tools/testing/selftests/bpf/test_pkt_access.c

   1 /* Copyright (c) 2017 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 #include <stddef.h>
   8 #include <string.h>
   9 #include <linux/bpf.h>
  10 #include <linux/if_ether.h>
  11 #include <linux/if_packet.h>
  12 #include <linux/ip.h>
  13 #include <linux/ipv6.h>
  14 #include <linux/in.h>
  15 #include <linux/tcp.h>
  16 #include <linux/pkt_cls.h>
  17 #include "bpf_helpers.h"
  18 #include "bpf_endian.h"
  19
  20 #define barrier() __asm__ __volatile__("": : :"memory")
  21 int _version SEC("version") = 1;
  22
  23 SEC("test1")
  24 int process(struct __sk_buff *skb)
  25 {
  26         void *data_end = (void *)(long)skb->data_end;
  27         void *data = (void *)(long)skb->data;
  28         struct ethhdr *eth = (struct ethhdr *)(data);
  29         struct tcphdr *tcp = NULL;
  30         __u8 proto = 255;
  31         __u64 ihl_len;
  32
  33         if (eth + 1 > data_end)
  34                 return TC_ACT_SHOT;
  35
  36         if (eth->h_proto == bpf_htons(ETH_P_IP)) {
  37                 struct iphdr *iph = (struct iphdr *)(eth + 1);
  38
  39                 if (iph + 1 > data_end)
  40                         return TC_ACT_SHOT;
  41                 ihl_len = iph->ihl * 4;
  42                 proto = iph->protocol;
  43                 tcp = (struct tcphdr *)((void *)(iph) + ihl_len);
  44         } else if (eth->h_proto == bpf_htons(ETH_P_IPV6)) {
  45                 struct ipv6hdr *ip6h = (struct ipv6hdr *)(eth + 1);
  46
  47                 if (ip6h + 1 > data_end)
  48                         return TC_ACT_SHOT;
  49                 ihl_len = sizeof(*ip6h);
  50                 proto = ip6h->nexthdr;
  51                 tcp = (struct tcphdr *)((void *)(ip6h) + ihl_len);
  52         }
  53
  54         if (tcp) {
  55                 if (((void *)(tcp) + 20) > data_end || proto != 6)
  56                         return TC_ACT_SHOT;
  57                 barrier(); /* to force ordering of checks */
  58                 if (((void *)(tcp) + 18) > data_end)
  59                         return TC_ACT_SHOT;
  60                 if (tcp->urg_ptr == 123)
  61                         return TC_ACT_OK;
  62         }
  63
  64         return TC_ACT_UNSPEC;
  65 }