1// SPDX-License-Identifier: GPL-2.0
 2/* Copyright Amazon.com Inc. or its affiliates */
 3#include <linux/types.h>
 4#include <linux/bpf.h>
 5#include <bpf/bpf_helpers.h>
 6#include <bpf/bpf_tracing.h>
 7
 8#define BUFF_SZ 512
 9
10/* Will be updated by benchmark before program loading */
11char to_buff[BUFF_SZ];
12const volatile unsigned int to_buff_len = 0;
13char from_buff[BUFF_SZ];
14const volatile unsigned int from_buff_len = 0;
15unsigned short seed = 0;
16
17short result;
18
19char _license[] SEC("license") = "GPL";
20
21SEC("tc")
22int compute_checksum(void *ctx)
23{
24	int to_len_half = to_buff_len / 2;
25	int from_len_half = from_buff_len / 2;
26	short result2;
27
28	/* Calculate checksum in one go */
29	result2 = bpf_csum_diff((void *)from_buff, from_buff_len,
30				(void *)to_buff, to_buff_len, seed);
31
32	/* Calculate checksum by concatenating bpf_csum_diff()*/
33	result = bpf_csum_diff((void *)from_buff, from_buff_len - from_len_half,
34			       (void *)to_buff, to_buff_len - to_len_half, seed);
35
36	result = bpf_csum_diff((void *)from_buff + (from_buff_len - from_len_half), from_len_half,
37			       (void *)to_buff + (to_buff_len - to_len_half), to_len_half, result);
38
39	result = (result == result2) ? result : 0;
40
41	return 0;
42}