selftests/bpf: Add a selftest for bpf_csum_diff()

Add a selftest for the bpf_csum_diff() helper. This selftests runs the
helper in all three configurations(push, pull, and diff) and verifies
its output. The correct results have been computed by hand and by the
helper's older implementation.

Signed-off-by: Puranjay Mohan <[e-mail]>
Signed-off-by: Daniel Borkmann <[e-mail]>
Acked-by: Daniel Borkmann <[e-mail]>
Link: https://lore.kernel.org/bpf/[e-mail]

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

···
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright Amazon.com Inc. or its affiliates */
+#include <test_progs.h>
+#include "csum_diff_test.skel.h"
+
+#define BUFF_SZ 512
+
+struct testcase {
+	unsigned long long to_buff[BUFF_SZ / 8];
+	unsigned int to_buff_len;
+	unsigned long long from_buff[BUFF_SZ / 8];
+	unsigned int from_buff_len;
+	unsigned short seed;
+	unsigned short result;
+};
+
+#define NUM_PUSH_TESTS 4
+
+struct testcase push_tests[NUM_PUSH_TESTS] = {
+	{
+		.to_buff = {
+			0xdeadbeefdeadbeef,
+		},
+		.to_buff_len = 8,
+		.from_buff = {},
+		.from_buff_len = 0,
+		.seed = 0,
+		.result = 0x3b3b
+	},
+	{
+		.to_buff = {
+			0xdeadbeefdeadbeef,
+			0xbeefdeadbeefdead,
+		},
+		.to_buff_len = 16,
+		.from_buff = {},
+		.from_buff_len = 0,
+		.seed = 0x1234,
+		.result = 0x88aa
+	},
+	{
+		.to_buff = {
+			0xdeadbeefdeadbeef,
+			0xbeefdeadbeefdead,
+		},
+		.to_buff_len = 15,
+		.from_buff = {},
+		.from_buff_len = 0,
+		.seed = 0x1234,
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+		.result = 0xcaa9
+#else
+		.result = 0x87fd
+#endif
+	},
+	{
+		.to_buff = {
+			0x327b23c66b8b4567,
+			0x66334873643c9869,
+			0x19495cff74b0dc51,
+			0x625558ec2ae8944a,
+			0x46e87ccd238e1f29,
+			0x507ed7ab3d1b58ba,
+			0x41b71efb2eb141f2,
+			0x7545e14679e2a9e3,
+			0x5bd062c2515f007c,
+			0x4db127f812200854,
+			0x1f16e9e80216231b,
+			0x66ef438d1190cde7,
+			0x3352255a140e0f76,
+			0x0ded7263109cf92e,
+			0x1befd79f7fdcc233,
+			0x6b68079a41a7c4c9,
+			0x25e45d324e6afb66,
+			0x431bd7b7519b500d,
+			0x7c83e4583f2dba31,
+			0x62bbd95a257130a3,
+			0x628c895d436c6125,
+			0x721da317333ab105,
+			0x2d1d5ae92443a858,
+			0x75a2a8d46763845e,
+			0x79838cb208edbdab,
+			0x0b03e0c64353d0cd,
+			0x54e49eb4189a769b,
+			0x2ca8861171f32454,
+			0x02901d820836c40e,
+			0x081386413a95f874,
+			0x7c3dbd3d1e7ff521,
+			0x6ceaf087737b8ddc,
+			0x4516dde922221a70,
+			0x614fd4a13006c83e,
+			0x5577f8e1419ac241,
+			0x05072367440badfc,
+			0x77465f013804823e,
+			0x5c482a977724c67e,
+			0x5e884adc2463b9ea,
+			0x2d51779651ead36b,
+			0x153ea438580bd78f,
+			0x70a64e2a3855585c,
+			0x2a487cb06a2342ec,
+			0x725a06fb1d4ed43b,
+			0x57e4ccaf2cd89a32,
+			0x4b588f547a6d8d3c,
+			0x6de91b18542289ec,
+			0x7644a45c38437fdb,
+			0x684a481a32fff902,
+			0x749abb43579478fe,
+			0x1ba026fa3dc240fb,
+			0x75c6c33a79a1deaa,
+			0x70c6a52912e685fb,
+			0x374a3fe6520eedd1,
+			0x23f9c13c4f4ef005,
+			0x275ac794649bb77c,
+			0x1cf10fd839386575,
+			0x235ba861180115be,
+			0x354fe9f947398c89,
+			0x741226bb15b5af5c,
+			0x10233c990d34b6a8,
+			0x615740953f6ab60f,
+			0x77ae35eb7e0c57b1,
+			0x310c50b3579be4f1,
+		},
+		.to_buff_len = 512,
+		.from_buff = {},
+		.from_buff_len = 0,
+		.seed = 0xffff,
+		.result = 0xca45
+	},
+};
+
+#define NUM_PULL_TESTS 4
+
+struct testcase pull_tests[NUM_PULL_TESTS] = {
+	{
+		.from_buff = {
+			0xdeadbeefdeadbeef,
+		},
+		.from_buff_len = 8,
+		.to_buff = {},
+		.to_buff_len = 0,
+		.seed = 0,
+		.result = 0xc4c4
+	},
+	{
+		.from_buff = {
+			0xdeadbeefdeadbeef,
+			0xbeefdeadbeefdead,
+		},
+		.from_buff_len = 16,
+		.to_buff = {},
+		.to_buff_len = 0,
+		.seed = 0x1234,
+		.result = 0x9bbd
+	},
+	{
+		.from_buff = {
+			0xdeadbeefdeadbeef,
+			0xbeefdeadbeefdead,
+		},
+		.from_buff_len = 15,
+		.to_buff = {},
+		.to_buff_len = 0,
+		.seed = 0x1234,
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+		.result = 0x59be
+#else
+		.result = 0x9c6a
+#endif
+	},
+	{
+		.from_buff = {
+			0x327b23c66b8b4567,
+			0x66334873643c9869,
+			0x19495cff74b0dc51,
+			0x625558ec2ae8944a,
+			0x46e87ccd238e1f29,
+			0x507ed7ab3d1b58ba,
+			0x41b71efb2eb141f2,
+			0x7545e14679e2a9e3,
+			0x5bd062c2515f007c,
+			0x4db127f812200854,
+			0x1f16e9e80216231b,
+			0x66ef438d1190cde7,
+			0x3352255a140e0f76,
+			0x0ded7263109cf92e,
+			0x1befd79f7fdcc233,
+			0x6b68079a41a7c4c9,
+			0x25e45d324e6afb66,
+			0x431bd7b7519b500d,
+			0x7c83e4583f2dba31,
