bpf/progs/sockopt_inherit.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 #include <linux/bpf.h>
0003 #include <bpf/bpf_helpers.h>
0004
0005 char _license[] SEC("license") = "GPL";
0006
0007 #define SOL_CUSTOM          0xdeadbeef
0008 #define CUSTOM_INHERIT1         0
0009 #define CUSTOM_INHERIT2         1
0010 #define CUSTOM_LISTENER         2
0011
0012 struct sockopt_inherit {
0013     __u8 val;
0014 };
0015
0016 struct {
0017     __uint(type, BPF_MAP_TYPE_SK_STORAGE);
0018     __uint(map_flags, BPF_F_NO_PREALLOC | BPF_F_CLONE);
0019     __type(key, int);
0020     __type(value, struct sockopt_inherit);
0021 } cloned1_map SEC(".maps");
0022
0023 struct {
0024     __uint(type, BPF_MAP_TYPE_SK_STORAGE);
0025     __uint(map_flags, BPF_F_NO_PREALLOC | BPF_F_CLONE);
0026     __type(key, int);
0027     __type(value, struct sockopt_inherit);
0028 } cloned2_map SEC(".maps");
0029
0030 struct {
0031     __uint(type, BPF_MAP_TYPE_SK_STORAGE);
0032     __uint(map_flags, BPF_F_NO_PREALLOC);
0033     __type(key, int);
0034     __type(value, struct sockopt_inherit);
0035 } listener_only_map SEC(".maps");
0036
0037 static __inline struct sockopt_inherit *get_storage(struct bpf_sockopt *ctx)
0038 {
0039     if (ctx->optname == CUSTOM_INHERIT1)
0040         return bpf_sk_storage_get(&cloned1_map, ctx->sk, 0,
0041                       BPF_SK_STORAGE_GET_F_CREATE);
0042     else if (ctx->optname == CUSTOM_INHERIT2)
0043         return bpf_sk_storage_get(&cloned2_map, ctx->sk, 0,
0044                       BPF_SK_STORAGE_GET_F_CREATE);
0045     else
0046         return bpf_sk_storage_get(&listener_only_map, ctx->sk, 0,
0047                       BPF_SK_STORAGE_GET_F_CREATE);
0048 }
0049
0050 SEC("cgroup/getsockopt")
0051 int _getsockopt(struct bpf_sockopt *ctx)
0052 {
0053     __u8 *optval_end = ctx->optval_end;
0054     struct sockopt_inherit *storage;
0055     __u8 *optval = ctx->optval;
0056
0057     if (ctx->level != SOL_CUSTOM)
0058         return 1; /* only interested in SOL_CUSTOM */
0059
0060     if (optval + 1 > optval_end)
0061         return 0; /* EPERM, bounds check */
0062
0063     storage = get_storage(ctx);
0064     if (!storage)
0065         return 0; /* EPERM, couldn't get sk storage */
0066
0067     ctx->retval = 0; /* Reset system call return value to zero */
0068
0069     optval[0] = storage->val;
0070     ctx->optlen = 1;
0071
0072     return 1;
0073 }
0074
0075 SEC("cgroup/setsockopt")
0076 int _setsockopt(struct bpf_sockopt *ctx)
0077 {
0078     __u8 *optval_end = ctx->optval_end;
0079     struct sockopt_inherit *storage;
0080     __u8 *optval = ctx->optval;
0081
0082     if (ctx->level != SOL_CUSTOM)
0083         return 1; /* only interested in SOL_CUSTOM */
0084
0085     if (optval + 1 > optval_end)
0086         return 0; /* EPERM, bounds check */
0087
0088     storage = get_storage(ctx);
0089     if (!storage)
0090         return 0; /* EPERM, couldn't get sk storage */
0091
0092     storage->val = optval[0];
0093     ctx->optlen = -1;
0094
0095     return 1;
0096 }