[PATCH bpf-next v2 2/2] bpf, selftests: Add test case for cgroup skb to get net_cls classid helpers

[Feng zhou <zhoufeng.zf@xxxxxxxxxxxxx>]

From: Feng Zhou <zhoufeng.zf@xxxxxxxxxxxxx>

This patch adds a test for cgroup skb to get classid.

Signed-off-by: Feng Zhou <zhoufeng.zf@xxxxxxxxxxxxx>
---
 .../bpf/prog_tests/cg_skb_get_classid.c       | 87 +++++++++++++++++++
 .../selftests/bpf/progs/cg_skb_get_classid.c  | 19 ++++
 2 files changed, 106 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/cg_skb_get_classid.c
 create mode 100644 tools/testing/selftests/bpf/progs/cg_skb_get_classid.c

diff --git a/tools/testing/selftests/bpf/prog_tests/cg_skb_get_classid.c b/tools/testing/selftests/bpf/prog_tests/cg_skb_get_classid.c
new file mode 100644
index 000000000000..13a5943c387d
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/cg_skb_get_classid.c
@@ -0,0 +1,87 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+/*
+ * Copyright 2024 Bytedance.
+ */
+
+#include <test_progs.h>
+
+#include "cg_skb_get_classid.skel.h"
+
+#include "cgroup_helpers.h"
+#include "network_helpers.h"
+
+static int run_test(int cgroup_fd, int server_fd)
+{
+	struct cg_skb_get_classid *skel;
+	int fd, err = 0;
+
+	skel = cg_skb_get_classid__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "skel_open"))
+		return -1;
+
+	skel->links.cg_skb_classid =
+		bpf_program__attach_cgroup(skel->progs.cg_skb_classid,
+					   cgroup_fd);
+	if (!ASSERT_OK_PTR(skel->links.cg_skb_classid, "prog_attach")) {
+		err = -1;
+		goto out;
+	}
+
+	if (!ASSERT_OK(join_classid(), "join_classid")) {
+		err = -1;
+		goto out;
+	}
+
+	errno = 0;
+	fd = connect_to_fd_opts(server_fd, NULL);
+	if (fd >= 0) {
+		if (skel->bss->classid != getpid()) {
+			log_err("Get unexpected classid");
+			err = -1;
+		}
+
+		close(fd);
+	} else {
+		log_err("Unexpected errno from connect to server");
+		err = -1;
+	}
+out:
+	cg_skb_get_classid__destroy(skel);
+	return err;
+}
+
+void test_cg_skb_get_classid(void)
+{
+	struct network_helper_opts opts = {};
+	int server_fd, client_fd, cgroup_fd;
+	static const int port = 60120;
+
+	/* Step 1: Check base connectivity works without any BPF. */
+	server_fd = start_server(AF_INET, SOCK_STREAM, NULL, port, 0);
+	if (!ASSERT_GE(server_fd, 0, "server_fd"))
+		return;
+	client_fd = connect_to_fd_opts(server_fd, &opts);
+	if (!ASSERT_GE(client_fd, 0, "client_fd")) {
+		close(server_fd);
+		return;
+	}
+	close(client_fd);
+	close(server_fd);
+
+	/* Step 2: Check BPF prog attached to cgroups. */
+	cgroup_fd = test__join_cgroup("/cg_skb_get_classid");
+	if (!ASSERT_GE(cgroup_fd, 0, "cgroup_fd"))
+		return;
+	server_fd = start_server(AF_INET, SOCK_STREAM, NULL, port, 0);
+	if (!ASSERT_GE(server_fd, 0, "server_fd")) {
+		close(cgroup_fd);
+		return;
+	}
+	setup_classid_environment();
+	set_classid();
+	ASSERT_OK(run_test(cgroup_fd, server_fd), "cg_skb_get_classid");
+	cleanup_classid_environment();
+	close(server_fd);
+	close(cgroup_fd);
+}
diff --git a/tools/testing/selftests/bpf/progs/cg_skb_get_classid.c b/tools/testing/selftests/bpf/progs/cg_skb_get_classid.c
new file mode 100644
index 000000000000..aef0265d24eb
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/cg_skb_get_classid.c
@@ -0,0 +1,19 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+/*
+ * Copyright 2024 Bytedance.
+ */
+
+#include <errno.h>
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+
+__u32 classid = 0;
+
+SEC("cgroup_skb/egress")
+int cg_skb_classid(struct __sk_buff *ctx)
+{
+	classid = bpf_skb_cgroup_classid(ctx);
+
+	return 1;
+}
-- 
2.30.2