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