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 */
20 struct eth_hdr {
21 unsigned char h_dest[ETH_ALEN];
22 unsigned char h_source[ETH_ALEN];
23 unsigned short h_proto;
24 };
25
26 SEC("simple")
27 int 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 }
49 char _license[] SEC("license") = "GPL";
50
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