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 __u32 page_size = 0;
13
14 struct sockopt_inherit {
15 __u8 val;
16 };
17
18 struct {
19 __uint(type, BPF_MAP_TYPE_SK_STORAGE);
20 __uint(map_flags, BPF_F_NO_PREALLOC | BPF_F_CLONE);
21 __type(key, int);
22 __type(value, struct sockopt_inherit);
23 } cloned1_map SEC(".maps");
24
25 struct {
26 __uint(type, BPF_MAP_TYPE_SK_STORAGE);
27 __uint(map_flags, BPF_F_NO_PREALLOC | BPF_F_CLONE);
28 __type(key, int);
29 __type(value, struct sockopt_inherit);
30 } cloned2_map SEC(".maps");
31
32 struct {
33 __uint(type, BPF_MAP_TYPE_SK_STORAGE);
34 __uint(map_flags, BPF_F_NO_PREALLOC);
35 __type(key, int);
36 __type(value, struct sockopt_inherit);
37 } listener_only_map SEC(".maps");
38
get_storage(struct bpf_sockopt * ctx)39 static __inline struct sockopt_inherit *get_storage(struct bpf_sockopt *ctx)
40 {
41 if (ctx->optname == CUSTOM_INHERIT1)
42 return bpf_sk_storage_get(&cloned1_map, ctx->sk, 0,
43 BPF_SK_STORAGE_GET_F_CREATE);
44 else if (ctx->optname == CUSTOM_INHERIT2)
45 return bpf_sk_storage_get(&cloned2_map, ctx->sk, 0,
46 BPF_SK_STORAGE_GET_F_CREATE);
47 else
48 return bpf_sk_storage_get(&listener_only_map, ctx->sk, 0,
49 BPF_SK_STORAGE_GET_F_CREATE);
50 }
51
52 SEC("cgroup/getsockopt")
_getsockopt(struct bpf_sockopt * ctx)53 int _getsockopt(struct bpf_sockopt *ctx)
54 {
55 __u8 *optval_end = ctx->optval_end;
56 struct sockopt_inherit *storage;
57 __u8 *optval = ctx->optval;
58
59 if (ctx->level != SOL_CUSTOM)
60 goto out; /* only interested in SOL_CUSTOM */
61
62 if (optval + 1 > optval_end)
63 return 0; /* EPERM, bounds check */
64
65 storage = get_storage(ctx);
66 if (!storage)
67 return 0; /* EPERM, couldn't get sk storage */
68
69 ctx->retval = 0; /* Reset system call return value to zero */
70
71 optval[0] = storage->val;
72 ctx->optlen = 1;
73
74 return 1;
75
76 out:
77 /* optval larger than PAGE_SIZE use kernel's buffer. */
78 if (ctx->optlen > page_size)
79 ctx->optlen = 0;
80 return 1;
81 }
82
83 SEC("cgroup/setsockopt")
_setsockopt(struct bpf_sockopt * ctx)84 int _setsockopt(struct bpf_sockopt *ctx)
85 {
86 __u8 *optval_end = ctx->optval_end;
87 struct sockopt_inherit *storage;
88 __u8 *optval = ctx->optval;
89
90 if (ctx->level != SOL_CUSTOM)
91 goto out; /* only interested in SOL_CUSTOM */
92
93 if (optval + 1 > optval_end)
94 return 0; /* EPERM, bounds check */
95
96 storage = get_storage(ctx);
97 if (!storage)
98 return 0; /* EPERM, couldn't get sk storage */
99
100 storage->val = optval[0];
101 ctx->optlen = -1;
102
103 return 1;
104
105 out:
106 /* optval larger than PAGE_SIZE use kernel's buffer. */
107 if (ctx->optlen > page_size)
108 ctx->optlen = 0;
109 return 1;
110 }
111