+			0x62bbd95a257130a3,
+			0x628c895d436c6125,
+			0x721da317333ab105,
+			0x2d1d5ae92443a858,
+			0x75a2a8d46763845e,
+			0x79838cb208edbdab,
+			0x0b03e0c64353d0cd,
+			0x54e49eb4189a769b,
+			0x2ca8861171f32454,
+			0x02901d820836c40e,
+			0x081386413a95f874,
+			0x7c3dbd3d1e7ff521,
+			0x6ceaf087737b8ddc,
+			0x4516dde922221a70,
+			0x614fd4a13006c83e,
+			0x5577f8e1419ac241,
+			0x05072367440badfc,
+			0x77465f013804823e,
+			0x5c482a977724c67e,
+			0x5e884adc2463b9ea,
+			0x2d51779651ead36b,
+			0x153ea438580bd78f,
+			0x70a64e2a3855585c,
+			0x2a487cb06a2342ec,
+			0x725a06fb1d4ed43b,
+			0x57e4ccaf2cd89a32,
+			0x4b588f547a6d8d3c,
+			0x6de91b18542289ec,
+			0x7644a45c38437fdb,
+			0x684a481a32fff902,
+			0x749abb43579478fe,
+			0x1ba026fa3dc240fb,
+			0x75c6c33a79a1deaa,
+			0x70c6a52912e685fb,
+			0x374a3fe6520eedd1,
+			0x23f9c13c4f4ef005,
+			0x275ac794649bb77c,
+			0x1cf10fd839386575,
+			0x235ba861180115be,
+			0x354fe9f947398c89,
+			0x741226bb15b5af5c,
+			0x10233c990d34b6a8,
+			0x615740953f6ab60f,
+			0x77ae35eb7e0c57b1,
+			0x310c50b3579be4f1,
+		},
+		.from_buff_len = 512,
+		.to_buff = {},
+		.to_buff_len = 0,
+		.seed = 0xffff,
+		.result = 0x35ba
+	},
+};
+
+#define NUM_DIFF_TESTS 4
+
+struct testcase diff_tests[NUM_DIFF_TESTS] = {
+	{
+		.from_buff = {
+			0xdeadbeefdeadbeef,
+		},
+		.from_buff_len = 8,
+		.to_buff = {
+			0xabababababababab,
+		},
+		.to_buff_len = 8,
+		.seed = 0,
+		.result = 0x7373
+	},
+	{
+		.from_buff = {
+			0xdeadbeefdeadbeef,
+		},
+		.from_buff_len = 7,
+		.to_buff = {
+			0xabababababababab,
+		},
+		.to_buff_len = 7,
+		.seed = 0,
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+		.result = 0xa673
+#else
+		.result = 0x73b7
+#endif
+	},
+	{
+		.from_buff = {
+			0,
+		},
+		.from_buff_len = 8,
+		.to_buff = {
+			0xabababababababab,
+		},
+		.to_buff_len = 8,
+		.seed = 0,
+		.result = 0xaeae
+	},
+	{
+		.from_buff = {
+			0xdeadbeefdeadbeef
+		},
+		.from_buff_len = 8,
+		.to_buff = {
+			0,
+		},
+		.to_buff_len = 8,
+		.seed = 0xffff,
+		.result = 0xc4c4
+	},
+};
+
+#define NUM_EDGE_TESTS 4
+
+struct testcase edge_tests[NUM_EDGE_TESTS] = {
+	{
+		.from_buff = {},
+		.from_buff_len = 0,
+		.to_buff = {},
+		.to_buff_len = 0,
+		.seed = 0,
+		.result = 0
+	},
+	{
+		.from_buff = {
+			0x1234
+		},
+		.from_buff_len = 0,
+		.to_buff = {
+			0x1234
+		},
+		.to_buff_len = 0,
+		.seed = 0,
+		.result = 0
+	},
+	{
+		.from_buff = {},
+		.from_buff_len = 0,
+		.to_buff = {},
+		.to_buff_len = 0,
+		.seed = 0x1234,
+		.result = 0x1234
+	},
+	{
+		.from_buff = {},
+		.from_buff_len = 512,
+		.to_buff = {},
+		.to_buff_len = 0,
+		.seed = 0xffff,
+		.result = 0xffff
+	},
+};
+
+static unsigned short trigger_csum_diff(const struct csum_diff_test *skel)
+{
+	u8 tmp_out[64 << 2] = {};
+	u8 tmp_in[64] = {};
+	int err;
+	int pfd;
+
+	LIBBPF_OPTS(bpf_test_run_opts, topts,
+		.data_in = tmp_in,
+		.data_size_in = sizeof(tmp_in),
+		.data_out = tmp_out,
+		.data_size_out = sizeof(tmp_out),
+		.repeat = 1,
+	);
+	pfd = bpf_program__fd(skel->progs.compute_checksum);
+	err = bpf_prog_test_run_opts(pfd, &topts);
+	if (err)
+		return -1;
+
+	return skel->bss->result;
+}
+
+static void test_csum_diff(struct testcase *tests, int num_tests)
+{
+	struct csum_diff_test *skel;
+	unsigned short got;
+	int err;
+
+	for (int i = 0; i < num_tests; i++) {
+		skel = csum_diff_test__open();
+		if (!ASSERT_OK_PTR(skel, "csum_diff_test open"))
+			return;
+
+		skel->rodata->to_buff_len = tests[i].to_buff_len;
+		skel->rodata->from_buff_len = tests[i].from_buff_len;
+
+		err = csum_diff_test__load(skel);
+		if (!ASSERT_EQ(err, 0, "csum_diff_test load"))
+			goto out;
+
+		memcpy(skel->bss->to_buff, tests[i].to_buff, tests[i].to_buff_len);
+		memcpy(skel->bss->from_buff, tests[i].from_buff, tests[i].from_buff_len);
+		skel->bss->seed = tests[i].seed;
+
+		got = trigger_csum_diff(skel);
+		ASSERT_EQ(got, tests[i].result, "csum_diff result");
+
+		csum_diff_test__destroy(skel);
+	}
+
+	return;
+out:
+	csum_diff_test__destroy(skel);
+}
+
+void test_test_csum_diff(void)
+{
+	if (test__start_subtest("csum_diff_push"))
+		test_csum_diff(push_tests, NUM_PUSH_TESTS);
+	if (test__start_subtest("csum_diff_pull"))
+		test_csum_diff(pull_tests, NUM_PULL_TESTS);
+	if (test__start_subtest("csum_diff_diff"))
+		test_csum_diff(diff_tests, NUM_DIFF_TESTS);
+	if (test__start_subtest("csum_diff_edge"))
+		test_csum_diff(edge_tests, NUM_EDGE_TESTS);
+}

