1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/bpf.h>
3 #include <bpf/bpf_helpers.h>
4 
5 char _license[] SEC("license") = "GPL";
6 __u32 _version SEC("version") = 1;
7 
8 #define SOL_CUSTOM			0xdeadbeef
9 #define CUSTOM_INHERIT1			0
10 #define CUSTOM_INHERIT2			1
11 #define CUSTOM_LISTENER			2
12 
13 struct sockopt_inherit {
14 	__u8 val;
15 };
16 
17 struct {
18 	__uint(type, BPF_MAP_TYPE_SK_STORAGE);
19 	__uint(map_flags, BPF_F_NO_PREALLOC | BPF_F_CLONE);
20 	__type(key, int);
21 	__type(value, struct sockopt_inherit);
22 } cloned1_map SEC(".maps");
23 
24 struct {
25 	__uint(type, BPF_MAP_TYPE_SK_STORAGE);
26 	__uint(map_flags, BPF_F_NO_PREALLOC | BPF_F_CLONE);
27 	__type(key, int);
28 	__type(value, struct sockopt_inherit);
29 } cloned2_map SEC(".maps");
30 
31 struct {
32 	__uint(type, BPF_MAP_TYPE_SK_STORAGE);
33 	__uint(map_flags, BPF_F_NO_PREALLOC);
34 	__type(key, int);
35 	__type(value, struct sockopt_inherit);
36 } listener_only_map SEC(".maps");
37 
38 static __inline struct sockopt_inherit *get_storage(struct bpf_sockopt *ctx)
39 {
40 	if (ctx->optname == CUSTOM_INHERIT1)
41 		return bpf_sk_storage_get(&cloned1_map, ctx->sk, 0,
42 					  BPF_SK_STORAGE_GET_F_CREATE);
43 	else if (ctx->optname == CUSTOM_INHERIT2)
44 		return bpf_sk_storage_get(&cloned2_map, ctx->sk, 0,
45 					  BPF_SK_STORAGE_GET_F_CREATE);
46 	else
47 		return bpf_sk_storage_get(&listener_only_map, ctx->sk, 0,
48 					  BPF_SK_STORAGE_GET_F_CREATE);
49 }
50 
51 SEC("cgroup/getsockopt")
52 int _getsockopt(struct bpf_sockopt *ctx)
53 {
54 	__u8 *optval_end = ctx->optval_end;
55 	struct sockopt_inherit *storage;
56 	__u8 *optval = ctx->optval;
57 
58 	if (ctx->level != SOL_CUSTOM)
59 		return 1; /* only interested in SOL_CUSTOM */
60 
61 	if (optval + 1 > optval_end)
62 		return 0; /* EPERM, bounds check */
63 
64 	storage = get_storage(ctx);
65 	if (!storage)
66 		return 0; /* EPERM, couldn't get sk storage */
67 
68 	ctx->retval = 0; /* Reset system call return value to zero */
69 
70 	optval[0] = storage->val;
71 	ctx->optlen = 1;
72 
73 	return 1;
74 }
75 
76 SEC("cgroup/setsockopt")
77 int _setsockopt(struct bpf_sockopt *ctx)
78 {
79 	__u8 *optval_end = ctx->optval_end;
80 	struct sockopt_inherit *storage;
81 	__u8 *optval = ctx->optval;
82 
83 	if (ctx->level != SOL_CUSTOM)
84 		return 1; /* only interested in SOL_CUSTOM */
85 
86 	if (optval + 1 > optval_end)
87 		return 0; /* EPERM, bounds check */
88 
89 	storage = get_storage(ctx);
90 	if (!storage)
91 		return 0; /* EPERM, couldn't get sk storage */
92 
93 	storage->val = optval[0];
94 	ctx->optlen = -1;
95 
96 	return 1;
97 }
98