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 <net/ip.h>
15#include <bpf/bpf_helpers.h>
16
17#define DEFAULT_PKTGEN_UDP_PORT 9
18
19/* copy of 'struct ethhdr' without __packed */
20struct eth_hdr {
21	unsigned char   h_dest[ETH_ALEN];
22	unsigned char   h_source[ETH_ALEN];
23	unsigned short  h_proto;
24};
25
26SEC("simple")
27int handle_ingress(struct __sk_buff *skb)
28{
29	void *data = (void *)(long)skb->data;
30	struct eth_hdr *eth = data;
31	struct iphdr *iph = data + sizeof(*eth);
32	struct udphdr *udp = data + sizeof(*eth) + sizeof(*iph);
33	void *data_end = (void *)(long)skb->data_end;
34
35	/* single length check */
36	if (data + sizeof(*eth) + sizeof(*iph) + sizeof(*udp) > data_end)
37		return 0;
38
39	if (eth->h_proto != htons(ETH_P_IP))
40		return 0;
41	if (iph->protocol != IPPROTO_UDP || iph->ihl != 5)
42		return 0;
43	if (ip_is_fragment(iph))
44		return 0;
45	if (udp->dest == htons(DEFAULT_PKTGEN_UDP_PORT))
46		return TC_ACT_SHOT;
47	return 0;
48}
49char _license[] SEC("license") = "GPL";
50