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}