1// SPDX-License-Identifier: GPL-2.0
 2#include <linux/bpf.h>
 3#include "bpf_helpers.h"
 4
 5char _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
13struct sockopt_inherit {
14	__u8 val;
15};
16
17struct {
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
24struct {
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
31struct {
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
38static __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
51SEC("cgroup/getsockopt")
52int _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
76SEC("cgroup/setsockopt")
77int _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}