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
13static __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
21SEC("tc")
22int 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
40char _license[] SEC("license") = "GPL";