Re: [PATCH bpf-next V7 8/8] bpf/selftests: activating bpf_check_mtu BPF-helper

Adding selftest for BPF-helper bpf_check_mtu(). Making sure
it can be used from both XDP and TC.

Signed-off-by: Jesper Dangaard Brouer <redacted>
---
 tools/testing/selftests/bpf/prog_tests/check_mtu.c |   37 ++++++++++++++++++++
 tools/testing/selftests/bpf/progs/test_check_mtu.c |   33 ++++++++++++++++++
 2 files changed, 70 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/check_mtu.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_check_mtu.c

diff --git a/tools/testing/selftests/bpf/prog_tests/check_mtu.c b/tools/testing/selftests/bpf/prog_tests/check_mtu.c
new file mode 100644
index 000000000000..09b8f986a17b
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/check_mtu.c

@@ -0,0 +1,37 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2020 Red Hat */
+#include <uapi/linux/bpf.h>
+#include <linux/if_link.h>
+#include <test_progs.h>
+
+#include "test_check_mtu.skel.h"
+#define IFINDEX_LO 1
+
+void test_check_mtu_xdp(struct test_check_mtu *skel)
+{
+	int err = 0;
+	int fd;
+
+	fd = bpf_program__fd(skel->progs.xdp_use_helper);
+	err = bpf_set_link_xdp_fd(IFINDEX_LO, fd, XDP_FLAGS_SKB_MODE);
+	if (CHECK_FAIL(err))
+		return;
+
+	bpf_set_link_xdp_fd(IFINDEX_LO, -1, 0);
+}
+
+void test_check_mtu(void)
+{
+	struct test_check_mtu *skel;
+
+	skel = test_check_mtu__open_and_load();
+	if (CHECK_FAIL(!skel)) {
+		perror("test_check_mtu__open_and_load");
+		return;
+	}
+
+	if (test__start_subtest("bpf_check_mtu XDP-attach"))
+		test_check_mtu_xdp(skel);
+
+	test_check_mtu__destroy(skel);
+}

diff --git a/tools/testing/selftests/bpf/progs/test_check_mtu.c b/tools/testing/selftests/bpf/progs/test_check_mtu.c
new file mode 100644
index 000000000000..ab97ec925a32
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_check_mtu.c

@@ -0,0 +1,33 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2020 Red Hat */
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+
+#include <stddef.h>
+#include <stdint.h>
+
+char _license[] SEC("license") = "GPL";
+
+SEC("xdp")
+int xdp_use_helper(struct xdp_md *ctx)
+{
+	uint32_t mtu_len = 0;
+	int delta = 20;
+
+	if (bpf_check_mtu(ctx, 0, &mtu_len, delta, 0)) {
+		return XDP_ABORTED;
+	}
+	return XDP_PASS;
+}
+
+SEC("classifier")
+int tc_use_helper(struct __sk_buff *ctx)
+{
+	uint32_t mtu_len = 0;
+	int delta = -20;
+
+	if (bpf_check_mtu(ctx, 0, &mtu_len, delta, 0)) {
+		return BPF_DROP;
+	}
+	return BPF_OK;
+}