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