43 lines
1.2 KiB
C
43 lines
1.2 KiB
C
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/* Copyright (c) 2016 Facebook
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of version 2 of the GNU General Public
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* License as published by the Free Software Foundation.
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*/
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#define KBUILD_MODNAME "foo"
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#include <linux/ip.h>
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#include <linux/ipv6.h>
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#include <linux/in.h>
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#include <linux/tcp.h>
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#include <linux/udp.h>
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#include <uapi/linux/bpf.h>
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#include "bpf_helpers.h"
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#define DEFAULT_PKTGEN_UDP_PORT 9
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#define IP_MF 0x2000
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#define IP_OFFSET 0x1FFF
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static inline int ip_is_fragment(struct __sk_buff *ctx, __u64 nhoff)
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{
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return load_half(ctx, nhoff + offsetof(struct iphdr, frag_off))
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& (IP_MF | IP_OFFSET);
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}
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SEC("ldabs")
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int handle_ingress(struct __sk_buff *skb)
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{
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__u64 troff = ETH_HLEN + sizeof(struct iphdr);
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if (load_half(skb, offsetof(struct ethhdr, h_proto)) != ETH_P_IP)
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return 0;
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if (load_byte(skb, ETH_HLEN + offsetof(struct iphdr, protocol)) != IPPROTO_UDP ||
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load_byte(skb, ETH_HLEN) != 0x45)
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return 0;
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if (ip_is_fragment(skb, ETH_HLEN))
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return 0;
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if (load_half(skb, troff + offsetof(struct udphdr, dest)) == DEFAULT_PKTGEN_UDP_PORT)
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return TC_ACT_SHOT;
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return 0;
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}
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char _license[] SEC("license") = "GPL";
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