1// SPDX-License-Identifier: GPL-2.0
2#include <linux/bpf.h>
3#include <bpf/bpf_helpers.h>
4
5char _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__s32 page_size = 0;
13
14struct sockopt_inherit {
15	__u8 val;
16};
17
18struct {
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
25struct {
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
32struct {
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
39static __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
52SEC("cgroup/getsockopt")
53int _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
76out:
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
83SEC("cgroup/setsockopt")
84int _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
105out:
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