LXR linux/samples/bpf/parse

   1/* Copyright (c) 2016 Facebook
   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#define KBUILD_MODNAME "foo"
   8#include <linux/ip.h>
   9#include <linux/ipv6.h>
  10#include <linux/in.h>
  11#include <linux/tcp.h>
  12#include <linux/udp.h>
  13#include <uapi/linux/bpf.h>
  14#include "bpf_helpers.h"
  15
  16#define DEFAULT_PKTGEN_UDP_PORT 9
  17#define IP_MF                   0x2000
  18#define IP_OFFSET               0x1FFF
  19
  20static inline int ip_is_fragment(struct __sk_buff *ctx, __u64 nhoff)
  21{
  22        return load_half(ctx, nhoff + offsetof(struct iphdr, frag_off))
  23                & (IP_MF | IP_OFFSET);
  24}
  25
  26SEC("ldabs")
  27int handle_ingress(struct __sk_buff *skb)
  28{
  29        __u64 troff = ETH_HLEN + sizeof(struct iphdr);
  30
  31        if (load_half(skb, offsetof(struct ethhdr, h_proto)) != ETH_P_IP)
  32                return 0;
  33        if (load_byte(skb, ETH_HLEN + offsetof(struct iphdr, protocol)) != IPPROTO_UDP ||
  34            load_byte(skb, ETH_HLEN) != 0x45)
  35                return 0;
  36        if (ip_is_fragment(skb, ETH_HLEN))
  37                return 0;
  38        if (load_half(skb, troff + offsetof(struct udphdr, dest)) == DEFAULT_PKTGEN_UDP_PORT)
  39                return TC_ACT_SHOT;
  40        return 0;
  41}
  42char _license[] SEC("license") = "GPL";
  43