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 
16 struct {
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 
24 static 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 
37 static 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 
46 SEC("len_hist")
47 int 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 
62 char _license[] SEC("license") = "GPL";
63