1 // SPDX-License-Identifier: GPL-2.0
2 /* Copyright (c) 2021 Facebook */
3 #include <linux/types.h>
4 #include <bpf/bpf_helpers.h>
5 #include <linux/bpf.h>
6 #include <stdint.h>
7 
8 #define TWFW_MAX_TIERS (64)
9 /*
10  * load is successful
11  * #define TWFW_MAX_TIERS (64u)$
12  */
13 
14 struct twfw_tier_value {
15 	unsigned long mask[1];
16 };
17 
18 struct rule {
19 	uint8_t seqnum;
20 };
21 
22 struct rules_map {
23 	__uint(type, BPF_MAP_TYPE_ARRAY);
24 	__type(key, __u32);
25 	__type(value, struct rule);
26 	__uint(max_entries, 1);
27 };
28 
29 struct tiers_map {
30 	__uint(type, BPF_MAP_TYPE_ARRAY);
31 	__type(key, __u32);
32 	__type(value, struct twfw_tier_value);
33 	__uint(max_entries, 1);
34 };
35 
36 struct rules_map rules SEC(".maps");
37 struct tiers_map tiers SEC(".maps");
38 
39 SEC("cgroup_skb/ingress")
40 int twfw_verifier(struct __sk_buff* skb)
41 {
42 	const uint32_t key = 0;
43 	const struct twfw_tier_value* tier = bpf_map_lookup_elem(&tiers, &key);
44 	if (!tier)
45 		return 1;
46 
47 	struct rule* rule = bpf_map_lookup_elem(&rules, &key);
48 	if (!rule)
49 		return 1;
50 
51 	if (rule && rule->seqnum < TWFW_MAX_TIERS) {
52 		/* rule->seqnum / 64 should always be 0 */
53 		unsigned long mask = tier->mask[rule->seqnum / 64];
54 		if (mask)
55 			return 0;
56 	}
57 	return 1;
58 }
59