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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 
19 struct 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 
29 struct 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 
log2(unsigned int v)37 static 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 
log2l(unsigned long v)50 static 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 
59 SEC("len_hist")
do_len_hist(struct __sk_buff * skb)60 int 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 
75 char _license[] SEC("license") = "GPL";
76