE(stop, 1);
 	pthread_join(srv_thread, &thread_ret);
 	CHECK(IS_ERR(thread_ret), "pthread_join", "thread_ret:%ld",
@@ -175,7 +195,7 @@ static void test_cubic(void)
 		return;
 	}
 
-	do_test("bpf_cubic");
+	do_test("bpf_cubic", NULL);
 
 	bpf_link__destroy(link);
 	bpf_cubic__destroy(cubic_skel);
@@ -197,7 +217,10 @@ static void test_dctcp(void)
 		return;
 	}
 
-	do_test("bpf_dctcp");
+	do_test("bpf_dctcp", dctcp_skel->maps.sk_stg_map);
+	CHECK(dctcp_skel->bss->stg_result != expected_stg,
+	      "Unexpected stg_result", "stg_result (%x) != expected_stg (%x)\n",
+	      dctcp_skel->bss->stg_result, expected_stg);
 
 	bpf_link__destroy(link);
 	bpf_dctcp__destroy(dctcp_skel);

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

@@ -6,6 +6,7 @@
  * the kernel BPF logic.
  */
 
+#include <stddef.h>
 #include <linux/bpf.h>
 #include <linux/types.h>
 #include <bpf/bpf_helpers.h>
@@ -14,6 +15,15 @@
 
 char _license[] SEC("license") = "GPL";
 
+int stg_result = 0;
+
+struct {
+	__uint(type, BPF_MAP_TYPE_SK_STORAGE);
+	__uint(map_flags, BPF_F_NO_PREALLOC);
+	__type(key, int);
+	__type(value, int);
+} sk_stg_map SEC(".maps");
+
 #define DCTCP_MAX_ALPHA	1024U
 
 struct dctcp {
@@ -43,12 +53,18 @@ void BPF_PROG(dctcp_init, struct sock *sk)
 {
 	const struct tcp_sock *tp = tcp_sk(sk);
 	struct dctcp *ca = inet_csk_ca(sk);
+	int *stg;
 
 	ca->prior_rcv_nxt = tp->rcv_nxt;
 	ca->dctcp_alpha = min(dctcp_alpha_on_init, DCTCP_MAX_ALPHA);
 	ca->loss_cwnd = 0;
 	ca->ce_state = 0;
 
+	stg = bpf_sk_storage_get(&sk_stg_map, (void *)tp, NULL, 0);
+	if (stg) {
+		stg_result = *stg;
+		bpf_sk_storage_delete(&sk_stg_map, (void *)tp);
+	}
 	dctcp_reset(tp, ca);
 }