1 // SPDX-License-Identifier: GPL-2.0
2 // Copyright (c) 2018 Facebook
3 
4 #include <linux/bpf.h>
5 #include <linux/pkt_cls.h>
6 
7 #include <string.h>
8 
9 #include "bpf_helpers.h"
10 
11 #define NUM_CGROUP_LEVELS	4
12 
13 struct bpf_map_def SEC("maps") cgroup_ids = {
14 	.type = BPF_MAP_TYPE_ARRAY,
15 	.key_size = sizeof(__u32),
16 	.value_size = sizeof(__u64),
17 	.max_entries = NUM_CGROUP_LEVELS,
18 };
19 
20 static __always_inline void log_nth_level(struct __sk_buff *skb, __u32 level)
21 {
22 	__u64 id;
23 
24 	/* [1] &level passed to external function that may change it, it's
25 	 *     incompatible with loop unroll.
26 	 */
27 	id = bpf_skb_ancestor_cgroup_id(skb, level);
28 	bpf_map_update_elem(&cgroup_ids, &level, &id, 0);
29 }
30 
31 SEC("cgroup_id_logger")
32 int log_cgroup_id(struct __sk_buff *skb)
33 {
34 	/* Loop unroll can't be used here due to [1]. Unrolling manually.
35 	 * Number of calls should be in sync with NUM_CGROUP_LEVELS.
36 	 */
37 	log_nth_level(skb, 0);
38 	log_nth_level(skb, 1);
39 	log_nth_level(skb, 2);
40 	log_nth_level(skb, 3);
41 
42 	return TC_ACT_OK;
43 }
44 
45 int _version SEC("version") = 1;
46 
47 char _license[] SEC("license") = "GPL";
48