1/* Copyright (c) 2016 Thomas Graf <tgraf@tgraf.ch>
2 *
3 * This program is free software; you can redistribute it and/or
4 * modify it under the terms of version 2 of the GNU General Public
5 * License as published by the Free Software Foundation.
6 *
7 * This program is distributed in the hope that it will be useful, but
8 * WITHOUT ANY WARRANTY; without even the implied warranty of
9 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
10 * General Public License for more details.
11 */
12
13#include "vmlinux.h"
14#include <bpf/bpf_helpers.h>
15
16struct {
17	__uint(type, BPF_MAP_TYPE_PERCPU_HASH);
18	__type(key, u64);
19	__type(value, u64);
20	__uint(pinning, LIBBPF_PIN_BY_NAME);
21	__uint(max_entries, 1024);
22} lwt_len_hist_map SEC(".maps");
23
24static unsigned int log2(unsigned int v)
25{
26	unsigned int r;
27	unsigned int shift;
28
29	r = (v > 0xFFFF) << 4; v >>= r;
30	shift = (v > 0xFF) << 3; v >>= shift; r |= shift;
31	shift = (v > 0xF) << 2; v >>= shift; r |= shift;
32	shift = (v > 0x3) << 1; v >>= shift; r |= shift;
33	r |= (v >> 1);
34	return r;
35}
36
37static unsigned int log2l(unsigned long v)
38{
39	unsigned int hi = v >> 32;
40	if (hi)
41		return log2(hi) + 32;
42	else
43		return log2(v);
44}
45
46SEC("len_hist")
47int do_len_hist(struct __sk_buff *skb)
48{
49	__u64 *value, key, init_val = 1;
50
51	key = log2l(skb->len);
52
53	value = bpf_map_lookup_elem(&lwt_len_hist_map, &key);
54	if (value)
55		__sync_fetch_and_add(value, 1);
56	else
57		bpf_map_update_elem(&lwt_len_hist_map, &key, &init_val, BPF_ANY);
58
59	return BPF_OK;
60}
61
62char _license[] SEC("license") = "GPL";
63