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1/* Copyright (c) 2016 Facebook2 *3 * This program is free software; you can redistribute it and/or4 * modify it under the terms of version 2 of the GNU General Public5 * 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 918#define IP_MF 0x200019#define IP_OFFSET 0x1FFF20 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