| 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 <bpf/bpf_helpers.h> |
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| 15 | #include "bpf_legacy.h" |
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| 16 | |
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| 17 | #define DEFAULT_PKTGEN_UDP_PORT 9 |
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| 18 | #define IP_MF 0x2000 |
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| 19 | #define IP_OFFSET 0x1FFF |
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| 20 | |
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| 21 | static inline int ip_is_fragment(struct __sk_buff *ctx, __u64 nhoff) |
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| 22 | { |
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| 23 | return load_half(ctx, nhoff + offsetof(struct iphdr, frag_off)) |
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| 24 | & (IP_MF | IP_OFFSET); |
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| 25 | } |
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| 26 | |
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| 27 | SEC("ldabs" ) |
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| 28 | int handle_ingress(struct __sk_buff *skb) |
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| 29 | { |
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| 30 | __u64 troff = ETH_HLEN + sizeof(struct iphdr); |
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| 31 | |
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| 32 | if (load_half(skb, offsetof(struct ethhdr, h_proto)) != ETH_P_IP) |
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| 33 | return 0; |
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| 34 | if (load_byte(skb, ETH_HLEN + offsetof(struct iphdr, protocol)) != IPPROTO_UDP || |
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| 35 | load_byte(skb, ETH_HLEN) != 0x45) |
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| 36 | return 0; |
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| 37 | if (ip_is_fragment(ctx: skb, nhoff: ETH_HLEN)) |
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| 38 | return 0; |
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| 39 | if (load_half(skb, troff + offsetof(struct udphdr, dest)) == DEFAULT_PKTGEN_UDP_PORT) |
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| 40 | return TC_ACT_SHOT; |
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| 41 | return 0; |
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| 42 | } |
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| 43 | char _license[] SEC("license" ) = "GPL" ; |
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| 44 | |
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