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 <net/ip.h>
  15#include <bpf/bpf_helpers.h>
  16
  17#define DEFAULT_PKTGEN_UDP_PORT 9
  18
  19/* copy of 'struct ethhdr' without __packed */
  20struct eth_hdr {
  21        unsigned char   h_dest[ETH_ALEN];
  22        unsigned char   h_source[ETH_ALEN];
  23        unsigned short  h_proto;
  24};
  25
  26SEC("simple")
  27int handle_ingress(struct __sk_buff *skb)
  28{
  29        void *data = (void *)(long)skb->data;
  30        struct eth_hdr *eth = data;
  31        struct iphdr *iph = data + sizeof(*eth);
  32        struct udphdr *udp = data + sizeof(*eth) + sizeof(*iph);
  33        void *data_end = (void *)(long)skb->data_end;
  34
  35        /* single length check */
  36        if (data + sizeof(*eth) + sizeof(*iph) + sizeof(*udp) > data_end)
  37                return 0;
  38
  39        if (eth->h_proto != htons(ETH_P_IP))
  40                return 0;
  41        if (iph->protocol != IPPROTO_UDP || iph->ihl != 5)
  42                return 0;
  43        if (ip_is_fragment(iph))
  44                return 0;
  45        if (udp->dest == htons(DEFAULT_PKTGEN_UDP_PORT))
  46                return TC_ACT_SHOT;
  47        return 0;
  48}
  49char _license[] SEC("license") = "GPL";
  50