[PATCH v2 bpf-next 3/3] net: new cgrp_sysctl test suite

[Raman Shukhau <ramasha@meta.com>]

Adding new prog_tests for sysctl BPF handlers, first version with
a single test to validate bpf_sysctl_set_new_value call

Signed-off-by: Raman Shukhau <ramasha@meta.com>
---
 .../selftests/bpf/prog_tests/cgrp_sysctl.c    | 103 ++++++++++++++++++
 .../testing/selftests/bpf/progs/cgrp_sysctl.c |  51 +++++++++
 2 files changed, 154 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/cgrp_sysctl.c
 create mode 100644 tools/testing/selftests/bpf/progs/cgrp_sysctl.c

diff --git a/tools/testing/selftests/bpf/prog_tests/cgrp_sysctl.c b/tools/testing/selftests/bpf/prog_tests/cgrp_sysctl.c
new file mode 100644
index 000000000000..12a160428a1d
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/cgrp_sysctl.c
@@ -0,0 +1,103 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright (c) Meta Platforms, Inc. and affiliates. */
+
+#define SYSCTL_ROOT_PATH "/proc/sys/"
+#define SYSCTL_NAME_LEN 128
+#define RESERVED_PORTS_SYSCTL_NAME "net/ipv4/ip_local_reserved_ports"
+#define RESERVED_PORTS_OVERRIDE_VALUE "31337"
+
+#define _GNU_SOURCE
+#include <unistd.h>
+#include <string.h>
+#include <fcntl.h>
+
+#include <sys/mount.h>
+
+#include "test_progs.h"
+#include "cgrp_sysctl.skel.h"
+
+struct sysctl_test {
+	const char *sysctl;
+	int open_flags;
+	const char *newval;
+	const char *updval;
+};
+
+static void subtest(int cgroup_fd, struct cgrp_sysctl *skel, struct sysctl_test *test_data)
+{
+	int fd;
+
+	fd = open(SYSCTL_ROOT_PATH RESERVED_PORTS_SYSCTL_NAME, test_data->open_flags | O_CLOEXEC);
+	if (!ASSERT_GT(fd, 0, "sysctl-open"))
+		return;
+
+	if (test_data->open_flags == O_RDWR) {
+		int wr_ret;
+
+		wr_ret = write(fd, test_data->newval, strlen(test_data->newval));
+		if (!ASSERT_GT(wr_ret, 0, "sysctl-write"))
+			goto out;
+
+		char buf[SYSCTL_NAME_LEN];
+		char updval[SYSCTL_NAME_LEN];
+
+		sprintf(updval, "%s\n", test_data->updval);
+		if (!ASSERT_OK(lseek(fd, 0, SEEK_SET), "sysctl-seek"))
+			goto out;
+		if (!ASSERT_GT(read(fd, buf, sizeof(buf)), 0, "sysctl-read"))
+			goto out;
+		if (!ASSERT_OK(strncmp(buf, updval, strlen(updval)), "sysctl-updval"))
+			goto out;
+	}
+
+out:
+	close(fd);
+}
+
+void test_cgrp_sysctl(void)
+{
+	struct cgrp_sysctl *skel;
+	int cgroup_fd;
+
+	cgroup_fd = test__join_cgroup("/cgrp_sysctl");
+	if (!ASSERT_GE(cgroup_fd, 0, "cg-create"))
+		return;
+
+	skel = cgrp_sysctl__open();
+	if (!ASSERT_OK_PTR(skel, "skel-open"))
+		goto close_cgroup;
+
+	struct sysctl_test test_data;
+
+	if (test__start_subtest("overwrite_success")) {
+		test_data = (struct sysctl_test){
+			.sysctl = RESERVED_PORTS_SYSCTL_NAME,
+			.open_flags = O_RDWR,
+			.newval = "22222",
+			.updval = RESERVED_PORTS_OVERRIDE_VALUE,
+		};
+		memcpy(skel->rodata->sysctl_name, RESERVED_PORTS_SYSCTL_NAME,
+		       sizeof(RESERVED_PORTS_SYSCTL_NAME));
+		skel->rodata->name_len = sizeof(RESERVED_PORTS_SYSCTL_NAME);
+		memcpy(skel->rodata->sysctl_updval, RESERVED_PORTS_OVERRIDE_VALUE,
+		       sizeof(RESERVED_PORTS_OVERRIDE_VALUE));
+		skel->rodata->updval_len = sizeof(RESERVED_PORTS_OVERRIDE_VALUE);
+	}
+
+	if (!ASSERT_OK(cgrp_sysctl__load(skel), "skel-load"))
+		goto close_cgroup;
+
+	skel->links.cgrp_sysctl_overwrite =
+		bpf_program__attach_cgroup(skel->progs.cgrp_sysctl_overwrite, cgroup_fd);
+	if (!ASSERT_OK_PTR(skel->links.cgrp_sysctl_overwrite, "cg-attach-sysctl"))
+		goto skel_destroy;
+
+	subtest(cgroup_fd, skel, &test_data);
+	goto skel_destroy;
+
+skel_destroy:
+	cgrp_sysctl__destroy(skel);
+
+close_cgroup:
+	close(cgroup_fd);
+}
diff --git a/tools/testing/selftests/bpf/progs/cgrp_sysctl.c b/tools/testing/selftests/bpf/progs/cgrp_sysctl.c
new file mode 100644
index 000000000000..1038e917c760
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/cgrp_sysctl.c
@@ -0,0 +1,51 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) Meta Platforms, Inc. and affiliates. */
+
+#include <string.h>
+#include <stdbool.h>
+
+#include <linux/bpf.h>
+
+#include <bpf/bpf_helpers.h>
+
+#include "bpf_compiler.h"
+
+#define SYSCTL_VALUE_LEN 16
+#define SYSCTL_NAME_LEN 128
+
+#define SUCCESS 1
+#define FAILURE 0
+
+const char sysctl_updval[SYSCTL_VALUE_LEN];
+volatile const unsigned int updval_len;
+const char sysctl_name[SYSCTL_NAME_LEN];
+volatile const unsigned int name_len;
+
+static __always_inline bool is_expected_name(struct bpf_sysctl *ctx)
+{
+	char name[SYSCTL_NAME_LEN];
+	unsigned int size;
+
+	memset(name, 0, sizeof(name));
+	size = bpf_sysctl_get_name(ctx, name, sizeof(name), 0);
+	if (size == 0 || size != name_len - 1)
+		return 1;
+
+	return bpf_strncmp(name, size, (const char *)sysctl_name) == 0;
+}
+
+SEC("cgroup/sysctl")
+int cgrp_sysctl_overwrite(struct bpf_sysctl *ctx)
+{
+	if (!ctx->write)
+		return SUCCESS;
+
+	if (!is_expected_name(ctx))
+		return SUCCESS;
+
+	if (bpf_sysctl_set_new_value(ctx, (char *)sysctl_updval, updval_len) == 0)
+		return SUCCESS;
+	return FAILURE;
+}
+
+char _license[] SEC("license") = "GPL";
-- 
2.43.0