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