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torvalds
GitHub Repository: torvalds/linux
 Path: blob/master/samples/bpf/parse_ldabs.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/bpf_helpers.h>

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#include "bpf_legacy.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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