| 1 | |
| 2 | *
|
| 3 | * This program is free software; you can redistribute it and/or
|
| 4 | * modify it under the terms of version 2 of the GNU General Public
|
| 5 | * License as published by the Free Software Foundation.
|
| 6 |
|
| 7 | #define KBUILD_MODNAME "foo"
|
| 8 | #include <linux/ip.h>
|
| 9 | #include <linux/ipv6.h>
|
| 10 | #include <linux/in.h>
|
| 11 | #include <linux/tcp.h>
|
| 12 | #include <linux/udp.h>
|
| 13 | #include <uapi/linux/bpf.h>
|
| 14 | #include <bpf/bpf_helpers.h>
|
| 15 | #include "bpf_legacy.h"
|
| 16 |
|
| 17 | #define DEFAULT_PKTGEN_UDP_PORT 9
|
| 18 | #define IP_MF 0x2000
|
| 19 | #define IP_OFFSET 0x1FFF
|
| 20 |
|
| 21 | static inline int ip_is_fragment(struct __sk_buff *ctx, __u64 nhoff)
|
| 22 | {
|
| 23 | return load_half(ctx, nhoff + offsetof(struct iphdr, frag_off))
|
| 24 | & (IP_MF | IP_OFFSET);
|
| 25 | }
|
| 26 |
|
| 27 | SEC("ldabs")
|
| 28 | int handle_ingress(struct __sk_buff *skb)
|
| 29 | {
|
| 30 | __u64 troff = ETH_HLEN + sizeof(struct iphdr);
|
| 31 |
|
| 32 | if (load_half(skb, offsetof(struct ethhdr, h_proto)) != ETH_P_IP)
|
| 33 | return 0;
|
| 34 | if (load_byte(skb, ETH_HLEN + offsetof(struct iphdr, protocol)) != IPPROTO_UDP ||
|
| 35 | load_byte(skb, ETH_HLEN) != 0x45)
|
| 36 | return 0;
|
| 37 | if (ip_is_fragment(skb, ETH_HLEN))
|
| 38 | return 0;
|
| 39 | if (load_half(skb, troff + offsetof(struct udphdr, dest)) == DEFAULT_PKTGEN_UDP_PORT)
|
| 40 | return TC_ACT_SHOT;
|
| 41 | return 0;
|
| 42 | }
|
| 43 | char _license[] SEC("license") = "GPL";
|