root/samples/bpf/lwt_len_hist_kern.c

DEFINITIONS

1. log2
2. log2l
3. SEC

   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_helpers.h"
  18 
  19 # define printk(fmt, ...)                                               \
  20                 ({                                                      \
  21                         char ____fmt[] = fmt;                           \
  22                         bpf_trace_printk(____fmt, sizeof(____fmt),      \
  23                                      ##__VA_ARGS__);                    \
  24                 })
  25 
  26 struct bpf_elf_map {
  27         __u32 type;
  28         __u32 size_key;
  29         __u32 size_value;
  30         __u32 max_elem;
  31         __u32 flags;
  32         __u32 id;
  33         __u32 pinning;
  34 };
  35 
  36 struct bpf_elf_map SEC("maps") lwt_len_hist_map = {
  37         .type = BPF_MAP_TYPE_PERCPU_HASH,
  38         .size_key = sizeof(__u64),
  39         .size_value = sizeof(__u64),
  40         .pinning = 2,
  41         .max_elem = 1024,
  42 };
  43 
  44 static unsigned int log2(unsigned int v)
  45 {
  46         unsigned int r;
  47         unsigned int shift;
  48 
  49         r = (v > 0xFFFF) << 4; v >>= r;
  50         shift = (v > 0xFF) << 3; v >>= shift; r |= shift;
  51         shift = (v > 0xF) << 2; v >>= shift; r |= shift;
  52         shift = (v > 0x3) << 1; v >>= shift; r |= shift;
  53         r |= (v >> 1);
  54         return r;
  55 }
  56 
  57 static unsigned int log2l(unsigned long v)
  58 {
  59         unsigned int hi = v >> 32;
  60         if (hi)
  61                 return log2(hi) + 32;
  62         else
  63                 return log2(v);
  64 }
  65 
  66 SEC("len_hist")
  67 int do_len_hist(struct __sk_buff *skb)
  68 {
  69         __u64 *value, key, init_val = 1;
  70 
  71         key = log2l(skb->len);
  72 
  73         value = bpf_map_lookup_elem(&lwt_len_hist_map, &key);
  74         if (value)
  75                 __sync_fetch_and_add(value, 1);
  76         else
  77                 bpf_map_update_elem(&lwt_len_hist_map, &key, &init_val, BPF_ANY);
  78 
  79         return BPF_OK;
  80 }
  81 
  82 char _license[] SEC("license") = "GPL";