| 1 |
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| 2 | |
| 3 | #include <stddef.h>
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| 4 | #include <string.h>
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| 5 | #include <linux/bpf.h>
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| 6 | #include <linux/if_ether.h>
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| 7 | #include <linux/ip.h>
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| 8 | #include <linux/pkt_cls.h>
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| 9 | #include <bpf/bpf_helpers.h>
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| 10 |
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| 11 | struct {
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| 12 | __uint(type, MAP_TYPE);
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| 13 | __uint(max_entries, 32);
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| 14 | __uint(map_flags, 0);
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| 15 | __uint(key_size, 0);
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| 16 | __uint(value_size, sizeof(__u32));
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| 17 | } map_in SEC(".maps");
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| 18 |
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| 19 | struct {
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| 20 | __uint(type, MAP_TYPE);
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| 21 | __uint(max_entries, 32);
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| 22 | __uint(map_flags, 0);
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| 23 | __uint(key_size, 0);
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| 24 | __uint(value_size, sizeof(__u32));
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| 25 | } map_out SEC(".maps");
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| 26 |
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| 27 | SEC("tc")
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| 28 | int _test(struct __sk_buff *skb)
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| 29 | {
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| 30 | void *data_end = (void *)(long)skb->data_end;
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| 31 | void *data = (void *)(long)skb->data;
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| 32 | struct ethhdr *eth = (struct ethhdr *)(data);
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| 33 | __u32 value;
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| 34 | int err;
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| 35 |
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| 36 | if (eth + 1 > data_end)
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| 37 | return TC_ACT_SHOT;
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| 38 |
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| 39 | struct iphdr *iph = (struct iphdr *)(eth + 1);
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| 40 |
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| 41 | if (iph + 1 > data_end)
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| 42 | return TC_ACT_SHOT;
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| 43 |
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| 44 | err = bpf_map_pop_elem(&map_in, &value);
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| 45 | if (err)
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| 46 | return TC_ACT_SHOT;
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| 47 |
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| 48 | iph->daddr = value;
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| 49 |
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| 50 | err = bpf_map_push_elem(&map_out, &iph->saddr, 0);
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| 51 | if (err)
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| 52 | return TC_ACT_SHOT;
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| 53 |
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| 54 | return TC_ACT_OK;
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| 55 | }
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| 56 |
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| 57 | char _license[] SEC("license") = "GPL";
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