| 1 | |
| 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 |
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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 |
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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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