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

···
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright Amazon.com Inc. or its affiliates */
+#include <linux/types.h>
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+#define BUFF_SZ 512
+
+/* Will be updated by benchmark before program loading */
+char to_buff[BUFF_SZ];
+const volatile unsigned int to_buff_len = 0;
+char from_buff[BUFF_SZ];
+const volatile unsigned int from_buff_len = 0;
+unsigned short seed = 0;
+
+short result;
+
+char _license[] SEC("license") = "GPL";
+
+SEC("tc")
+int compute_checksum(void *ctx)
+{
+	int to_len_half = to_buff_len / 2;
+	int from_len_half = from_buff_len / 2;
+	short result2;
+
+	/* Calculate checksum in one go */
+	result2 = bpf_csum_diff((void *)from_buff, from_buff_len,
+				(void *)to_buff, to_buff_len, seed);
+
+	/* Calculate checksum by concatenating bpf_csum_diff()*/
+	result = bpf_csum_diff((void *)from_buff, from_buff_len - from_len_half,
+			       (void *)to_buff, to_buff_len - to_len_half, seed);
+
+	result = bpf_csum_diff((void *)from_buff + (from_buff_len - from_len_half), from_len_half,
+			       (void *)to_buff + (to_buff_len - to_len_half), to_len_half, result);
+
+	result = (result == result2) ? result : 0;
+
+	return 0;
+}