samples/bpf/parse_simple.c

   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_helpers.h"
  16
  17 #define DEFAULT_PKTGEN_UDP_PORT 9
  18
  19 /* copy of 'struct ethhdr' without __packed */
  20 struct eth_hdr {
  21         unsigned char   h_dest[ETH_ALEN];
  22         unsigned char   h_source[ETH_ALEN];
  23         unsigned short  h_proto;
  24 };
  25
  26 SEC("simple")
  27 int 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 }
  49 char _license[] SEC("license") = "GPL";