lib: Move IP checksum to commonlib

This patch moves the IP checksum algorithm into commonlib to prepare for
it being shared with libpayload. The current implementation is ancient
and pretty hard to read (and does some unnecessary questionable things
like the type-punning stuff which leads to suboptimal code generation),
so this reimplements it from scratch (that also helps with the
licensing).

This algorithm is prepared to take in a pre-calculated "wide" checksum
in a machine-register-sized data type which is then narrowed down to 16
bits (see RFC 1071 for why that's valid). This isn't used yet (and the
code will get optimized out), but will be used later in this patch
series for architecture-specific optimization.

Change-Id: Ic04c714c00439a17fc04a8a6e730cc2aa19b8e68
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/80251
Reviewed-by: Yidi Lin <yidilin@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Jakub Czapiga <czapiga@google.com>

2 files changed, 103 insertions, 0 deletions

diff --git a/tests/commonlib/bsd/Makefile.mk b/tests/commonlib/bsd/Makefile.mk
index bf17b6d56d..3de223e707 100644
--- a/tests/commonlib/bsd/Makefile.mk
+++ b/tests/commonlib/bsd/Makefile.mk
@@ -2,8 +2,12 @@
 
 tests-y += helpers-test
 tests-y += gcd-test
+tests-y += ipchksum-test
 
 helpers-test-srcs += tests/commonlib/bsd/helpers-test.c
 
 gcd-test-srcs += tests/commonlib/bsd/gcd-test.c
 gcd-test-srcs += src/commonlib/bsd/gcd.c
+
+ipchksum-test-srcs += tests/commonlib/bsd/ipchksum-test.c
+ipchksum-test-srcs += src/commonlib/bsd/ipchksum.c
diff --git a/tests/commonlib/bsd/ipchksum-test.c b/tests/commonlib/bsd/ipchksum-test.c
new file mode 100644
index 0000000000..2aed94c0cf
--- /dev/null
+++ b/tests/commonlib/bsd/ipchksum-test.c
@@ -0,0 +1,99 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <commonlib/bsd/ipchksum.h>
+#include <tests/test.h>
+#include <string.h>
+#include <stdlib.h>
+#include <types.h>
+
+static const uint8_t test_data_simple[] = {
+	0x64, 0x3b, 0x33, 0x17, 0x34, 0x74, 0x62, 0x30, 0x75, 0x73, 0xf3, 0x11, 0x30, 0x2c,
+	0x34, 0x35, 0x6d, 0x39, 0x69, 0x32, 0x23, 0x24, 0x76, 0x71, 0x77, 0x30, 0x39, 0x75,
+	0x76, 0x35, 0x71, 0x32, 0x40, 0x46, 0x34, 0x34, 0xBB, 0x03, 0x66, 0x52};
+static const size_t test_data_simple_sz = ARRAY_SIZE(test_data_simple);
+static const uint16_t test_data_simple_checksum = 0x4267;
+
+static uint8_t test_data_zeros[1024];
+static const size_t test_data_zeros_sz = ARRAY_SIZE(test_data_zeros);
+static const uint16_t test_data_zeros_checksum = 0xFFFF;
+
+static int setup_test_group(void **state)
+{
+	memset(test_data_zeros, 0, test_data_zeros_sz);
+
+	return 0;
+}
+
+static void test_ipchksum_zero_length(void **state)
+{
+	uint16_t res = ipchksum(test_data_simple, 0);
+
+	/* Expect checksum to be in initial state as there are were no data provided. */
+	assert_int_equal(0xFFFF, res);
+}
+
+static void test_ipchksum_zero_buffer(void **state)
+{
+	uint16_t res = ipchksum(test_data_zeros, test_data_zeros_sz);
+	assert_int_equal(test_data_zeros_checksum, res);
+}
+
+static void test_ipchksum_simple_data(void **state)
+{
+	uint16_t res;
+	uint16_t check_res;
+	const size_t helper_buffer_size = sizeof(uint8_t) * (test_data_simple_sz + 2);
+	char *helper_buffer = malloc(helper_buffer_size);
+
+	/* Self test */
+	assert_non_null(helper_buffer);
+
+	/* Expect function to generate the same checksum as stored in */
+	res = ipchksum(test_data_simple, test_data_simple_sz);
+	assert_int_equal(test_data_simple_checksum, res);
+
+	/* Copy test data and checksum to new buffer. Expect computed checksum to be zero,
+	   as it proves the data and the checksum are correct. */
+	memcpy(helper_buffer, test_data_simple, test_data_simple_sz);
+	helper_buffer[helper_buffer_size - 2] = res & 0xFF;
+	helper_buffer[helper_buffer_size - 1] = (res >> 8) & 0xFF;
+	check_res = ipchksum(helper_buffer, helper_buffer_size);
+	assert_int_equal(0, check_res);
+
+	free(helper_buffer);
+}
+
+static void test_ipchksum_add_empty_values(void **state)
+{
+	uint16_t res;
+
+	res = ipchksum_add(0, 0xFFFF, 0xFFFF);
+	assert_int_equal(0xFFFF, res);
+
+	res = ipchksum_add(1, 0xFFFF, 0xFFFF);
+	assert_int_equal(0xFFFF, res);
+}
+
+static void test_ipchksum_add(void **state)
+{
+	uint16_t res_1 = ipchksum(test_data_simple, test_data_simple_sz / 2);
+	uint16_t res_2 = ipchksum(test_data_simple + test_data_simple_sz / 2,
+						  test_data_simple_sz / 2);
+	uint16_t res_sum = ipchksum_add(test_data_simple_sz / 2, res_1, res_2);
+
+	assert_int_equal(test_data_simple_checksum, res_sum);
+}
+
+int main(void)
+{
+	const struct CMUnitTest tests[] = {
+		cmocka_unit_test(test_ipchksum_zero_length),
+		cmocka_unit_test(test_ipchksum_zero_buffer),
+		cmocka_unit_test(test_ipchksum_simple_data),
+
+		cmocka_unit_test(test_ipchksum_add_empty_values),
+		cmocka_unit_test(test_ipchksum_add),
+	};
+
+	return cb_run_group_tests(tests, setup_test_group, NULL);
+}