1 // SPDX-License-Identifier: GPL-2.0
2 // Copyright (c) 2018 Facebook
3
4 #include <vmlinux.h>
5 #include <bpf/bpf_helpers.h>
6 #include <bpf/bpf_core_read.h>
7 #include "bpf_tracing_net.h"
8 #define NUM_CGROUP_LEVELS 4
9
10 __u64 cgroup_ids[NUM_CGROUP_LEVELS];
11 __u16 dport;
12
13 static __always_inline void log_nth_level(struct __sk_buff *skb, __u32 level)
14 {
15 /* [1] &level passed to external function that may change it, it's
16 * incompatible with loop unroll.
17 */
18 cgroup_ids[level] = bpf_skb_ancestor_cgroup_id(skb, level);
19 }
20
21 SEC("tc")
22 int log_cgroup_id(struct __sk_buff *skb)
23 {
24 struct sock *sk = (void *)skb->sk;
25
26 if (!sk)
27 return TC_ACT_OK;
28
29 sk = bpf_core_cast(sk, struct sock);
30 if (sk->sk_protocol == IPPROTO_UDP && sk->sk_dport == dport) {
31 log_nth_level(skb, 0);
32 log_nth_level(skb, 1);
33 log_nth_level(skb, 2);
34 log_nth_level(skb, 3);
35 }
36
37 return TC_ACT_OK;
38 }
39
40 char _license[] SEC("license") = "GPL";
41
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