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
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