| 1 | /* Copyright (c) 2016 Facebook |
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| 2 | * |
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| 3 | * This program is free software; you can redistribute it and/or |
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| 4 | * modify it under the terms of version 2 of the GNU General Public |
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| 5 | * License as published by the Free Software Foundation. |
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| 6 | */ |
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| 7 | #define KBUILD_MODNAME "foo" |
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| 8 | #include <linux/ip.h> |
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| 9 | #include <linux/ipv6.h> |
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| 10 | #include <linux/in.h> |
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| 11 | #include <linux/tcp.h> |
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| 12 | #include <linux/udp.h> |
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| 13 | #include <uapi/linux/bpf.h> |
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| 14 | #include <net/ip.h> |
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| 15 | #include <bpf/bpf_helpers.h> |
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| 16 | |
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| 17 | #define DEFAULT_PKTGEN_UDP_PORT 9 |
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| 18 | |
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| 19 | /* copy of 'struct ethhdr' without __packed */ |
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| 20 | struct eth_hdr { |
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| 21 | unsigned char h_dest[ETH_ALEN]; |
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| 22 | unsigned char h_source[ETH_ALEN]; |
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| 23 | unsigned short h_proto; |
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| 24 | }; |
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| 25 | |
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| 26 | SEC("simple" ) |
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| 27 | int handle_ingress(struct __sk_buff *skb) |
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| 28 | { |
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| 29 | void *data = (void *)(long)skb->data; |
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| 30 | struct eth_hdr *eth = data; |
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| 31 | struct iphdr *iph = data + sizeof(*eth); |
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| 32 | struct udphdr *udp = data + sizeof(*eth) + sizeof(*iph); |
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| 33 | void *data_end = (void *)(long)skb->data_end; |
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| 34 | |
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| 35 | /* single length check */ |
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| 36 | if (data + sizeof(*eth) + sizeof(*iph) + sizeof(*udp) > data_end) |
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| 37 | return 0; |
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| 38 | |
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| 39 | if (eth->h_proto != htons(ETH_P_IP)) |
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| 40 | return 0; |
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| 41 | if (iph->protocol != IPPROTO_UDP || iph->ihl != 5) |
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| 42 | return 0; |
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| 43 | if (ip_is_fragment(iph)) |
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| 44 | return 0; |
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| 45 | if (udp->dest == htons(DEFAULT_PKTGEN_UDP_PORT)) |
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| 46 | return TC_ACT_SHOT; |
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| 47 | return 0; |
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| 48 | } |
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| 49 | char _license[] SEC("license" ) = "GPL" ; |
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| 50 | |
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