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 <bpf/bpf_helpers.h>
15#include "bpf_legacy.h"
16
17#define DEFAULT_PKTGEN_UDP_PORT	9
18#define IP_MF			0x2000
19#define IP_OFFSET		0x1FFF
20
21static inline int ip_is_fragment(struct __sk_buff *ctx, __u64 nhoff)
22{
23	return load_half(ctx, nhoff + offsetof(struct iphdr, frag_off))
24		& (IP_MF | IP_OFFSET);
25}
26
27SEC("ldabs")
28int handle_ingress(struct __sk_buff *skb)
29{
30	__u64 troff = ETH_HLEN + sizeof(struct iphdr);
31
32	if (load_half(skb, offsetof(struct ethhdr, h_proto)) != ETH_P_IP)
33		return 0;
34	if (load_byte(skb, ETH_HLEN + offsetof(struct iphdr, protocol)) != IPPROTO_UDP ||
35	    load_byte(skb, ETH_HLEN) != 0x45)
36		return 0;
37	if (ip_is_fragment(skb, ETH_HLEN))
38		return 0;
39	if (load_half(skb, troff + offsetof(struct udphdr, dest)) == DEFAULT_PKTGEN_UDP_PORT)
40		return TC_ACT_SHOT;
41	return 0;
42}
43char _license[] SEC("license") = "GPL";
44