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 <uapi/linux/bpf.h>
14#include <uapi/linux/if_ether.h>
15#include <uapi/linux/ip.h>
16#include <uapi/linux/in.h>
17#include <bpf/bpf_helpers.h>
18
19struct bpf_elf_map {
20	__u32 type;
21	__u32 size_key;
22	__u32 size_value;
23	__u32 max_elem;
24	__u32 flags;
25	__u32 id;
26	__u32 pinning;
27};
28
29struct bpf_elf_map SEC("maps") lwt_len_hist_map = {
30	.type = BPF_MAP_TYPE_PERCPU_HASH,
31	.size_key = sizeof(__u64),
32	.size_value = sizeof(__u64),
33	.pinning = 2,
34	.max_elem = 1024,
35};
36
37static unsigned int log2(unsigned int v)
38{
39	unsigned int r;
40	unsigned int shift;
41
42	r = (v > 0xFFFF) << 4; v >>= r;
43	shift = (v > 0xFF) << 3; v >>= shift; r |= shift;
44	shift = (v > 0xF) << 2; v >>= shift; r |= shift;
45	shift = (v > 0x3) << 1; v >>= shift; r |= shift;
46	r |= (v >> 1);
47	return r;
48}
49
50static unsigned int log2l(unsigned long v)
51{
52	unsigned int hi = v >> 32;
53	if (hi)
54		return log2(hi) + 32;
55	else
56		return log2(v);
57}
58
59SEC("len_hist")
60int do_len_hist(struct __sk_buff *skb)
61{
62	__u64 *value, key, init_val = 1;
63
64	key = log2l(skb->len);
65
66	value = bpf_map_lookup_elem(&lwt_len_hist_map, &key);
67	if (value)
68		__sync_fetch_and_add(value, 1);
69	else
70		bpf_map_update_elem(&lwt_len_hist_map, &key, &init_val, BPF_ANY);
71
72	return BPF_OK;
73}
74
75char _license[] SEC("license") = "GPL";