tools/testing/selftests/bpf/progs/sockopt_sk.c

   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
   8 char _license[] SEC("license") = "GPL";
   9 __u32 _version SEC("version") = 1;
  10
  11 #define SOL_CUSTOM                      0xdeadbeef
  12
  13 struct sockopt_sk {
  14         __u8 val;
  15 };
  16
  17 struct {
  18         __uint(type, BPF_MAP_TYPE_SK_STORAGE);
  19         __uint(map_flags, BPF_F_NO_PREALLOC);
  20         __type(key, int);
  21         __type(value, struct sockopt_sk);
  22 } socket_storage_map SEC(".maps");
  23
  24 SEC("cgroup/getsockopt")
  25 int _getsockopt(struct bpf_sockopt *ctx)
  26 {
  27         __u8 *optval_end = ctx->optval_end;
  28         __u8 *optval = ctx->optval;
  29         struct sockopt_sk *storage;
  30
  31         if (ctx->level == SOL_IP && ctx->optname == IP_TOS)
  32                 /* Not interested in SOL_IP:IP_TOS;
  33                  * let next BPF program in the cgroup chain or kernel
  34                  * handle it.
  35                  */
  36                 return 1;
  37
  38         if (ctx->level == SOL_SOCKET && ctx->optname == SO_SNDBUF) {
  39                 /* Not interested in SOL_SOCKET:SO_SNDBUF;
  40                  * let next BPF program in the cgroup chain or kernel
  41                  * handle it.
  42                  */
  43                 return 1;
  44         }
  45
  46         if (ctx->level == SOL_TCP && ctx->optname == TCP_CONGESTION) {
  47                 /* Not interested in SOL_TCP:TCP_CONGESTION;
  48                  * let next BPF program in the cgroup chain or kernel
  49                  * handle it.
  50                  */
  51                 return 1;
  52         }
  53
  54         if (ctx->level != SOL_CUSTOM)
  55                 return 0; /* EPERM, deny everything except custom level */
  56
  57         if (optval + 1 > optval_end)
  58                 return 0; /* EPERM, bounds check */
  59
  60         storage = bpf_sk_storage_get(&socket_storage_map, ctx->sk, 0,
  61                                      BPF_SK_STORAGE_GET_F_CREATE);
  62         if (!storage)
  63                 return 0; /* EPERM, couldn't get sk storage */
  64
  65         if (!ctx->retval)
  66                 return 0; /* EPERM, kernel should not have handled
  67                            * SOL_CUSTOM, something is wrong!
  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 }
  76
  77 SEC("cgroup/setsockopt")
  78 int _setsockopt(struct bpf_sockopt *ctx)
  79 {
  80         __u8 *optval_end = ctx->optval_end;
  81         __u8 *optval = ctx->optval;
  82         struct sockopt_sk *storage;
  83
  84         if (ctx->level == SOL_IP && ctx->optname == IP_TOS)
  85                 /* Not interested in SOL_IP:IP_TOS;
  86                  * let next BPF program in the cgroup chain or kernel
  87                  * handle it.
  88                  */
  89                 return 1;
  90
  91         if (ctx->level == SOL_SOCKET && ctx->optname == SO_SNDBUF) {
  92                 /* Overwrite SO_SNDBUF value */
  93
  94                 if (optval + sizeof(__u32) > optval_end)
  95                         return 0; /* EPERM, bounds check */
  96
  97                 *(__u32 *)optval = 0x55AA;
  98                 ctx->optlen = 4;
  99
 100                 return 1;
 101         }
 102
 103         if (ctx->level == SOL_TCP && ctx->optname == TCP_CONGESTION) {
 104                 /* Always use cubic */
 105
 106                 if (optval + 5 > optval_end)
 107                         return 0; /* EPERM, bounds check */
 108
 109                 memcpy(optval, "cubic", 5);
 110                 ctx->optlen = 5;
 111
 112                 return 1;
 113         }
 114
 115         if (ctx->level != SOL_CUSTOM)
 116                 return 0; /* EPERM, deny everything except custom level */
 117
 118         if (optval + 1 > optval_end)
 119                 return 0; /* EPERM, bounds check */
 120
 121         storage = bpf_sk_storage_get(&socket_storage_map, ctx->sk, 0,
 122                                      BPF_SK_STORAGE_GET_F_CREATE);
 123         if (!storage)
 124                 return 0; /* EPERM, couldn't get sk storage */
 125
 126         storage->val = optval[0];
 127         ctx->optlen = -1; /* BPF has consumed this option, don't call kernel
 128                            * setsockopt handler.
 129                            */
 130
 131         return 1;
 132 }