1 /* Copyright (c) 2017 Facebook
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.
9 #include <linux/if_ether.h>
10 #include <linux/if_packet.h>
12 #include <linux/ipv6.h>
14 #include <linux/tcp.h>
15 #include <linux/pkt_cls.h>
16 #include "bpf_helpers.h"
17 #include "bpf_endian.h"
19 #define barrier() __asm__ __volatile__("": : :"memory")
20 int _version SEC("version") = 1;
23 int process(struct __sk_buff *skb)
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;
32 if (eth + 1 > data_end)
35 if (eth->h_proto == bpf_htons(ETH_P_IP)) {
36 struct iphdr *iph = (struct iphdr *)(eth + 1);
38 if (iph + 1 > data_end)
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);
46 if (ip6h + 1 > data_end)
48 ihl_len = sizeof(*ip6h);
49 proto = ip6h->nexthdr;
50 tcp = (struct tcphdr *)((void *)(ip6h) + ihl_len);
54 if (((void *)(tcp) + 20) > data_end || proto != 6)
56 barrier(); /* to force ordering of checks */
57 if (((void *)(tcp) + 18) > data_end)
59 if (tcp->urg_ptr == 123)