LXR linux/tools/testing/selftests/bpf/progs/sockopt

   1// SPDX-License-Identifier: GPL-2.0
   2#include <string.h>
   3#include <netinet/in.h>
   4#include <netinet/tcp.h>
   5#include <linux/bpf.h>
   6#include <bpf/bpf_helpers.h>
   7
   8char _license[] SEC("license") = "GPL";
   9__u32 _version SEC("version") = 1;
  10
  11#ifndef PAGE_SIZE
  12#define PAGE_SIZE 4096
  13#endif
  14
  15#define SOL_CUSTOM                      0xdeadbeef
  16
  17struct sockopt_sk {
  18        __u8 val;
  19};
  20
  21struct {
  22        __uint(type, BPF_MAP_TYPE_SK_STORAGE);
  23        __uint(map_flags, BPF_F_NO_PREALLOC);
  24        __type(key, int);
  25        __type(value, struct sockopt_sk);
  26} socket_storage_map SEC(".maps");
  27
  28SEC("cgroup/getsockopt")
  29int _getsockopt(struct bpf_sockopt *ctx)
  30{
  31        __u8 *optval_end = ctx->optval_end;
  32        __u8 *optval = ctx->optval;
  33        struct sockopt_sk *storage;
  34
  35        if (ctx->level == SOL_IP && ctx->optname == IP_TOS) {
  36                /* Not interested in SOL_IP:IP_TOS;
  37                 * let next BPF program in the cgroup chain or kernel
  38                 * handle it.
  39                 */
  40                ctx->optlen = 0; /* bypass optval>PAGE_SIZE */
  41                return 1;
  42        }
  43
  44        if (ctx->level == SOL_SOCKET && ctx->optname == SO_SNDBUF) {
  45                /* Not interested in SOL_SOCKET:SO_SNDBUF;
  46                 * let next BPF program in the cgroup chain or kernel
  47                 * handle it.
  48                 */
  49                return 1;
  50        }
  51
  52        if (ctx->level == SOL_TCP && ctx->optname == TCP_CONGESTION) {
  53                /* Not interested in SOL_TCP:TCP_CONGESTION;
  54                 * let next BPF program in the cgroup chain or kernel
  55                 * handle it.
  56                 */
  57                return 1;
  58        }
  59
  60        if (ctx->level == SOL_IP && ctx->optname == IP_FREEBIND) {
  61                if (optval + 1 > optval_end)
  62                        return 0; /* EPERM, bounds check */
  63
  64                ctx->retval = 0; /* Reset system call return value to zero */
  65
  66                /* Always export 0x55 */
  67                optval[0] = 0x55;
  68                ctx->optlen = 1;
  69
  70                /* Userspace buffer is PAGE_SIZE * 2, but BPF
  71                 * program can only see the first PAGE_SIZE
  72                 * bytes of data.
  73                 */
  74                if (optval_end - optval != PAGE_SIZE)
  75                        return 0; /* EPERM, unexpected data size */
  76
  77                return 1;
  78        }
  79
  80        if (ctx->level != SOL_CUSTOM)
  81                return 0; /* EPERM, deny everything except custom level */
  82
  83        if (optval + 1 > optval_end)
  84                return 0; /* EPERM, bounds check */
  85
  86        storage = bpf_sk_storage_get(&socket_storage_map, ctx->sk, 0,
  87                                     BPF_SK_STORAGE_GET_F_CREATE);
  88        if (!storage)
  89                return 0; /* EPERM, couldn't get sk storage */
  90
  91        if (!ctx->retval)
  92                return 0; /* EPERM, kernel should not have handled
  93                           * SOL_CUSTOM, something is wrong!
  94                           */
  95        ctx->retval = 0; /* Reset system call return value to zero */
  96
  97        optval[0] = storage->val;
  98        ctx->optlen = 1;
  99
 100        return 1;
 101}
 102
 103SEC("cgroup/setsockopt")
 104int _setsockopt(struct bpf_sockopt *ctx)
 105{
 106        __u8 *optval_end = ctx->optval_end;
 107        __u8 *optval = ctx->optval;
 108        struct sockopt_sk *storage;
 109
 110        if (ctx->level == SOL_IP && ctx->optname == IP_TOS) {
 111                /* Not interested in SOL_IP:IP_TOS;
 112                 * let next BPF program in the cgroup chain or kernel
 113                 * handle it.
 114                 */
 115                ctx->optlen = 0; /* bypass optval>PAGE_SIZE */
 116                return 1;
 117        }
 118
 119        if (ctx->level == SOL_SOCKET && ctx->optname == SO_SNDBUF) {
 120                /* Overwrite SO_SNDBUF value */
 121
 122                if (optval + sizeof(__u32) > optval_end)
 123                        return 0; /* EPERM, bounds check */
 124
 125                *(__u32 *)optval = 0x55AA;
 126                ctx->optlen = 4;
 127
 128                return 1;
 129        }
 130
 131        if (ctx->level == SOL_TCP && ctx->optname == TCP_CONGESTION) {
 132                /* Always use cubic */
 133
 134                if (optval + 5 > optval_end)
 135                        return 0; /* EPERM, bounds check */
 136
 137                memcpy(optval, "cubic", 5);
 138                ctx->optlen = 5;
 139
 140                return 1;
 141        }
 142
 143        if (ctx->level == SOL_IP && ctx->optname == IP_FREEBIND) {
 144                /* Original optlen is larger than PAGE_SIZE. */
 145                if (ctx->optlen != PAGE_SIZE * 2)
 146                        return 0; /* EPERM, unexpected data size */
 147
 148                if (optval + 1 > optval_end)
 149                        return 0; /* EPERM, bounds check */
 150
 151                /* Make sure we can trim the buffer. */
 152                optval[0] = 0;
 153                ctx->optlen = 1;
 154
 155                /* Usepace buffer is PAGE_SIZE * 2, but BPF
 156                 * program can only see the first PAGE_SIZE
 157                 * bytes of data.
 158                 */
 159                if (optval_end - optval != PAGE_SIZE)
 160                        return 0; /* EPERM, unexpected data size */
 161
 162                return 1;
 163        }
 164
 165        if (ctx->level != SOL_CUSTOM)
 166                return 0; /* EPERM, deny everything except custom level */
 167
 168        if (optval + 1 > optval_end)
 169                return 0; /* EPERM, bounds check */
 170
 171        storage = bpf_sk_storage_get(&socket_storage_map, ctx->sk, 0,
 172                                     BPF_SK_STORAGE_GET_F_CREATE);
 173        if (!storage)
 174                return 0; /* EPERM, couldn't get sk storage */
 175
 176        storage->val = optval[0];
 177        ctx->optlen = -1; /* BPF has consumed this option, don't call kernel
 178                           * setsockopt handler.
 179                           */
 180
 181        return 1;
 182}
 183